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General control line discussion => Open Forum => Topic started by: RC Storick on March 23, 2009, 08:31:50 AM
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I had set out to make my world beater this year in the 40tys. The Viper has been a long project of refinements. The first one being 41 oz with a FP .40. Flew rather well however it would never had enough drive for the high winds at the NATS. My favorite on was the Super glide at 50 oz but was still powered by a FP .40 on a pipe. A string of Vipers were built using different power configurations including Super-tiger big blocks.
My disappointment has always fallen in the concentrated weight in the nose. The tug feeling you get coming over the top is this thing going to turn. This feeling is prevalent in my larger ships.
So Viper 8 started out as a pipped PA.40UL ship. Clean yet sparse on Clear to keep the weight down. 47.5 OZ.The first test flight showed great promise. The were a few trim problems. Seemed the outboard wing had a slight warp in it. SO the flaps were tweaked to get it to fly level. This caused the butt to set. Always looking for groove. So after 10 flights on this plane I knew in my mind do things would have to make plane more positive. After landing on the 10th flight I conferred with Ron O'tool what I had in mind.
He arrived at my house to Find the tea kettle already steaming .We steamed the wing straight and reset the flaps to neutral. First problem solved. I knew I wanted more drive for the wind so I opted for the PA.65. After careful assessment and fitting I got it into the tight confines of the .40 size plane. Refitting the larger pipe and 8 oz tank.
A trip out to the field for 10 more flights to see what can be learned. All trim was left the same. Lead-out placement, WT weight etc. I was a little apprehensive at the nose heaviness of this airplane. At 2.5 inches it was extreme. 4 flights were made with no trim change. Directional stability was at its utmost (nose-heavy) and the turn was diminished somewhat. It was hinging in the turn. So lead-outs came foreword 3/8 of a inch. It got much better in the turn and set. Around the 15th flight we decide to add some tail weight. Approx 1 oz of solder was added to the tail wheel wire. WOW what a difference. No hinging and the turn was again like lightning. The CG moved to 2.75 from LE. I have great directional stability and lightning turn. I don't know Doodley squat about pi times radius squared and the alpha numbers but when you see this airplane fly you will know what I say is true. Its all set in weight!
I will remove the solder from the tail wheel and shoot some more clear on it to move the CG to where it is at now.I have also ordered a MAG spinner, back plate and drive washer to reduce the weight in the nose. Target weight now is 52 OZ.
You have to ask yourself why did he opt for the .65 if he's worried about weight? Propeller my friends.. I am now turning a 13.5 under cambered Phelps propeller for massive drive in the wind. The winds at the NATS are generally 15 to 20 MPH and not called off till it reaches sustained 25 MPH. I wanted the positive drive of the larger propeller for the only contest that this plane really was designed for.
Oh by the way Viper 1.0 is now under construction for the PA.75 Numbers will be 60 inch span, .8.25 nose 17.5 tail target weight is 55 OZ. You ask why the .75? 15 inch prop.
Try to remember I am a mechanic and learn by doing. If you don't believe my results on weight try it for your self. Its not as easy as it sounds to get the airframes this light and still be structurally sound. But if you can you will realize the pay off and never look back again.
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Great report Robert. Nothing like hands on experience as I think Ron went thru same process when he was the terror of the stunt circles. Still gets me when the people still the written word is the way to go. With the next one are you going to shorten the nose for the heavier power plant? I am glad you are getting it to work. Having fun, DOC Holliday
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Yes the nose gets shortened by 1 inch and the tail lengthened by 1 inch to accommodate the larger power plant but gross weight has to stay down to achieve balance. The Marbles are in my pocket.
By the way by PA.40 UL setup is for sale. Engine, header and pipe $275.00 plus shipping (sold pending funds)
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Windy has always said, run the biggest prop you can run on that plane, and it will fly better. Upping the powerplant up to a .65 sure does allow you to run a much bigger prop. What prop were you running originally???
Sounds like that plane is going to be a winner y1 #^
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And here is me, trying to use the smallest prop I can get away with. Silly me.
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Bob,
Wow, a big change in plans from February, that's for sure.
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Bob,
Wow, a big change in plans from February, that's for sure.
Ah yes what a month will do. You have seen the airplane in person and know its vision and capability's. The March winds have given me some foresight in what to expect at the NATS. You have to give a little to gain allot. I have MAG parts coming for the engine and should be able to lighten it up some. This also affords me some clear paint on the back half of the airplane. It still will not have the dipped look but will shine. The plan of attack is now I am working on fixing the dings and the things I wanted to before test flights. I will then spray clear dope on the back half of the airplane and Urethane on the nose. I only have 1 OZ to play with. As gross weight comes up CG moves back. Even if its nose heavy I still have something in my corner. Because the gross weight is way down it does still turn and is manageable.
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Keep us posted as to how it works out. Seems a bit like Dave Fitzgerald's set up. At least you don't have to build another plane.
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Nothing like Fitz's plane.
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Bob,
I think he meant in concept, not in execution. Small plane; bing engine.
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Right Randy. I think both are about 630 squares and 75 powered?
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Bob,
I think he meant in concept, not in execution. Small plane; bing engine.
Small plane big engine yes. But mine is 52 oz now and his is 65. 9.5 nose on mine and 10.5 on his. I would have liked the .40 to work and to be in the fourty ounce range. But I think tis is the correct way to go.
So his numbers are still a big plane. 60 inch WS for his, 57 for mine. 18.5 tail for his, mine 16.5
Edit weight from 58 to where it really is at 52
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I guess it depends on what you see as a "big plane". I have a 750 square inch USA-1 sort of design that seems big to me. My current plane is about 615 square inches. Seems smallish. The new profile I'm working on is about 580. Also seems smallish.
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Small plane big engine yes. But mine is 52 oz now and his is 65.
9.5 nose
52 for mine.
mine 16.5
Bear 65 nearly exactly.
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Bear 65 nearly exactly.
Who built this at 52 oz Bob?
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Jim Pollack wanted to get a discussion started on SSW about drive in the wind. This is what I posted.
Viper 8 is a approx 650 SQ in wing and a 9.5 nose and 16.5 tail. Now with the .65 in the nose it weighs 52 oz. The turn diminished somewhat from the original .40 at 47.5. It did yaw at first but after moving lead outs foreword 3/8 of a inch this went away. I am using a 13.5 prop and after adding a 1/2 of tail weigh the turn is specular. I have ordered MAG parts for the engine to reduce concentrated weight in the nose. I have always said the base line characteristic is set in weight and this experiment proves it.
