Warts

All,

I've decided that I need to use a wart on my outboard flap in order to carry the amount of tip weight that the airplane seems to like. I was just woundering where a good starting point might be. I certianly don't want to start with on that's too small! Oh, the plane is an Intrepid X/L with 685 Square inches of wing area (standard flap area that I can't seem to remember what is right now) and it weighs a whopping 63.75 ounces now! Ideas?????

I'd start with 6.85 square inches. Seems logical, but then we all know how that works.

The latest M.A.A.C. magazine (Canadian Model Aviation I believe ) contains an article by Chris Cox on that very subject. HE specifically refers to his Saturn.First thing is to find out what weight is needed to level the wings both up and inverted . NOw he is recomending to take some cards stock and fold it to 3" by 1" or so and tape it on to the outer end of right flap so that the area of the test piece is 3 by 1/2 inches and try that and try other sizes as needed only taped on until the tip throwing goes away then make a permanent one from some clear material and be sure that it ge]oes straight back and does not impart any up or down elevator and permanently install it. hardly noticable in clear material.If it is too big you will encounter the oposite of tip throwing and it will be immediately apparent. He has ended up with about 1 and 1/2 sq " of material. I have done the same thing on my new Saturn and I have ended up with 3 sq. inches of clear of clear heavy plastic. Doesnt look bad at all and now I have level wings and no tip throwing. Makes a nice neat turn. Try to get a copy of the magazine from M.A,.A.C. They have a web site. THis is the Canadian equive lant of A.M.A.Contains a photo. I installed my final clear wart by slotting the outer edge of the right flap and inserting the new piece in about 1/2" . with epoxy Keith Varley

Jim, try a temporary one first and you can then adjust it to what you actually need before making it permanent. We did this on Matt's latest. Cut a couple of pieces of 1/32 plywood oversize of what you might think and about half to three quarters of an inch wider than needed. Use silicone sealer to "glue" one on top and one on the bottom of the outboard flap, overlapping them with the flap by the above amount, and leaving enough sealer in between to join them together. This will stick and stay absolutely fine until you test out whether or not you really need this, and, if so, how much. Don't worry about the extra weight because you are adding weight in the weight box anyway. Take it out, fly, adjust the weight, and when you get it in trim, ask yourself if this helped. If it did, take a little off and trim again. This way you can test to see if it is needed, and, if so, how much is needed. When you determine you have found the correct size, measure the area and also hold the plane upside down with the outboard tip on a gram scale, and holding it by the tail wheel and prop weigh the tip.

Now you can peel off the temporary wart and replace it with something permanent. Then go back and weigh the outboard tip as before and adjust the tip weight to what you had before. You should be right close to being on trim at that point.

Hi

If you are proposing to extend outer flap area to counter tip throwing, that makes no sence to me. I would suggest, tip throwing indicates the CG is not trimmed correctly in the spanwise direction.

This is not apparent in level flight because line tension tends to hold the wing flat. In a turn, both lift and enertia through the CG are greatly increased. If centre of lift and CG are misaligned in the spanwise direction, a turn will greatly magnify their force moment couple beyond the ability of line tension to keep the wing flat. Surely this is the basic reason for tip throwing. Seems to me, adding flap area at the tip is a bandaid and not solving the real problem of too much or too little tip weight.

On the other hand, am I missunderstanding this thread?

Although what you say is true, Ken, there are other factors involved. Adding area to the outboard flap will allow for more tip weight to be carried which can help in other areas.

If the flap hinge line is not taped, just tape half the out board flap hinge line. If it's not enough, tape the whole outboard hinge line, but I have a feeling half will be plenty, and maybe even too much, might have to go down to 1/4 of the outer span, but start with half and fire for effect. Done it to lots of planes, works great, and looks better than an WART. Works very well on the new ARF Nobler too.

Eric (No Warts Please) Viglione

>If the flap hinge line is not taped, just tape half the out
>board flap hinge line. If it's not enough, tape the whole
>outboard hinge line, but I have a feeling half will be
>plenty, and maybe even too much, might have to go down to
>1/4 of the outer span, but start with half and fire for
>effect. Done it to lots of planes, works great, and looks
>better than an WART. Works very well on the new ARF Nobler
>too.
>
>Eric (No Warts Please) Viglione
Hmmmm, Eric,

While your suggestion could certainly prove beneficial to the tip throwing problem, what does it say about the effieciency of the unsealed flap segments (to say nothing of unsealed stab/elevator hingelines)?

Hi Ted! I'd say it speaks volumes. But...to my defense, I did start with a delineator of "IF" the hinge line was not already sealed...

First off, let me say I bow to you as the master of such things, and if I'm out of whack here, I've always appreciated your help. I've drawn some conclusions from my own exprerices with tape sealing, and what works for me (at my current level). Please add or correct where you see fit:

My feelings as towards tape sealing, I say it all depends. Why not use it as an adjustment based on your own particular ship? Built a classic ship with a small tail, asymmetrical wing? How did it come out, heavy or light? If heavy, seal the stab/elevator and all the outboard flap/hinge and 3/4 (or so, experiment) of the inboard flap/hinge. If it's a super light job, only seal a little of the outboard flap/hinge line, leave the inboard alone, try seal all the stab/elevator later if needed to help compensate for heavy modern engine. Etc.

