Things to fix for Hermes 3 Fin Can in GREEN!!
Procedure Overview
Below is the detailed procedure for how the second flight candidate fin can was manufactured. insert more detail
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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. | |
| 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) | ||
Layup preparation | |||
| Laser-cut CF cutouts | |||
| Spray-glue to wax paper | |||
| Sand fillets | |||
| Prep vacuum materials | |||
| Layup | |||
| Wet plies/weight | |||
| Layup | |||
| Put on vacuum bagging | |||
| Vacuuming | |||
| 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 | |||
| Clean up edges | |||
| Static load test | |||
| Design/build jig | |||
| Determine testing loads | |||
| Static load test | |||
| Analyze data | |||
| Post-processing | |||
| Sand fillets/outside | |||
| Outer fillets on low spots | |||
| Paint | |||
| Total manufacturing time |
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- Phenolic Airframe Tubing PT-6.0, 6.007" ID (https://publicmissiles.com/product/airframes) Get a stronger phenolic tube (canvas, instead of cardboard, for example)
- 60-grit sandpaper
- 220-grit sandpaper
- Carbon fiber (HOW MUCH)
- System 3000 epoxy (resin + hardener)
- Layup jig (wooden jig, metal pole, nuts and bolts to secure jig)
- Mylar
- Squeegees
- Popsicle sticks
- Epoxy boats or paper cup (for mixing epoxy)
- Painter's tape
- Scissors
- Ruler
- Acetone and shop towels (to clean up epoxy on squeegees)
- Gloves
- Safety goggles
- Respirator
Procedure:
- Sand inside of tube by hand with 60-grit sandpaper (this took a long time: next time use using a flapper wheel , 60-grit). (attaches to a drill)
- Periodically see it if fits over the motor case. If not, repeat step 1.
- Once it finally fits, sand with 220-grit sandpaper to give it a smoother finish.
- Now it's time for the tube layup. Prepare the layup jig (make sure it's stable, put a pole over it and wrap it with Mylar so that once you start the tube layup, the tube doesn't stick to it)
Carbon fiber is difficult to work with because it snags and frays easily, so make sure whatever surface you're using is completely cleared off. Also make sure that this surface is large enough for the entire piece of carbon fiber, because the fiber will warp if it overhangs.
Length (in) Length + Offset (in) Outer diameter (OD) of tube Circumference of phenolic tube (OD x π) Length of phenolic tube Mark a (INSERT DIMENSIONS) area on the carbon fiber using painter's tape and cut along the tape. It's much easier to cut on tape than cutting the fiber directly, to avoid snags and make sure the dimensions are correct. The dimensions were determined using the table above.
- MIX EPOXX, DO LAYUP
- Let tube cure at room temperature for at least 24 hours
- Sand tube
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