Viper 1.0 will have a 8.5 inch nose and a 17.5 tail with the 75 in it. Pulling the weight back helps but does not get totally rid of the base line I speak of. Before anyone comes back to dispute this Build one of your own for this experiment. Using the same plane but with different engines.
Because of its light weight it turns on a dime yet the CG is far foreword WAY FOREWORD. What does this mean? It means the directional stability is of the utmost. (nose heavy) Yet manageable because of my controls are sped up and the overall weight of the aircraft.
The things that are your friends in my opinion. Engine offset, a foreword CG for centrifugal force. Prop size for drive. The only reason to run a larger engine is to turn a larger prop. More prop more drive!
I have already flown this in strong winds and it offers great line tension everywhere. The only trim change I am going to make is pull the pipe foreword and up the nose size so it runs rich on the ground and unloads in the air. I will go from a .4 pitch to a 3.75 or a 3.5 pitch and turn up the engine a little. It does not wind up at all now. But I want to go from a 5.2 to a 5.5 lap speed. Just something else to try. This experiment has just prov-en to me what I have known all along.
Many ways to skin a cat so to speak this is what I choose.
EDIT: I would have put the .75 in the nose but I would have had to add too much to the gross weight to get it to balance.
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Bob,
So if I built a smaller airplane than 650 squares lets say about 600 and can swing a 12 or 13 inch prop, then I would get the drive that you're describing?
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Yes a strong .40 on a smaller plane turning the largest prop it can will have more drive. As long as its light weight bleeds off horsepower. This would be more desirable to me as the concentrated weight is less than what I am doing.
The ideal .40 engine would weigh 8.5 and have the power of a .90 to swing a 15 inch prop.
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Who built this at 52 oz Bob?
I built mine at 52 oz. I extended the wing a little and got it up to 675, normally it is right at 650. Still had the same tail so it was 19% with stablets. Tiny tails build light. Stablets make it turn very easy while using a small tail section. It flew great. I won alot of contests with it and placed very high at the nats many times in adv.
Building light isnt very hard. Just pay attention when buying wood. The selection process is as important a step as any of it.
Use thin CA in one of those dropper applicators. 5 minute epoxy around the wing joint. Finish sparingly and you will have a light plane. That is how I do it.
My Geo Bear, billy winged based Bear, I flew into the Top5 is Quite a bit bigger plane all the way around. I finished that one off at 58oz. After 6 years of service, and several repairs, it weighs in around 62 and still flys very good.
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I built mine at 52 oz. I extended the wing a little and got it up to 675, normally it is right at 650. Still had the same tail so it was 19% with stablets. Tiny tails build light. Stablets make it turn very easy while using a small tail section. It flew great. I won alot of contests with it and placed very high at the nats many times in adv.
Building light isnt very hard. Just pay attention when buying wood. The selection process is as important a step as any of it.
Use thin CA in one of those dropper applicators. 5 minute epoxy around the wing joint. Finish sparingly and you will have a light plane. That is how I do it.
My Geo Bear, billy winged based Bear, I flew into the Top5 is Quite a bit bigger plane all the way around. I finished that one off at 58oz. After 6 years of service, and several repairs, it weighs in around 62 and still flys very good.
Glad it worked for you
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Who built this at 52 oz Bob?
All of Bob's were 52 to 54 oz...
Doug's too...
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12" or smaller has won more...
Large props can be quite nice on super light planes. Something has to bleed off the power... I was having a lot of fun flying Bob Howard's plane with the 14-6 TF Power Point and the PA 65 RE muffled running at 7200 RPM. It was pretty wicked in the wind, and had lots of drive without over speeding. probably very similar to the Retro setup.
Of course, that plane has a 20" tail moment...
Since then I am back to 12" three blades (or 13" two blades). Doug tried larger than 12"...back to 12" now.
12" prop = 45 degrees.
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Viper 1.0 will have a 8.5 inch nose and a 17.5 tail with the 75 in it.
Furias...
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I have already flown this in strong winds and it offers great line tension everywhere. The only trim change I am going to make is pull the pipe foreword and up the nose size so it runs rich on the ground and unloads in the air. I will go from a .4 pitch to a 3.75 or a 3.5 pitch and turn up the engine a little. It does not wind up at all now. But I want to go from a 5.2 to a 5.5 lap speed. Just something else to try. This experiment has just prov-en to me what I have known all along.
Doug's PA 65 setup. 3.6 pitch at 10600 to 11000 rpm.
This does work.
Try some 20% nitro.
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Furias...
Yeah, it is 8.5, 18.
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Furias...
And how much does this puppy weigh?
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I built mine at 52 oz. I extended the wing a little and got it up to 675, normally it is right at 650. Still had the same tail so it was 19% with stablets. Tiny tails build light. Stablets make it turn very easy while using a small tail section. It flew great. I won alot of contests with it and placed very high at the nats many times in adv.
Building light isnt very hard. Just pay attention when buying wood. The selection process is as important a step as any of it.
Back in the late 60tys and early 70tys we could build them at 37-40 Please show me the wood today..
Sure am glad we get weighed this year to see whats what.
To whomever it may concern. If the bell crank location doesn't matter why does Bill Netzeband say in his own words it should be just behind the CG?
So according to his own words it does matter or he would not have said that. SN July/Aug 2008 page 51 Entitled Recycling Wild Bill.
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......
Viper 8 is a approx 650 SQ in wing and a 9.5 nose and 16.5 tail. Now with the .65 in the nose it weighs 52 oz. The turn diminished somewhat from the original .40 at 47.5. It did yaw at first but after moving lead outs foreword 3/8 of a inch this went away. I am using a 13.5 prop and after adding a 1/2 of tail weigh the turn is specular. I have ordered MAG parts for the engine to reduce concentrated weight in the nose. I have always said the base line characteristic is set in weight and this experiment proves it.
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I dont follow. You have always said, and I am paraphrasing here, that weight is of the utmost importance. Right?
Then you added 4.5 oz of weight to your plane and it flew better. Yeah the motor is bigger but that does not change the simple fact that you are flying a heavier plane. It now has MORE wing loading.
It appears to me that the opposite is coming out.
