Set in weight, A Viper report

[Joey Mathison 9806]

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.

[Bradley Walker]

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.

[RC Storick]

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.

[Matt Colan]

"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.

[RC Storick]

"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.

[Matt Colan]

Robert my Ares weighs 43 ounces.  I am going to get more trim flights on it tomorrow to really see how it flies.

[Dennis Adamisin]

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...      

[Joey Mathison 9806]

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.

[Matt Colan]

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 

[Brian Hampton]

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 .

[Bradley Walker]

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.

[Bob Reeves]

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..

[RC Storick]

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

[Randy Powell]

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.

[Bradley Walker]

As they say, practice makes stunt pilots..

No, not always.  Practice makes permanent.

[Randy Powell]

Ever notice how these sorts of discussions seem to take on more weight in the winter when none of us can fly?   

[RC Storick]

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!

[Randy Powell]

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!

[Doug Moon]

....... 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?

[phil c]

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.

[Eric Viglione]

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

[RC Storick]

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.

[Brian Hampton]

I've always flown under FAI rules where the only requirement is that the lines don't break during the pull test 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 . 

[RC Storick]

I've always flown under FAI rules where the only requirement is that the lines don't break during the pull test 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 . 

  Netzeband Wall   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.

[Bill Little]

IN my mind, you can build a stunt plane too light, I just have never seen one of them.   

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.   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

[Matt Colan]

IN my mind, you can build a stunt plane too light, I just have never seen one of them.   

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.   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?

[RC Storick]

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.

[Doug Moon]

Netzeband Wall   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.

[Bradley Walker]

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.

[RC Storick]

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.

[Michael Floerchinger]

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

[Eric Viglione]

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