freeair

i,ve just finished setting up my new Viper and had no problems with the factory set 0-0-0 all seamed to be spot on going by my reliable spirit levels etc. the only problem i had was getting the COG correct at 3 inches, with an OS46ax up front and the fuel tank positioned at the COG line, small servo just behind tank and the 2 other small sized servos plus a micro jr receiver behind the wing section i had to position the 600 mah battery opposite the throttle servo plus also add a few grams of lead weight behind the front engine bulkhead. now the COG is also spot on the recommended position, the model wil be tested this weekend and i,ll let yous know how it went.

DMyer

My Feedback: (2)

Well... that was a quess... it is actually closer to 1/8". I can shim the trailing edge up slightly and when I find the right balance re-pot it permanently and make a note for how much it actually takes. Thanks for the tips!


Dan


I went down blocked up the fuse/nose/tail to 0 and re-measured the wing incidence - By ruler the leading edge is just a touch more than + 1/16" - by meter it is just a little over +1/2 degree. The amount of shim and potting in the saddle is a heavy 1/8" at the leading edge(looks like a ton) which means the original incidence was quite negetive which explains why Vipers like first flight outside loops so much!

garys

Dan,
You're probably pretty close then, I'd like to hear how it goes

DMyer

My Feedback: (2)

Well - test flew the new Viper yesterday and the positive incidence I mgave the wing was just about dead on as the plane flies very well with the tail/nose set at zero with no elevator trim. Tracks really well to/from #1 (no creepin). The only problem I found with the plane was the wing has a warp from wingtip to wingtip (knew about it from the initial setup) which required a significant amount of left aileron trim to stop it from rolling. I am going to really check the wing out very closely to determine the best way to cut the trailing edge(s) and adjust out the aileron trim. That is my only real complaint with the Viper is that I have not gotten one wing that was perfect tip to tip - usually they are close enough to not be too bad for 424, but this one is horrible and certainly is not good enough as is to put a Nelson on to support our upcoming local 428 race. I assume the variance is in how the trailing edges are attached (by lowest paid humans) since it is not a full sheeted/cored wing.


Dan

freeair

its not easy to remove a warp from a foam core wing compared to a built up wing, if your racing this Viper and want it to go at its peak i sugest you toss the wing and use a good one. otherwise counteract the roll with lead as we do to balance models laterally.

DMyer

My Feedback: (2)

The old fashioned trick, back from when we built simple foam wings with balsa trailing edges, is to cut the trailing edge loose on the offending side and adjust out the warp. I am willing to bet that the actual core is fairly straight but they did a poor job attaching the trailing edge. I currently have a touch of washout on the high wing and and the bubble on the line washin on the low wing(about 1/2 degree). I will cut both trailing edges and adjust as needed to even it out. I am sure it will be just about as good as any other typical viper wing when I am done and will carry no trim (that is the goal).

I actually have a spare high quality full length cored foam/balsa wing of the same airfoil and cord that I built many years ago. I intend to build a good fuse for it one day but it could always be used as a viper replacement wing as the wing saddle is the same.


dan

Super Splatter

I will fix my foamy warps by working with the end thats warped up by making a slice along the underside just behind the ailieron and continue the slice for a few inchs past the control surface. Than make another slice to create a 64th inch gap in the balsa. Than I'll apply a small amount of med. CA and close the gap and hit it with kicker while using my hand and fingers to hold the wing to keep the gap shut until the CA is done and see how far the warp came back.

One a real bad wing I might to this process 2 or 3 times , making slices slightly more inboard of the first. Than clean up the slice with a little covering.

garys

Dan,

Glad to hear the wing incidence change, with the engine and tail at zero, seemed to work It sounds like your thoughts of fixing the TE are pretty much what I did on a couple airplanes that needed excessive aileron trim. I'd just slice the TE outside of the aileron and adjust it. I usually managed to do it only on the side that needed to come "up" (if the airplane was rolling right, I'd adjust the left TE).

DMyer

My Feedback: (2)

Well it took two adjustments of the left wing trailing edge to get it right... but finally it flew perfect carrying no trim at all. Raced it this saturday at PGRC... my first race in three years... got fast time with it. Was very happy with the way the Viper flew as it tracked very well... I even set up a mix for a Nelson for the afternoon 428 race but unfortunately, I had a takeoff midair in the last 424 heat that ruined the fuse. I was surprised how different the setup was for a Nelson versus a Thunder Tiger. It was a lot more pitch sensitive at high speed, but once it was adjusted, flew surprisingly well for a $125 ARF. I will continue with my ultimate goal of of whooping as many Composites as possible and going as fast as possible with the lowest cost equipment! On to next year.


Dan