Also, as many have said over the years myself included, a good strong motor run is the most important thing. You are proving that without a doubt. You put in more usable power in your plane while adding 4.5 oz and it flew better.
If you really want to prove the weight theory once and for all you have to build a plane with a ballast box on it.. Build it super light, no finish just clear fuel proof dope. Then add and remove weight in the box, located on the CG of course, and see where it really flies best. Even then nothing has really been proven because the weight that is added and removed is concentrated in one area......and the discussion continues....
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Back in the late 60tys and early 70tys we could build them at 37-40 Please show me the wood today..
Gee, I got a huge box of 4.0-4.5 lb wood in my bedroom right now!
Brett
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And how much does this puppy weigh?
The Furias is no light weight. Never said it was either. 67oz.
But it is no small plane either. 62" span, Geo-Bolt wing. 26% tail giving it a 29" span. The tail is sheeted foam. Over all length from spinner to tail is 47". 3" wide fuse.
Ultra light was not the goal on this one. It began its life at 65oz. I could live with that. Not the best but decent. I knew it would be heavier because of some of the techniques i used when building it. Plus it has a Saito 62 in it and a larger 2.5" spinner. Then in its 4th flight, second time out, a gust of wind caught it on landing and it picked it up and dropped it on the nose crushing the cowl and cracking the top block. That repair cost an oz. Then at its contest debut and what would be flight 32 and 33 someone dropped their line reel through the top of the outboard wing. That repair added another oz. I have flown it since that final repair it is flies good. Needs some trim but should be a good plane.
In the photo on the stand you can see the font on the AMA number is different from the other two. I ended up having to repair the whole outboard wing, ouch. it wasnt fun. Lots of cussing along the way. But I learned alot too....
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I dont follow. You have always said, and I am paraphrasing here, that weight is of the utmost importance. Right?
Then you added 4.5 oz of weight to your plane and it flew better. Yeah the motor is bigger but that does not change the simple fact that you are flying a heavier plane. It now has MORE wing loading.
It appears to me that the opposite is coming out.
Also, as many have said over the years myself included, a good strong motor run is the most important thing. You are proving that without a doubt. You put in more usable power in your plane while adding 4.5 oz and it flew better.
If you really want to prove the weight theory once and for all you have to build a plane with a ballast box on it.. Build it super light, no finish just clear fuel proof dope. Then add and remove weight in the box, located on the CG of course, and see where it really flies best. Even then nothing has really been proven because the weight that is added and removed is concentrated in one area......and the discussion continues....
You are obviously talking hypothetic as you have not done it.
Once again you have missed the point. It does not fly better It has more power! You guys are always trying to goat me into a argument you can not win! Start your own thread.
And to Brett I am from the SHOW ME STATE so your going to build a light one now right? Oh ya don't forget to add the ballast in the belly.
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And to Brett I am from the SHOW ME STATE so your going to build a light one now right? Oh ya don't forget to add the ballast in the belly.
Uh, Sparky, I was building 630-640 square inch airplanes in the low 40s with ST46s - and flying legitimate 500 point patterns - 25 years ago. In fact all but one of my ST46 airplanes was in the 40's. But why would I spend the time to build something uncompetitive just to show you I could do it? There's no great skill associated with building light, nor does it significantly improve contest results. Believing otherwise with religious fervor doesn't bother me too much, but it also doesn't make it true.
And I still haven't seen your explanation as to why adding 8 full ounces of dead weight to a 40-oz Tucker special made it fly so much better. Or maybe you think Ted Fancher and I either don't know how to trim, or can't tell whether it flies better or not? Also, why did the lightest wing loading to win at the NATs in the past 20+ years was around 13 oz/square foot.
Brett
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Uh, Sparky, I was building 630-640 square inch airplanes in the low 40s with ST46s - and flying legitimate 500 point patterns - 25 years ago. In fact all but one of my ST46 airplanes was in the 40's. But why would I spend the time to build something uncompetitive just to show you I could do it? There's no great skill associated with building light, nor does it significantly improve contest results. RS: (Please tell this to Billy W and get his response) Believing otherwise with religious fervor doesn't bother me too much, but it also doesn't make it true.
And I still haven't seen your explanation as to why adding 8 full ounces of dead weight to a 40-oz Tucker special made it fly so much better. Or maybe you think Ted Fancher and I either don't know how to trim, or can't tell whether it flies better or not? Also, why did the lightest wing loading to win at the NATs in the past 20+ years was around 13 oz/square foot. RS: I would think winning the world is a better acheivement. 2004 Razor back 53 oz 700 SQ whats the wing loading?
Brett
Here is my thoughts. Just because you say so don't make it right. Ron O'tool will be at the NATS this year tell it to him and get his response. Also to build planes back then that light was not as difficult as it is now. Wood availability. Please send me that 4 LB stuff seeing as you don't need it. I will pay 2 or 3 times what you paid for it.
Just because a guy has all the time in the world to practice to fly a model airplane does this make him a smarter /better person than lets say the 40th place guy. Does this make him a better builder? No it makes him a better flier. After not agreeing with all of what Wild Bill has to say I had to re read his stuff which everyone seems to hold a gospel. But I am not sure people understand what he wrote. I gave the page number on his writings heres a web site. http://www.iroquois.free-online.co.uk/netze/wildbill.htm
His writings in stunt news have a different flavor. Lets give a for instance. His writing state the BC should be just behind the CG? (does it matter?) in the next breath he says for a sluggish airplane move the cg back? But now the BC is in front of the CG (unless you have that mystery floating BC). What happens when the BC is in front of the CG? encase some don't understand Line tension is diminished. (but it don't matter).
Congrats on winning the NATS thats a achievement I hope to do someday. But to talk down to me come on.. Ain't happening.
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Here is my thoughts. Just because you say so don't make it right. Ron O'tool will be at the NATS this year tell it to him and get his response. Also to build planes back then that light was not as difficult as it is now. Wood availability. Please send me that 4 LB stuff seeing as you don't need it. I will pay 2 or 3 times what you paid for it.
Robert, you are right here. The older wood was better. I was wild grown. The light wood had much denser grain. The new wood is farm grown. You can almost see through it. Bob Howard had a box of very old balsa. It was AMAZING!!!
The balsa dust is much worse now too. Explain that!!!
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Also, why did the lightest wing loading to win at the NATs in the past 20+ years was around 13 oz/square foot.
