anyone used special spray glue to fix dry fibers overhead before lamination?

[Franziska]

Hi,


we've got a big overhead lamination on a catamaran ahead of us.


I was told that there is a method where dry reinforcement material can be fixed to the core material with a light coat of a special spray glue before wetting out with epoxy.


It's news to me, in the past I prewetted the fibers on a plastic film, rolled them up and unrolled them onto the prewetted hull surface. Works, but is a bit messy.
Works up to 350g/m2 fibers, more is getting difficult.


With the spray glue method one might be able to use heavier cloth?


Did anyone ever use this dry spray glue method? What spray glue did you use?


Secondly we need to bond new Divinycell overhead.
I'm planning to do that in strips and glue with thickened epoxy with a lot of Aerosil/Silica gel to prevent it from dripping.
I'm also thinking of using a dab of a thickened Cyanoacrylat glue or similar every meter so that the strips are instantly held in place while the epoxy cures. Anyone ever used that method? Alternatives?

[thinwater]

Originally Posted by Franziska

Hi,


we've got a big overhead lamination on a catamaran ahead of us.


I was told that there is a method where dry reinforcement material can be fixed to the core material with a light coat of a special spray glue before wetting out with epoxy.


It's news to me, in the past I prewetted the fibers on a plastic film, rolled them up and unrolled them onto the prewetted hull surface. Works, but is a bit messy.
Works up to 350g/m2 fibers, more is getting difficult.


With the spray glue method one might be able to use heavier cloth?


Did anyone ever use this dry spray glue method? What spray glue did you use?


Secondly we need to bond new Divinycell overhead.
I'm planning to do that in strips and glue with thickened epoxy with a lot of Aerosil/Silica gel to prevent it from dripping.
I'm also thinking of using a dab of a thickened Cyanoacrylat glue or similar every meter so that the strips are instantly held in place while the epoxy cures. Anyone ever used that method? Alternatives?

That just smells crazy. Let's put some weaker glue between the epoxy and the surface. It will also just take longer and just is not needed.


I've done a good bit of overhead work, and the trick is to wet the cloth on a flat surface, like a large cutting board, normally in several layers according to the weight, and then roll it into the place. The sections should not be larger than you can handle, about 8x10 inches at the very most. Strips can be a little longer, but don't get carried away; smaller actually goes much faster. Overlap them as needed; one piece is no stronger than two overlapped pieces. The core is likewise held into place with thickened epoxy. It is quite light. Small sections; big sections are not stronger.


https://www.practical-sailor.com/boa...rom-underneath

[coopec43]

I've never done over-head work and I can't think of a situation where I would need to.

I would go along with Thinwater's advice but maybe you could PM Chotu to see what he has to say?

[pcmm]

For overhead work, the best method I've found is to apply a thin layer of thickened resin to the overhead surface first. I generally mix my resin with cabosil to a thickness just a bit stiffer than mayonnaise. then separately wet out your fibreglass and the roll it up around a cardboard roll. Then roll it out to the overhead surface. The thickened resin really helps the fibreglass want to stick. You can apply pretty large pieces this way. I did the whole underside of my fore-deck this way last fall.

[Fore and Aft]

Franziska I have used a hot glue gun to hold objects in place while the epoxy glue dried. Just some small dabs of glue. I don't think it really matters strength wise when the other 99% of the surface is epoxy glue.
Cheers

[Chotu]

Originally Posted by Franziska

Hi,


we've got a big overhead lamination on a catamaran ahead of us.


I was told that there is a method where dry reinforcement material can be fixed to the core material with a light coat of a special spray glue before wetting out with epoxy.


It's news to me, in the past I prewetted the fibers on a plastic film, rolled them up and unrolled them onto the prewetted hull surface. Works, but is a bit messy.
Works up to 350g/m2 fibers, more is getting difficult.


With the spray glue method one might be able to use heavier cloth?


Did anyone ever use this dry spray glue method? What spray glue did you use?


Secondly we need to bond new Divinycell overhead.
I'm planning to do that in strips and glue with thickened epoxy with a lot of Aerosil/Silica gel to prevent it from dripping.
I'm also thinking of using a dab of a thickened Cyanoacrylat glue or similar every meter so that the strips are instantly held in place while the epoxy cures. Anyone ever used that method? Alternatives?

this is a case where you should really show us the pictures. A lot of it depends on how tight the curve is, how thick the Divinycell is, etc.

As to your question about using superglue to hold some core in place while you are waiting for the epoxy to kick, that’s perfectly good. Good technique. I have often mixed adhesive like that to gain the advantage of a quick grab sometimes when you are trying to hold something in place. Hot melt glue works pretty well in a lot of cases for these types of things as well. It’s very very instant. And then the real bond comes from the stuff that takes a while to kick.

when making your shape, be sure to fair the foam core before you start glassing. Make sure that is perfectly fair. It’s easier to sand than epoxy, and it will save weight to do it that way. Also, when you go to put the fiberglass on, the smoother the surface, the better it will stick when it is upside down.

When it comes to wetting out that fiberglass upside down, that’s going to be a nightmare anyway. You are going to get full of epoxy. One of the worst Boat building jobs there is. I had to do something similar during my build when doing part of the fairing that is forward of the main structural bulkhead on the bridgedeck. The forward-most part of tye bridgedeck.

Building my hulls, I started with naked foam, just like you were talking about. And since I did vacuum resin infusion, I had to get all of the dry materials up there and put a bag on it before the epoxy touched it.

