Fiberglass over plywood roof

[garbler]

Mako
Believe it or not this was not an attempt at a Master’s Thesis, not by a long way, but perhaps a bit of background and some light technical tid bits is beyond the reach and scope of this site. I guess if I had done some prelim reading I’d have realized this and never commented. I’ll let you guys get back to your ‘ chat and BS ‘ and I apologize if I created any thematic issues

Regards
Rick

 

[psneeld]

Interesting comments but on the whole you’re missed my points. First BS 1088 is not a brand of plywood but a manufacturing spec so there are literally dozens or hundreds of mills laminating to these specs. Like anything else there are some companies that do it better than others. The best I ever used was from two mills in Israel so you just can’t make a statement that 1088 is no good.

My point with bulkhead tabbing had nothing to do with hard or soft fits, solid lam or cored hulls and cushion tabs. It was all about the need to strip and prep the ply for reliable secondary bonds. Some of you guys are like Kudzu you just take off in every direction and eventually smother the message

Regards

I used to think that a thread should be like a river...pretty much flowing in one direction, getting stronger and getting to the destination sooner or later with bends along they way.....

Now I see it more like a free for all where like an autopilot I let the the ship wander off course then try and nudge it back on course when the new direction is just not right in my tiny little chip brain.

 

[Mako]

@Garbler I think your technical input was excellent and it even gave me something to think about (de-lamination of poorer quality plywood). But it's okay to relax a bit regarding thread drift. In fact, you should feel good as you're probably one of the few guys here who doesn't have A.D.D.

 

[lghawk]

Hi again everyone!

I've started experimenting with epoxying the front sunbed before I tackle the roof. Its been quite successful so far and I am happy with the results. Method so far has been:
1. Apply the epoxy to the raw plywood
2. Lay over the fibreglass matt
3. Roll it out

So far so good!

Question though as it is very new to me...

The above provides me with a watersealed plywood and the glass matt obviously ties it all together. However the end result is quite "rough"... eg not a smooth finish.

To obtain a smooth finish - do I add another compound to the top of it? Is this Fairing Compound?

Or - am I approaching this all wrong?

Thanks for the advice guys!

Cheers,

Lyndon.

 

[Comodave]

Epoxy isn’t usually recommended for wetting out mat due to the chemical binders in the mat. The epoxy resin doesn’t break down the binders like the styrene in poly resins do. Unless the mat is part of some glass like 1708 where the mat is sewn to the other layers of glass and binders are not used. If you are going to use epoxy then you probably should use cloth instead of mat.

 

[lghawk]

Thanks Comodave! My bad i just checked and what they gave me was called "Cloth Plain 195G"... so Ia m assuming it is cloth??

I purchased it all from Allnex in Sydney and they said it was all the correct stuff to be using

 

[Comodave]

Ok, that is more better…. You can roll it out using a fiberglass roller but other than using something like peel ply sanding it will be your best bet.

 

[lghawk]

Awesome! Thanks mate! I will give the sanding a go! Just trying to get it right on the smaller things before I attempt it on a larger scale!

 

[Comodave]

Keep in mind that some epoxy resin hardens and leaves an amine blush on the surface. If you don’t wash it off with fresh water it will clog your sand paper very quickly and make sanding a never ending PITA. Wash it with water and scrub lightly with a brush, then rinse.

 

[lghawk]

Genius! I did not know that! That is great info and really appreciate it! Cheers!

 

[Comodave]

Check the epoxy, some blush some don’t.

 

[Bmarler]

Genius! I did not know that! That is great info and really appreciate it! Cheers!

i like using epoxy that doesn't amine blush. it lets you laminate or build the thickness without scrubbing. i've been using system three, but i don't know what's available in your area.
after you get the cloth rolled out and cured, you can add additional coats of thickened epoxy to fill the weave. a squeegee is a good tool for spreading this out. two coats should give enough film build so you can sand it smooth.

 

[lghawk]

i like using epoxy that doesn't amine blush. it lets you laminate or build the thickness without scrubbing. i've been using system three, but i don't know what's available in your area.
after you get the cloth rolled out and cured, you can add additional coats of thickened epoxy to fill the weave. a squeegee is a good tool for spreading this out. two coats should give enough film build so you can sand it smooth.