That is a sticky wicket...
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This is like arguing religious conviction. The proof is in the pudding. Guess we'll see at the Nats.
Truth is, no one component makes for the "best" plane. It's all about balance. Other things being equal, I will agree with Robert that lighter is better. But as it turns out, all things are not equal. Weight needs to be balanced with lift capacity of the wing design (among several other factors) along with usable power. You can bolt a 1.5 in the nose, but how much of the power is usable (forget about the weight)? Much like a bigger prop. Again, all things being equal, the bigger prop your engine can efficiently turn, the more thrust generated. But again, all things are not equal. Other factors enter into it (such as GP and P-factor among others).
The point is, no one element is the deciding factor. You can argue this all day long, but simple logic will tell you that all factors have to work together to create something competitive.
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The point is, no one element is the deciding factor. You can argue this all day long, but simple logic will tell you that all factors have to work together to create something competitive.
I have lost count of how many people I have seen go from 35's to 46's "so they could handle the wind, then from 46's to 60's for the same reason. Now a lot of those guys are flying 75's and wishing they had 90's so they "could handle the wind...."
Thus I hold these to be self evident:
* If you know how to fly in the wind then it does not matter what you fly.
* If you really do not know how to fly in the wind then it really does not matter what you fly either.
I am waiting to be shown otherwise.
Personally I love it when I see my competitors show up with 60 oz birds, & big motors. Historically, I know if the wind blows my job gets a lot easier!
Sparky has taken an interesting tack on his current Viper and has aggressive plans for his new one. Light weight and excess power gives him a LOT of room for experimentation. A big piece of the wind flying puzzle is confidence in your equipment, and he believes he is on the right track; time will tell whether it pays off for him. Ironically I think he has created the ultimate CALM weather machines, which was not his intent, but will be a pleasant surprise. My prediction is that he will QUICKLY abandon the 16" prop in the wind - but he has options all over the place.
I know this is sacrilege, but I always RICHEN an engine and/or go to a less aggressive prop to fly in the wind - you need LESS power. The guys flying electrics with dataloggers on board are PROVING the same things with 3-4 digit accuracy: power usage is LOWER in the wind than in the calm. Some of them are "throttling up" to use that "free" power out of their batteries (ie to go faster). While I am as proud of David Fitz as anyone, and impressed with the logic he used to develop his Championship machine, remember that the "vice champion" Igor Burger was flying a 6 year old gassie airframe converted to electric with fixed throttle settings - a distinctly flat power approach.
..and THESE discussions are what the forum is for!!!
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Well let me put this out there. I know that light planes fly better in the wind! We have a guy here (he is on this forum) who fly's in rough wind when my heavy stuff is put away. His plane weighs 18oz? Hum is that light enough? .015 diesel on 52 foot lines. After seeing this humming bird fly in the wind got me to think of old school again. (been thinking this way sense I came back) but because of lack of good wood have not been able to accomplish this. So some different construction approaches were enacted. Some different finishing techniques were applied. End result was a relatively light airframe. My coach/mentor gave me a target weight and I beat it.
Personally I love it when I see my competitors show up with 60 oz birds, & big motors. Historically, I know if the wind blows my job gets a lot easier!
I have the best of both worlds. Light weight and more power.
Now back to the diesel. A diesel swings a large prop (for its size). So the plane is over powered and over propped. Yes most of my gross weight was added to the nose. It diminished the turn. Period! (base line set in weight) It would not have matted if it had it (the engine) on the leading edge of the wing and a 20 inch tail. It would still have the same characteristics. I decided to remove the .40 and opt for the .65 for more drive. I am also working on taking weight off this engine. Better to remove then add to balance. The plan is to DE-pitch and speed up the engine in the air.This gives the first gear affect. Should have little wind up as the engine will already be racing.
One problem to overcome is take off. With the engine racing it shoots out like a bullet. Can't have this as it is imposable to keep on the ground very far. So I will pull the pipe foreword and open the venturi till its rich on the ground and leans out (unloads) in the air. Allowing a slow take off speed yet a constant speed in the air. I know this will work. NO DOUBT!
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I'll be a chicken and say everyone has good points here. I'll also go out on a limb with a few observations (remember, these are just my opinions).
Lighter can be better TO A POINT. Definitely better than a porker that stalls beyond the lift capability of the surfaces or opens up corners and loops in the wind. But what's too light? Ever had one so light you were thankful you had Morris adjustable controls so you could dial out a bunch of flap to get it to corner properly? That's too light for the original design parameters. Yeah, you salvaged it by dialing out flap, or trimming off flap with a number 11, but does it fly better than the original? Maybe, maybe not...
Also, these things have to last more than one or two flights in those conditions you are optimizing them for. Sure, the heavier, the more the G's add up against you, but you still need a minimum amount of structural soundness to last at least a few years we like to get out of one of these. I've got the stress cracks to prove it on my super light weight Jap tissue Tony after flying it in some 25MPH stuff at Whitehouse several years back. It now hangs on the wall...
Bigger props give more thrust and can be better TO A POINT. (I dislike the handle loading and GP when the props over a certain size for a given air frame/engine.) Every pilot/plane /engine combo seems to have it's own limit on reasonable prop size, and you know it when you feel it.
One problem I see is the design mentality we've kinda locked into as late. Many of the designs I see built have some un-achievable target weight for your average builder, unless you are a master builder/finisher.(or use plastic film or something.) So, you set out to build your 62 ounce world beater, and it comes out 72 ounces, which for many designs means grossly tail heavy. I would posture that if you know what level weight you typically can build at, rather than keep building the same tail heavy overweight ships one after another, why not shift gears and change the design you choose to build. Or, modify that design a smidge. Shorten that tail moment 1/2" and lengthen the nose moment 1/2"? Try a different built up tail design, sweep the rudder forward instead of back,mold the rear blocks, and I like Doug's thoughts on stablets, but I'm not sure what weighs more, the glue, fillets and stablets, or a little more tail area, but it sounds reasonable.
I guess what I'm saying is, the right tool for the right job. Maybe the right stunt ship for you or me, isn't universally the right stunt ship design for everyone else. That's a GOOD thing. Man, it sure would be boring if we all agreed on the ultimate design and the flight line was just full of one single optimum design. I like the variety of approaches people come up with to build a better mouse trap. It's what keeps this whole thing interesting for me, and challenging.
