slab-wing/built-up construction

NEW222 wrote:That is a good idea.  I do like it.  I really like the looks of the sheet wing stunter you drew up.  Have you tried using dope on the wings or other built up structures?

Nope on the dope.. I've only used Mono-Kote. If I were to build the Stunter again for reed-valve, I'd scale the design down some.. probably to 20" span and 5" chord making for a 100 sq. in. wing. Maybe shorten the tail-moment a bit too.

What is the main point of dope?

Usually for applying silk to the rib wings to adhere to surface and tighten , also fuel proofing , Very light weight stuff can bee used for a light weight aircraft .

Hi Jack ( and I am briefly going to hijack Roddie's excellent post on his method of built up slab wings)

DOPE is just one of several methods used for covering and finishing a model

There are basically two types, Nitrate and Buyrate Dope (actually there are many other sub classes with different properties but basically we use these two "TYPES")

There are variations but you must remember Butyrate OVER Nitrate never the other way

Of the two, Butyrate dope is referred to a HOT FUEL PROOF and is more or less resistant to deterioration when we get raw fuel and exhaust residue on the model. That said it is still important to clean off any spillage or exhaust as soon after flying as possible because even a dope finish can soften if the fuel is left on the plane

A raw wood model airplane needs to be completely sealed so the oil and fuel does not soak into the wood and make it very heavy, and weaken glue joints

One method is to paint the entire plane with Nitrate dope first and cover it with tissue (a very light paper that is a lot like the wrapping you see on gifts), or real silk, or man made covering like polyspan (there are many others)

When you prep the wood first with Nitrate then when you put on the tissue or silk we use Nitrate OR Butyrate dope to make the covering "glue" down to the wood. The dope on the top of the covering flows into the tissue or silk and softens the dope on the wood and then they both dry and bond.

Some DOPE shrinks a lot and some is designed to not shrink too much but they all SHRINK and we use this property to make the covering say on the wing, tauten, and keep the covering nice and tight

Look around this site and other places like stunthanger, RC groups, RC universe and learn all you can about finishing a model airplane

At your age I would recommend newer easier man made iron on coverings. The learning curve is much easier, they are cheaper, and the smells more agreeable to your parents...dope is bad to to breath, and it smells very bad in a house

Hi Roddy,

 I really like your idea of a built up wing for 1/2A planes, so much that I am going to build my version of the "All American"! Its scaled down a little from the original 09 sized plane. The new wing will be 24" x 5"- 120 sq.in. I 'll also use a profile fuse instead of the built up version. I plan on using a Gold Bee for power.

 Thanks again, RK Flyer  

RK Flyer wrote:Hi Roddy,

 I really like your idea of a built up wing for 1/2A planes, so much that I am going to build my version of the "All American"! Its scaled down a little from the original 09 sized plane. The new wing will be 24" x 5"- 120 sq.in. I 'll also use a profile fuse instead of the built up version. I plan on using a Gold Bee for power.

 Thanks again, RK Flyer  

Hi Richard! Good to hear from you! I'm actually surprised that this topic has gotten some interest.. but I'm happy that you're going to give it a try. I plan to try this method on at least one of the four 1/2A plans that you mailed to me last year! I may need to very slightly shorten the tail-moments.. because this method does produce a lighter wing. If you're building a mono-plane.. I would recommend incorporating a spruce spar; butt-jointed behind the leading edge. For example; if you're building a 1/8" slab-wing; you might want to back-up the L/E with a strip of 1/8" x 1/2" spruce, to stiffen it up. You can use a scrap piece of the spruce; chord-wise.. near the inboard root, for a bell-crank mount, supported by gussets.. or construct the center of the wing panel, using 1/8" plywood running through the joint in the fuselage. Either way, it provides a good strong bell-crank mount.

That is Sweet Roddie , looks like you monakote the whole thing ? Were the flight charastics in between slab and air foil ?

I've used this on empannage parts for RC glider rebuilds. The weight saving is pretty helpful, as is the MATERIAL savings. It is pretty awesome to build a tail assembly from scraps without fuss!

I have never tried it for a slab main wing.

as a kid i built quite a few rubber band powered models (mostly peanut scale). every bit of those things was built that way and then tissue covered. i would imagine being covered with monokote creates a stronger, much lighter rigid wing.

very cool!! had to save a lot of weight on that tripe

getback wrote:That is Sweet Roddie , looks like you monakote the whole thing ? Were the flight  charastics in between slab and air foil ?

Hi Eric, It's still a slab-wing.. so it's got that same feel.. except you're saving a little weight. A lighter model is going to respond better to your control inputs. Yes; the wing is all mono-koted with this method. I don't know how other iron-on products would work though. The MOST important thing; is to build accurate, perpendicular joints into the structure.. because they're butt-jointed and they need to fit "nice-nice"..  Take your time with fitting the pieces.. and keep everything perfectly-flat with wax-paper underneath. I used CA glue on the edges to be joined.. and held each piece tightly together for at least 10 seconds. I never found the need to use accelerator/kicker. If you build the perimeter first.. (highly recommended) you can then "piece-in" the faux-ribs afterward.. which will ensure a flat-framework. Once you've built this type of construction.. you'll find that it's not difficult. You just have to be mindful of fitting nice snug/square joints.. like you should with any construction. Layout and cut your faux-ribs using a square and miter-box.. and make them slightly "long". You can block-sand the edges bit by bit; until they fit in snug between the L/E and T/E.

