How do you make professional fillets?

I have tried a few things in the past and none have worked very well. any suggestions?


Leo Malkin
Currently working on a wild man eagle claw

What have you tried that has not worked and what was the size of the airframe?

Maybe it's process rather than the materials.

That said, one method may work well for modrocs, whereas other methods may work better for HPRs.

Greg

GregGleason said:

What have you tried that has not worked and what was the size of the airframe?

Maybe it's process rather than the materials.

That said, one method may work well for modrocs, whereas other methods may work better for HPRs.

Greg

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Greg is correct we need more info to give you good sound answers.

Technically, you'd pay someone to make professional fillets, right? :wink:

For high performance HPR, I've used West Systems (or your favorite epoxy system) mixed with silica and/or microballoons to a mayonnaise consistency. Then I use a tongue depressor to shape the fillet and clean up any excess. I've also used a popsicle stick and Titebond No Run, No Drip for cardboard/ply MPR/HPR rockets.

I use PVC for my fillets and they always come out amazing. What are you using now to make them??

ChrisAttebery said:

Technically, you'd pay someone to make professional fillets, right? :wink:

For high performance HPR, I've used West Systems (or your favorite epoxy system) mixed with silica and/or microballoons to a mayonnaise consistency. Then I use a tongue depressor to shape the fillet and clean up any excess. I've also used a popsicle stick and Titebond No Run, No Drip for cardboard/ply MPR/HPR rockets.

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I got you beat. I thicken mine to a peanut butter consistency. Works like a charm. No running AT ALL.

Mask well with blue tape. Proline 4500, wait for it to thicken a bit before laying it in. Smooth with a short piece of PVC pipe dipped in alcohol. Wait a couple minutes, carefully pull the tape. Wait 4-6 hours and rotate.


As others have asked, what are you doing?

ChrisAttebery said:

Technically, you'd pay someone to make professional fillets, right? :wink:

For high performance HPR, I've used West Systems (or your favorite epoxy system) mixed with silica and/or microballoons to a mayonnaise consistency. Then I use a tongue depressor to shape the fillet and clean up any excess. I've also used a popsicle stick and Titebond No Run, No Drip for cardboard/ply MPR/HPR rockets.

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I just use mayonnaise instead. It's already the correct consistency and whatever I have left over I make a ham sandwich

For all my FB rockets :

Aeropoxy 6209 + 1/4" Fiberglass CHOPPED STRAND if no other layer over it

or Aeropoxy pr2032 + 1/4" Fiberglass CHOPPED STRAND if I make fins to fins layer over it.

Thick fillets of pure epoxy break to easy, colloidal filler or not.

I'm going to try epoxy clay for my current build. You can check my Vertical Assault build thread if you want to see how it turns out.

I have used a plastic spoon in the past for shaping, but I'm guessing that won't work for clay. I like the PVC idea!

Bat-mite said:

I'm going to try epoxy clay for my current build. You can check my Vertical Assault build thread if you want to see how it turns out.

I have used a plastic spoon in the past for shaping, but I'm guessing that won't work for clay. I like the PVC idea!

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Seriously on the clay the best thing would be a dowel dipping in alcohol or use your finger. I tape of the fillet and pull the tape off once I get it shape. The ridges you want to smooth out with your finger and blend it into the fin and body tube or else you will have a lot sanding and filing to do. Clay works great and gives you a lot of work time. It hardens like concrete and last a long time.

To shape I use needle files to knock down most of the unevenness and then come back over with a wood dowel wrapped with sand paper. After them smooth the final phase would be to use some putty to fill the low spots and sand again then primer. Apogee has a video on this. I think it's explained on the L2 project Tim was working on.

I've used West systems, Proline and Aeropoxy, with success, but for external fillets, I've started to use Rocketpoxy which is like an epoxy paste. It is a 1 to 1 mix and I usually let it stand for about 15 minutes and then apply the epoxy and smooth the fillets with alcohol, using similiar techniques posted here. I got my rocketpoxy from Wildman rocketry, I noticed Apogee also carries it.

I show an easy way in my Certify Level 1 video, at 23:25. Note that as others have said, it depends on using bonding epoxy (thick) rather than laminating epoxy.

I agree with Diswolf about Proline. I do one thing different- I level my rocket on both axis's- GRAVITY levels perfectly. Pull tape while wet. Keep bubbles out of epoxy and gravity makes them perfect. https://www.rocketryforum.com/album.php?albumid=567 for pictures

Ok, this may cause some to laugh, but I was having issues with previous rockets having brittle fillets and they would either separate from the body tube or crack. I was scratch building 4" dia. test bed generic rocket, about 3 lbs., which would use 38MM mount and likely a I-161 motor or larger. It would be about average on speed etc.. I was trying to figure out something to make fillets with, that would adhere well, be paint-able, be a little bit flexible, have easy application and clean up and be cheap. I looked on my pegboard and saw a new tube of DAP, Dynaflex 2320 caulking. It met all of my criteria. I made a test piece out of an old piece of body tube and 1/4" glassed plywood. It was super easy to make a perfect fillet, cleaned up with water. I used filler primer and yellow from a rattle can from Rustoleum.

I have flown that rocket many, many times, with H-I motors and the fillets look like new. They turned out better than anything else I have tried.

Of course, this was a quick throw together rocket. But since then I have used this method several times on "prettier" rockets that flew faster and used better paint; so far, so good!! Anyway, just thought I'd mention an out of the box idea...Cheers!!