Flame away,
EricV
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Viper 8 is a approx 650 SQ in wing and a 9.5 nose and 16.5 tail. Now with the .65 in the nose it weighs 52 oz. The turn diminished somewhat from the original .40 at 47.5. It did yaw at first but after moving lead outs foreword 3/8 of a inch this went away. I am using a 13.5 prop and after adding a 1/2 of tail weigh the turn is specular. I have ordered MAG parts for the engine to reduce concentrated weight in the nose. I have always said the base line characteristic is set in weight and this experiment proves it.
Viper 1.0 will have a 8.5 inch nose and a 17.5 tail with the 75 in it. Pulling the weight back helps but does not get totally rid of the base line I speak of. Before anyone comes back to dispute this Build one of your own for this experiment. Using the same plane but with different engines.
So what airfoil / wing thickness are you using on these current Vipers ?
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So what airfoil / wing thickness are you using on these current Vipers ?
root is 2.5 X 10.5 tip is 1.75 X 7.5 Generic airfoil
Please remember I have been working with this platform sense 1990 and much has been tried. The best looking one is hanging on the wall with only about 10 to 20 flights on it. It did not make the cut.
(http://stunthanger.com/smf/gallery/17_31_12_06_2_00_02.jpg)
There are so many things that can happen in figuring a design. Weight density of the wood and placement of that. The spraying of the paint placement. On this one I missed in Bell crank location. (I know it don't matter LL~ ) This one also had a thinner airfoil and it was at 54 oz. Yes it flies but it was not what I was looking for.
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I dont follow. You have always said, and I am paraphrasing here, that weight is of the utmost importance. Right?
Then you added 4.5 oz of weight to your plane and it flew better. Yeah the motor is bigger but that does not change the simple fact that you are flying a heavier plane. It now has MORE wing loading.
I kept trying to tell Sparky that if its too light then Brownian Motion will disturb it in flight....
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I kept trying to tell Sparky that if its too light then Brownian Motion will disturb it in flight....
Can't make it too light in todays world.
Then you added 4.5 oz of weight to your plane and it flew better. Yeah the motor is bigger but that does not change the simple fact that you are flying a heavier plane. It now has MORE wing loading.
You know its not really worth it form me to talk to the wall but one last time. Larger engine added for drive. IT FLEW BETTER with the .40 but the other reason to run a .40 was line size and now I still can use .015. So why not use the .65 small trade off if I can keep the gross weight down.
To everyone who doesn't agree with me. Fine by me. I relay these findings as my personal incite. You can lead a horse to water but can not make him drink.
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"The race dosen't always go to the swiftest - but that's still how the smart money bets" (-anonymous)
I'll bet on LIGHT and POWERFUL for a good starting point. I'll also bet on Sparky the "mechanic" to work it out. However, I think the 40 would have been plenty..! (but I ain't flyin it)
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Are you not a teensy bit worried of those 0.015s breaking with that howling PA-65 up there?
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Are you not a teensy bit worried of those 0.015s breaking with that howling PA-65 up there?
Nope not a bit!
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Why should one be worried? Plane weight is about the same and there is propably no change in lap times. I fly .75 with .015" lines and plan to do so also with the new .77 engine. L
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Setting up for the same lap times is irrelevant. It's when the pipe coupler pops off in a 20MPH wind that I'd be worried about. Those motors have a tremendous amount of reserve power. Hang on for a wild ride. A run-away on a 75 on .015's? Eeek! I've heard and felt my .018's creaking and groaning with a normal run in 25Mph winds and was afraid they would let go any moment. No thanks.
I don't see the big attraction to .015's anyways. They always felt spongy to me on anything with a ST46 or larger. Tom Morris .018's seem to be the best compromise of low drag and solid control for me. To each his own I guess, but I hope people will use some common sense with these new rules. Just because you can, doesn't mean you should, Yada yada yada...
EricV
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I applaud you Robert. Our approach differs, but what's wrong with that? I've been told for years that this idea or that wouldn't work. Mostly the local experts have been right. But sometimes not. One of my most treasured modeling memories is seeing Brett Buck walk up to one of my planes at the NW Regionals, look at it, shake his head and walk away. And I really liked that plane! (you can see that incident really deterred me ;D ).
To each his own. You have to follow your own path. If it works for you, rock on!
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Robert,
I do believe the lighter plane would do better in a TOC type contest (where there are side judges, corner judges and shape judges). If indeed pilots were rewarded for blinding corners and a true 45 degree patterns , ala Gene Schaefer, in today's stunt game I do believe there might be more lighter wing loading planes out there.
As it is, there is no really "bonus points" given to blinding corners. Heavier ships *appear* smoother and track better. They "look prettier" in the pattern and more locked in. You only need *enough* corner as to not look "soft" to compete. Doing more does not gain you any competitive advantage.
I have flown Bob's real light planes with the big engines. They are indeed easy to fly. You can also use ridiculously large props on them, because the plane is so light and slippery it does not load the motor. I am not sure they score better in a contest however...
PS: Gene Shaefers planes were not large and they were light.
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Are you not a teensy bit worried of those 0.015s breaking with that howling PA-65 up there?
i am using .033 on my 65 but my lap times are a we bit quicker than most. :)!
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I think it is great that Robert is thinking out the box.
The box has been changed, it is good time to do it. I explained this in my article.
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I think it is great that Robert is thinking out the box.
The box has been changed, it is good time to do it. I explained this in my article.
Actually its not outside the box. It has been my thinking all along. Just trying to figure out how to achieve what I desire.
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"Lighter can be better TO A POINT"
I agree, if you do build a super light plane wouldn't that make it a more darty airplane. With such a light wing loading I would imagine that it would take just a little control input to have it jump around. I just think it wouldn't be that stable. You could adjust it at the handle or cut into the plane to slow down the controls, but I still think the stability of the plane wouldn't be that great. I do think that balance is also one of the most important points to get it to turn great and be stable. My Ares balances right where the cg was shown on the plans and has a great turn.
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"Lighter can be better TO A POINT"
I agree, if you do build a super light plane wouldn't that make it a more darty airplane. With such a light wing loading I would imagine that it would take just a little control input to have it jump around. I just think it wouldn't be that stable. You could adjust it at the handle or cut into the plane to slow down the controls, but I still think the stability of the plane wouldn't be that great. I do think that balance is also one of the most important points to get it to turn great and be stable. My Ares balances right where the cg was shown on the plans and has a great turn.
