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 Scratch Building with Balsa - some queries...
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Author Previous Topic: Rusty Stumps RC board, styrene and Gatorfoam ... Topic Next Topic: Using Canopy Glue for window glass - 1st attempt  


Posted - 03/06/2011 :  10:12:57 PM  Show Profile  Reply with Quote
Hello fellow modellers,

Please forgive me for posting this thread here, but I wasn't sure where else to post it.

Understand that I certainly do not consider myself a craftsman - more of merely a tinkerer, I like to think. But I do have a question of you wise and gifted builders.

I have had varying degrees of success over the years working with sheet and strip balsa wood.

I agree with another poster who maintains that nothing resembles wood grain better than balsa, as is what you would assume. It also takes staining and texturing well, and is very easy to work with. Sometimes too easy, as it is quite simple to permanently damage a balsa timber finish with an errant thumbnail, usually right where it shows the most...

Sometimes my projects turn out well, and others, well - not so well. You know what I mean.

Please have a look at the following pix, and perhaps someone could offer me some pointers.

This first one is a set of four O scale doors that I made up to fit a goods shed that I built some time ago.

You will notice the unacceptable warping that has taken place over time. Each door is two thin sheets of scribed balsa, bonded together with (I think, if I can recall) balsa cement. If I had had the choice, I would have placed the two sheets at right angles to each other, in order to keep warpage to a minimum. However, I needed the scribed boards to follow the grain of the balsa on both sides.

This one is the interior of an English passenger coach: it is a styrene Peco 0-16.5 kit, and I have added scratch built seats and some figures, as well as balsa wall panelling.

Note the outward bowing of the styrene ends...

...And the guard's end, too.

They both should be perfectly vertical...

I am not certain which adhesive I used here, as I use half a dozen different types in my modelling, and I usually select the one which will give the best bonding for the task.

It was most likely Tarzan's Grip, which is a general purpose adhesive that we have here in Australia. I like it because it can be used either as a direct bond glue, or as a contact adhesive. It dries clear, and allows some degree of movement after bringing the surfaces together, which is often desirable.

Now I know that you blokes Stateside have different adhesives like Elmer's Goo and Pliobond, but we have nothing like that here.

I can choose from PVA (White Glue), Aquatect (a PVA-like adhesive that dries clear and waterproof), CA (Superglue), Contact Adhesive (both acyrlic and oil based), RTV Silicone, and the aforementioned Tarzan's Grip, and Balsa Cement. (Both of which smell and work pretty much the same...)

So, if anyone can help me out with a few pointers on attaching balsa to itself and to other surfaces, so that it will not warp later, I would be very appreciative.

Thank you.

Time is the Gauge of Existence

Country: Australia | Posts: 1349


Premium Member

Posted - 03/06/2011 :  10:27:26 PM  Show Profile  Visit closetguy's Homepage  Reply with Quote
Wood is a funny thing. It's never really dead. It has a tendency to grow and shrink across the grain. If you look at full size solid wood panels, instead of 1 wide piece you will see smaller pieces glued together to form the larger panel. The grain also alternates or is reversed on each piece to help with the cupping issue. The other way to minimize cupping is to mimic plywood. 2 pieces glued together with one perpendicular to the other. Also wood needs to be sealed equally on both sides to minimize warping and cupping. That way it absorbs moister equally on both sides. Since you have glued 2 pieces together try the perpendicular route. or 3 thinner pieces with the center perpendicular to the 2 outer pieces.
Good luck
Mike M

Country: USA | Posts: 1855 Go to Top of Page


Posted - 03/06/2011 :  11:11:34 PM  Show Profile  Visit adrian_batey's Homepage  Reply with Quote
You may like to try Weldbond ( i think thats what its called). You can get it from bunnings and only a little bit more then normal PVA i couldnt tell you what or why its different then normal home brand PVA but i have had a lot better results with it. Also works ok on plastics and a bunch of other surfaces i have found. fairly fast drying to.
I hvaent done much with balsa for a while but i remember the last time i used it on balsa i didnt get and warp in the finish but i did laminate it with another sheet going across the grain.

Owen Pass Lumber Company
HO Logging Layout in a Shed.

Country: Australia | Posts: 1266 Go to Top of Page


Premium Member

Posted - 03/07/2011 :  12:13:43 AM  Show Profile  Reply with Quote
I have very limited experience with balsa, but in attaching balsa to other materials would a coat of sanding sealer prior to building help? I realize that you would probably lose the wood grain if sanding sealer is used, but in some projects is it an option? I also do not know if it is possible to apply a sanding sealer and then 'grain' the balsa using techniques like what is used to 'grain' basswood. Just thinking out loud, so hopefully someone who knows can add some additional input.

