How many layers fiberglass on new deck

[mitiempo]

Originally Posted by Chotu

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.

There are no binders in 1708. It is stitched. Not sure what you mean by "no strength". The mat weighs very little compared to the stitched roving, which is very strong.

Epoxy is the best choice for adhesion.

[Time2Go]

Check out Mads on youtube channel” Sailife”
Did a whole corr replacement on a Warrior 38
a bit ago
Cheers
Neil

[Cadence]

Originally Posted by theglo

I'm doing my shopping for our haulout next month. We are replacing a few large areas of the deck that are shot and causing sponginess and water leaks in the cabin. Boat is 45' Dufour.

I'm planning on using this lay up over the new core:

1.5oz mat
24oz woven roven
then
1.5oz mat
24 oz woven roven
and then
10 oz cloth to finish

Any ideas on what type of thickness that may deliver?

Is that sufficient or should I add another layer?

Any other suggestions? Planning to order this soon so its on hand before we get in the yard. THANKS!

Forget the cloth, mat will finish better. Other than that your layup schedule looks fine. Make sure you have an adequate area ground back for overlap of the deck not being replaced.

[KP44]

Originally Posted by theglo

I'm doing my shopping for our haulout next month. We are replacing a few large areas of the deck that are shot and causing sponginess and water leaks in the cabin. Boat is 45' Dufour.

....

Any ideas on what type of thickness that may deliver?

Is that sufficient or should I add another layer?

Any other suggestions? THANKS!

I removed our teak deck over 20 years ago. Sanded the underlying cored fiberglass deck and filled the thousand little screw holes.
Then we put down 5 to 7 layers of 17 ox biaxial cloth with west system epoxy. The finished deck is lighter in weight than the teak and it is incredibly strong.
Probably 2 layers of 17 oz biaxial cloth is good. I bought a roll of 12" wide cloth and put down a mishmash of 3 foot pieces. Each piece took about 5 or 6 oz of epoxy. We mixed the epoxy in little paper cups; one at a time. Otherwise the epoxy will harden long before you are ready for it. Just doing a 2.5 to 3 foot piece of cloth. Then doing another. And another.
The first layer had some air pockets where it was not wetted out properly and we sanded thase out and re-did those spots. As we learned to use the epoxy, it went smoother and faster. After it was finished, we faired our new deck with light, sandable, epoxy putty.
I bought two 5 gallon jugs of epoxy and did not use it all for the deck on a 45' cutter.

I have found lighter cloth is difficult to use. I used 6 oz cloth to fabricate battery boxes and it is much harder to use than the 17 oz biaxial cloth.

[Calaban-Alleria]

I second the suggestion of reviewing Madds Sail Life channel. He has done what you are planning and does a good job of explaining what and why.


Also check out Andy of Boatworks Today. He has great videos of how to carry out small and large fiberglass and paint projects. I believe he also provides a consultancy service over video you might consider to get specific questions answered. (Madds talked his core replacement over with him).


Good Luck

[Chotu]

Wow. I’m a bit astounded at the lack of understanding of why you don’t use 1708 with epoxy and by how many people here wasted epoxy, weight and money with it.

The 17oz biax part is all you needed.

Again, mat has no place in epoxy construction and provides no strength to the laminate. You’re wasting epoxy, money and weight using anything but straight uni, biax or triax.

Mat was created for polyester projects.

You’re throwing away money and making your boat 1/3 heavier if you use it with epoxy.

[Chotu]

Originally Posted by mitiempo

There are no binders in 1708. It is stitched. Not sure what you mean by "no strength". The mat weighs very little compared to the stitched roving, which is very strong.

Epoxy is the best choice for adhesion.

What I mean by no strength is directional fibers are the only thing you need when building with epoxy. A mat bulking layer provides no strength at all. None. It’s fluff. The 17oz biax is doing everything in epoxy construction of this type. The mat is along for the ride adding 1/3 extra weight and wasting 1/3 of your epoxy.

A very poor decision to use that with epoxy.

Although again, this is just a little repair. But build a boat like that and you have a piece of junk that weighs more, has the same strength as if you just used 17oz biax and used 1/3 more epoxy and all the money that goes with it.

Not good engineering at all.