And finally, if it's a unusually heavy beast, and you need to offset a ton of tip weight as well, seal it all and add the wart. I am all for the final results, after all. A well trimmed heavy ship with is still better...

I guess I'm saying to use the tape trick to trim for final effect of an overall package. I just don't like to jump straight to the warts if it can be avoided.

The ones that kill me are where you see a sealed flap/hinge line, and he has too much flap, so instead of trying to unseal the line first, he starts cutting off strips of flap, and having to sand/fill/repaint that edge...I'm way too squeamish & lazy for that!

I have read that the unsealed areas can cause more than just efficiency issues, with odd vortexes and turbulence and such, but I am only speaking to the much simpler issues here.

Eric(OK, warts are OK sometimes, but still trying to avoid them, and oh yes, don't play with frogs!)Viglione

Working to defend you both, Ted advocates taping of the hinge line the full length. If you have gaps of different widths, and/or these gaps open and close--even fractionally--with the flap deflection, then leaving the hinge line unsealed can cause major problems. If the gaps are very narrow, then you may not feel the effect of sealing at all. But then, sealing only part of the flap isn't going to help, either.

Well, maybe I am defending Ted more than Eric, here, because if the gaps are sufficient that sealing them makes a noticeable difference, then not sealing them can cause problems if the gaps open and close under deflection. Score one for Ted. If sealing them does not make any difference, then sealing only part of the flap won't help, either. Score one for nobody.

Since sealing the hingeline is such an easy thing to do, then I would agree that doing so should be done before trying anything else. And since that was done with Jim's plane in question, well, either adding the wart, or making the inboard flap shorter or narrower are going to be his choices.

Hi Leonard

What other factors? I'd like to know more about these warts and what they do.

Len,

My idea is to start with a permanent one that's probably a little too big and cut it down to the right size. I have an old custom front licese plate that's the same color as the plane that I was tinking of making it out of. I could then trim it down a little at a time (with my tin snips) until it's just right for the weight the plane wants to carry. I'm really trying to figure out what's more than enough, but not way too much or too little. Oh, yes, Eric, my flap and elevator hinge lines are completely sealed and staying that way. That's makes trimming a lot more predictable. The more I fly the more I can see and feel every little wiggle or wobble the plane makes and it makes me most unhappy when it does more than I think that I can get away with from a judging standpoint. I know I need the wart because when the airplane is happy with it's tip weight for the speed it's flying then the backside corners of the triange and bottom corner of the hourglass give me fits due to the outboard wing dropping too much.

I will need to get a picture of Matt's wart that we were playing with so you can see what was done. This is quite simple, as a matter of fact, and an easy experiment to make to see if it is really going to help before any modifications are made to the plane.

On yours, are you using full length flaps or only partial? With partial flaps the effect of the wart will not be as great.

Next question, do you have the right amount of flap, too much, or not engough? If not enough, the wart will help. If too much, you may wish to consider shortening the inboard flap. This is the route we have considered with Matt's. He has too much flap as it is with a flap that does not go all the way to the tip. And this one has caused problems, which has made me wonder if full length flaps may not have been better. But it wouldn't look right to make them much narrower, and that is a problem. Shortening the moveable portion of the inboard flap may be the solution all around.

A few VSCs back I was admiring Phil Granderson's pastel stunt plane. Ted walks over with some tape and "wart" material and requests I hold Phil's ship so he can apply a tab. Then someone calls for Ted, who excuses himself, leaving me holding the plane. Guess who walks up and wants to know what's going on? "Whatcha' doin' with my plane, man?". I'd probably been found lying next to that plane if Ted had decided to cut off some flap or sand some away! Some time ago the Nats or some other big contest was held in Reno. Gary McClellan and Ted flew out there and wrote an article about their experience in the high elevation. I can't recall the magazine- but a part of the article was about sealing hinge lines. Sometimes it doesn't do much and other times it turns a dog into a real performer. I'm mulling over ways to seal the hinge lines during construction so as to have a nice looking end result. So far the clear tape leaves a liitle to be desired. All the best,

Phil is not physically dangerous. He is, however, a master salesman. If he is annoyed with you, he may convince you, for example, to give him your car.

Len,

Question #1: Not full span a little more than 3/4.
Question #2: Not enough, the design weight for the plane is about
55-58 ounces. My behemoth comes out at 63.75 ounces.

Jim Pollock:

Well,

I just went back into the AMA archives and found that Ted used 2.25 Sq inches on his wart as a starting point. I guess that I will do the same. His was 3" X 3/4". What about 2.25" X 1" would that be an aerodynamic equivelant or not? Just full of questions these days huh!

