Choosing the right density Balsa for a build
 

I am about to build a Mick Reeves 1/6 Spitfire. All previous experience is from build kits that normally come with all the Hardware. However the Mick Reeves model comes with all the main shapes pre cut, but all the sheet and Spars needs to be purchased separately.

So my dilemma is making the correct choice of wood density for the build. Can someone please give guidance on what density to use eg, light medium or hard for the following areas:

1. Wing sheeting (i will be using 3.32" sheet).
2. Packing between spars.
3. Wing spars 1/4 by 1/4 (top and bottom)
4. Ailerons and control surfaces.
5. Wing leading edges.

Any other tips will be greatly appreciated

Thanks in advance

RE: Choosing the right density Balsa for a build
 

Mr Jolly I think I can help. I want to state that contest grade balsa in the 4-6 # range is what I mean for contest balsa.

1 Contest grade or as light a standard grade as you can. Beware of balsa that is too soft.

2 contest grade just again beware of soft wood.

3 The hardest you can find. I reccomend going to basswood. I don't like balsa spars.

4 Medium grade wood.

5 I would say fairly hard wood. Medium would do if the wings are sheeted.

I hope this helps. I would sheet with contest grade as well. Be careful of heavy wood in the tail feathers. My suggestion is to buy some contest grade in the sizes you need. Then buy bundle deals (I like dealing with Lone Star for wood) and select the wood you think will work the best for your particular application. Buy extra in the bundles so you have choices. You can always use the wood for later projects. It won't go to waste.

Mark Shuman

PS look for some polyurethane glues to join sheets together for sheeting. It will require you to really pin the sheets down to hold them together. But this glue is very easy to sand the joints. It will foam out between sheets. Don't worry about that, it's normal. It will sand very well. Just a suggestion.

RE: Choosing the right density Balsa for a build
 

I agree with phread59 on all points except two.

2) Use medium balsa for webs. I wouldn't use contest balsa here.

I would also not use polyurethane to join wing sheets. The foamed part sands easily, but the part that soaks into the wood doesn't. Use regular airplane glue (Ambroid) and wipe down the seam with acetone while it's still wet. It dries faster than polyurethane and is much easier to sand.

RE: Choosing the right density Balsa for a build
 

Thanks very much for the feedback. Very helpful.

Just one more question from the comments posted.

Is basswood the same as spruce wood ?? Never heard of basswood before.

Many thanks.

JoLLy

RE: Choosing the right density Balsa for a build
 

Spruce is a better choice than basswood, but it's gotten very expensive. If you build a wing properly and fly it as intended, you won't break wings, so you don't have to change the design by using different woods.

There's no easy way to explain when and why you would use basswood or spruce instead of balsa and what size to use, etc. There are just too many variables involved. Most of us figure out what works by building a variety of kits. That gives us enough experience to know what to use in what situation.

If you have a specific application we can give you specific answers.

RE: Choosing the right density Balsa for a build
 

Hey CafeenMan thanks for the post.

You are mention a need for the specific, so here is my specific! [:-]

On the Mick Reeves 1/6 Spitfire wing ( 74" ) the centre section has 2 mainspars both 1/2" by 1/4".
The main wings have top and bottom main spars 1/4" by 1/4" and rear spars 1/8" by 1/8".

Should any of these be spruce or just dense balsa is the big question?

Nigel Wagstaff

RE: Choosing the right density Balsa for a build
 

MrJolly - the wing is fully sheeted, correct? Those spars will be strong enough - especially if you use webs. What engine are you using?

RE: Choosing the right density Balsa for a build
 

I will be using a Laser 150. Recommended for taking off from grass as I will be doing.

Yes the wing is fully sheeted with 3/16" sheet (I guess medium to soft) and I will be glassing the wing after that.

I don't know what you mean by webs?? [:o]

JoLLy

RE: Choosing the right density Balsa for a build
 

umm... I hope you mean 3/32" sheet. 3/16" sheet and you don't need ribs, spars or webs. :D Webs go in between spars. I think you called them packing.

I'm really undecided on the spars now. If you fly in a scale manner, then the balsa spars are fine. If you get wild with it, you should probably replace them with basswood or spruce. Either is fine.

About Shear Webs

RE: Choosing the right density Balsa for a build
 

Ah yes . . . I was testing you . . . . Oh OK you got me, I blundered, it is 3/32" sheet.

Very interesting page on Concepts. That’s in the favourites!!

With the Laser 150 I suppose there can be a slight encouragement to go silly every now and then. I will play it safe and use spruce for the main 1/4" by "1/14 and hard balsa of the small 1/8" by 1/8" rear spar.

Packing is expected and will be used at 1/16".

Many thanks for the speedy comments CaffeenMan. I shall now order my wood!

JoLLy.