trying to salvage an e-bay bad purchase

Bought a SIG Zlin Akrobat on e-bay. Unfortunately, it was a box of crud. The only parts in the kit were the tail surfaces. I read somewhere you can by a SIG Chipmunk wing kit. If I remember, the wings of the planes were similar, except for the tips. My local dealer, however, said the Chipmunk wing kit wasn't in the book. I did order a new set of plans and cowling. Figure I can make a fuselage easy enough as the kit did have an intact canopy (the only fuselage part in the box). Wondering if anyone knows where I can get a wing kit for an Akrobat or a Chipmunk or a foam wing that would work. Original span was 51", but I figure 51" to 55" would work. Thanks for any info. (Please don't lecture me on e-bay, as I now call it F-bay and won't use it ever again).

Why not just make the wing yourself. If you have the plans you can make a root rib template from the fuselage drawing and then interpolate (a big word meaning "guess") the dimensions of the tip rib off of the wing plan. There is nothing to say it has to be exact or even that the original was a "perfect" airfoil anyway. Just keep the spar location the same and figure the high point of the airfoil at about that point. Keep the same thickness ratio or a little thicker at the tip is fine, too. I do have the Chipmunk plan with each rib outline superimposed (another big word) over the rib location, but I don't think you need it. If nothing else, you will have the satisfaction of being able to say, "I scratch built this one." And you will be much better off in that a lot of the SIG kits had some "slightly" heavy wood.

While you are building the kit, I would recommend using a 4 inch belcrank, using heavier hardware than what came with the kit, a carbon fiber pushrod, adjustable leadout guide, adjustable tip weight box, And make the gear leg ends that extend into the wing the full height of the rib and place a piece of motor mount stock on end and drill through it to hold the gear. The gear, as designed, got a bit wobbly and this makes it much stronger.

Oh, yes, make the tank removeable out the front and adjustable in height.

Tell us how it comes out.

Leonard Neumann

Not all deals on E-bay are bad. In fact, most are good. But you have just warned others about the occasional one that can go sour if the seller isn't upfront on everything.

I suggest Flying Foam.
www.flyingfoam.com
If you aren't a foam cutter, these are reasonable
prices and spot on for contour. I am
setting up to use them for full size race car wing
cores.
I have no affiliation with or financial interest in these guys.
I just got samples and was impressed.

Scott Correa

Let's fix a bad deal...John Duncan cuts GREAT foam wings, and has super delivery. He was cutting and sheeting a Chipmunk wing this afternoon! Call him (518) 583-8839. No baloney, John's an honest businessman, fair prices, and a good friend. Good stunt flyer, too!

Thanks, so far for your comments. I think I will go with foam, but I don't know enough about it. How do you put in a bellcrank, does it need spars, what about sheeting, etc. I'm no good at making ribs on swept wings and the plans I have have no template. I could probably get close, but my brainstorm is to order a SIG mustang stunter wing kit. About the same size and available for $37 (I assume hardware comes with it). I'm afraid I don't know enough to order a custom cut foam wing.
Thanks
P.S. The seller replied and is going to refund a big part of the purchase price for the kit.

The Mustang wing is a different animal altogether (really a "Mustunt" in disguise). It, also is not cored, and that is what you really need if you are going with a foam wing. It has a different airfoil, different span, well, as I said, it is a different wing.

A properly cut foam wing for stunt will be fully cored with one or two foam spars in it. If you build the gear into the wing you can have a plywood stub spar put in the foam spar up to that point to help support it. You can use a "floating" belcrank on a rod with a plywood anchor on top and bottom of the wing sheeting.

If you have never done a foam wing before, it is going to be much more difficult than building the built up wing, and chances are it will get heavy on you as well. I would still suggest you go with a built up wing.

To make the ribs for a built up wing, make a plywood template of the center rib and another of the tip rib. Then cut enough blanks out of 1/16 balsa to make the number or ribs you need, and sandwitch these in between the two templates. You can drill two holes through the templates to bolt the templates and balsa blanks together, and then sand the stack to the outline shape of the templates. This will leave you with the proper number of ribs all ready for assembly. It is not too difficult. And, who knows, once you have done it for this plane, you might decide to build others from "scratch".