Thanks so much! Appreciate the advice on this!

 

[Marco Flamingo]

To avoid dealing with amine blush with epoxy, look into Peel Ply. If the deck area isn't too complex, you simply lay down the Peel Ply after wetting out the cloth. Peel Ply is rolled (you will have to remove extra epoxy around the edges). When the Peel Ply is yanked off, it leaves a very fine textured surface with no amine blush. Paint or Kiwi Grip.

The mention of Borden Chemical above (and thread drift) reminded me of something I did with success years ago. Based on an old-timer's recommendation. I mixed one gallon of Elmer's glue (Borden product) with one gallon of acrylic paint and a quart of water. The plank deck was overlaid with cheap jute hop sack and "painted" (w/squeegee). The finish was nonskid because of the texture, flexible (every time it got wet), and waterproof. It also attracted dirt, which meant your best choice of color was brown.

That system is too primitive for today, but the suggestions of acrylic coatings listed above sound promising and a lot easier than removing the paint to bare wood, applying cloth/epoxy, and then applying an acrylic paint.

 

[syjos]

After using WEST Epoxy since the 70's, I switched to System Three Silvertip Epoxy System 10 years ago, to avoid blush.

The other advantage of S3 epoxy is that the epoxy can be recoated without sanding between coats up to 72 hours.

Not having to deal with blush and sanding between coats is a huge time and labor savings.

I still follow Gougeon Brothers book on boat construction but now use S3 Quickfair and Gel Magic for fairing and gluing instead of mixing powders.

 

[garbler]

Epoxy resins have their place but a big flat hardtop with more sun/UV exposure than just about anywhere is not the place. There are some epoxy resin blends with a “ UV inhibitor “ but it’s more gimmick than solution. It may last longer in Northern ports with shorter seasons but Australia I don’t think so. When epoxy breaks down from UV’s it first whitish like milky looking then crazes with small faint cracks and finally releases or peels.

Removing spent epoxy resin is not a desirable job as it demands very aggressive abrasives. If you do decide to lay down some fabric with epoxy then Dynel cloth is preferred bu most good pros. Dynel is polyprolene and stretches and is tricky to wet out and lay down but monel or SS staples will answer. I would then paint with high metallic silver paint that provides excellent bond for a final or dress coat of paint and most important is a great reflector of heat. Then topcoat with a good solid white paint high in titanium dioxide ( which reflects UV’s as good as anything available ). You now will have a strong flexible epoxy base, great silver heat reflector and attractive white dress coat. Almost the best of both worlds. Maintain the white paint by sanding off the chalky spent paint and recoat when necessary.

 

[syjos]

Epoxy resins have their place but a big flat hardtop with more sun/UV exposure than just about anywhere is not the place. There are some epoxy resin blends with a “ UV inhibitor “ but it’s more gimmick than solution. It may last longer in Northern ports with shorter seasons but Australia I don’t think so. When epoxy breaks down from UV’s it first whitish like milky looking then crazes with small faint cracks and finally releases or peels.

Removing spent epoxy resin is not a desirable job as it demands very aggressive abrasives. If you do decide to lay down some fabric with epoxy then Dynel cloth is preferred bu most good pros. Dynel is polyprolene and stretches and is tricky to wet out and lay down but monel or SS staples will answer. I would then paint with high metallic silver paint that provides excellent bond for a final or dress coat of paint and most important is a great reflector of heat. Then topcoat with a good solid white paint high in titanium dioxide ( which reflects UV’s as good as anything available ). You now will have a strong flexible epoxy base, great silver heat reflector and attractive white dress coat. Almost the best of both worlds. Maintain the white paint by sanding off the chalky spent paint and recoat when necessary.

I've done several top, roof and deck repairs and builds on a variety of boats. I use epoxy and fiberglass cloth over plywood with several coats of white marine paint on top to protect the epoxy.

Some of the jobs are approaching 30 years in age and show no sign of deterioration.

Epoxy only breaks down when there is no protecting paint over it.

The white paint keeps surface temperature low without a silver heat reflector.

And Jasco Epoxy and Paint Remover will easily remove old, hard epoxy coating.

I use a two part LPU paint that does not chalk up.

