Fibreglass sandwich construction, core?

[watchtherocks]

I planned to make a sandwich construction, however all the mat and foam you can buy is far too thick for my purposes. I need about a 5 mil core, and there are lots of corners involved. I thought about cutting my own end-grain balsa, but Ive come across something called q-cell, used for surfboard repairs, which is a fibreglass filler. Are there any limitations to using a filler for the core in a sandwich construction? Obviously it's not going to be perfectly flat like mat would be, but its light, cheap, strong, and bonds perfectly. Does anyone have any experience with this?
cheers, tom.

[Guest625101138]

I use Klegecell PVC foam that is supplied in 3mm thick sheets. Normal sheet is 2.5m by 1.1m.
http://www.matweb.com/search/GetMatl...&tn=Klegecell®

I know you can get Corecell down to 6mm. It might go thinner.

I believe q-cell is an epoxy filler. I do not understand how you will achieve a consistent thickness with it. I use about 4:1 of this with epoxy to get a paste. That is going to be a lot heavier than 60kg/Cu.m foam.

Rick W

[Landlubber]

...and why , pray tell, is the purpose of this.

Foam and glass are easily available in different weights and thicknesses, you are obviously building a very small light weight boat, but that does not matter, what is it you wish to build that troubles you so.

[waikikin]

Watchtherocks, have a look at coremat or upicamat, it will give you some extra stiffness, although its pretty resin hungry so not gunna end up so light. All the best from Jeff.

[watchtherocks]

ah, sorry, its for a camera housing, so tiny. Weight isnt too much of a deal, an extra few dozen grams isnt too much of an issue right now, i just want to get it to work. A 4:1 q-cell mix could be pasted on easily to the proper thickness, i had a small trial. I havent tried foam yet, but there are some corners that have to be precise and i dont know if foam would form around them properly.

[Guest625101138]

You can heat form the PVC foam but I doubt that you will want to spend AUD80 on a sheet to use a tiny piece of it.

If it is so tiny and not structural why not use balsa as you originally proposed. It does not even need to be end grain. It is just a filler.

The problem with the filler is that it droops. In your test did you wait for the cured end result or just did an initial test for thickness?

Rick W

[watchtherocks]

I allowed it to cure. I would have to do it in sections, though, to beat droopage. I would prefer not to use balsa as it isnt as solid a filler and becomes waterlogged more easily, something bound to happen here.
The filler can also be sanded to give a perfect surface all around.

[Landlubber]

OK, so now we know what you are making, flat sheet balsa will be quite OK, as Rick says, it is only a filler.

You can glass both sides, it will not get wet at all then, and as a sandwich it will be very strong, and easy to do the job.

[tunnels]

Originally Posted by watchtherocks

I planned to make a sandwich construction, however all the mat and foam you can buy is far too thick for my purposes. I need about a 5 mil core, and there are lots of corners involved. I thought about cutting my own end-grain balsa, but Ive come across something called q-cell, used for surfboard repairs, which is a fibreglass filler. Are there any limitations to using a filler for the core in a sandwich construction? Obviously it's not going to be perfectly flat like mat would be, but its light, cheap, strong, and bonds perfectly. Does anyone have any experience with this?
cheers, tom.

First off what do you want to build ?
Qcells mixed with risin is a totall waste of time and effort and it will crack and fall apart . As long as you are not making a hull Cormatt is what could be better suited to what you want. Its a glass cloth impregnated with Q cells But it is completely floppy and limp when its been wet out with resin untill it goes hard . By its elf it also is brittle and have little to no impact strenght what so ever !!. Core matt comes in thicknesses from 2 mm to 5 mm in thickness!!

[Landlubber]

"its for a camera housing, so tiny"....back on the topic eh.

[tunnels]

When i worked for television i made lens hoods from just flat fibreglass sheet with 3 mm corematt between and cut it to shape when it was hard and epoxyed the corners sand papered etc and sprayed it all inside and out matt black !!
One layer of csm 450 gram inside and out withe the core between and used Vinylester resin and a little black gelcoat to change the color . and to get it smooth inside and out laid it on a sheet of glass with another sheet of glass over the top and pressed fin the centre so the surplus resin and air was quashed to the outside and then left till it went hard .
Ended up making a few ,alsorts of shapes and sizes !

[watchtherocks]

Originally Posted by tunnels

Qcells mixed with risin is a totall waste of time and effort and it will crack and fall apart.

I cant imagine a 5 mil filler sandwiched between fibreglass falling apart, and even if it does it's got nowhere to go. I initially just wanted something there to seperate the fibreglass, but with this I can also shape it exactly around edges and buttons/lens port. Products such as corematt may be better, but for the effort that its gonna take I might as well give the filler a shot. I'll get back to you with how it goes. Where is a good supplier of core matts? I've tried FGI and Martinis, and a good few boat supply stores.

[Landlubber]

...just go to any plastic boatbuilder, he will give you all you are going to need...

[tunnels]

Originally Posted by watchtherocks

I cant imagine a 5 mil filler sandwiched between fibreglass falling apart, and even if it does it's got nowhere to go. I initially just wanted something there to seperate the fibreglass, but with this I can also shape it exactly around edges and buttons/lens port. Products such as corematt may be better, but for the effort that its gonna take I might as well give the filler a shot. I'll get back to you with how it goes. Where is a good supplier of core matts? I've tried FGI and Martinis, and a good few boat supply stores.

I can see i am wasting my time with this so for get what i have said and forget i was here !

[waikikin]

Originally Posted by watchtherocks

Where is a good supplier of core matts? I've tried FGI and Martinis, and a good few boat supply stores.

FGI should have all, But for small quantities FMS(Fiberglass Material Services) could be the go for you, depending on where in OZ your at. All the best from Jeff.