Where should I buy balsa wood?

[DoomedCarrot984]

Hey Coach Chuck!

Where would you recommend buying balsa? I'm experimenting with new designs including a chinook design, and I want quality balsa wood for them. I have tried ordering on Amazon and other department stores, but it is always basswood, which is harder to laser cut and weighs more. Thanks so much!

[coachchuckaahs]

For Science Olympiad, I usually get my sheets from Specialized Balsa in Colorado. This is full size 3x36 sheets in standard thicknesses (1/32, 1/16, etc). They charge a premium (100%) for grain selection, and a premium (100%) for density selection, so it can get pricey, but its very nice wood. I would strip my own sticks out of sheets. Full premium sheets are in the $12 range.

For Indoor Free Flight, where you may need thicknesses as low as 0.009" with grain and density specified, Indoor Free Flight Supply custom cuts wood. This is highly specialized for indoor free flight. the sheets are $8 each I think, and are 1.5-2" wide (usually 2"), and 18-20" long.

There are some other hobby suppliers, but a lot of them do not grade balsa, you gets what you gets. Sig used to to grain and density selection, but I think they are in the middle of a changover now and don't currently have wood. I have not checked with them for awhile.

Coach Chuck

[jander14indoor]

Personally, I only buy balsa from local sources. Hobby shops, craft shops, etc.
BUT, you have to learn how to be very selective, knowing what to look for and how to find it.

First, know what density you need and what grain type you need (typically called A-grain, B-grain and C-grain, look it up for more detailed explanation).
Second, build a table of balsa sheet size vs thickness vs density vs weight of the sheet. I found a good general rule of thumb. For 3 by 36 inch sheets, a 1/32 sheet weighs in grams about its density in lb/ft3. Simple to do the math for other thickness sheets from there. Example, a 1/32 3X36 sheet weighing 5 gm is close enough to 5 lb/ft3 to not matter. By simple math, a 1/16 sheet weight 10 gm is also 5 lb/ft3. and so on.
Third, when you go to your local store, carry some sort of scale with you. I use a simple postal scale, close enough for a start. Now, sort through the sheets of the size and thickness you need for the sheets that give you the density you want. Then hold the sheet up to the light and reject any sheets not having straight grain. Then examine surface for grain type you need. Finally, assuming you still have a selection to choose from, gently flex the sheets and select the stiffest.
Fourth, buy ONLY those sheets that pass all the above tests.

On some trips I only find one or two sheets, others maybe 5 or six. And I have to space out trips to any given source to allow stock turnover. It takes time to build a significant stock of quality balsa this way, but not crazy amounts of time.
This process will get you good sheets at a fraction of the cost (in terms of money) that buying from Specialized will. But at course at the cost of your TIME. Your choice over which is more valuable.

If you need the really thin stuff, yeah, on-line sources are about your only choice.

Jeff Anderson
Livonia, MI

[coachchuckaahs]

I agree with Jeff about hand selecting yourself if you have that option. We had a good hobby store in Albuquerque, but in more recent years they were unable to get Sig wood, and the wood they did get was very heavy.

Hobby lobby has a stock of wood, but it has been a number of years since I have seen a good sheet (just one) at a HL store, and there is insufficient turnover at most of them to get a new supply to pick through.

We have a local hobby shop in my new town that is part of a national chain. To date (3 years now) I have not found any useable wood in their small selection. Not many modelers (bigger planes, R/C) build anymore, and the balsa sits there.

If you can find a store with some turnover, by all means what Jeff suggests is by far better than ordering from Specialized. I had a lot of old stock that held me for years, but when doing props with as many as 20 students and parents, I could not get enough 1/32 C-grain 5-8# wood to keep up and started ordering it in.

Like Jeff notes, it takes time, but finding that golden nugget is worth it.

Coach Chuck

[DoomedCarrot984]

For Science Olympiad, I usually get my sheets from Specialized Balsa in Colorado. This is full size 3x36 sheets in standard thicknesses (1/32, 1/16, etc). They charge a premium (100%) for grain selection, and a premium (100%) for density selection, so it can get pricey, but its very nice wood. I would strip my own sticks out of sheets. Full premium sheets are in the $12 range.

For Indoor Free Flight, where you may need thicknesses as low as 0.009" with grain and density specified, Indoor Free Flight Supply custom cuts wood. This is highly specialized for indoor free flight. the sheets are $8 each I think, and are 1.5-2" wide (usually 2"), and 18-20" long.

There are some other hobby suppliers, but a lot of them do not grade balsa, you gets what you gets. Sig used to to grain and density selection, but I think they are in the middle of a changover now and don't currently have wood. I have not checked with them for awhile.

Coach Chuck

For Science Olympiad would balsa density or grain make a great difference? For example, what would the difference in flight time be for a FFM-like heli be using no premium vs using premium? If there are specific details like selecting Extra Light Balsa vs Light Balsa or Grade A vs Grade B, and which would you recommend for Scioly? Thanks so much!

[coachchuckaahs]

Generally SO you will want 6-8# wood, but that depends on the application. Generally what you find in craft stores will be in the 10-20# range, though they are generally not graded, and you may find some lightweight sheets on occasion. More likely in a true hobby shop.

For may SO applications grain won't matter too much. But in Flight if you are making props from sheet, you will want C grain.

I use A grain for wet-formed ribs (wet form then slice), but C grain if slicing the ribs from a flat sheet.

For MS it generally does not matter because you have a nearly square cross section. However, bending and buckling stiffness are important, and density will be critical (a high density can make the whole heli very heavy, low density will not be strong enough for 1/8" rubber).

Coach Chuck

[jander14indoor]

If you want to hit a target weight (and you do) you need to know what density you are targeting for each part. And different parts need different density. Hitting minimum mass is critical for longest flight time.

Example, helicopters this year. Even at nationals I saw few right at 4 gm. Many at 4.5 to 5 gm. Since for any given design you only get so much thrust/lift, there is a maximum total mass of your helicopter and rubber. So every gm over the minimum mass is a gm less rubber you can carry. That is a big percentage of your rubber/stored energy/turns. Thus a big hit on time. Planes aren't quite as straight forward as we typically have limited motor mass in SO, but heavier planes will still burn up energy faster to keep them up, thus killing time.

For example, the TOP spar on helicopter and front spar on planes takes the most abuse. You need stronger wood there. Often I use 10-12 lb/ft3 wood for main spars. Notice, for many kits today, it is these spars that are replaced with carbon fiber for the needed strength. Other spars take less abuse and can use less dense balsa as long as they are stiff enough. For balance on planes, the tail spars in particular need to be light, so again lower density. Whereas the ribs need little strength and you can save weight by using lower density (weaker) wood there. Motor sticks need to be strong enough to resist a wound motor, but how they are designed can drive very different density requirements.

So, yes, balsa density is critical for top times. And not unimportant for good times.