Here is the deal. If your plane was 38 oz like Billy's you could run the CG farther foreword and have better turn. It gives you better penetration in the wind with the cg Foreword and because of less gross weight it takes less input on the controls to make a tighter turn. I wish my viper was mid 40tys and still had the .65 But the base line is set in the weight of the power plant.
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Robert my Ares weighs 43 ounces. I am going to get more trim flights on it tomorrow to really see how it flies.
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i am using .033 on my 65 but my lap times are a we bit quicker than most. :)!
Hey Joey, I'll bet you do not have much trouble with wind penetration either... ;D #^ LL~
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none what so ever the beast laughs at the wind. it is built like a tank to withstand the 150 lbs pull test. and the 65 really sings with the 8" prop. now all i need is to get my lap times down to 1.5 sec and all will be well.
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none what so ever the beast laughs at the wind. it is built like a tank to withstand the 150 lbs pull test. and the 65 really sings with the 8" prop. now all i need is to get my lap times down to 1.5 sec and all will be well.
Joey this is Precision Aerobatics not speed LL~
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I have to say I'm in Robert's corner here with low wing loadings. I designed a model with everything that I could think of which (in my mind) would make a very good stunter. First up was low wing loading so I went for a large wing at 830 sq inches but for maximum lift I had a thickness of 2 3/4", a 15" root chord (with flaps) and a forward high point. Tail moment, hinge to hinge line, was 21.5" for turning power with small elevator deflection using an airfoiled tailplane. All controls were seperately adjustable. Weight turned out to be 59 ounces with an ST G51 up front so wing loading was 10.23 ounces/sq foot. Weightwise I had the advantage of flying under FAI rules so didn't need the 8 ounces of paint used for appearance points :).
I guess the question is how did it fly? Well I didn't have time to trim it properly because of the month I spent trying to get the engine to run right before I entered a state championship so it had a slight stall on some corners because I hadn't got around to making the flaps operational, not enough tip weight so the reverse wing over was decidedly iffy and it'd go free flight across the top of the hourglass (that was exciting :)). On my first competitive flight the judges were overheard commenting on how tight and smoothly it turned and I ended up leading the competition after that round (a bit of free flight not withstanding). The high point for me in that round was that I was in front of Peter White, something I'd never done before. Peter almost always was in the top 3 at our National championships.
Yep, I'm sold on low wing loading :D.
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I have lost count of how many people I have seen go from 35's to 46's "so they could handle the wind, then from 46's to 60's for the same reason. Now a lot of those guys are flying 75's and wishing they had 90's so they "could handle the wind...."
Thus I hold these to be self evident:
* If you know how to fly in the wind then it does not matter what you fly.
* If you really do not know how to fly in the wind then it really does not matter what you fly either.
That is my opinion also.
Doug is a great wind flyer. I do not know why... it simply does not matter to him much if the wind is blowing. He flies the same in the wind no matter what he is flying. Heck, he could fly your plane in the wind better than you fly it.
Doug has flown some great wind flights with 40's, 46, 61, 65. He did fly the 75 for a short time, I do not believe he would tell you that it improved wind performance. Quite the contrary. I think it just makes it harder work. Maybe he will comment.
I am fair weather flyer... I fly MUCH better when it not horrible conditions. There, I said it... I did have one good flight in the rain though.
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Haven't seen Doug fly in quite some time but I can tell you how Joe Gilbert became so good in the wind.. He flys in it and doesn't quit when the rest of us are packing it in. As they say, practice makes stunt pilots..
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If you guys want wind practice come fly with me. The wind blows at 10-20 straight in at you everywhere and is very turbulent because of the trees.
Ask Allen Goff about the time I was judging and he was flying. Because of the wind the judges went 360 around the circle
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Best wind plane I've ever flown is my first Slider. Originally had an OS40VF. 610 square inches and weighed about 49 oz. Helped to bias for wind a bit, but not a lot. things just plodded along, never really speeding up or slowing down. The second version was about 54oz and wasn't as good. Not bad and probably a better airplane overall, but not quite as good in the wind. Changed out for a RO-Jett .65 (it needed tail weight and the RO-Jett is lighter than the OS so I was able to lose a bit of tail weight bringing it down a ounce or so overall). While I like the additional power, I think the OS has a better run quality overall. The new Slider is a bit bigger at about 630 square inches and in the mid 50oz for weight with the RO-Jett 65. Waiting for weather to test fly it.
I'm building a plane for profile that will have an OS40VF on pipe and is going to come in at around 42oz on about 590 square inches. I have some real concerns that I will have to either cut the flaps down and reduce the throw or ballast the thing. We'll see. I don't expect it to be much of a wind flier, but hey, you never know.
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As they say, practice makes stunt pilots..
No, not always. Practice makes permanent.
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Ever notice how these sorts of discussions seem to take on more weight in the winter when none of us can fly? ;D
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Randy I have been hunting this for 5 years now. I finally came up with one that works. Now the flights are in the bottom of the fuel can. I was going flying tomorrow but it doesn't look like it. You see when I flew heavy stuff it was not fun to practice. The lighter planes make it more enjoyable for me.
I don't care what anyone says they do not perform. They slide around the corners and the 4 strokes push around. I can see the weight in the wings and in the nose. Might be OK for some but its not my cup of tea!
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I think that's great, Robert. Find something that you like, that fits what you think it should do and burn fuel. As far as I'm concerned, that's the point. We all have different approaches and theories that we put into practice. That's what makes this fun. Good luck with it!
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....... The lighter planes make it more enjoyable for me......
That is the key to all of it of you ask me. If it isnt enjoyable what is the point?
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Eric, 015's may have felt spongy because the plane was too heavy! 015's are comfortable up to about 8-9 lb. of line tension. Doesn't matter whether it is a 90 mph 16 oz. combat plane or a 50 mph 45 oz. stunter. If the load is more than that the lines are getting up into the higher end of their strength and are going to be stretching more. Someone here not too long ago quoted a elongation of 1% for stainless steel lines at breaking strength. That's 7 inches on a set of 60 ft lines. At 8-9 lb. the elongation would be less than 2 in., giving the controls a lot more solid feel.
