How many layers fiberglass on new deck

[FPNC]

Your layup schedule is fine for this project. No need to use expensive glass on a deck core covering. The devil is in the secondary bond to the old laminate. Vinylester will give a great bond without the hassle and expense of epoxy. Finish with mat. Thick enough that you can sand the top layer smooth. Roll a final coat of resin with paraffin wax melted into it as a finish coat. This will dry tack free and allow you to sand it smooth to prepare for a top coat of whatever and nonskid.

Thin woven cloth like 7oz or 10oz is a waste of time and money and does not finish as well as mat. The top layer is in compression so you don't need much fabric on the top layer. Figure about .043" thick for a layer of 24oz woven and .030" thick for a 1oz layer of mat. Stay out of the sun and make sure the catalyst you use with the vinylester is correct. Vinylester can sometimes be particular about which catalyst works best.

[Chotu]

Originally Posted by thinwater

Incorrect. Unlike most mat, 1708 does not use binder that needs to be dissolved by the resin. In addition to many other projects, I built a pair of hull extensions on my PDQ using 1708 using epoxy. No problems at all.


I've used this with epoxy, polyester, and vinyl ester. I'm going to avoid this part of the debate. All three will work equally well with 1708.


I think some assume plywood as a core will make it stronger. In fact, the plywood is weaker in shear than end grain balsa, so the result is often weaker. It also rots faster, because it wicks the water crosswise much faster than balsa. Finally, bonding is more difficult because it does not conform as well. So yes, use a real core material.

That’s weird. Never heard this before. I wouldn’t say “incorrect”, even though you can probably use 1708 with epoxy and get away with it. It’s just a waste of material and weight because mat isn’t necessary for epoxy projects. So using 1708 is 1/3 heavier for no reason at all. Provides no strength (only directional fibers do) and is simply a bulker for polyester construction. So even if the binders do the right thing, the mat is adding 1/3 more weight for no strength.

That’s the real reason.

But here, we have a monster of a laminate schedule anyway so weight is of no concern. So... carry on with 1708.

[Spot]

https://compositeenvisions.com/fiber...17oz-576-4gsm/


I am coming up .130-160" with 3 layers 1708, once as adding layers and once as info off the interwebs with gaps calculated.

[boatpoker]

US Composites say their 1708 is compatible with epoxy.
Specialty Fabrics

[deltaten]

The only problem, of sorts, that I encountered using 1708 with epoxy was wetting out. The tight, linear strands didn't seem to want to absorb the resin very fast. I pre-wetted (turned) edges, then field and edges again. Due to the density of the strands, this left slightly cloudy striations. All were fully saturated; just visibly marked by glass density.
HTH

[boatpoker]

Originally Posted by deltaten

The only problem, of sorts, that I encountered using 1708 with epoxy was wetting out. The tight, linear strands didn't seem to want to absorb the resin very fast. I pre-wetted (turned) edges, then field and edges again. Due to the density of the strands, this left slightly cloudy striations. All were fully saturated; just visibly marked by glass density.
HTH

There are numerous types of epoxy. Did you use laminating epoxy ? A thicker less viscous epoxy may be more appropriate for a final coat. Viscosity can also be slightly changed with different hardeners. My preferred epoxy is System 3. Their number one hardener makes it quite thin while their number 3 hardener I find makes it thicker and cures faster

[theglo]

Originally Posted by thinwater

Incorrect. Unlike most mat, 1708 does not use binder that needs to be dissolved by the resin. In addition to many other projects, I built a pair of hull extensions on my PDQ using 1708 using epoxy. No problems at all.


I've used this with epoxy, polyester, and vinyl ester. I'm going to avoid this part of the debate. All three will work equally well with 1708.


I think some assume plywood as a core will make it stronger. In fact, the plywood is weaker in shear than end grain balsa, so the result is often weaker. It also rots faster, because it wicks the water crosswise much faster than balsa. Finally, bonding is more difficult because it does not conform as well. So yes, use a real core material.

It had balsa.core. I tried plywood with crappy results. I plan to use balsa.

[Celestialsailor]

Originally Posted by theglo

Was planning to use epoxy. I think I've switched to 3 layers of that 1708. Looks simpler.

There is a wealth of information on Youtube. This is close to how I did it.

https://www.youtube.com/watch?v=JAtjHjJhBV0

https://www.youtube.com/watch?v=RVViKMbvjDI

https://www.youtube.com/watch?v=oCyMEQHfEIw

[pcmm]

If you do 3 layers of 1708 mat side down and a final (additional) layer of mat on top you should end up with a thickness really close to the original laminate. It will be easier to lay down than mat/roving and much stronger. Either poly based or epoxy is fine (price out the volume of epoxy you need..get expensive fast) balsa core or foam core (scored) is easier to lay down with some bonding putty and go from there.

Get a bunch of finned rollers, they are the most important tool for a good laminate result!

[Celestialsailor]

Originally Posted by thinwater

Incorrect. Unlike most mat, 1708 does not use binder that needs to be dissolved by the resin. In addition to many other projects, I built a pair of hull extensions on my PDQ using 1708 using epoxy. No problems at all.

Quite correct on the 1708. Used with epoxy, a much stronger lay-up is achieved. There is at least one company that sells Mat with a different formulated binder for epoxy.

[Scubaseas]

No love for 1808 which is 90* bias where 1708 is 45* bias? I'd use Vinylester or epoxy, 1.5csm, 1708, 1808, 1708 and then a veil or another 1.5 or .75oz mat.

You can use epoxy with stitch mat.

Get a copy of Dave Gerr's "Elements of boat strength for builders, designers and owners" Excellent tome that will be able to answer all you questions and more.

[EarlWer]

Originally Posted by pcmm

Get a bunch of finned rollers, they are the most important tool for a good laminate result!

Are these rollers cleaned and reused or thrown away?

If cleaned, what do you use?

[thinwater]

Originally Posted by deltaten

The only problem, of sorts, that I encountered using 1708 with epoxy was wetting out. The tight, linear strands didn't seem to want to absorb the resin very fast. I pre-wetted (turned) edges, then field and edges again. Due to the density of the strands, this left slightly cloudy striations. All were fully saturated; just visibly marked by glass density.
HTH

Did you use a roller? It should wet out quickly. I've layed up a LOT of layers.


Yes, you can clean the roller. Don't wait too long, and...
* if epoxy scrub lightly with vinegar first, then soap and water.
* if polyester/vinyl ester clean with acetone.



Chotu, the purpose of 8 ounce mat is to improve bonding between layers and improve conformation. Yes, you can use just 17 oz. biax (I have), but the 1708 is a little easier to work with and is thus quite popular builder and DIYs. I didn't invent it, but a smart guy did.

[pcmm]

Originally Posted by EarlWer

Are these rollers cleaned and reused or thrown away?

If cleaned, what do you use?

Finned rollers are used for consolidating the laminate, getting the air out. You can get reusable ones that you just clean with acetone. Or you can get. Plastic disposable ones. I just keep mine in a tub of acetone while I’m laminitis and then shake it out before I use it (probably not the best practice but it works for me).

I use a 4 inch paint roller for applying the resin. It’s efficient nd faster then trying to use a chip brush.

[mitiempo]

Originally Posted by Chotu

1708 is for polyester and vinylester. Not epoxy.

Incorrect. 1708 is epoxy compatible.

Match the current deck thickness of the top layer.