Set in weight, A Viper report

[RC Storick]

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.

[john e. holliday]

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

[RC Storick]

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)

[Matt Colan]

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 

[Randy Powell]

And here is me, trying to use the smallest prop I can get away with. Silly me.

[Crist Rigotti]

Bob,
Wow, a big change in plans from February, that's for sure.

[RC Storick]

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.

[Crist Rigotti]

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.

[RC Storick]

Nothing like Fitz's plane.

[Randy Powell]

Bob,

I think he meant in concept, not in execution. Small plane; bing engine.

[Crist Rigotti]

Right Randy.  I think both are about 630 squares and 75 powered?

[RC Storick]

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

[Randy Powell]

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.

[Bradley Walker]

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.

[RC Storick]

Bear 65 nearly exactly.

Who built this at 52 oz Bob?

[RC Storick]

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.

[Crist Rigotti]

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?

[RC Storick]

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.

[Doug Moon]

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.

[RC Storick]

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

[Bradley Walker]

Who built this at 52 oz Bob?

All of Bob's were 52 to 54 oz...

Doug's too...

[Bradley Walker]

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.

[Bradley Walker]

Viper 1.0 will have a 8.5 inch nose and a 17.5 tail with the 75 in it.

Furias...

[Bradley Walker]

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.

[Doug Moon]

Furias...

Yeah, it is 8.5, 18.

[RC Storick]

Furias...

And how much does this puppy weigh?

[RC Storick]

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.

[Doug Moon]

......
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.
......

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....

[Brett Buck]

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

[Doug Moon]

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....

[RC Storick]

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.

[Brett Buck]

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

[RC Storick]

    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.

[Bradley Walker]

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!!!

[Bradley Walker]

  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...

[Randy Powell]

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.

[Dennis Adamisin]

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!!!

[RC Storick]

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!

[Eric Viglione]

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


 

[Allan Perret]

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 ?

[RC Storick]

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.



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  ) 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.

[Steve Fitton]

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....

[RC Storick]

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.

[Dennis Adamisin]

"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)

[Steve Fitton]

Are you not a teensy bit worried of those 0.015s breaking with that howling PA-65 up there?

[RC Storick]

Are you not a teensy bit worried of those 0.015s breaking with that howling PA-65 up there?

Nope not a bit!

[Lauri Malila]

 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

[Eric Viglione]

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

[Randy Powell]

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 ).

To each his own. You have to follow your own path. If it works for you, rock on!

[Bradley Walker]

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.