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Phil - Knowing the stretch limits of the lines is all well and good. Just do the math and get your line tension for a given speed, right? I don't think that tells the whole story. It's great info if all you ever did was fly around straight and level in dead calm air.
Maybe somone can tell me what happens when you do some squares down wind in a 15 mph wind on those 15 lines. The jerk of the lines entering and exiting a square must add a huge amount of extra load on the lines, and the wind adds to tension depending on side area. Now what weight, size, ship does it take to feel some spongy control on 15's in my scenario? Not sure if it can be calculated, but I know it's a lot lower weight than most people think and I've felt it. The plane doesn't have to be a porker.
Personally, I wouldn't use 15's on anything much bigger than a Nobler with a 40. Maybe something like a light weight Vector 40 would be my personal limit for 15's, but even then I'd be tempted to go 18's. Keep in mind, I'm not talking safety here, I'm talking about preferred feel of solid control of the model. Hey, maybe that's just me. What do I know...
EricV
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Well think of this my new plane has to pull 32.5 LBS for pull test. Do you think it pulls that hard in flight in high winds? It might pull 20 but I doubt it. As far as more positive? Well watch the .018 lines drag behind the airplane and then see the difference of .015. That extra bow takes some time to transfer to the control surfaces. So my money is on .015. Less line diameter less wingtip weight. I am using .25 oz. Thats less weight trying to line up in hard corners. Once again I am sure there will be a argument but I KNOW!
Everything is set in weight. These small amounts mean nothing statically but when you add in the G's and centrifugal force they add up big time. Just as water seeks its own level so do the weights.
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I've always flown under FAI rules where the only requirement is that the lines don't break during the pull test :D so I've only ever used .015" lines. My heaviest model is a rather porky 69 ounces with a 40VF and next is a 54 ounce with Stalker 61. Neither of them have ever given me any concerns with "rubbery" feel other than the one time I was flying the Stalker model in a competition when a sudden storm blew through as I reached the square eights. I should have waved off but I kept going, sort of. That gave me my first taste of the infamous "Netzeband Wall" and I've never felt so much line tension, all on one line, with a model that would barely turn. Somehow it survived :).
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I've always flown under FAI rules where the only requirement is that the lines don't break during the pull test :D so I've only ever used .015" lines. My heaviest model is a rather porky 69 ounces with a 40VF and next is a 54 ounce with Stalker 61. Neither of them have ever given me any concerns with "rubbery" feel other than the one time I was flying the Stalker model in a competition when a sudden storm blew through as I reached the square eights. I should have waved off but I kept going, sort of. That gave me my first taste of the infamous "Netzeband Wall" and I've never felt so much line tension, all on one line, with a model that would barely turn. Somehow it survived :).
HB~> Netzeband Wall HB~> LL~ Bill N is a guy stating the LE are too blunt yet Billy W and Bob H are making them blunter and blunter? Whos right? He also thinks you can build too light?? Yet I have never seen on of those planes if set up right.
Bill N A sharp-pointed leading edge will stall very gradually, but at a lower angle of attack than a blunt leading edge. The blunt airfoil will stall at a greater angle of attack, hence giving more maximum lift, but it stalls very sharply or sudden-like, which leads to surprise landings at three-foot altitudes and such. Therefore, the medium radius.
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IN my mind, you can build a stunt plane too light, I just have never seen one of them. ;D
I have thought that since I first started flying model airplanes and I still do. But then I tend to really believe in Mr. Werwage's designs. Am I now, or will I ever be the Walker Trophy winner? Not unless I am the only one entered. ;D Never the less, I have flown airplanes that are so-called *World Class*, I have had a former WC fly some of my planes, and I do at least know what they are supposed to feel like when they are flying well. I do not like a *heavy* model at all. I was an unlimited class power lifter so *strength* is not an issue, feel is. A lighter model is much easier to control in a more precise manner.
If Billy Werwage can win 2 World Championships, 32 years apart, I think he must know a *little* something about all of this stuff. He says you *CAN* build a stunt plane too light, but he has never been able to do it! And he is one of the lightest builders in the World. Also, unless Mr. Robin Hunt has changed philosophies lately, he says the same basic thing.
We all have our own preferences, that's for sure, but I don't even come close to knowing as much about all of this stuff as those two men have forgotten......... for me, I will always try to build the model as light as I can get away with. So far, I have never been disappointed with a light model.
Mongo
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IN my mind, you can build a stunt plane too light, I just have never seen one of them. ;D
I have thought that since I first started flying model airplanes and I still do. But then I tend to really believe in Mr. Werwage's designs. Am I now, or will I ever be the Walker Trophy winner? Not unless I am the only one entered. ;D Never the less, I have flown airplanes that are so-called *World Class*, I have had a former WC fly some of my planes, and I do at least know what they are supposed to feel like when they are flying well. I do not like a *heavy* model at all. I was an unlimited class power lifter so *strength* is not an issue, feel is. A lighter model is much easier to control in a more precise manner.
If Billy Werwage can win 2 World Championships, 32 years apart, I think he must know a *little* something about all of this stuff. He says you *CAN* build a stunt plane too light, but he has never been able to do it! And he is one of the lightest builders in the World. Also, unless Mr. Robin Hunt has changed philosophies lately, he says the same basic thing.
We all have our own preferences, that's for sure, but I don't even come close to knowing as much about all of this stuff as those two men have forgotten......... for me, I will always try to build the model as light as I can get away with. So far, I have never been disappointed with a light model.
Mongo
Bill, after flying his Ares and how little trimming i have to do on it, I guarantee you it will not be my last Bill Werwage design. He also one those 2 World Championships with totally different desgins, USA-1 with an ST .46 and conventional construciton, blocks and I-beam wing. His P-47, PA .61 Lost foam wing, molded fuselage. The thing they have in common, very light. I think USA-1 was 55 ounces (730ish squares) and 52 ounces? for his P-47 with a large wing also. Don't you think there is something there?
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Seeing as we had bad flying weather this weekend I have been re trimming my plane. First off I shortened the pipe 3/8 of a inch and went from a #11 venturi to a #8. I have DE pitched the prop from 4 to 3.75 I turned down the drive washer to remove 3 grams and changed spinners to magnesium for 9 grams difference So a total of 12 grams was removed from the nose so far.I have called Randy on a MAG head and back plate but he had none left. I either have to have one made or if someone has those Items for sale I would buy them. I changed out the tail wheel to add 4 grams behind the CG.
