GSJames

As a newbie to racing I am trying to pick up some of the construction techniques that are commonly used.

The alignment of the wing hold down screws seems to be a "one-shot deal" to me. IAW, It's simple enough to mount the original wing by temporarily holding it in place, drilling through the 3/4" dowels into the hold down plates and then installing the blind nuts on the bottom side of the plates. But what if you want/need to use a different wing due to a crash or other reason? The Viper must use fixtures to insure that each wing and fuselage can be used together but I've never seen mention of any type of fixture of that sort that can be used on a kit or scratch built airplane. Any ideas? Thanks!

redfox435cat

It's been done quite a bit, I've done it twice both worked fine. For it to work you need to understand how to align the wing,
The wing needs to be even side to to side,
you need to know the CG of the wing, if you use a wing with a different airfoil you have to adjust the CG, that could be moving servos, battery's ,even a new motor mount to move the engine.
The wing's incidence have to be maintained, with your viper that incidence is set by the wing saddle of the fuse. If you use a different wing you'll probably have to build up and or cut out the wing saddle to produce the incidence required by the new airfoil, though if you using another 427 wing it'll stay 0-0 and the saddle adjustment will be minor. If the wing you replace it with is also a foam core balsa sheeted wing it's simply drill through the wing into the existing holes.
All this works fine for sport models you just want to burn holes in the sky with, you won't make a competitive racer this way, your, cutting and re gluing will add weight and will take a couple tried to get everything lined up if it's your first time doing it, you add weight you lose.

wrstew

My Feedback: (30)

You could use the factory Viper wing to fabricate a drill Jig, make a ply semi fuse that conforms to the wing , use dowels to make drill guides, and all of the wings drilled using this would be interchangeable.

rbg

Years ago we took a nylon bolt cut the head off put a PIN in it. Screwed the bolt to the wing hold down and then aligned the wing on top off those pins sticking up very carefully no rush.

GSJames

All of those are excellent ideas. Thanks!

Bill Vargas

My Feedback: (5)

A good trick that works for me is to "pot" the wing to the fuselage,,, then drill out the holes,,, then "pop" off the wing and tap out the holes accordingly


BV

rbg

Hey BV You need to remember you are talking to a newbie. Pot the wing is a HUH... us older established racer know what you mean

freeair

the majority of the time when say a Viper should crash, its more likely that the Fuselage will be damaged and not really the wing.
stick with the original Viper wing as its design [ Selig ] is one of the best going for Quickie 500 racing.

GSJames

I know what potting a wing is. I'm new to RC Pylon racing but I've been an AMA member for 45 years. But thanks for the consideration, because there will be those who don't know what potting a wing is. BTW, rbg, your suggestion about using a pin in a nylon bolt seems to be the best idea for my particular application, if modified to be a sharpened 6-32 bolt (or whatever hold down bolt happens to be on any particular airplane)

My interest in all this is not so much to repair semi-busted Vipers but rather to use the same fuselage/tail group to flight test different wings with different airfoil sections and varying spanwise lift distributions to determine if there is a REAL WORLD performance difference as compared with the CFD analysis that I have done on a matrix of wings used in Q-500. The CFD analysis says that there is, but I don't necessarily blindly believe computerized wind tunnel results without actual tests. Using the same fuselage/tail group for all wings would remove one experimental variable from the test. I have posted pictures of the CFD-generated pressure distributions in another posting and provided the integrated graphical results to several racers who have directly helped me in this research.

Best Wishes.

Duane-RCU

My Feedback: (5)

Correct me if I'm wrong, but you want to be able to bolt several (different) wings on the same fuse, ALL the bolt holes need to line up, or if the mount area is large enough, there could be a few different sets of holes in the hold down plate. But each different airfoil will need to be potted at the needed angles. So I guess you would need to do the potting on the wing, not the fuse. I have an old Viper fuse that you could cut the bottom sheeting out and use it for a jig to drill the wings from the bottom, just need to build something to keep the drill bit straight and square, I have ideas how to make that work.... I can't wait to see your results, the stuff you posted on the airfoils was great.

GSJames

Duane, you are right, the variations in airfoil profile at the root will cause problems. However, it's the hold down plates that keep the wing in place and not the balsa wing saddle. My plan is to index each wing to the standard fuselage at the zero-lift angle of attack (this will vary with the airfoil) and then fill in the gap with some temporary method. This isn't for a racer for competition, it's just to run some tests. We missed you at last weeks Q-25 race. I was pathetic, my OS 25FX would only turn up 15,900, but still had a lot of fun. See ya next month.

Speaking of tests, attached is the 3D drag polar of 4 different Q-500 wings at Q-25 speeds Rn=750,000 I'm rather surprised by the results.

Duane-RCU

My Feedback: (5)

As much as I wanted to be there, I was not about to go racing on Mother's Day!!! At least Joe was the winner that day.

djlyon

I make drill guides out of brass tubing.  I run the tubes through the hold down bolt hole and thru the bottom of the fuselage. Then I mount the new wing, align it and tape it down tight. Then I use a long drill and run it thru the tubing from the bottom of the plane and drill through the wing from the bottom.

Denis

Duane-RCU

My Feedback: (5)

Denis, I wish I would have thought about that a while back, I had a new Viper and the wing was drilled incorrectly, just the front holes. So I plugged the front hold down holes, and drilled the fuse to match the wing. Worked great, but now I won't be able to swap anything from that plane to another (without some work)