|Fin Design and
G10 Fiberglass Stock
fins finish up easily, are strong, and allow for complex
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
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
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.
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 was facililiated by using a simple fin jig
Great fin fillets
can be achieved with this method