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hcmbanjo

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In response to all the forum questions about Fin Alignment Tools, I decided to produce one of my own.
It was to be part of the initial Odd’l Rockets product line of three kits and three accessories.

The Finwheel Fin Alignment Toolool won’t be making it to the market.

I tried to make it simple and affordable.
The designed it based on the old FSI Fin Alignment Tool. The disadvantage with the FSI product was it only worked with FSI diameter tubing and three finned rockets. With my product, two different tools would be able to align three and four fins models with either 13mm, 18mm and 24mm single engine mounts. The rocket engine mount would be set over engine casings on a central spidle.
It was drawn, then re-drawn too many times on Corel Draw. Supplies were bought and instructions drawn up. Four different sets of prototypes were laser cut using 1/8" plywood. The Finwheel name was inspired by the shape. From above, it’s shaped like a child’s pinwheel toy.

The bulk of LPR kits use 3/32" thick balsa fins. I set up the test tools for the 3/32" thickness. With simple cardstock shims you also could glue on 1/16" thick fins.

The problem occurred with the laser burning. Lasers do draw and burn accurately. But, the laser cut line is always a little wider on the top of the piece than on the bottom. The cut is sort-of a vertical “Wedge” shape with the widest cut at the top tapering to the bottom. On thicker stock the shape of the vertical burn is more apparent.

On my design, the vertical pieces are important. With the Wedge-cut slots, there was too much play with the 90 degree vertical pieces. Granted, the play was minimal but enough to put the fins out of alignment.
An interesting point - the alignment on three fin models looked great! On four fin models (with the fins in a true “X” cruciform) your eyes can pick up the slightest misalignment. The bad alignment on the four fin unit is one reason that stopped production.

I tried to get this thing to work from last May until the product line debut last month.

I take time on my rocket builds and am not satisfied with something being close, especially if it is a product for sale. If I couldn’t get this thing to work, I doubt a inexperienced modeler would be satisfied.

I may have lost time and some money in the project. But it was a great learning experience. It taught me a few things about the laser cut process and more Corel Draw.
Right after I decided not to make the Finwheel, I read that Semroc is coming out with a fin alignment tool. Maybe it’s a good thing I didn’t release it!
Anybody want to buy some magnets?

Finwheel 1.jpg


Finwheel 2.jpg


Finwheel 3.jpg


View attachment Finwheel 4.pdf
 
Watch for the ad in the next Sport Rocketry:

The Odd'l Rockets Finwheel Fin Alignment Tool - available exclusively from JonRocket.com ... not. :)

-- Roger
 
to bad about the laser cutting messing things up that is a really cool idea.

And flipping the sheet over and recutting would probly not average it out and give you a tapered edge (plus increase cost).
 
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