Balsa vs. Papered Balsa vs. Basswood

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BigMacDaddy

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Probably an age-old debate but I am really surprised that more people do not use basswood plywood given the cost / challenge of finding balsa.

Has anyone done a weight comparison of 2mm balsa vs. papered 2mm balsa vs. 1.5mm basswood plywood vs. 2mm basswood? I bet that basswood is negligibly heavier than papered balsa (especially if you compare to the thinner basswood that is similar strength to thicker balsa - basswood might even win out on weight here). I am not going for any altitude records or anything so maybe I am not appreciating the impact of small differences in weight.

Basswood is so much more durable, you do not need to worry about direction of grain as much, can make more complex fin shapes that will not snap, can make massive fins/wings out of a single piece of basswood, etc... On the negative side, basswood is definitely harder to cut (I forget how easy it is to cut balsa till I get back to a kit). Also, I am by no means great at finishing / painting, but it seems that the tighter grain of the basswood with a bit of sanding makes it really similar to papered fins for finishing (especially if you are using a filler-primer as a first coat).

The determining factor for me is that I can get 200mmx300mm sheets of 2mm basswood for like $1 a sheet (20 sheet order from Amazon).

I would not both to upgrade a kit and swap out all the balsa for basswood, but in scratch-building I am using all 2mm basswood (1.5mm is more expensive for some reason).
 

DigBaddy

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I was at a home improvement store yesterday, rhymes with Hynards, to pick up our new home entry door. There was no balsa in the hobby wood section. Plenty of birch ply and basswood.

I used basswood on my BT-60 scaled Big Daddy and it has survived a few chute-less falls fine. Will rip the fin off the tube before a fin would break. Will use more where I can.
 

BigMacDaddy

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The Amazon listings change all the times -- when I click back on my past links they are no longer the same exact product specifications... Need to look around on Amazon a little but 2mm or 1.5mm 200mmx300mm sheets (sometimes in standard measurements so like 8"x12"x1/16" or 3/32") are out there for less than $1 per sheet (free shipping if you order $25).
 

waltr

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I only use balsa on gliders to keep weight minimum.
For LPRs I do use Basswood or lite plywood for fins.
Both work very well without too much weight penalty.
 

Mike Haberer

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I have one two stager that called for 3/32" balsa on the booster and 1/32" basswood on the sustainer. My first use of basswood, I was impressed. The 1/32" is plenty strong for the design. I have to paper the 3/32" balsa lest the fins disintegrate on a hard landing. Once my stock of balsa is gone I'll likely switch completely to basswood for LPR builds, going 1/32" thinner than the balsa that's would normally be used.
 

neil_w

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I like basswood in some situations but in my experience even a heavy coat of filler/primer did not yield the perfect smoothness I get from papered balsa.

Also, and this is totally subjective, basswood doesn't feel that strong to me parallel to the grain (whereas it seems very strong perpendicular to the grain). I'm not convinced that you can be lax with grain direction.
 

BigMacDaddy

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I like basswood in some situations but in my experience even a heavy coat of filler/primer did not yield the perfect smoothness I get from papered balsa.

Also, and this is totally subjective, basswood doesn't feel that strong to me parallel to the grain (whereas it seems very strong perpendicular to the grain). I'm not convinced that you can be lax with grain direction.
I may not be very good at papering fins...

I do feel that the middle layer of basswood is not exactly the same as the outer layers - not solid wood maybe?
 

heada

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Basswood (aka Linden, aka German Linden, aka stinkberry tree) is denser than balsa but also stronger. I'm not sure which has a higher strength per mass ratio but they should be close.

1/8" balsa that is papered vs 1/8" basswood that is papered, the balsa will be lighter but the basswood will be stronger. Can't compare solid balsa to basswood ply or different thicknesses, thats not a good comparison.
 

Back_at_it

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I've never measured the weight of Basswood vs Balsa but I can tell you that I have gone to basswood or plywood on all of my scratch build and upscales. I'm not concerned with weight as I can always put a bigger motor in it and I'm finding that I'm upsizing my motor mounts to the next largest size anyway.
 

BigMacDaddy

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1/8" balsa that is papered vs 1/8" basswood that is papered, the balsa will be lighter but the basswood will be stronger. Can't compare solid balsa to basswood ply or different thicknesses, thats not a good comparison.
My point was to compare effort to outcomes (weight, strength, looks- EDIT: Also cost & availability) so actually I was proposing that we should compare papered balsa against unpapered basswood as well as unpapered basswood that is thinner but comparable strength (to see weight differential).

I am not sure that I am papering as well as most experienced folks so not sure I can do that part but I could cut 1.5 and 2mm basswood fins in a standard size (e.g., use a common fin like a Big Bertha fin as a common size metric) and weigh them. Not sure how to compare strength -- maybe weight on fin spanning a certain distance to look at flex or break weight?

Experienced folks may have tried all these options but many inexperienced folks may not realize that basswood is a good option for many models (or maybe this is not as much of an issue since most people are building kits and make using whatever materials comes in the kit).
 
