CSM before laying roving?

[F14CRAZY]

I'm glassing some new engine mounts in my buddy's Wellcraft. Is a layer of CSM required before laying the 18 oz? Using premium polyester resin not my usual epoxy. Thanks

 

[Cadwelder]

Re: CSM before laying roving?

I'm glassing some new engine mounts in my buddy's Wellcraft. Is a layer of CSM required before laying the 18 oz? Using premium polyester resin not my usual epoxy. Thanks

Yep

 

[F14CRAZY]

Re: CSM before laying roving?

I whipped it last night, complete with CSM. Why is this needed when working with poly?

 

[Woodonglass]

Re: CSM before laying roving?

"Woven roving is mostly used for buildup when thickness is needed. It is alternated with layers of chopped strand mat to fill in the heavy weave pattern of the woven roving.
The combination gives good thickness and strength. On a weight basis, woven roving is cheaper than cloth, and more expensive than chopped strand mat.. The advantage of using woven roving, is that is gives a quicker buildup of thickness , compared to using cloth. Because of the heavy thick weave, you are not going to get the nice smooth finish of cloth when you use woven roving. , that is why it is generally used for buildup, after you use cloth for your first layer , to get the smooth finish. Like cloth. Woven roving uses less resin then chopped strand mat. That is why in situations that require waterproof ness, chopped strand mat is used in combination with woven roving.
"

This comes for Fiberglassing 101

 

[Yacht Dr.]

Re: CSM before laying roving?

I'm glassing some new engine mounts in my buddy's Wellcraft. Is a layer of CSM required before laying the 18 oz? Using premium polyester resin not my usual epoxy. Thanks

Actually .. when using just woving and 1.5 oz mat .. you should Start with 2 layers of Mat ..then end with mat ..

This is coming from YD ..

 

[ondarvr]

Re: CSM before laying roving?

The reason it's needed is because if only roving is used, there will be a resin rich layer between the roving and the substrate, this resin rich layer is weak compared to the rest of the laminate and can fail when stressed. Mat fills the gap between the roving and substrate with random glass fibers that can more easily conform to the shape of each one. On relatively smooth surfaces one mat is fine, if the surface is rough or irregular a second mat may help.

 

[oops!]

Re: CSM before laying roving?

just to add to what ondarvr said.

(and he is correct), resin by it self is very brittle, even weak. take the left over stuff in your bucket after glassing......you can crumble it in your hand ! this is what is between the substraight and the deep pockets of the roving material.....each deep pocket is filled with resin.
thats why the csm is needed to fill those gaps.

remember....allways when using poly resin.......csm over the substraight and between each layer of roving.....any where that resin will pool

 

[F14CRAZY]

Re: CSM before laying roving?

How come I don't remember CSM being mentioned while using epoxy? Is it because epoxy is that much stronger than poly? I mean I took a hammer to come leftover epoxy in a cup and couldn't do much more than scratch it...nothing like crumbling it in my hand

 

[ondarvr]

Re: CSM before laying roving?

Yes, epoxy is stronger and there is less chance of the resin rich layer failing.

 

[mysouthernwings]

Re: CSM before laying roving?

um, no. The binding agent that holds the CSM together is not compatible with epoxy. Polyester (Vinyl Ester, Orthothalic, Isophthalic, etc) resins dissolve the binding agent so that it becomes the workable "mush" that makes it so easy to work with. I would put a light (6oz) cloth in between the layers of roving if there is a concern of the epoxy failing due to lack of reinforcement (Sheer?) Sorry to butt in.....

 

[oops!]

Re: CSM before laying roving?

um, no. The binding agent that holds the CSM together is not compatible with epoxy. Polyester (Vinyl Ester, Orthothalic, Isophthalic, etc) resins dissolve the binding agent so that it becomes the workable "mush" that makes it so easy to work with. I would put a light (6oz) cloth in between the layers of roving if there is a concern of the epoxy failing due to lack of reinforcement (Sheer?) Sorry to butt in.....

the above is correct.......csm is not needed with epoxy, is such a good glue that it does not matter if the resin pools.

southern wings, ondarvr (if i may be so bold to speak for him) is aware of this and just answered the above question with out going into great detail of stuff he has typed a gazillion times).
i can tell by your responce that this aint your first (poly) BBQ.
welcome, and i look forward to seeing your insights.

cheers
oops