How best to remove a cracked epoxy fillet?

Hi troops-

I've got a cracked fillet on my Intimidator 4. It's a large fat fillet; made with West 105/205. Cracked all the way along its' length - gonna have to remove it and replace it. But how to remove a big honkin' fillet like this? Grind it? Chip it away? Heat it? Inquiring minds want to know :roll:

(it's always something, right? :lol: )

A Dremel grinding bit will go through it nicely.

Pat_B said:

A Dremel grinding bit will go through it nicely.

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+1 dont go to fast its easy to take off and harder filling in the hole in the body tube when the dremel slips

Don't

Use a Dremel tool as noted (I like to use the spherical cutter) to sculpt a wider crack. You actually benefit from making it rough and kind of ugly. Then fill the gap in with a filled epoxy - I use milled glass. Shape, sand, and paint.


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I found that West with silica could be brittle and had to remove some fillets. Dremel with cutting wheel and sanding drum was the ticket after chipping out anything that would pop out easily. New Rocketpoxy fillets turned out much better.

Doug

H_Rocket said:

Don't

Use a Dremal as noted (I like to use the spherical cutter) to sculpt a wider crack. You actually benefit from making it rough and kind of ugly. Then fill the gap in with a filled epoxy - I use milled glass. Shape, sand, and paint.


Sent from my iPad using Rocketry Forum

Click to expand...

Old gunsmiths trick, when you widen the crack with the Dremel try and under cut the edges a bit and use a small drill bit (under 1/16 inch) to punch small holes on the interior of the cut out area, just to give the repair epoxy more "bite"

dcbertelsen said:

I found that West with silica could be brittle and had to remove some fillets

Click to expand...

Yeah. This rocket was built by me a long time ago; I hadn't yet discovered Proline and RocketPoxy. I'll use one of them for the fix here.

I have a Dremel MultiMax tool, I might give it a whirl and see how well it deals with the removal task.

https://www.dremel.com/en-us/Tools/Pages/CategoryProducts.aspx?catid=2094

rharshberger said:

Old gunsmiths trick, when you widen the crack with the Dremel try and under cut the edges a bit and use a small drill bit (under 1/16 inch) to punch small holes on the interior of the cut out area, just to give the repair epoxy more "bite"

Click to expand...

Yeah, that's why I use the round cutter. It naturally undercuts. Never thought of drilling holes.

cvanc said:

Yeah. This rocket was built by me a long time ago; I hadn't yet discovered Proline and RocketPoxy. I'll use one of them for the fix here.

I have a Dremel MultiMax tool, I might give it a whirl and see how well it deals with the removal task.

https://www.dremel.com/en-us/Tools/Pages/CategoryProducts.aspx?catid=2094

Click to expand...

I have almost every Dremel tool made and that is one I just cannot find a use for in rocketry. Lord knows I have tried though.

H_Rocket said:

I have almost every Dremel tool made and that is one I just cannot find a use for in rocketry. Lord knows I have tried though.

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LOL now I *have* to try it! I'll let you know how it goes...

Sharp chisel & mallet/hammer. Use the chisel upside down.......bevel edge down, will grab the fillet better and won't damage fin/airframe.
Start on one end and work to the other

I can remove a fillet on large rocket in less than a minute! Both fin & airframe. It will pop off in large sections......wear eye protection as chunks fly at high rate of speed everywhere.

blackjack2564 said:

Sharp chisel & mallet/hammer. Use the chisel upside down.......bevel edge down, will grab the fillet better and won't damage fin/airframe.
Start on one end and work to the other

I can remove a fillet on large rocket in less than a minute! Both fin & airframe. It will pop off in large sections......wear eye protection as chunks fly at high rate of speed everywhere.

Click to expand...

I'm assuming fiberglass fins and tubes, not cardboard and plywood.

Carl, for that airframe I am with CJ.

Personally, I would do different fillets in the repair. Proline or Aeropoxy laminating resin mixed with Kevlar pulp. I like to use a bunch of pulp almost to the point of it being a paste. Work it into the fillet shape and let set. Once set, cover with your favorite epoxy based filler and sand smooth.


Mark Koelsch
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I redid all the fillets on my PR full scale ARCAS. They were Bob Smith 30 min mixed with milled glass.
When I applied new fillets I used Pro-Set 273 fast epoxy.


JD