 

[garbler]

I've done several top, roof and deck repairs and builds on a variety of boats. I use epoxy and fiberglass cloth over plywood with several coats of white marine paint on top to protect the epoxy.

Some of the jobs are approaching 30 years in age and show no sign of deterioration.

Epoxy only breaks down when there is no protecting paint over it.

The white paint keeps surface temperature low without a silver heat reflector.

And Jasco Epoxy and Paint Remover will easily remove old, hard epoxy coating.

I use a two part LPU paint that does not chalk up.

Good advice but you have to remember where you are located compared to more Southern latitudes and the effect of a higher sun and longer hours under it. Paint and bright work just can’t last as long down South.

Rick

 

[chriscritchett]

+1 for peel-ply. Once you figure out how to use it, it makes the post-processing SO much nicer. And a hint: it doesn’t need to be ‘marine-grade’ ‘peel-ply’; I’ve had plenty good success going down to the fabric store and grabbing whatever cheap-o synthetic (slippery) fabric they had on sale. Test a small piece first, obviously, and it probably didn’t give quite as nice a finish as real peel-ply, but it did the job and smoothed out the resin and peeled right up once it was cured.

 

[Comodave]

Quite true that southern sun is much more damaging but I don’t know anyone that wouldn’t paint the epoxy fiberglass. Because it looks like crap if it isn’t painted or gel coated. And the paint will have to be maintained. But none of that is a reason not to use epoxy resin. We lived in Tucson, AZ for 30 years and never had any problems using epoxy resin. Of course it was painted.

 

[syjos]

Quite true that southern sun is much more damaging but I don’t know anyone that wouldn’t paint the epoxy fiberglass. Because it looks like crap if it isn’t painted or gel coated. And the paint will have to be maintained. But none of that is a reason not to use epoxy resin. We lived in Tucson, AZ for 30 years and never had any problems using epoxy resin. Of course it was painted.

Hey Dave,

We finally get to agree on something.

Other than our dislike for exterior teak.

 

[lghawk]

Hey Simi,

You have mentioned before using Emerclad. I have found the product - but wanted to check - have you ever used it over Epoxy Resin? I plan on using Emer Clad with a textured roller to get the grip in it - eg - so I can walk on it and not slip Just wanted to check how it will stick to the Expoy Resin and what to prime it with? I have contacted Emer-Clad directly but thought I would also check with you!

Cheers!

Lyndon.

 

[lghawk]

A quick update!

So far so good with what I have done. Method so far:
1. Sanded off the existing paint back to bare plywood
2. Laid down cloth matting 195gm.
3. Mixed Epoxy Allnext R180 Resin and poured it over the cloth matting.
4. Used squeegy to spread the resin all over.
5. Once dry, sanded for any imperfections and then poured another layer of resin over

The end result is awesome. Completely waterproof and smooth. Ready for paint in some areas, and Emer-Clad (THANKS SIMMI-60) where I will be walking over, applied with a textured roller for anti-slip.

I have now applied the above method to the sunbed on the foredeck, and the new roof that I installed a year ago. Both are now completely water-tight, free from mould and so maintence-free compared to the painted plywood I had before! Very happy with the result!

Thanks again for everyone's input on this!

 

[Mambo42]

A quick update!

I have now applied the above method to the sunbed on the foredeck, and the new roof that I installed a year ago. Both are now completely water-tight, free from mould and so maintence-free compared to the painted plywood I had before! Very happy with the result!

Thanks again for everyone's input on this!

Sounds like a great result. Have a quick question for you. How did you connect the bed to the foredeck ? You bolted it down or did you sand away the paint, then bolted is down and then put the Fiberglass ?

I want to change my flybridge set up, have to cut away the old seating arrangement, but then need to figure out how to secure the new set up.

 

[lghawk]

Hi Mambo!

I secured it down with some large bugle screws. I made it as a frame underneath (think like a stud wall) with a bottom plate of timber. I then simply secured this bottom plate straight down with the bugles. I didn't sand away the fibreglass first.

After I installed the plywood sides, I then ran the fibreglass matting down the vertical face of the plywood and then about 100mm onto the horizontal face of the deck itself. Then flooded it with epoxy and it has been water tight ever since. Worked a treat!