how to design TTW fins for a SBB

i have 1/8 hobby ply i have the fin pattern but not for a TTW design. is there one out there? i will be using bt80 of course. and bt50 for a 29mm motor.

Your gonna come up a few millimeters shy with that BT-50 if you want use 29mm motors, BT-50=24mm. You can purchase 29mm motor tubing from a variety of sources, I usually buy mine at Balsa Machining Service or hobbylinc.

I recommend that you download Open Rocket free rocket design software. It will let you design the fins including the through the the wall portion and enable you to print a template. Or you can go old school and subtract the OD of your motor tube from the OD of your airframe then divide by two, that will give you the depth of your fin tabs. The length of the tabs will depend on your centering ring placement. Really though Open Rocket has so many other valuble tools you really should get it.

A Super Big Bertha built according to the plans flys great on AeroTech 24mm motors. I would only build a TTW model if your wanting to step up to 29mm and then I'd seriously think about using thicker walled airframe tubing. The landings can be rough on the Estes tubing, this has been my experience.

3boydad said:

i have 1/8 hobby ply i have the fin pattern but not for a TTW design. is there one out there? i will be using bt80 of course. and bt50 for a 29mm motor.

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Your gonna have to rethink using a 29mm motor in a BT-50.

Find the differance between the O.D. of the air frame and the O.D. of the right sized motor tube, divide by 2. Use that number to draw the fin tab onto the drawing of the fin template yourself.

im sorry i have the 29mm tube from semroc was a typo

Here's a quick template I did in Open Rocket.



View attachment sbb_fin_29mm.pdf

qquake2k said:

Here's a quick template I did in Open Rocket.

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that is awesome. man i wish i could design those too. thank you i have it saved in my rocket/template folder

3boydad said:

that is awesome. man i wish i could design those too. thank you i have it saved in my rocket/template folder

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It's easy with Open Rocket. I highly recommend that you download it and start using it. It's free, and will allow you to open Rocksim files, too.

https://openrocket.sourceforge.net/

qquake2k said:

It's easy with Open Rocket. I highly recommend that you download it and start using it. It's free, and will allow you to open Rocksim files, too.

https://openrocket.sourceforge.net/

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i have it. but it's not as easy for me as i don't know what im doing with it.

3boydad said:

i have it. but it's not as easy for me as i don't know what im doing with it.

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I didn't either when I first started using it. But I kept at it until I figured it out. And I'm still learning. I finally figured out how to use the motor database for simulations just this week. Trust me, it's well worth the effort.

3boydad said:

i have it. but it's not as easy for me as i don't know what im doing with it.

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Just start playing with it and in no time you'll be designing rockets and launching them in cyberspace.

This page can help you get started. https://sourceforge.net/apps/mediawiki/openrocket/index.php?title=User's_Guide