Making large sheets of balsa help please (Ryans Rebel)
 

Hi,
I need large sheets of 1/8 balsa, 50" x 6&1/2", for the fus sides of my winter project, an 80" span Ryans Rebel. Unfortunately the largest sheets I can buy in England are 48" x 4" so I was wondering what you experienced scrach-builders would recommend as being the easiest/strongest/lightest method of gluing pieces together to achieve the necessary size?

I have attached a sketch of my initial idea.

BTW, there is a full-height 1/8 lite-ply fus doubler that runs from the firewall to just behind the wing cut-out with a diagonal taper to the bottom edge of the fus side. This doubler has several cut-outs in it to remove some material and hence lighten it. I was thinking of altering these square lightening holes so that a diagonal piece of material would be left which will cover the joint in the balsa and strengthen it.

I hope my written description gets the idea across [sm=confused.gif]

Many thanks in advance for your help!
Steve

RE: Making large sheets of balsa help please
 

Use 1/16" ply as a doubler. Just as strong and much thinner. Glue it together with aliphatic wood glue (Moo Glue!). You might consider using the lite ply as the forward section of the fuse side.

As to the lamination; one lenght of 4" and one of 3", tape one side and use the MooGlue. Could be watered down just a tad. Of course both edges should be square in length as well as edge to edge.

The 1/16" splice is used all the time in large built up sailplanes as is the lite ply forward section.

RE: Making large sheets of balsa help please
 

Steve: Your plight is not much different than here in N.A.

Those big sheets always seem to be advertised, but seldom in stock. They often cost about 3 times their equavalent smaller size. Joining or laminating are the fastest ways to get going.

Then, you can also consider going to thin plywood, as big sheets there are more often the norm. We have a local place which sells 60" by 24" lite ply for less than one sheet of big balsa, and they will cut to size while waiting.


Wm.

RE: Making large sheets of balsa help please
 

There is another thread about large sheets of Luan from the home construction material stores (NEW SHEETING MATERIAL). It comes in 4' X 8' and is very thin and flexible. It may just be what the Dr. ordered for you. Check it out. Sina

RE: Making large sheets of balsa help please
 

What's wrong with simply using a straight edge to get nice edges on each piece and gluing together with wood glue? A doubler isn't needed.

Do it over wax paper, press together, squeegee out the excess, tape together with masking tape, and weigh down (with another piece of wax paper on top) until dry.

This is how I make very large skin sheets out of 36 x 3 sheets. Note when making really large sheets to stagger the joints (kind of like laying a hardwood floor). Also, the long edges of the individual pieces should ideally be perpendicular with whatever curve you may be laying over.

RE: Making large sheets of balsa help please
 

That works for skins, but using a plain butt joint in a fuse side isn't a really good idea. Butt joints (as in skins) are the weakest of all joints, and fuse sides have to tolerate stresses much higher than the stresses imposed on skins.

$0.02

RE: Making large sheets of balsa help please
 

Sounds like a plan. If the pre-cut doubler still has the knock-outs in it, why not leave them in place and glue the whole thing up ? The weight "penalty" of a few missing lightening holes isn't severe.

RE: Making large sheets of balsa help please
 

lamination... definatly not worth buying the 50" sheets... or the 48" for that matter... get 4 , 36x3 inchers and laminate like this... the red line is the cut path.

yup, the end of the wood is Very very porus and soaks up all the glue making for a very weak bond. however a diagonal joint like the 1 i showed eliminates this problem because it allows you to glue to cross grain and creates a much larger gluing area.

RE: Making large sheets of balsa help please
 

Thanks for catching me, plumber- I missed that part of the question, and didn't realize this was the structural member of the fuselage.

RE: Making large sheets of balsa help please
 

Hey guys,
Thanks for all the replies - much appreciated.

So, basically you're all saying that my basic method of contructing the sides is o.k. (?). Well, I suppose I'll just have to suck it and see!:D

Cheers,
Steve

RE: Making large sheets of balsa help please (Ryans Rebel)
 

Steve,

Your idea will work just fine. I normally edge true two pieces and tape them together with masking tape. Next hinge open the two sheets and fill gap with wood glue. Close up, wipe off access and allow to dry. I normally weigh down with wax paper & magazines. I would not be terrible concerned about having a doubler over the entire joint. Reason being is any glue used is stronger than the balsa being glued together.

Another option is to splice near the leading edge of the stab where then plans already call off for a doubler.

Either will work fine.

Ryan

RE: Making large sheets of balsa help please (Ryans Rebel)
 

Oops, sorry wrong thread!

RE: Making large sheets of balsa help please (Ryans Rebel)
 

Hi Ryan,
Many thanks for your reply and reassurance re. my method of constructing the fus sides.

After a journey to the other side of England and back (the shipping company messed up) my order of selected, light-weight, balsa for the Rebel eventually arrived today - looks like I'm going to have a busy weekend - yeeharr! :D

All the best,
Steve

RE: Making large sheets of balsa help please (Ryans Rebel)
 

Aloha,

I'm building a Ryans Rebel too. I'm having a Laser Cutter cut the ribs, formers, and yes the fuse sides. The laser cutter can only supply 1/8 inch ply in 24 inch lengths. My plan is to have the laser cutter cut the fuse sides in three pieces and then I'll use 10:1 scarf joints to glue the pieces together. It really doesn't take that long to feather out the edge of a piece of 1/8 inch ply .... use the plys to guide you concerning how even the edges are feathered. Then use some moo glue and 24 hours later the sides are one piece (the glue has to cure for 24 hours). Titebond works too. When done properly, the joints are actually stronger than the wood. They use the scarf joint to make spar splices in full scale airplanes .... see FAA Advisory Circular 43-13.2B for full details.

I used this method to repair a fuse on a 60 size RightFlyer for a friend a couple of years ago.

I'll try to get some pix to post as I do the job.

Ahui Ho

Safetywrench