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| Design fin can | Approx. Time Required | # People Required | Notes |
|---|---|---|---|
| Fin Design & Manufacturing | 36 hours | The more the merrier. | Manufacturing procedure and detailed breakdown described in "Hermes 2 Fin Design & Manufacturing" |
Design/make jigs | |||
| Root bond jig | 3 | Allow for tolerance so fins fit, but don't make slots too loose. Make sure you have a top plate. | |
| Fillet jig | 3 | Two wooden pieces with a U-shaped slot on which the fin can rests horizontally. Need a larger fillet tool so that the fillets for Hermes 3 are larger | |
Tube preparation | |||
| Sand tube | 2 | Sand inside with flapper wheel so that it fits over the motor case | |
| Tube layup | 6 | 2-4 | Rough up the outside of the tube before layup. |
| Root bond | 1 | 5-minute is ok, but if you have time, use a stronger epoxy. Do not use 5-minute, it's not strong enough!! Make sure the root of the fin is roughed up to improve the bond. | |
| Root fillets | Need 4 sets of fillets but it takes 8 rounds cause you gotta do the ends of each side separately (read below for more detail). You'll have to backtrack from when you want to do the layup to when each fillet has to be done by (can speed up using heat gun) Use System 3000 epoxy and make sure there are NO bubbles (degas the epoxy)! Also consider proline fillet + epoxy fillet to add strength. Make sure the area of the fins where the root fillet is applied is roughed up with sandpaper so the bond with epoxy is stronger! | ||
Layup preparation | |||
| Laser-cut CF cutouts | Be careful not to laser-cut over the taped edges of the carbon fiber squares that you use for the cutouts (the tape will be difficult to remove and fray the fibers). Also, don't spray glue wax paper until after laser cutting because the wax paper might catch fire or start smoldering in the laser cutter. | ||
| Spray-glue to wax paper | |||
| Sand fillets | |||
| Prep vacuum materials | |||
| Layup | |||
| Wet plies/weight | |||
| Layup | |||
| Put on vacuum bagging | |||
| Vacuuming | Watch the gauge on the vacuum pump to make sure it drops to at least ________ Did this overnight | ||
| Oven Cure | |||
| Set up oven/vacuum materials | |||
| Follow epoxy cure cycle | 12 hours | Make your life a lot easier by assigning shifts (i.e. have 3-4 people helping so you don't have to sit in front of the oven the whole time). Even better, find access to an Autoclave so you don't have to adjust the temperature manually. | |
| Remove vacuum materials | This takes a while, but it can be done with patience. Make sure you don't lose track of any of the vacuuming supplies (like the vacuum pump attachment) when you throw out the bagging materials. | ||
| Clean up edges | Did this using a Dremel right after the fin can was taken out of the vacuuming materials so that people don't get hurt on the sharp edges. | ||
| Static load test | |||
| Design/build jig | Make sure jig is rigid enough (we used 80/20, which bent when the fin can was tested in the Instron) | ||
| Determine testing loads | |||
| Static load test | |||
| Analyze data | |||
| Post-processing | |||
| Sand fillets/outside | Don't sand the fillets too much! Instead, smooth by adding Bondo or epoxy to add material instead of taking it away. (see row directly below for more details) | ||
| Outer fillets on low spots | We used Bondo to fill in the low spots for Hermes 2. Consider using something stronger, like epoxy (but keep in mind Bondo is easier to sand. If you're going to use something stronger, account for lots of sanding time) | ||
| Paint | |||
| Total manufacturing time |
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