PDA

View Full Version : foam



peterd51 - n/a
21-Aug-07, 11:50 AM
hi Guys,



yet another query...



there was a box made of foam to hold the fuel tank, but the foam was damaged.



The foam looks like some kind of insulation material, about 1" thick, fairly hard/compacted (not flaky) and some sort of orange tint.



It probably had fine glass fibre and resin laid over it for strength and then it was glued/painted.



I think two of the rudders were made of the same material

with the middle rudder being wood.



Any idea what type of foam it would be and where I could get some please?



Regards

Peter

Ian Brooks - n/a
21-Aug-07, 01:57 PM
Hi



It's probably foam core material, such as Tricast:



http://www.tridentfoams.co.uk/tricast.html (www.tridentfoams.co.uk/tricast.html)



For a non-structural parts, ie rudders etc, the low densities can be used (2 or 2.5 lb/cu ft), which can be bought from CFS:

http://www.cfsnet.co.uk/acatalog/CFS_Catalogue__Polyurethane (www.cfsnet.co.uk/acatalog/CFS_Catalogue__Polyurethane_Foam_Sheet_59.html) _Foam_Sheet_59.html



For structural parts, Tricast 4 would be used. CFS can also supply this to order, but in 4' x 8' sheets, and its not cheap.



Construction is easy; cut the foam to size with a knife, and lay-up a single payer of 200gm/m^2 cloth either side with polyester resin. When cured, roughly glue the panels into the assembly shape using hot melt glue, fill any gaps with micro-balloons mixed with resin, then apply a 2" bandage of 300gm/m^2 CSM with a 3" bandage of cloth over that - all in the same operation.



The construction is varied depending on the use - a layer or two of csm may be applied to either side with cloth on top for structural components, or to resist walking on, etc.



Using this construction, a 1/2" thick panel will be 6 times stronger and 12 times stiffer, weight for weight, than standard GRP.



More info is here:



http://www.boatdesign.net/articles/foam-core/index.htm (www.boatdesign.net/articles/foam-core/index.htm)



Cheers

Ian

jon_curtis - n/a
21-Aug-07, 05:52 PM
hi ian



just to add to your advice, this stuff can be used with polyester resin also!

Ian Brooks - n/a
21-Aug-07, 06:54 PM
Oops... I meant polyester...

Ian

peterd51 - n/a
21-Aug-07, 07:14 PM
Hi,



Thanks...there's a lot of info there.



I'll be reading it over the next couple of days.



Regards

Peter

Derek Sweetman - n/a
23-Aug-07, 07:56 PM
Another link for choosing foam for composite sandwich construction.

http://www.netcomposites.com/education.asp?sequence=48

peterd51 - n/a
24-Aug-07, 12:01 PM
Hi,



thanks for the link.



I've been reading up on various foams, resins, etc, and like everything else it gets very complicated very quickly...



It'd be nice to find a local supplier who can give advice over the counter but it looks like all the local fibre-glass outfits are 'construction' only with no trade counters.



Hopefully the weather will be half-decent this weekend and I can get the bottom half repaired, glass the seams, paint and fit some skids.



I should be able to get that finished by Saturday evening then we can flip it over and I can start replacing the deck on Sunday.



Then it can be painted on Monday and it's a long way towards being finished.



Just the skirt to sort out after that...



Regards

Peter

GaryH - n/a
25-Aug-07, 08:21 AM
i use a mail order company called CFS. they have been very helpfull and willing to advise over the phone. there website is also full of technical info. best of all there prices are some of the lowest on the net.

there at www.cfsnet.co.uk

peterd51 - n/a
25-Aug-07, 01:13 PM
Hi,



yes I found them from an earlier link and bought the resin & tape from them.



About three hours ago I used some resin on the tape around the bottom joints to ensure a seal. I also used some standard CSM to strengthen a couple of parts where the hull had been scuffed.



It's a lot better than the car type of resin/hardener!



I always have trouble getting the right proportions and it goes off in about ten minutes but this stuff being liquid I found I could get the exact measure...



a one litre measuring jug for the catalyst and a medicine measure to add whatever millilitres of hardener to it.



I'd found some of these tin-foil containers like you get from a chinese take-away in a shop uptown, 69p for five, and they're ideal for things like 200ml of catalyst and 4ml or hardener, or cleaning paint-brushes, etc...



Now I'm just going back outside to paint the lower hull...



Regards

Peter

profqwerty - n/a
27-Aug-07, 03:34 PM
gaz: I second CFS. they're grrrrreat!

but yeah, phone them up they're good for help and advice.