The DogSh*t Fillets Thread. A step up from Gravel Fillets.

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Rocketpoxy on again.

fmhDdw8.jpg
 
Looking much better. Another general rule is, if you don't want glue in a spot, put tape there. For example, the spots between the fins should have some tape. You can fix it by sanding away the glue afterwards, but it is much less work to put some tape down beforehand.
 
I'll check that when it's dry. That's why I wasn't going to use a big massive fillet radius like a 1" pipe because it would legit be unstable and crash. This Wildman RB-05A Sport really only has enough packing volume for a 24" drogue, nomex, kelvar 12.5 ft 3/16", and a RMS 38/480. It'll be a stretch to AV bay it. You might be able to shoe horn a 38/600 into it. Packing is kind of a nightmare. You can sim a 38/720 or a 38/600 I don't see how practical realistically that is. 720 almost takes up the entire tube space. The stoutest motor I got is an I1299N-P from that time Utah at a student launch when I originally attempted cert then had the chute pop while packing it due to inexperience with timers. Tested it before flight then bang when showing it to an RSO and connecting it on packing. Then flew it on an I300T at Vast shock cord snap, had an .ORK for it that needs updating, and now planning a H219T-14A but you are correct I'll need to check stability and rail velocity exit again. It was 2.04 stability cal before the fillets were added. Even an I motor and we're talking it wants to break 5k feet. With any of the 38/480 loads it was around 1.7 stability. I'll need to recheck everything.

I CAD modelled a longer SAAB BAMSE for a 720 casing when that time comes. And I've got a Wildman Sandhawk in pieces ready to build that might take a loki 38-1200. (It would probably make a lot better rocket to cert on but **** it. I'm getting practice in.) I've got a TeleGPS too.

This part was a pound dry before dinking with it. I used Cotronics 4700 on the CR and tube to keep mass down. I did not fill it for that reason. The nosecone is nearly double the mass for CG reasons since it had negative stability without any lead counterweight.
 
Pulled the tape off at 1 hour 51 min into epoxy curing and while it's tacky when the ridges rise, you just take your finger and lightly press it then the ridges comform to tube again.

Anyways...
4ycxeqB.jpg
 
I feel way more confident in the structural integrity.

The actual tube whole thing filleted is around 475 grams. I subtracted the fin sets that were overrided at 142 g for forward set and 21.6 grams for aft which is 311.4 grams. The tube mass was 168 grams bare. So I have a fillet mass of 143.4 grams which isn't necessarily "nothing".
For now I have approximated the fillet mass as a long rod from front leading edge of fin to aft fin set trailing edge at 143.4g. I had measured everything from the kit before assembly. 61 Ft per second off rail now updated on a H219T.

With a H219T-14 it sits at 1.75 Stability Cal.
 
Last edited:
Looks much better Andrew, plenty strong now for sure. More rockets will only improve your skills in fillets too!
 
Definitely an improvement on the second set, practice is usually the answer, if not ask the TRF builders, many of us have special areas of interest and many (if not very technical) explanations and techniques to get things done. As for recovery packing in a smaller rocket if there is room the shock cord can be packed around the motor casing if it sticks up into the recovery bay (usually) just make sure and put it in there in such a way it will pull out easily. Small payload bays require some serious thoughts on thin mill nylon chutes vs. standard weight nylon, thin kevlar vs tubular nylon, wadding vs. nomex ( I have been known to use wadding on a few MPR and HPR rockets instead of nomex).
 
Looking much better! It's going to be hard to get perfect fillets when you are going over existing ones. Looks to me like you are using way to much epoxy for the fillets. The tape should be basically void of epoxy after you strike the fillets off. That would eliminate the ridges. I wouldn't suggest this to anybody as I never became sensitized to epoxy yet, but I just use my finger to strike off the fillets. I don't tape anything. I puddle the epoxy on using a wooden Kooler stick to the approximate size I want, and then a swipe of the finger and done. Different pressure = different size fillet. Here's a couple pics. already painted though,and no it's not a dog sh*t paint job, metallic, looks like it's pitted.

DSCF0003.JPGDSCF0002.JPG
 
I have never understood why everyone uses tape when doing fillets. I've never used tape; it's unnecessary and would just create a ridge which I would then have to sand down.

For example, here are the fillets on my DX3 done with no tape . . .

25975959677_29199457ae_o.jpg
 
How are you even applying or with what tool? Someone really practiced like you can it off with very few noticeable to human eye errors, but that kind of attention is a unique trait.
 
Andrew looking much better. Now just fill in the few voids with a filler and your good to go. I would not wait 1.5 hours to pull the tape.
 
The second set is looking pretty good. A coarse flat file and round file are really good tools for taking off epoxy where you didn't want it. Jus tstop when you see red dust, because that's when you're getting into your tube.

I also don't use tape much, but I am careful of how much epoxy I put on, clean off the excess right away, and plan to spend some time sanding. The Rocketpoxy stuff can make gorgeous fillets, but I'm a sucker for where I started in boats--laminating epoxy and wood flour mixed to creamy peanut butter consistency. It's not as sticky as the Rocketpoxy so it doesn't get everywhere as easily and it's easier to clean up when you get it somewhere you don't want it to be. I also plan to put a thin layer of epoxy filled with microballoons for the final coat because that sands like a dream. If you use tape, the sooner you pull it, the more time is has for the ridges to settle.

The best coaches/leaders are relentlessly positive. If they are giving negative feedback, it's in the form of "what you can do better next time is..." I am not that person, but I try to be. I'm glad you're here asking positive questions about how to improve your skills.
 
All of us can also nicely fillet a bathtub or kitchen sink!

(or was it the numerous bathtubs & sinks that got us to make sweet fin fillets?!)

either way, it's a transferable skill!
 
How are you even applying or with what tool? Someone really practiced like you can it off with very few noticeable to human eye errors, but that kind of attention is a unique trait.

I spread on Aeropoxy 6209 and then just level it with my finger, in a nitrile glove wetted with alcohol.

If it doesn't look good enough after the first pass I add a second thin coat of Bob Smith 15 minute epoxy, which starts out pretty thin so it levels out better than the Aeropoxy. If it's still not perfect then I use Bondo spot putty as needed. Then finish up by sanding with 220 grit to shape it.
 
I have never understood why everyone uses tape when doing fillets.

It depends on how you apply the tape. I use carbon paper to mark off the lines then when I apply the tape I apply it on the outer edge. This way the purpose of the tape is simply to keep the BT clean and when you pull the tape off you're not pulling off the edge of the fillet.
 
It depends on how you apply the tape. I use carbon paper to mark off the lines then when I apply the tape I apply it on the outer edge. This way the purpose of the tape is simply to keep the BT clean and when you pull the tape off you're not pulling off the edge of the fillet.

its likely I have too much epoxy down, but I put the tape lower on the line to catch the ridge of excess epoxy that builds when I pull the pipe/spoon/Depressor. If I was neater I could move the tape up, but I don’t see myself being as clean as Nathan to not need tape. I’m going to blame the rocket fairies that live in his garage.
 
Back
Top