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carlosfandango
12-07-2004, 10:23 PM
I repaired, modified and manufactured GRP panels for Chinook Helicopters when serving in the RAF. Micro Ballum inserts, honeycomb inserts, moulds, fairings, fuel tanks etc etc.

If anyone wants info or advice while attempting such, feel free to PM or Email me.

Karl

Schmleff
12-07-2004, 11:19 PM
I repaired, modified and manufactured GRP panels for Chinook Helicopters when serving in the RAF. Micro Ballum inserts, honeycomb inserts, moulds, fairings, fuel tanks etc etc.

If anyone wants info or advice while attempting such, feel free to PM or Email me.

Karl

Cool. This fourm is turning into what I had hoped it would at c.net, but never made it there.

Glad to see a bunch of composite fabricators here. I have lots of expierence with everything from hand lay ups to vac bagging.

I am going to make Johns intercooler pipes out of glass. Someone had mentioned a good high themp resin a while back but I don't recall what it is. The cooling baffles on my airplane are glass with West Systems epoxy and hold up to 500 degree heat well, but they are under no pressure. Any suggestions?

carlosfandango
12-11-2004, 12:57 AM
I think you need to be looking at temps up to 1400 degrees farenheit, pressure up to 20PSi, have you considered using carbon fibre composite? in my opinion an epoxy resin would become brittle at those temps, an araldite resin should be able to withstand those kinds of temps, I used araldite resins for jet engine cowlings and it held up to the heat pretty well, combined with carbon fibre sheeting, that would be one strong pipe and would look real cool, would probably stand 2 bar, not that it would ever see such pressure.

How would you fabricate this pipe work? that i would be interested to hear. with angles/bends how would you make it a 'one piece' modification, because joining sections together would lose strength where it's needed. unless the pipes where stepped up for elbow pieces like a male and female.

yup, you have my interest with this one Jeff..

Schmleff
12-11-2004, 04:26 AM
I don't really think that we will be looking at temps in that range. Possilby over 200. Why do you think they would get that hot?

As for the design, Have you ever torn down an Allison 250? Right after the axial stages it goes through a centrefugal stage that acts as both a compressor and diffuser. In the 90 degree bend back to the combustion section there are air vanes inside the pressure line. I have a pict I will upload tomorrow.

They will be glass over plastic taped foam. I will split the tubes, install vanes in the elbows and rejoin them. The vane concept may not be entirly necessarry, but I need to do a for a ram air scoop on my airplane anyway, I I need to figure out how to best build that scoop.

If I don't use vanes, I will just melt it all out with acetone. I don't intend it to be pretty, but the finish will be nice anyway. I don't think I will bag them. Just a hand layup of a whole lot of bias cut glass. :squint:

How would you go about it?

carlosfandango
12-11-2004, 06:35 AM
according to my manual, the engine bay can rise to the temps i mentioned.

i thought of making the straight pieces by wrapping your sheet glass cloth around a steel or plastic pipe of the required diameter, obviously covered in silicone spray, then carefully slide the cured grp off the pipe, that way you get a nice smooth piece of pipework. for angles, like youve mentioned, use flexible foam pipe lagging and pull it through or burn it out once cured. to keep the shape, i would probably insert something into the faom lagging, wire or something that is strong enough to keep shape but pliable enough to give and bend when pulling out.

foam lagging http://www.plumbworld.co.uk/images/sanflexinsulation.jpg

slvrblt
12-11-2004, 01:11 PM
I've seen people use cardboard tubes to make carbon fiber tube for large scale rockets, they removed the cardboard by sumerging it in water and waited for the cardboard to sofen. If you could bend some cardboard tubes into the shape that is needed this method might work.

carlosfandango
12-12-2004, 11:46 PM
never thought of that, cool idea..

Schmleff
12-13-2004, 12:58 AM
Its hard to make 90 degree bends no matter how wet the cardboard is :wiggle:

Hooligan
12-13-2004, 02:52 AM
Could you paper mache something up to later wet and remove?

carlosfandango
12-13-2004, 03:14 AM
yes but you'd have to use a quick hardening resin or it would just soak into the paper mache, and card board for that matter.

I think plumbers pipe lagging with a wire insert to keep the shape would be the best idea, it would keep its shape and would pull out easily if well sprayed with silicone before lay up to prevent it bonding. thick household electrical wire, that goes to the fuse box, would be good to keep it at a 90 degree angle and that would also pull through the inside of the lagging.