Fin Design and construction using
G10 Fiberglass Stock

G10 fins finish up easily, are strong, and allow for complex shapes

Close up of the Evil Grimace Fin Can

Fin Design and Construction

This design tip came about form my construction of the Evil Grimace.
I did a lcost benefit analysis and decided to make my fins from .062 G10 Glass. I chose .062 thick after doing a little research about similar sized rocket kits, and figured this would be an appropriate thickness. I orderd my G10 from MacMaster-Carr. I got a 24"X 24" sheet for $22, including shipping. I split the sheet with my buddy Dave, so I was able to make the three fins with plenty of stock left over for future projects.

Transferring the Fin Design to the Stock.
Hand to eye coordnation has always been a problem for me, so I transfered my fin patterns to the sheet by making a template on my old Macintosh. I laid out the fins on the template to get the maximum yield from the sheet. I accomplished that by enmeshing the fins as much as possible. I worked Dave's fins into the template as well, so we could cut all the fins at once. The template printed out on six sheets of ledger paper, So I added contrasting color alighment marks to the to the printout to help align the template onto the material.

Cutting the fins

My first thought was to cut the material on my Dad's band saw, but his does not accomodate a metal cutting blade, so instead, dave and I used his Dewalt hand held heavy duty ig saw, this saw has a ballbearing guide to support the blade. I don't think I would have wanted to tackle the job with my old Craftsman.
We started of using a thing wood cutting blade, which we discovered made a fine cut in the G10. We also discovered it wore out after cutting perhaps 24 linear inches in the G10, enough cut for maybe one and a half fins. After we wore those out, we switched to a thick metal cutting blade. This one cut the G10 like butter, but the blade was too wide and thick for any turns in the material. We decided to use this blade for straight cuts, cause it was easier to keep on straight path, and didn't wear. You will still need a thin blade for curved cuts.

After cutting, the fins look like so.

An additional cut was needed tin the center of fin and the. Too long a fin slot would have weakened the tube excessivley. The front of and back of the fin interlocked with the centering rings.

Cutting Fin Slots

This was accomplished with my dremel tool I put two cut off blades into the mandrel to ge the correct length of slot. The seperation line between the two discs made it easy to keep the tool on center and get a straight groove. Cutting tube slots free hand like this is easier than it looks, and the smell offresh- ground epoxy resin is strangely exilarating.
Fin Mounting
Fin mounting was facililiated by using a simple fin jig
Fin Fillets

Great fin fillets can be achieved with this method

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