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Alan15578

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My point was to compare effort to outcomes (weight, strength, looks) so actually I was proposing that we should compare papered balsa against unpapered basswood as well as unpapered basswood that is thinner but comparable strength (to see weight differential).

I am not sure that I am papering as well as most experienced folks so not sure I can do that part but I could cut 1.5 and 2mm basswood fins in a standard size (e.g., use a common fin like a Big Bertha fin as a common size metric) and weigh them. Not sure how to compare strength -- maybe weight on fin spanning a certain distance to look at flex or break weight?

Experienced folks may have tried all these options but many inexperienced folks may not realize that basswood is a good option for many models (or maybe this is not as much of an issue since most people are building kits and make using whatever materials comes in the kit).
It is not hard to find data on structural woods. Sitka Spruce has the highest strength to weight ratio of any wood, and it is commonly used in wing spars and stick fuselages. However, recently it has become harder to find at the LHS, and it is not good in thin sections. Balsa of course is the lightest with good strength to weight ratios. Higher density balsa also has higher strength to weight ratio. Basswood is not as good structurally, but it has a very uniform grain that makes it a favorite with other hobbiests, and thus is easy to find at your LHS. I prefer aircraft plywood to basswood in most rocketry applications, The only time I use basswood for fins is in scale modeling when I want replicate a scale airfoil on the fins.

Certainly papering ( and tissuing, fiber-glassing, etc.) muddies the data comparison, but testing for a specific fin or other application trumps bulk structural data.
 
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aerostadt

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I have used papered 1/8" balsa for the large wings on my rocket gliders for the Double Shuttle and the 4x OT half-shell gliders and it is has worked, although it is tedious to make. I have made one short-cut, but it still takes effort. The material is strong and light enough.
 

icyclops

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Ha, with a can of 3M super 77 spray adhesive and .10 or .20 sheet styrene (Evergreen) you can make those Balsa fins just a strong as BassWood . Basswood is OK if not worried about weight restrictions…but I paper all my wood fins anyway as the painted finish is so much nicer and I hate to do all that sanding... :)
 

BigMacDaddy

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Ha, with a can of 3M super 77 spray adhesive and .10 or .20 sheet styrene (Evergreen) you can make those Balsa fins just a strong as BassWood . Basswood is OK if not worried about weight restrictions…but I paper all my wood fins anyway as the painted finish is so much nicer and I hate to do all that sanding... :)
But I would think that a balsa fin with two layers (either side) of styrene glued to it would be much heavier than basswood...
 

BigMacDaddy

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I think part of the difference in perspective is different goals and different size rockets - I should have clarified I am doing LPR with relatively small rockets (BT80 is largest I have done but mostly doing BT60 and smaller).

Also for me cost is a big factor and getting a 200x300x2mm sheet of basswood for around $.75 is nice. Also I should note that my basswood is some type of plywood (3 layers) - is that always the way it is?
 
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heada

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I think part of the difference in perspective is different goals and different size rockets - I should have clarified I am doing LPR with relatively small rockets (BT80 is largest I have done but mostly doing BT60 and smaller).

Also for me cost is a big factor and getting a 200x300x2mm sheet of basswood for around $.75 is nice. Also I should note that my basswood is some type of plywood (3 layers) - is that always the way it is?
What you're describing is lite-ply. Plywood with layers that are about 1/32" The top veneers can be anything so basswood is an option but normally its birch.

Solid basswood in sheets has a look of dense balsa with little to no grain. Except where extreme mass control is a concern like gliders, you can swap balsa with solid basswood and notice no difference
 

BigMacDaddy

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What you're describing is lite-ply. Plywood with layers that are about 1/32" The top veneers can be anything so basswood is an option but normally its birch.

Solid basswood in sheets has a look of dense balsa with little to no grain. Except where extreme mass control is a concern like gliders, you can swap balsa with solid basswood and notice no difference
Thanks for clarifying - I assumed that "basswood" was always a plywood since this was what I had received when I ordered basswood online from a couple of vendors (1.5mm and 2mm versions) and it seemed like all the "basswood" on amazon was a plywood ...

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BEC

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I have never done papered fins, so I can't address the weight or strength of them. But here is a little data about relative weights:

These three sheets are each 2 1/8 x 7 5/8 inches. The basswood and balsa sheets are 3/32 inch thick. The plywood one (bottom in the picture, never mind it also says bass on it) is 2mm thick. The balsa sheet (middle) weighs 0.23 ounce. The basswood sheet (top) weights 0.39 ounce and the poplar ply sheet (bottom) weighs 0.37 ounce. The balsa is about 16 lb/cu. ft. density, so fairly dense balsa (at least from a model builder's perspective).

IMG_5118.jpg


(edit: deleted redundant copy of picture)
 
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BigMacDaddy

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I have never done papered fins, so I can't address the weight or strength of them. But here is a little data about relative weights:

These three sheets are each 2 1/8 x 7 5/8 inches. The basswood and balsa sheets are 3/32 inch thick. The plywood one (bottom in the picture, never mind it also says bass on it) is 2mm thick. The balsa sheet (middle) weighs 0.23 ounce. The basswood sheet (top) weights 0.39 ounce and the poplar ply sheet (bottom) weighs 0.37 ounce. The balsa is about 16 lb/cu. ft. density, so fairly dense balsa (at least from a model builder's perspective).

