Laminating in fibreglass

[wannabefree]

Hi.

 

I'm in the middle of laminating a wooden cabin - sheathing it in fibreglass.

 

This is my first time fibre-glassing. So far it has laminations of CSM and I'm using west system epoxy.

 

Now I've been asked "are you going to gel-coat it to get a nice smooth finish?".

 

I'm confused. Isn't gel-coat just for when you are making something in a mould rather than for when you are laminating over a structure?

 

 

Maybe one of you will be able to advise the best way to achieve a smooth finish to paint - and one that won't make me bankrupt!

 

Epoxy is seriousy expensive!

 

 

In the absense of a better idea, the plan is to roller on several coats of epoxy until the weave is filled in the CSM, then to sand and paint, probably in a matt finish to help hide any imperfections...

[wonderdust]

Easysand maybe!

[Bojangles]

The professional way to finish off epoxy sheathing is with 'Peelply'. This is a silicone impregnated material that you cover the final epoxy coat with and squeegy any excess epoxy thru. Then when all gone off you peel off this material leaving a good finish for painting etc.

 

This WEST EPOXY guide from Robbins you may find a useful on how to epoxy sheath.

Edited September 1, 2008 by Bojangles

[wannabefree]

The professional way to finish off epoxy sheathing is with 'Peelply'. This is a silicone impregnated material that you cover the final epoxy coat with and squeegy any excess epoxy thru. Then when all gone off you peel off this material leaving a good finish for painting etc.

 

This WEST EPOXY guide from Robbins you may find a useful on how to epoxy sheath.

 

Thanks Bojangles, that was very helpful.

 

With regards to the peel ply, can it be applied over the top of the CSM immediately after it has been wetted out or should the weave of the CSM be filled out with several layers of epoxy before applying the peel ply?

[Chris J W]

Just for info, can I ask what "CSM" is?

[Big Steve]

"Chopped strand mat" bits of glass fibre lightly bonded together in a random manner, gives a much stiffer finish than woven mat.

[Chris J W]

"Chopped strand mat" bits of glass fibre lightly bonded together in a random manner, gives a much stiffer finish than woven mat.

 

Ta!

[DHutch]

When i sheathed our wheelhouse roof (new ply built thing) i looked into peelply.

- It think one of the main reasons is to removed the surface residue formed in the curing process, so its ready for painting.

- However what i did was just wet the cloth through, then roller over two layers of pigmented (white) epoxy and call it a day.

- Then cleaned off the residue with warm vingar, and its done four years since. Although yellowed a little as its not uv stable epoxy.

 

However that was using 125g/m^2 woven cloth, rather than CSM (not sure what thickness you using) so the levaling out required was less.

 

I might also, in the future, prehaps paint it with some twopack polyerthene or somthing, so its more wipe-clean able rather than a chalky matte finish.

 

 

 

Danel

[wonderdust]

Can i ask

1 Why are you laminating the cabin

2 Using epoxy

3 Using fibreglass mat

[Bojangles]

Thanks Bojangles, that was very helpful.

 

With regards to the peel ply, can it be applied over the top of the CSM immediately after it has been wetted out or should the weave of the CSM be filled out with several layers of epoxy before applying the peel ply?

 

We've never sheathed hulls, cabins etc where it will be on show, using CSM . We always used either woven or bi-axial, tri-axial etc.

 

The peel ply is a cloth and placed over the epoxy saturated glass. Then with a pliable scraper any excess epoxy is worked thru the peel ply. This should leave the peel ply smooth without wrinkles. When the epoxy has gone off you tear off the peel ply and the woven cloth will have a smooth finish ready for painting. If the surface is looked at very carefully you will find the surface is very very slightly 'pin pricked'. This ensures good adhesion of any following painting. The peel ply can be left on the cured epoxy for months if so required. We used to sheath sole boards then bulid the boat before tearing off all of the peel ply. If you want to bond another item to a peel plied surface just mark the area with a sharp stanley knife and tear off a piece of peel ply to allow the bonding.