LN's correct on doing a wood wing.
If you haven't done foam before, do it in wood.
There are a couple things that are really cool
about wood wings. They have large hollow spaces
in them that don't weigh anything. 1 #/cf foam
weighs .009 oz/cu in. It adds up fast on a thick
stunt wing. Wood errors are easier to correct
when you are building. Have fun whatever you decide.

I have wing parts for a Chipmunk! Email me and we will get you fixed up.

>The Mustang wing is a different
>animal altogether (really a "Mustunt"
>in disguise)...

>Leonard Neumann

Leonard, you are certainly not claiming the SIG Mustang & the Rabe "Mustunt" to being the same animal, are you?

>Leonard, you are certainly not claiming
>the SIG Mustang & the Rabe "Mustunt" to
>being the same animal, are you?
>
>Curt
>

Al Rabed claimed it was. Of course, there were a lot of "new" designs that were Noblers in disguise, too. Certainly the fuselage on the SIG design is different, and uses plastic and an inverted engine and all that. But we built a SIG Mustang and mounted the engine upright. It works good, and looks good. Got a Mustunt, also....with a foam wing. They are brothers!

Take a look at 'em. The airfoil is almost identical. The areas are almost identical. The moments are almost identical.

There was either a lot of "influence" or a lot of "coincidence" at work here.

Nothing wrong with that. Just an observation. The Mustunt is a good plane.

Oh fiddle!
STOP thinking about what you can't do or don't know, and start doing I can and I will. You will be amazed at how much you really do know and can do, if you will get out of the track of assuming you aren't good enough. I have learned so much stuff, about so many things in just the last five years or so, just because I didn't listen to anyone except me, and really felt I could do it, that it amazes me even now.
I'll go with Leonard. Build a scratch balsa wing, finish your Zlin, you CAN do it, it might take time and patience, but if you stick to it, it can be done. YOU are your own worst critic, and you can do anything you want if you just get beyond the juvenile "I can't do it, don't know it" stage.

Best,

Oh I know I can do it. I've done it plenty. I just absolutely hate doing it. The idea of bolting the ribs together, actually, never occurred to me (too simple and common sense). I'll contact De about the Chipmunk wing and make it work.
Thanks all. Although, I do want to explore this foam thing because I like what I see with a lot of them.

Myself, I like foam wings as they are easier to build straight ( you might take this to mean I cannot build a balsa wing....)
Any way, this is my method.......
I build and skin the 2 wing halves, then cut the cores to lighten them a little, I dont "core" the outer wing as it needs to be heavier anyway....
Make a ply centre rib and cut biggish holes in it or it will be heavy.
Put a long bolt through the bellcrank and fix the crank firmly in the middle, the bolt must be just longer than the wing thickness, yes, heavy but you need STRENGTH here....
Fix the bolt to the outboard side of the rib.
I drill small holes either side of the bolt and tie it down with strong twine, or you could use fishing line or.........
epoxy the twine, you will be amazed how strong this is.
Epoxy the wing halves together, Yes with the rib in the middle.......
Fibre-glass over the join.
If you can't figure a way to get the flap pushrod done I am not going to tell you.......
I built my last 4 or 5 planes this way, including my twin which pulls about 15-20 pounds, the control system has never failed me, my brain failed me at a crucial point, but we'll gloss ove r that.......
More seriously I hope this is some help, I don't pretend to be an expert, but this works for me.

Two comments on this, Dave. We tried the bolt method and most of these are too soft. They bend under pressure. But your method of attaching it to a plywood center rib probably takes care of that. However, if you use an 1/8 inch music wire rod, it will be strong enough to be self supporting, and you can eliminate the center rib altogether.

SIG sells some 1/8 inch eyelets. Brodak carries these and I include them with some of the belcranks I sell. You can either solder or JB Weld these to the wire on each side of the belcrank and it makes a perfect bearing. Make the wire long enough to extend out beyond the wing top and bottom, and then cut two small pieces of 1/8 inch plywood with an 1/8 inch hole drilled in them. Slide one over the bottom of the wire rod and solder a washer on the end so it would center the belcrank when it is flush against the plywood and the plywood is flush against the bottom of the wing.