-- KP --
Life is to short to build all of the models I want to.

Country: USA | Posts: 7214 Go to Top of Page


Posted - 03/07/2011 :  01:22:25 AM  Show Profile  Visit Graffen's Homepage  Reply with Quote
Balsa by itīs own is very much likely to bow over time, I use epoxy to glue balsa to other items or to balsa, and that minimises the bow tendencies.
When glueing styrene to other materials, stay away from evaporating glues!!
They have a nasty habit of remaining in the bond for a VERY long time! I built a boat for a client some years back, and I glued the plasticard decks to a plywood substructure with a solvent based adhesive.
It took 2 years before the terrible thing happened; the deck bowed up and looked terrible!
I remade it and glued it together with No Nails this time. That was 3 years ago, and it still looks nice!

Michael Graff
"Deo Adjuvante Labor Proficit"
Swedish custom model builder.

Country: Sweden | Posts: 1569 Go to Top of Page


Premium Member

Posted - 03/08/2011 :  4:46:44 PM  Show Profile  Visit closetguy's Homepage  Reply with Quote
Was I just blowing steam out my butt when I responded to this topic.
Wood will bow,cup, twist if it is not equally sealed on both sides. Wood shrinks, grows and moves across the grain. It does not matter what glue you use. It does not matter if you use sanding sealer on just one side. To minimized cupping glue 2 pieces together with the grain perpendicular to each other. That is the only way to minimize the cupping chance. I have 35 years experience as a furniture/cabinet maker. I don't understand what good does it do to post correct information if it's ignored and the information that follows is incorrect.
Mike M

Country: USA | Posts: 1855 Go to Top of Page


Posted - 03/08/2011 :  5:01:00 PM  Show Profile  Reply with Quote
Thanks to all for your comments.

Mike, I know that you are right about the sealing of timber - balsa included. It just never occurred to me.

It is true that I never sealed any of the jobs that have since warped.

Would it do any good if I were to seal it all now? Would that remove the warping?

Or do I have to redo all the bent bits?

Time is the Gauge of Existence

Country: Australia | Posts: 1349 Go to Top of Page


Posted - 03/08/2011 :  6:27:17 PM  Show Profile  Reply with Quote
If you can get it, try UHU Glue, I think that's how it is spelled but it is pronounced " You-hue". It is made for wood and will not shrink or warp the wood. Guys who build ship models use it, I( think it's made in Germany or Sweden. My dad use to swear by that glue. It comes in a tube.


Clowning around with trains.

Country: Canada | Posts: 1584 Go to Top of Page


Posted - 03/09/2011 :  08:30:44 AM  Show Profile  Reply with Quote
If you re-wet the items and put them under some weight it should flatten them out. You can then try sealing them but this is a 50-50 proposition.
I use alcohol to wet my items as it drys faster and doesn't penetrate as deep. But you may want to use water and let the items set under weight for a few days.
It's all an experimental thing. If they do flatten out, glue some bracing on the backside, made from basswood or something harder than balsa, so the grain runs perpendicular to the grain in your part.
Of course your showpiece doors wouldn't look right but possibly you could pop off those top and bottom headers and replace with a stronger wood.
When the glue is wet they may come right off. It's a bit of work but worth it to save some of those nice pieces.

Country: USA | Posts: 6700 Go to Top of Page


Premium Member

Posted - 03/09/2011 :  09:02:21 AM  Show Profile  Visit closetguy's Homepage  Reply with Quote
I'd try Dave's recommendation. In your instance, the diagonal wood on the back is not moving while the vertical grained wood on the front has grown, become wider. A heavier timber on the top and bottom, try something other than balsa, may have enough strength to help flatten the door. Just remember the wood in front is now bigger than when you first glued everything together. Personally, I'd build a new door and laminate 3 pieces together. The center, hidden piece, perpendicular to the front piece. And than add the front detail rails and center stile. I'd also go to basswood over balsa. Its a tighter grained wood and will tend to move less.
Oil based stain is better than water based and Alcohol is better than oil. It drys fast and does not leave moister in the wood to cause the grain swell. Or, just make the front from individual board as well as the diagonal back.
Mike M

Country: USA | Posts: 1855 Go to Top of Page

Martin Welberg

Posted - 03/09/2011 :  12:26:39 PM  Show Profile  Visit Martin Welberg's Homepage  Reply with Quote
I'll second Mikes advice, take a look at thin triplex, it's what the name says 3 thin layers...

Country: Netherlands | Posts: 6727 Go to Top of Page
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