I was already asked why the pipe change and venturi change? first off I am only using 6.5 oz of fuel for the pattern. So I have a gob of power left in the PA. Pipe comes foreword and venturi goes up so I can richen it up on the ground. I am looking for it to run rich on the ground and lean out int the air to a hard four. The prop change is like lowering the gear so to speak. I want a 5.5 lap time instead of 5.2. In order to keep good line tension the engine RPM has to come up. I know some people back up the rpm in the wind but I turn it up. I want this plane set up for the wind.
I have also been working on all the dings dents and blemishes to bring this to NATS quality.
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HB~> Netzeband Wall HB~> LL~ Bill N is a guy stating the LE are too blunt yet Billy W and Bob H are making them blunter and blunter? Whos right? He also thinks you can build too light?? Yet I have never seen on of those planes if set up right.
He is not stating they are too blunt. In the quote you provided us he was simply stating the type of stall characteristic you will have with each type of LE. And somewhere in the middle is probably a good place to be. And by the way he is correct.
Sharp LE stall at a more shallow AoA than a Blunt one. Why do you think Billy Bob Ted BB PW Randy and many others use them? (Billy and Bob H are no where near what BB and Ted use and they are not even too blunt) BUT if you do get your blunt LE to stall it will be a nasty one and can cause damage if you are near the ground.
It works this way due to the fact the sharper LE causes the air separation point, the point at which air is directed over the top and over the bottom of the wing, to be in a very distinct position on the LE of the wing. It cant move. Too sharp and AoA and you get air separation from one side of the wing and a stall occurs. Since the model is at a low AoA when this occurs recovery is much more quick and probable. The blunted LE will allow the leading separation point where air splits and goes over the top and over the bottom of the wing to move around the LE of the wing as it rotates. Therefore allowing a much more AoA before and actual separation of Air all together off of one side of the wing and a stall. Now you have a stall with a very sharp AoA and recovery is going to take longer since you have to come out of the steep AoA and that takes time. If you have pulled out at 5' and stall your blunted LE you will probably hit the ground.
And yes I have proved this to myself to be true running LE shape tests in flight. It isnt hard to do and the results can be very enlightening and helpful when designing a LE shape. Many people have done it and there are volumes written on it. But like you, in this case, I wanted to see the effects for myself so I did it and it happened just as so many engineers and full sized aircraft pilots said it would.
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Seeing as we had bad flying weather this weekend I have been re trimming my plane. First off I shortened the pipe 3/8 of a inch and went from a #11 venturi to a #8. I have DE pitched the prop from 4 to 3.75
I was already asked why the pipe change and venturi change? first off I am only using 6.5 oz of fuel for the pattern. So I have a gob of power left in the PA.
Watch that short pipe. I do not recommend it. It can get you in real trouble.
Instead DROP THE HEAD... to .015" shims. Go to 15% nitro. Then you will burn another ounce to ounce and a half.
You should be able to de-pitch to 3.5 RPM. You are looking for 10,600 to 11,000 RPM or so on the ground.
Stay away from the 4 cycle plugs. They lead to charging.
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Watch that short pipe. I do not recommend it. It can get you in real trouble.
Instead DROP THE HEAD... to .015" shims. Go to 15% intro. Then you will burn another ounce to ounce and a half.
You should be able to de-pitch to 3.5 RPM. You are looking for 10,600 to 11,000 RPM or so on the ground.
Stay away from the 4 cycle plugs. They lead to charging.
Well this is a area I am quite sure of I can speak with authority. A tuned pipe works at one rpm. You must match the wave to the RPM. Pulling the pipe foreword decreases the distance the wave must travel to reach the first cone, in this case the first baffle. I have used 1/4 wave pipes with no problem so a full wave pipe at a shorter length is a breeze. In order to achieve this desired RPM the nose and head must be adjusted also. Seeing as I don't have a dyno its kinda trail and error. However I have enough hands on knowledge (my bolt number 2 being one of these) of exactly how to do this it will be easy to get it close the first time.
Pipe tuning is easy if you pay attention. If you have the model running a hard four on the ground and it backs up in level flight the pipe is too long.
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Great discussion, it seems that everyone has a formula for a great flying airplane. Over the years I have had many influences with my building and flying. I have seen first hand Bob’s construction and finishing technique and he is truly an artist. I have seen others builder techniques and although different they have achieved what they set out to do. My skills are different than every body else’s but I usually accomplish what I set out to do, build something that I am comfortable with. All of our goals are the same, to build a great flying plane that fits our preferences and skills. Many people have won the Nats with a variety of airplanes and at that point in time their method of building was the “right” way to build.
I had always built “out of the box” a different way of doing things. I always bought American and at the time when everyone was moving to Super Tigre 46s I stayed with the Fox 35, I am just s stubborn old German! When Fox came out with a CL Schnerle 45 I bought it and designed a plane around it. what I basically did was take a Nobler and increase everything by a percentage except the nose moment because the engine was a little heavy. The engine mounts was wider than a Super Tigre 46 or even a 60, even with machining the mounts down. So the plane had a wide nose that tapered down. The model was about my 5th attempt to scratch build an airplane and it turned out fairly heavy, I think at about 56 to 57 ounces. But when I first flew the plane I could tell I had something that was a winner, it was very stable and I liked the way when it came out of a wingover or corner it would just stick, like it knew where to go. I had build very few planes like that, all had to be tweaked one way or another and even though they eventually flew well they did not fly like this one did. I eventually tuned the engine that would race away every once in a while, I kept restricting the venture and added a head gasket and played around with restricting the holes in the tongue muffler until I had a great, fat four cycle run. I still have a Fox 50 that I played with that runs like a 35 on steroids.
My point is that even though the plane and engine combination was different than what was the winning combination at the time, the plane flew well for me, won contests and flew in some of the windiest conditions. I would fly the plane when no one else would fly at the field Bob was talking about where you never knew where the wind would come next. There are as many “right” designs and building conventions as there are flyers. That is what I really like about CL Precision Aerobatics, the diversity of the planes and people and the tight nit community that we have all across the country and world.
Mike
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Mike, sounds like you'd get along very well with Bill Wilson over in Texas... as local flyers, Brad or Doug can comment better on this than I can, but the contest results I see speak pretty well for themselves...
EricV