Basswood or Balsa?

Howdy Folks,

I'm upscaling an unnamed Estes kit I rarely see and am unsure what to use for fin stock. It is a 2x upscale (BT 80) with a fin span of 5" and a fin root of 4 1/2". The fins are just about square. I'm planning on a fin thickness of 1/8". The fins will be surfaced mounted and utilizing glue rivets. This rocket will be draggy so will not see much altitude or speed so I won't need to use ply. Oh, I'll be using 24mm x 3.75" MMT.

What would be the decision maker in chosing one wood over the other?

Thanks.

Judo said:

Howdy Folks,

I'm upscaling an unnamed Estes kit I rarely see and am unsure what to use for fin stock. It is a 2x upscale (BT 80) with a fin span of 5" and a fin root of 4 1/2". The fins are just about square. I'm planning on a fin thickness of 1/8". The fins will be surfaced mounted and utilizing glue rivets. This rocket will be draggy so will not see much altitude or speed so I won't need to use ply. Oh, I'll be using 24mm x 3.75" MMT.

What would be the decision maker in chosing one wood over the other?

Thanks.

Click to expand...

I would use balsa and paper laminate them. I did this for my upscaled baby bertha (BT80) and has made many flights with no problems.

Personally for something bigger than BT-70, I'd go basswood. It's a bit of a harder wood, and if you're near a H.L. you can pick some up with a 40% off coupon relatively cheap.

I'd use balsa, especially if you aren't going to land on pavement or hard bare ground. Most "fin damage" I've had in the past consisted of the fin staying together and ripping the body tube paper off, glue rivets and all. If you haven't tried paper lamination and want to give it a shot, this would be a good project to try it. If the fins are swept behind the body tube, I'd give TTW a second thought to keep them cracking a fillet or tearing loose from the BT on landing.

BTW, if you are upscaling an Estes rocket that originally had 1/8" fins, think about upscaling fin thickness and using 1/4" balsa. It's still light and it helps with the draggy theme of "Low and Slow" with lots of smoke and fire for up close demo flights. My BT-80 Goblin, Red Max, and Citation Patriot all have 1/4" TTW balsa for this purpose. For extra strength, you could laminate two or three pieces of balsa together and get whatever custom thickness you want as a bonus.

I'd go for balsa, but make sure its a strongish one. provided the 'chute's good enough, then balsa fins will be fine, basswoods strong but heavier, lowering the cg. paper lamination is good, but you could give solar film a try (model aircraft wing covering) its less messy and gives a good finish.
if your upscaling a model, have a look at EMRR's website, the 2008 challenge has a section on up and down scales.

The original kit fins are 3/32". I decided to go with 1/8" balsa with my usual paper lamination. I used a 40% coupon on the last $3.19 piece in the rack. I'm going to pick up a digital caliper at Harbor Freight tomorrow. They have 8" calipers on clearance for about $20. It's way more than I need so I may end up with just the 6". I may need to spend the night at a Holiday End Express.