The secret I found for holding the fiberglass in place was composite staples. I just use the staple gun and these plastic/fiberglass staples. They held everything in place pretty nicely. It wasn’t as completely upside down as what you are describing, however. But you might be able to make use of them.

in your case, however, I would use manageable size pieces, wet out the foam where you are going to apply them, and then with a couple of people, just press it in place and stick it to the foam. It will stick like a wet t-shirt sticks. And just start wetting it out.

I don’t like that whole technique of doing them on plastic somewhere and then carrying them up wet to the surface. The fibers get all out of alignment, the epoxy is just dripping everywhere on you. It’s so messy. It’s a little bit neater in my opinion to wet the surface, stick the dry fiberglass, and then wet over the dry fiberglass.

It may drip just a little bit on the floor when you are doing it the way I just described, but at least it’s not dripping on you. You can stand out of the way while you use the roller.

no matter how you do it this job will not be fun.. Godspeed.

[CatLove]

I used both hot glue and superglue (the gel variety, not the watery low viscosity ), both work well .
I do not like to use cabosil to thicken epoxy for Divinycell application, because after cure it becomes much harder than the foam and then fairing is much more difficult when you encounter very hard areas due to cabosil, alternating with soft foam areas.
Cabosil thickened epoxy is perfect for structural applications .


In places that required fairing I mix epoxy with phenolic microballoons , find a ratio where the cured mix has about the same hardness as the foam , which then becomes much easier to fair .

The same phenolic microballoons epoxy mix is also good for joining pieces of Divinycell without creating hard spots so really there's no reason to use large pieces of foam. The end result will turn out better if you cut and shape the foam as needed, rather than trying to maximize the piece size.
Then after fairing laminate the glass , vacuum bag or not but use peel ply regardless. It saves a lot of work and time afterwards .

[CatLove]

forgot to add, depending on foam size and shape requirements and what it needed to be attached to, it may be possible to use Raptor nails or staples. These are left in place after epoxy cures .

[sailorboy1]

I have used spray on contact cement glue. It works like, well like contact cement glue.

[Tupaia]

Just curious and it might be obvious but why do you need to do this?

[Wanderbird]

Have done this before using Super 77 or Hi-Strength 90. I was never a fan, somebody elses idea, but it worked fine. A very light mist of spray adhesive on the core. For the instant bonding try an industrial cross linked hot glue gun if you can get one, they are $$ and be careful, I have nasty scars from one.


https://www.gluegun.com/collections/...LYXKLo1TeXWQHw

[JPA Cate]

@Tupaia,

They are helping restore a very nice, but badly injured catamaran. Here's a link to the thread: https://www.cruisersforum.com/forums...as-294939.html

Ann

[Sun and Moon]

A lot of people here know a lot more than I do, so you should probably believe them not me.

But here's my concern about using any form of glue to hold your cloth in place. No doubt it will work in the short run, but how does this not create essentially a void in the epoxy? That glue spot is not going to have the same flexing characteristics as the epoxy area, thus with time, as the boat flexes, it seems to me you will have a delamination. And delaminations grow bigger over time.

Chotu's staples do seem to solve both problems at once. I'd do that.

[Franziska]

Originally Posted by Sun and Moon

A lot of people here know a lot more than I do, so you should probably believe them not me.

But here's my concern about using any form of glue to hold your cloth in place. No doubt it will work in the short run, but how does this not create essentially a void in the epoxy? That glue spot is not going to have the same flexing characteristics as the epoxy area, thus with time, as the boat flexes, it seems to me you will have a delamination. And delaminations grow bigger over time.

Chotu's staples do seem to solve both problems at once. I'd do that.

Thanks to you and the other replies.


It's a new method.
I have only heard about it and thought it's interesting and wanted to hear if others have used it.

I've never used it before and, it looked interesting because my usual wetpreg (=wet out cloth on a sheet of film & roll it up, then wet out overhead area & roll on prewetted cloth) works but is a bit messy.
After all I used the wetpreg method to do the emergency repair.
The glue in question is also interesting because it may allow (! not necessarily does) a heavier cloth to be used in one go overhead.
The spray glue is something similar to this:
https://www.diatex.com/de/diatex-pro...ruehklebstoff/
So it is specifically made for laminating, it's not a normalspray glue.
I'll also check with Diatex to hear what they think about using it with hand layup.


Chotu's method with the staples sounds great too.

Reading the above comments, I think after all I'll make some trials with my classic wetpreg method using a 450g/M2 Triaxial which I can get.
Roll on first layer. Then, when it has started to kick off and is still tacky roll on the second layer and wet it out.

The area in question is along the keel & vertical overhanging, so, as much as I would love to use a pure microballoon mix for fairing because it sands similar to the core material that's going to be difficult because it will drip.

The only option there seems to be is to put enough silica gel thixotropic agent in the mix that it doesn't drip.
Happy to hear about alternative solutions.

Boatbuilding upside down is easy, fixing a boat the right way up is more cumbersome.

[Wandering1]

Originally Posted by pcmm

For overhead work, the best method I've found is to apply a thin layer of thickened resin to the overhead surface first. I generally mix my resin with cabosil to a thickness just a bit stiffer than mayonnaise. then separately wet out your fibreglass and the roll it up around a cardboard roll. Then roll it out to the overhead surface. The thickened resin really helps the fibreglass want to stick. You can apply pretty large pieces this way. I did the whole underside of my fore-deck this way last fall.

I could have written what you did. We just recently laminated two layers of 7oz cloth to the whole of the underwater area on our 44ft hull. We did exactly what you described.
I think it helps to have an epoxy with the right consistency as well. The wetted cloth can drip epoxy unless it's naturally a little more viscous. We used Gurit Ampro epoxy. This is an updated formula of the old SP Resins 106. It's an excellent underwater construction epoxy with blendable hardners so you can achieve a cure to suit your needs. Also it solvent free.