Roger, the tripe's wings are built entirely of 1/8" balsa sheet.. except for the bell-crank mount on the center-wing; which is 1/8" x 1/2" spruce with gussets running inboard for support. I used 3/16" diameter hardwood dowels for struts, which tie the three wingtips together. A "mono-plane" should incorporate a hardwood strip-spar to stiffen-up the wing. This is very important.. because of the fragile construction. A "hard" landing could snap the wing at it's root without one. You can get creative with your choice of spar materials. Whatever you use, is only going to be a small percentage of the wing's area.. so we're only talking "grams"; as far as weight is concerned. Set your table-saw's ripping-fence to the required thickness.. (1/8" in our case here..) and carefully feed a span-length piece of 1/2" or thicker hardwood through.. and you've made your strip-spar. Remember this when you're throwing away an old piece of hardwood furniture.. like an old bureau. Hardwood panels can be ripped-down on a table-saw to provide all sorts of useful model stock. One single panel from a maple drawer could provide a lifetime of beam-style engine mounts!

Roddie,

I am getting ready to build and I was wondering if anyone has tried drilling 2"- 3" holes in a solid wing then covering with Mono Kote or something similar?

RK Flyer

I think I might try that idea of making a triplane. But first I'd better get my skills up with scratch building.

RK Flyer wrote:Roddie,

I am getting ready to build and I was wondering if anyone has tried drilling 2"- 3" holes in a solid wing then covering with Mono Kote or something similar?

RK Flyer

Yes. I have done that as a method of making lighter for a plane that built overweight and out of balance. I removed crazy material from behind the CG. I would have been better to custom build a slab wing.

The plane was a white lightening when I started.

Phil

pkrankow wrote:

RK Flyer wrote:Roddie,

I am getting ready to build and I was wondering if anyone has tried drilling 2"- 3" holes in a solid wing then covering with Mono Kote or something similar?

RK Flyer

Yes.  I have done that as a method of making lighter for a plane that built overweight and out of balance.  I removed crazy material from behind the CG.  I would have been better to custom build a slab wing.

The plane was a white lightening when I started.  

Phil

Interesting! The White Lightning was one of the four plans that Richard mailed to me!



Surely you can drill lightening holes.. anywhere you need to, in order to balance. We often use a different engine for a model that was "optimized" for a certain power-plant of the era that the airframe was designed. Modern engines of the same recommended displacement, tend to be much lighter; creating balance issues with a vintage airplane design. You can easily extend the length of the nose-moment slightly.. during the building of a profile fuse.. and trim it back after finish.. to balance your engine/fuel tank placement.

Scratch-building my own designs is something that I've always enjoyed. They'll always fly and be controllable.. as long as they're not tail-heavy. It all depends on what you want the model to do. If you're looking for aerobatic performance.. then the balance has to be spot-on.

The whole idea of this flat-frame construction is to save on weight.. and materials too. We're talking SMALL airplanes here.. 1/4A to 1/2A size.. 16" to 20" wingspans. There's no sense in using solid 2" to 3" balsa sheet; butt-jointed to build a slab-wing.. only to end up having to core it with lightening holes, in order to balance it.

The profile fuse is another area where you can get really creative. Conventionally; it's usually a solid sheet of 1/4" balsa for your average 1/2A kit. You've probably got lots of 1/4" balsa cut-offs in your balsa scrap-stock box (I do..) Try making a framed-fuse; the same as this wing construction. The fuse is not subjected to the same forces as a wing is. If you're skeptical about this.. then use 1/4" square-spruce/hardwood for the perimeter of your fuse-frame.. and use cored-pieces of 1/4" balsa for filler-pieces. It will require a skin.. but so will the wing. When it's finished, it won't show .. and it will be lightweight and rigid.

Here's a couple photos of how I used hardwood to strengthen the slab-wing and profile fuse on my speed-model. If you're building a scale-design that has wing-mounted gear.. then this really helps to strengthen the wing-root against the shock of a hard landing.



I'm not sure what type of wood I used.. but it's HARD.. and it has some serious load-carrying properties. It's just a "strip" though.. so I'm not adding a lot of weight.

This fuse has 1/4" square spruce rails top and bottom.. from nose to back far beyond where nose-doublers would extend. This is a speed model.. so I wasn't overly concerned with weight.. but it's very strong. If you notice; I built-in the hardwood "rails" first..  (simple parallel beams with conventional plywood nose-doublers) and finished the top/canopy and bottom/belly contours with 1/4" sheet balsa.