At this point you can slot the wing and put the belcrank anywhere you want. Some mount it in the exact center of the wing. I reverse the belcrank and mount it somewhat outboard in the outboard wing half. Either way, you can then leave the belcrank "floating" while you assemble the wing in the normal manner (epoxy it together and then wrap the center section with several layers of different width 1/2 to 3/4 ounce fiberglass, making sure the bottom layer extends out beyond the width of the fuselage. With the wing assembled, glue the bottom piece of plywood to the bottom of the wing, and slip the other piece of plywood over the top of the wire and glue it to the top of the wing. Then pull the wire up snug and solder another washer on top. You are done. Some will use small pieces of plywood maybe an inch to an inch and a half square. We have tried to make it so the pieces of plywood but up against the inner fuselage side (and plywood doubler). It will stand the pull test and won't come loose.

Some of the belcranks come this way with the wire rod already in place on the belcrank with its own bearing mount.

I can vouch that the Chipmunk wing kit is available as I'm a SIG dealer. It is in the dealer catalogue.

Chipmunk wing kit SIGRPBK019 $34.95.

About 7 years ago, I bought an Akrobat from a guy who did a wonderful job building it. Exactly like the box art, in the red, blue and white. It is beautiful.

I'm probably never going to fly it, and would like to sell it, but the problem is shipping. It would cost something like $200.

Anyone "near" southeast Michigan interested?

Thanks everyone for your help. De Hill here in Tulsa is going to help me with a Chipmunk wing he has and Tony Bagley, in CA, is going to run a computer program to give me drawings for the ribs for the Akrobat. Since the only part I purchased was the tail (the easiest part of the plane to make), I think I'll end up with an Akrobat AND and Akromunk. My "bad deal" has suddenly turned very fun!! It was also nice to get an apology and offer to adjust from the seller. He was very nice. I haven't attacked his seller rating and won't now.
My next plane will have a foam wing. I'm guessing you have to have special tools to core one, though. Any attempt I've ever made at cutting foam with a knife was a disaster.

LAST EDITED ON Aug-15-01 AT 08:57 AM (EST)

No offense to Sig, but the Ebay seller may have saved you some aggravation by misleading you. I built a sig Akrobat about a year and a half ago from a mint in box kit. At least I started from a kit. The only wood I deemed remotely usable were the wing ribs and the motor mount bearers-everything else I used only as templates, the wood was VERY heavy and warped. (in fairness the kit had been in somebody's closet since the 1970s, so maybe that ruined the wood-the more recent superchipmunk kits I have built had better wood) Essentially my complete kit became my first scratch-building project.
The superchipmunk wing kit(as mentioned above available from SiG) is a good place to start. I believe sig also sells the landing gear wire, canopy and plastic cowling to the present day. I made several changes to my akrobat based on my experience with the Superchipmunks I had built. First and foremost I discarded the plastic cowling, which after assembly and making the cutouts still weighed in excess of two ounces-too much weight to put on the very front of the airplane if you are using a OS FP 35 or similiar motor. I carved a nobler-style cowl (my first) which allowed me access to the fuel tank if needed and only weighed half an ounce. I made the tail surfaces and rudder from 1/4" sheet instead of built up-this was faster, easier and helped balance the weight of the FP motor without having to add tail weight. My finished Akrobat came out at 40 ounces thanks to replacing the wood with contest balsa. If I built another one I would make the former just behind the wing a bit narrower-compared to the chipmunk fuselage the Akrobat fuse make a bit of a sharp bend just past this former and can give you a hard time. Making the former a bit narrower lets the fuse start to taper sooner and makes the bend at that point less severe.
Whatever you do I hope you enjoy it. My Akrobat is in temporary retirement after 150 flights and a 1st in Pampa Intermediate at Charlotte last year and a 5th in Advanced at this years KOI. It is a hard plane to fly as well as a Time Machine or other modern job but it is a very easy plane to fly the pattern with overall-a vast improvement from small profiles, etc. I've really enjoyed mine.

Have you contacted the seller on the grounds that they may have misrepresented their goods for sale?

Just curious, but was this seller located in Riverside, Calif? I got ripped bad, only once, by a seller that had an Ares for sale. Claimed it to be 99% there. It is only 55% there, so I made patterns and now have a full kit. Construction starts Friday. Other Ares will be out of the way by then. This guy refused to answer my e-mail. I'll bite the bullet this time. But lead tastes bad.