Sig Super Chipmunk

My wife bought me a Sig Super Chipmunk for my birthday.I am wondering how many others have built this model and whether they followed the building instructions supplied or not.
I started building this model and soon found some problems with the way the parts were marked or already die cut, the cut out in the fuselage sides didnt match the wing root ribs and several other differences that I was glad I discovered prior to building as I basicaly dry build models before building them for "real" and with this kit I am glad I did.
Anyway my problem is that if the wing is built as directed in the instructions it would end up warped or with wing droop, I am used to building both halves of a main wing as seperate items and then when ready to sheet the leading edge and centre section, I join the two halves, I dont have the luxury of a wing jig that can hold a 55" inch wing but have not ended up with any problems.However with splicing the t/e edge as they call to splice it that isnt possible.
Anyway I feel several modellers here would have built this kit and I am wondering how they laid out the wing and braced it while building, Sig kits says to pin the main spar to the board and doesnt mention anything about having tip ribs raised to allow for the taper from root rib to tip rib just pin the trailing edge to the board and then pin ribs to it and putting support scraps of balsa under the main spar to support the front of the wing to me these instructions are scrappy at best and they certainly don't mention raising the tip ribs to accomadate for the taper in the wing, could anyone give suggestions as until I can see in my own mind a good way to build this wing it is taking up the dining room table and if I am not happy about a method of construction I just cannot bring myself to build the wing or anything else.I guess I am out of practise with built up wings having only built foam combat models since the 70's.

Thanks guys I just know I will get some help here, I have had alot of help before which just reinstated my view that model builders no matter the country they are in are always ready to help or share information.

.....Don't let them grind you down keep on flying.....

I've built a couple. Didn't even realize the droop thing existed on the first (about 20 years ago as a sophmore in HS).

If you want to build in halves, then just don't glue in the center rib. When you join the halves, manipulate them to get the wing to taper evenly. This will have the effect of canting the rest of the ribs just a tad, but won't matter at all.

My most recent wing, I built all at once with a billion little shims. I have a 7', 16" jointer which served as a perfectly flat reference surface to make it all work out, not a common luxury, I know...

I also have a super chip wing flying in a old CL-3 conversion, the wing was assembled by god knows who. I'm certain it was just built per the instructions, but it's really had to detect droop issue and doesn't cause any flying problems.

Lastly, consider revamping the nose to allow you to remove the tank thru the front. Put 1/2 balsa between the motor mounts, with the grain running perpendicular, get rid of the front former and build a box around the tank, only about 1/4 taller so you can move the tank up and down for trim purposes.

There's about a gagillion good mods to make to this plane. It's also a great candidate for making into the older cl-3 version by sig, by buying a new canopy, changing the shape of the rudder, making the horizontal stab and elevators bigger (helps flying) and making a wooden cowl which gets rid of weight. Then you can fly it in classic as well.

Decide exactly how you want to go and ask more questions, they'll all get answered here, great resource.

Tools

Hi Richard,
I have never built the Super Chip, but I did have to build all my wings in halves when I started back and before I acquired all the tubes, rods, and jig fixtures I have now. I am guessing that the kit has about a 36" piece of TE stock, and a filler piece to finish it out. (??) If that is the case, it won't hurt to make a new piece that will allow the wing to be built in halves. Just cut a new piece to allow the TE to join in the center.
You can go as far as making shims to hold up each rib station to it's correct height, or maybe every other rib. Just pin them under the spar.
Not trying to insult your intelligence, since you might have already thought of this, but if not, it will work.
Good luck! The ones I've seen seem to be real good fliers.
Bill <><

Hey Richard,

I've built four Super Chipmunk wings, one CL-3 (Van Loo) Chipmunk wing, and a Sig Akrobat (same wing). I did it pretty much as the destructions said to. TE pinned to the board. Shims here and there under the spar since that part gets built up off the board. I don't recall if I had to shim more at the tips or not, I would have to look at my old plans and check my notes. Its actually a very nice wing with good kit quality for its day. I would submit that newer kits typically have better wood quality and die cutting, but thats progress for you. Diecutting wise, the adjusting of the slots for the 1/8th spar on the Super Chip always took me alot of time, and sometimes I replaced parts that were both very hard and warped. I also remember that the rear spar did not quite seem to fit with the method of construction, and I always sanded a bevel on the rear spar so it was angled back toward the very trailing edge of the wing. If you look at the side view of the model on the plans, it seems the spar is angled back in relation to the TE sheeting it is glued to, and in fact I always copied that angle to a piece of scrap balsa to serve as a jig for getting the tilt of the rear spar just right before gluing it down to the sheeting. For what its worth, a Sig Super Chipmunk was just my second built up ship, the first being a Super Ringmaster back when I was 12 or so. And every Chipmunk wing I built came out perfect, with no detectable warps, droop, etc. So a rookie can do one and not totally bungle it!

To me, the hardest part of the Super Chip or Akrobat was the planking of the top of the fuselage, and here I was cautious and replaced the 1/8th inch sheet supplied with contest grade sheet, and carefully steamed (I actually painted water/ammonia onto the wood and then steamed it with a monokote iron) the sheet to get it to conform to the formers. This technique worked perfectly every time. The kit wood might have been ok here but why take chances?

I still have a NIB Sig CL-3 Chipmunk I need to get built to replace my scratchbuilt one I wrecked. They are nice looking and nice flying airplanes.

PS, It may be that Mike Gretz will see this thread and can further comment on the wing construction, if anybody should know it, he should. I wish Sig would come out with the old CL-3 again.....

