Bruiser
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- Joined
- Jun 7, 2018
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I am working on a design now and am scratching my head a little. Here's the fin shape
The fin is thirteen inches long. The radius of the curve at the front is .75 inch. The width is 2.625 at the back. This a BT-80 rocket, 29mm powered. The fins will be 1/8th" thick. I haven't decided if I want to use balsa (lighter) or ply (tough but heavier).
If I were to use balsa and cut it to align with the "rake" of the fin, the very front edge radius would be end grain which is generally not good. It's just the 3/4" radius but 29mm...
Then I thought maybe I could make the fin two piece where the front inch or two would have the grain going away from the body. It's be more work with a butt-glue joint. I wonder if that is needed?
With ply fins OR is projecting 3.5 ounces of nose weight (with a G64). With bare balsa it shows I could lose an ounce. Not sure how to account for the papering.
What do you all think?
-Bob
The fin is thirteen inches long. The radius of the curve at the front is .75 inch. The width is 2.625 at the back. This a BT-80 rocket, 29mm powered. The fins will be 1/8th" thick. I haven't decided if I want to use balsa (lighter) or ply (tough but heavier).
If I were to use balsa and cut it to align with the "rake" of the fin, the very front edge radius would be end grain which is generally not good. It's just the 3/4" radius but 29mm...
Then I thought maybe I could make the fin two piece where the front inch or two would have the grain going away from the body. It's be more work with a butt-glue joint. I wonder if that is needed?
With ply fins OR is projecting 3.5 ounces of nose weight (with a G64). With bare balsa it shows I could lose an ounce. Not sure how to account for the papering.
What do you all think?
-Bob