 

Times have moved on and materials may have changed but we were told when epoxying to never use CSM that was for produced for ordinary fibreglassing using polyester resin . That CSM has a fine white powder on the strands ( cannot be seen by eye) which enables the polyester resin to adhere to the strands but this white powder rejects epoxy. We were told only ever to use e-glass, which is not coated with the powder. If offered a roll of cheap e-glass , ensure it has never been wet/damp as the epoxy will not adhere.

 

Hope this helps you

 

PS. To fully answer your question. However many layers of glass you want to apply try not let a layer fully cure before applying the next layer. Wet a layer then lay on next cloth layer and wet thru etc etc till all the layers are wetted thru, then apply peel ply. If you do let a layer cure any subsequent layer will only achieve a mechanical bond rather than the much stronger chemical bond.

Edited September 2, 2008 by Bojangles

[wannabefree]

Thanks for the replies.

 

I'm concerned about the comments regarding not using CSM with epoxy, but I'll have to live with it and hope for the best now! Also, with the weather it has not been possible to complete the job and the work done so far has cured.

 

 

------------------------------

 

Wonderdust Q's:

 

1 Why are you laminating the cabin?

 

Because it was initially painted, which subsequently cracked and let water penetrate the plywood laminations and threatened to ruin the cabin in short order.

I want a near permanent solution, to make it weatherproof and presentable. The carpentry that went into constructing the cabin was, well not great lol and fibreglass laminations hide that from view.

 

2 Using epoxy?

 

Because I heard/read that polyurethane resin is more susceptible to cracking/peeling and is less effective at keeping out moisture.

Epoxy is certainly more expensive!

 

3 Using fibreglass mat?

 

Not sure what you mean by this question. Do you mean instead of woven cloth? Or do you mean instead of just resin?

If the former, choosing CSM instead of woven cloth may have just been a mistake on my part. If the latter, I wanted to improve the stiffness of the roof (theres some flex when walking on it) and to strengthen the cabin sides because I want to install some pretty heavy scuttles.

 

----------------------------

 

 

I think I'm going to try the peel ply method. Am I correct in assuming that the 'weave' of the mat needs filling in with several coats of resin prior to the final application of resin through the peel ply, or can I apply the peel ply immediately over the top of the wetted out CSM and then apply a thick coat of resin through the peel ply in an attempt to get a smooth finish in one coat?

 

Oh one final question - is using peel ply any harder (for an amateur like me) than rolling on gel coat?

[Bojangles]

..................................

I think I'm going to try the peel ply method. Am I correct in assuming that the 'weave' of the mat needs filling in with several coats of resin prior to the final application of resin through the peel ply, or can I apply the peel ply immediately over the top of the wetted out CSM and then apply a thick coat of resin through the peel ply in an attempt to get a smooth finish in one coat?

 

Oh one final question - is using peel ply any harder (for an amateur like me) than rolling on gel coat?

 

I would apply the peel ply immediately over the wetted out CSM and I doubt whether you'll have to apply much more ( if any) resin. Work any excess resin thru the peel ply. You can easily see the peel ply getting wet as it becomes a darker colour. The peel ply will help to hold the resin in a flat surface, even if vertical.

 

If you feel you're not getting a smooth enough finish on the CSM you could try mixing a few 'micro-fibres', which are actually chopped up cellulose cotton fibres, into your resin mix. This will bulk up your mix and also act more as a filler

 

If you're unsure about the system or the epoxy adhesion to your CSM why not try a test piece first on a scrap piece of ply before proceeding any further.

 

I don't know if peel ply or rolling on a gel coat would be easier for you. On a flat surface may be gel coat would be easy but cabin sides if you painted the gel coat thick enough to cover the CSM strands I think you'd get 'curtains'. We used to have a sprayer nicknamed 'curtains'. lols