>All,
>
>I've decided that I need to use a wart on my outboard flap
>in order to carry the amount of tip weight that the airplane
>seems to like. I was just woundering where a good starting
>point might be. I certianly don't want to start with on
>that's too small! Oh, the plane is an Intrepid X/L with 685
>Square inches of wing area (standard flap area that I can't
>seem to remember what is right now) and it weighs a whopping
>63.75 ounces now! Ideas?????
>
>Jim Pollock

Jim,
I looked through my notes and found that a piece of balsa 1/2" x 2" added to the out board flap tip would allow about an additional 1/4 ounce of tip weight to be carried. I just taped the piece of balsa to the back of the flap (making sure it was centered and not acting like an aileron) and it worked like a charm. This was on the Magnum Force with full span flaps. If you have 3/4 span flaps I would increase the length to 2-1/2" as a starting place and add one flat Sig weight (1/4 ounce) and fly the model.

Mikey

Oh, the plane is an Intrepid X/L with 685
>Square inches of wing area (standard flap area that I can't
>seem to remember what is right now) and it weighs a whopping
>63.75 ounces now!

You're joking, right? 13.5 oz per square foot is a NON-ISSUE with these types of airplanes. It's lighter than mine, and mine flies pretty well. I wouldn't get worked up about something like this, it's irrelevant to performance.

Trim problems are another issue, of course.

Brett,

It does fly O.K. except for the third corner of the triangle and the bottom of the hourglass and that's what I'm shooting at correcting. Now that it happens to be sporting an RO Jett .61 RE I know that it will fly as honestly as I can get it trimmed to. Oh, one other thing. I know you have a nylon over your venturi. Is that because it's impossible to strech a Bru-Line green filter over it?

>Brett,
>
>It does fly O.K. except for the third corner of the triangle
>and the bottom of the hourglass and that's what I'm shooting
>at correcting. Now that it happens to be sporting an RO Jett
>.61 RE I know that it will fly as honestly as I can get it
>trimmed to.

But it's surely not the weight/wing loading per se.

> Oh, one other thing. I know you have a nylon
>over your venturi. Is that because it's impossible to
>strech a Bru-Line green filter over it?

No, the Bru-line filter goes over it just fine. But the cowl wont fit over it, and it's non-trivial to cut away enough to make it fit. The stocking takes up virtually no space. By the way, with any filter the bottom of the airplane stays much cleaner -probably because the filter intercepts the cone of fuel that stands above the intake.

>Brett,
>
>It does fly O.K. except for the third corner of the triangle
>and the bottom of the hourglass and that's what I'm shooting
>at correcting. Now that it happens to be sporting an RO Jett
>.61 RE I know that it will fly as honestly as I can get it
>trimmed to. Oh, one other thing. I know you have a nylon
>over your venturi. Is that because it's impossible to
>strech a Bru-Line green filter over it?
>
>Jim Pollock

Jim,

Just curious, what exactly is it doing in the triangle and hourglass bottoms? If it's stalling (which isn't unheard of at those spots in the pattern) the wart might not be the right solution.

>>Brett,
>>
>>It does fly O.K. except for the third corner of the triangle
>>and the bottom of the hourglass and that's what I'm shooting
>>at correcting. Now that it happens to be sporting an RO Jett
>>.61 RE I know that it will fly as honestly as I can get it
>>trimmed to. Oh, one other thing. I know you have a nylon
>>over your venturi. Is that because it's impossible to
>>strech a Bru-Line green filter over it?
>>
>>Jim Pollock
>
>Jim,
>
>Just curious, what exactly is it doing in the triangle and
>hourglass bottoms? If it's stalling (which isn't unheard of
>at those spots in the pattern) the wart might not be the
>right solution.
>

If it's really stalling (and I still find that very difficult to believe, although these are the usual spots), then maybe we ought to send Jim some old flying lines and tape!

Brett,

Old lines and tape? Turbulator?

Ted,

I don't think it's stalling, but if it is, it will do it with a wart too. We'll see what it's actually doing after I get back to Virginia and try it out with the new RO Jett .61.

>Brett,
>
>Old lines and tape? Turbulator?

Yeah. If stalling is your problem, that's certainly a possible fix. But geez, 64 oz/685 sq inches, hard to believe.

One easy way to find out. Use hinge-sealing tape (clean release type) and tape a length of old flying line to the top and bottom of both wings, near the high point. Easy to do in 10 minutes in the field, and easy to back out of if it doesn't work.

Jim,

Describe what is happening in the bottom of the triangle and the hourglass. What is it that has you searching for a solution?

How sharp is the leading edge?

LAST EDITED ON Mar-14-04 AT 10:03 AM (CDT)
 
Ted,

It's just dropping the outboard wing on hard 3rd corners in the triangles and the bottom of the hourglass. If I back off the controls it doesn't do it, and if I speed it up it doesn't do it, but when it's going so fast I have trouble getting precision. So if the wart works, good, if not well, turbulator here I come.

Ted,

The leading edge radius is the same as any other SV series wing.

J.P