T2T

I think there is some confusion in this thread. The broken fins were on his FG ARCAS but he wants to try tip-to-tip on a Blackhawk 38.

timbucktoo said:

I think there is some confusion in this thread. The broken fins were on his FG ARCAS but he wants to try tip-to-tip on a Blackhawk 38.

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precisely

o1d_dude said:

He laid down his fiberglass plies and covered it with a porous peel ply and waxed paper, then weighted down the fins/plies/waxed paper with baggies of sand to provide compression.

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I have a 54mm rocket with no tip to tip and it flies fine up to Mach 2. For smaller rockets, it isn't necessary for normal flight, but my point in posting a method is that it may make the rocket last longer and survive more abuse.

A few years back, I made a jig for doing what we called "bag-O-mortar" at the time. I wasn't very happy with the way the mortar was working, so I tried out bag-O-water. That seemed to work better until the day that the bag broke. That's when I discovered that peel ply alone works pretty well. I use a foam roller when applying it, and one reason for that is that the foam will soak up the extra epoxy as you smooth down the peel ply.

Regarding the sand method, a few calculations show that it might not be particularly effective. If the bulk specific gravity of sand is taken as 1.5, then a column of sand about 22 feet high would be required to provide the same pressure as vacuum bagging (assuming your vacuum is perfect, which isn't really the best approach). So, one or two feet of sand doesn't result in much compression. A breather (or paper towels) is needed if compression is used - otherwise, you're just pushing around the epoxy.

Jim

Anyone buy from here? https://www.fibreglast.com/

Sorry to be the new guy, but what is T2T?

tip to tip - covering fins with carbon fiber for reinforcement on min diameter builds.

I buy from fiberglast fairly regularly. Not the best price on carbon cloth (try soller composites for that), but they have a lot of good products for all types of composite work.

littlemisterbig said:

Anyone buy from here? https://www.fibreglast.com/

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Too expensive I would not recommend it. I have never ordered from them.

If anything Soller Composites and Composite Envisions is my recommended sources.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

wfcook said:

I buy from fiberglast fairly regularly. Not the best price on carbon cloth (try soller composites for that), but they have a lot of good products for all types of composite work.

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I agree here. Fibreglast is sort of like Apogee, the prices are a bit higher but they have great support.

I used them when I was building a race car and had very little composite experience.

Not going to lie. There are a lot of great composite sellers on eBay that sell top notch fabrics for much cheaper then what the sites above list them for.

timbucktoo said:

tip to tip - covering fins with carbon fiber for reinforcement on min diameter builds.

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Thanks! Which tips are the tips referred to? Nose tip to the beginning of the fins, or fin tip to fin tip?

Fin tip to fin tip.

JimJarvis50 said:

Regarding the sand method, a few calculations show that it might not be particularly effective. If the bulk specific gravity of sand is taken as 1.5, then a column of sand about 22 feet high would be required to provide the same pressure as vacuum bagging (assuming your vacuum is perfect, which isn't really the best approach). So, one or two feet of sand doesn't result in much compression. A breather (or paper towels) is needed if compression is used - otherwise, you're just pushing around the epoxy.

Jim

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I would generally agree with this. In the build OD references, I was pretty stingy with the weight of epoxy used in the laminate and I suspect from visual inspection that there was a little excess epoxy up in the peel ply layer and wax paper above, but there probably was not a lot "forced" out from the weight of the sand.

The sand bags "seemed" (I haven't scientifically quantified this) to provide force on the laminate to stay in place while curing to the leather state. When I pulled off the wax paper, I was happy with how the layup followed the contours of the airframe, fillets and fins.

timro said:

The sand bags "seemed" (I haven't scientifically quantified this) to provide force on the laminate to stay in place while curing to the leather state.

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I have vacuum bagged my more recent fin cans, but when I was doing hand layups, I always had problems keeping the carbon and peel ply "down" in the compound curve areas on either end of the fins. I partially solved this by slitting the cloths in those areas. Even so, they still lifted from time to time. A little weight in just those areas probably would have solved the problem.

Jim