View attachment 486264View attachment 486264
This is really great information -- thank you so much for weighing / sharing. Never would have guessed that someone had exactly comparable fin-sheets on hand to compare like that...
 

BEC

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I was working with James Cramton at Rocketry Works on those Alpha fins (both the original shape and the current one) and got the sheets to verify them. So it just sort of happened that I had such directly comparable bits to hand.

[thread drift] So, if anyone is looking for laser-cut fins for an Alpha that match the original shape as shown on the SP-25 fin template (and the subsequent die-cut fins), you can get them in 3/32 inch balsa or basswood or 2mm plywood from Rocketry Works. They also have the current shape (which has been the shape in Alpha kits once they began being laser cut in the early 2000s) in all three materials. [/thread drift]
 

boomtube-mk2

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If balsa is getting in such short supply and thus more expensive, why don't the low power rocket kit producers look to replacing balsa with basswood?
Especially if the quality of the available balsa has gone into the crapper.
 

heada

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If balsa is getting in such short supply and thus more expensive, why don't the low power rocket kit producers look to replacing balsa with basswood?
Especially if the quality of the available balsa has gone into the crapper.
weight. Basswood is light but still almost 2 times heavier than balsa. (see post #20 for weights of similar sized sheets, 0.23oz vs 0.39oz)

It has been many years but there was a company called "Scale Kits" and they had a line of ~5 or 6 kits that were...imagine this...scale. I built their SA-2 Guideline. Lots of fins, a nosecone and a transition. Nosecone and transition in balsa but fins were basswood. That rocket wasn't stable and needed more noseweight. It could be that if the fins were balsa rather than basswood, it could have been stable in the stock config.

 

icyclops

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But I would think that a balsa fin with two layers (either side) of styrene glued to it would be much heavier than basswood...
Nope…not at .10 or .20 thickness….about the same weight as some thick paper card stock…..basswood compared is weigh more (pun) :)
 

icyclops

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Thanks for clarifying - I assumed that "basswood" was always a plywood since this was what I had received when I ordered basswood online from a couple of vendors (1.5mm and 2mm versions) and it seemed like all the "basswood" on amazon was a plywood ...

View attachment 486253
I have found that many of the sellers on Amazon label the product wrong…they don’t really know the difference between Basswood and Balsa. Some of the Basswood is actual ply or birch ply, or you can find it in solid too in the thicker sizes…and true Balsa is very hard to find. You need to read the feedback as there is some balsa being properly sold, but you have to really search and you won’t find it in the long sheets like you used to at the hobby/craft stores…it will be in smaller sheets like 4x6 or 3 x 8.
 

BigMacDaddy

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It has been many years but there was a company called "Scale Kits" and they had a line of ~5 or 6 kits that were...imagine this...scale. I built their SA-2 Guideline. Lots of fins, a nosecone and a transition. Nosecone and transition in balsa but fins were basswood. That rocket wasn't stable and needed more noseweight. It could be that if the fins were balsa rather than basswood, it could have been stable in the stock config.
That is a great looking kit -- however, I bet that the sustainer would need nose weight regardless of fin material, those fins are pretty far up on the body...
 

prfesser

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Nope…not at .10 or .20 thickness….about the same weight as some thick paper card stock…..basswood compared is weigh more (pun) :)
I think you mean 0.010" or 0.020". With 0.10" on each side the fin would be about a quarter inch thick or more.
 

boomtube-mk2

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weight. Basswood is light but still almost 2 times heavier than balsa. (see post #20 for weights of similar sized sheets, 0.23oz vs 0.39oz)

It has been many years but there was a company called "Scale Kits" and they had a line of ~5 or 6 kits that were...imagine this...scale. I built their SA-2 Guideline. Lots of fins, a nosecone and a transition. Nosecone and transition in balsa but fins were basswood. That rocket wasn't stable and needed more noseweight. It could be that if the fins were balsa rather than basswood, it could have been stable in the stock config.

But by using Basswood, would you not then be able to use thinner stock than balsa?
Even back a few years I was getting some low power kits whose balsa fins were practically unusable unless they were papered and even then attempting to put an airfoil on the edges was a nightmare, the stuff didn't "Sand" it just fell apart, kind of like sanding burnt toast.
 

BigMacDaddy

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But by using Basswood, would you not then be able to use thinner stock than balsa?
Even back a few years I was getting some low power kits whose balsa fins were practically unusable unless they were papered and even then attempting to put an airfoil on the edges was a nightmare, the stuff didn't "Sand" it just fell apart, kind of like sanding burnt toast.
Agree (on using thinner stock) -- at least with the plywood that I (and Amazon sellers) was referring to as basswood, you could definitely use a 1.5mm fin that would be stronger than a 2mm balsa fin (and likely comparable to a 2mm balsa fin that was papered)...
 
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