Foam Board Fin Template.

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86mustang408w

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Well I got foam board at the Dollar tree(they had white and black and you haveto look and make sure they aren't creased badly) for $1.25, lol!! I didn't have a use for it, but decided to get rid of that old panel wood fin one I had. This was the 2nd try, idk why I went out to the garage but I have my new hobby mat in here(its been a minute since I had one) and in the garage marked it all out and was terribly off. But this time I started out with a 10" square piece, cut and traced it exactly, tape all 4 side so it won't move these boards are 20" so you just cut it in half. Then centered the BT for my build in the middle of the 2 pcs. Traced that, then measured 3 inches out from the tube and 1/8" wide using the degree lines in the mat. Did that one at a time after marking the lines on the mat, I started and marked them all but they moved, but I only had the other 2 marked bot cut yet. Best to do one then another, mock it up constantly, and mark/make lines only as you get to that fin. But my thinking was to double it(and put a bunch of small foam spacers in between the 2 pcs about 2 " thick) at the outermost 4 corners and tape it together. But one reason I chose this over cardboard or plywood today is that its foam, so if you cut it a little tight, this will push back and hold the stuff securely in place, I can pick this up and move it without issue. My last one everything would fall apart if you didn't hold it all. But just left the two pcs taped together. You can get w templates out of this board that size for $1.25, plus the obvious tools. But its better than cardboard for just that it almost holds it in place like glue!! But thats one thing I did on this rainy day...

Check out the video its with no glue at all...
 

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I've made several out of that board but have issues getting really straight cuts. I'm going to get a nearby rocket guy to do a couple out of plywood with his laser cutter
I just used a new Exacto blade. And ruler, and patience. I severely messed the first one up, but I wanted this to be prefect, it darn close, oh and I added a spacer...
 

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I use the PayloadBay.org fin guides glued to the foam board as a guide to cut them exactly right, works every time.

I've been searching for a site. Ill try that out! I used the stuff I printed out from OpenRocket.

That’s what I use too. I print out the guide on a sheet of label paper, then stick that on the foam board, and use it to cut out the guide With a hobby knife.

Here’s the site with the tools. It’s changed location on the Interwebz from where it used to be. https://www.payloadbay.com/page-Tools.html
 
Rhis
That’s what I use too. I print out the guide on a sheet of label paper, then stick that on the foam board, and use it to cut out the guide With a hobby knife.

Here’s the site with the tools. It’s changed location on the Interwebz from where it used to be. https://www.payloadbay.com/page-Tools.html
This foam is 100x better than wood or cardboard, thanks!!
 
That’s what I use too. I print out the guide on a sheet of label paper, then stick that on the foam board, and use it to cut out the guide With a hobby knife.

Here’s the site with the tools. It’s changed location on the Interwebz from where it used to be. https://www.payloadbay.com/page-Tools.html
I also use 3M spray adhesive to attach the guide and just use regular printer paper, the 3M 77 (iirc) doesn't usually wrinkle the paper unless I wrinkle the paper.
 
I just used a new Exacto blade. And ruler, and patience. I severely messed the first one up, but I wanted this to be prefect, it darn close, oh and I added a spacer...

The spacer is a massive improvement, as it leads to the geometry being constrained to keep the fins parallel to the airframe. That is more important than the radial spacing or alignment and a single flat plate doesn't get it done.

This is the concept I'm in the process of building:
https://www.rocketryforum.com/threads/jig-gallery.33976/#post-317815
 
I cannot overstate the importance of using a sharp blade when cutting foamboard. It'll be the difference between a quick and easy cutting job, with nice clean cuts, and a nightmare of frustration and shredded foam. I don't think I've encountered a material that was so sensitive to the quality of the blade.

Always snap off a new blade before cutting (with a straight-edge, of course).
 
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