Please reread the instructions. It does not say "to pin the main spar to the board". I believe you are assuming that, and that is why you are having trouble visualizing a straight result.

The correct proceedure is
1) Pin the entire trailing edge down flat and straight on the building board.
2) Then pin the rear end of all the ribs securely to the trailing edge. The front part of each rib will stick up above the board. There is no way you can have the trailing edge and the front spar notches down on the board - the curvature of the airfoil won't allow that. That's why you have to shim up the front spar in the next step.
3) Slide the bottom front spars into the notches in the bottom of the ribs, placing scrap balsa supports between the spars and the building board to support the front of the wing (this is what compensates for the tapering thickness of the ribs towards the tips.

It's a pretty simple proceedure that has worked well for this kit since 1975.

Mike Gretz

yes that is what I did but when I slid scrap wood under the spar I had to lift the front of the tip rib to get the same thickness shim under the main spar and no I wasnt pinning the main spar to the board all I pinned tight to the board was the lower trailing edge with the spar attached to it as it says in the instructions.
Thank you for your reply's so far.
the only way I can see to make sure the wing is straight and warp free is to temporarily attach the leading edge to the ribs and measure up from the board as I shim the spar and keep the leading edge parralel to the board that way it will be straight with the trailing edge, once again thanks for replys.

.....Dont let them grind you down keep on flying.....

"I had to lift the front of the tip rib to get the same thickness shim under the main spar "

The spar shims will not be "the same thickness". The thickness changes at each rib location.

Why don't you just forget about the "destructions" and just jig the sucker?

Wish I did have a jig also wish I hadn't bothered putting this post on here seems all I have done is upset Mike Gretz and make him very indignant, I can't help it if Sig are unable to make a usable kit out of the box without being put right and wood replaced, I sure wont get another one, obviously its far less frustrating to scratch build and a much quicker way of building even though all parts have to be cut out but it beats messing around with a manufacturer's mistakes.
Guys I thank you all for your advice guess this model will be used as a practise model for the local kids to learn to fly with seems that is all its going to be useful for.Almost $100 for a trainer for the local kids, oh well.

>Wish I did have a jig also wish I hadn't bothered putting
>this post on here seems all I have done is upset Mike Gretz
>and make him very indignant, I can't help it if Sig are
>unable to make a usable kit out of the box without being put
>right and wood replaced, I sure wont get another one,
>obviously its far less frustrating to scratch build and a
>much quicker way of building even though all parts have to
>be cut out but it beats messing around with a manufacturer's
>mistakes.
> Guys I thank you all for your advice guess this model will
>be used as a practise model for the local kids to learn to
>fly with seems that is all its going to be useful for.Almost
>$100 for a trainer for the local kids, oh well.

OKCFLYER,
I know Mike and he is one of the nicest guys you'll find. I doubt that you upset Mike and made him indignant. Lots of Chipmonks have been built and Mike will offer all the help it takes so you'll have a good flying model too. Hang in there.

I'm not upset. If my posts seem short, it's not because I am indignant, it's because I'm trying to type one handed, after sticking my other hand in a spinning prop on tuesday (3 cut fingers and a few stitches - just enough to get me elected club "safety officer" at our club meeting wednesday night - my "buddies" have a warped sense of humor).

OKCFLYER
The method described in the manual does work, but by all means jig up the wing whichever way makes sense to you. There's more than one way to do it.

Mike,
I am sorry to hear of your accident I fully understand there is nothing like tuning a Rossi running full power at beginnig of a combat bout, while readjusting the needle and have it blip and the knuckles going into the 7x31/2 fibreglass prop at start of combat joist and still having to fly with half the knucles or at leat the skin hanging of.
What I ended up doing was joining the leading edge and holding it in place with blocks and using a straight edge I.E. a 4ft level in front of the leading edge adjusting the ribs to fit properly and then glueing the main spar and upper spar onto the ribs later I will post a pic of what I did that seems to have worked out and the wing looks warp free on the board and symetrical, I realise I was a little cruel and apologise, I was just getting frustrated as U seemed to treat me like a rank amater, the last stunt ship I built prior to quitting flying stunt in the early seventies was a Sirotkin Spacehound and now that is complicated if built according to the plans, since my return I have built a Shark 46 ready for covering and a Gieske Nobler that is also waiting for covering I am still trying to make up my mind the best material and method to cover them with,
I shall be using automotive paint very thinly and 2 coats of very thin clear coat all eurathane as I used to be a car painter and wreck builder and know these materials as well as having the equipment.

By the way I always liked liked Dupont Chromabase paints easy to apply and get a good finish with, before that product came out I used brush on dope for color and never did like the finish, but you have to realise that was in early 70's I am sure there has been improvements made.On combat models I used fastcal I think it was called I have a friend able to supply it real cheap still have 2 rolls left.

OKCFLYER
Sounds like the exact same injury i have now. was readjusting a tight needle valve and got the back of my knuckles too far forward and inito the prop tip. the least time i had to be stitched up from a prop injury was 18 years ago. i thought i was done doing that.

i'm curious about the space hound. how did it fly? i met juri sirotkin (the designer of the space hound) in 1974, and at several scale world championships after that. i'll never forget ralph burnstine demonstrating the "new" ca glue to the ussr team in '76 and gluing yuri's fingers together. LOL

Richard:
Looks like you are flying something somewhere in the OKC area. We have had standing room only at the Topping Park circles pretty much every decent weekend afternoon and some week days as well but have not seen you there.
Come out next decent weekend afternoon if you can. Does not look like it will be today or tomorrow though. Spring contest is on Sat. May 15th. Details have been deleted from this board but remain on Flightlines.