[DougR]

Originally Posted by Chotu

Wow. I’m a bit astounded at the lack of understanding of why you don’t use 1708 with epoxy and by how many people here wasted epoxy, weight and money with it.

The 17oz biax part is all you needed.

Again, mat has no place in epoxy construction and provides no strength to the laminate. You’re wasting epoxy, money and weight using anything but straight uni, biax or triax.

Mat was created for polyester projects.

You’re throwing away money and making your boat 1/3 heavier if you use it with epoxy.

For an accurate description of 1708 go to compositeenvisions.com, a supplier of fiberglass products.

Here they point out that the weight of one yard of 50” width material is about 17 oz... consisting of 17 oz of 45* biaxial roving and 3/4 oz of stitched on mat. Certainly not 1/3 heavier. Thickness is .044”. Suitable for use with polyester resin, vinyl ester resin and epoxy.

[rslifkin]

Originally Posted by DougR

For an accurate description of 1708 go to compositeenvisions.com, a supplier of fiberglass products.

Here they point out that the weight of one yard of 50” width material is about 17 oz... consisting of 17 oz of 45* biaxial roving and 3/4 oz of stitched on mat. Certainly not 1/3 heavier. Thickness is .044”. Suitable for use with polyester resin, vinyl ester resin and epoxy.

Keep in mind, those weights are likely not comparable. Cloth and roving is typically measured in weight per square yard, mat is typically measured per square foot. So in apples to apples terms, a square yard of material would be 17 oz of roving plus 6.75 oz of mat.

[mitiempo]

Originally Posted by rslifkin

......a square yard of material would be 17 oz of roving plus 6.75 oz of mat.

8 oz of mat from what I have found. Hence 1708

I have used a fair amount of 1708 to glass bulkheads in my boat. The mat doesn't seem to make it much thicker or heavier. I don't consider it a problem. I use epoxy. Very easy to wet out with West 105/205 epoxy.

Mads on SailLife used 1708 as well if I recall.

The mat traditionally used between layers of woven roving is to even things out between layers. Not sure it is needed with stitched roving but the few ounces added certainly will not hurt.

[pcmm]

Originally Posted by mitiempo

There are no binders in 1708. It is stitched. Not sure what you mean by "no strength". The mat weighs very little compared to the stitched roving, which is very strong.

Epoxy is the best choice for adhesion.

1708 does have binders in the mat, but they are epoxy compatible

[pcmm]

Originally Posted by mitiempo

8 oz of mat from what I have found. Hence 1708

I have used a fair amount of 1708 to glass bulkheads in my boat. The mat doesn't seem to make it much thicker or heavier. I don't consider it a problem. I use epoxy. Very easy to wet out with West 105/205 epoxy.

Mads on SailLife used 1708 as well if I recall.

The mat traditionally used between layers of woven roving is to even things out between layers. Not sure it is needed with stitched roving but the few ounces added certainly will not hurt.

One of the nice things about 1708 is the mat stabilizes the biaxial. I've used just biaxial AND 1708 and I find biaxial by itself moves and can distort easily. The mat in 1708 makes the biaxial less "squirrely" at the beginning, making placement an shaping a bit easier. Both are great products!

[Benz]

Originally Posted by mitiempo

8 oz of mat from what I have found. Hence 1708

I have used a fair amount of 1708 to glass bulkheads in my boat. The mat doesn't seem to make it much thicker or heavier. I don't consider it a problem. I use epoxy. Very easy to wet out with West 105/205 epoxy.

Mads on SailLife used 1708 as well if I recall.

The mat traditionally used between layers of woven roving is to even things out between layers. Not sure it is needed with stitched roving but the few ounces added certainly will not hurt.

It may not "seem" to make it heavier, but mat soaks up resin like a sponge and uses up a frightful lot of it over a large surface. I've used 1708 with epoxy quite a bit, but for my own purposes: professionally I don't now any boatbuilders that do. They're usually using engineered laminate schedules and the point of paying for epoxy is lightness, which you lose by adding the weight of mat.
I find that it's harder to wet out 1708 with epoxy than with vinylester--you have to give it longer.
So, it works, but there's better ways.

[coopec43]

As someone else on these forums said the Gougeon Brothers have done a pretty slick marketing job on promoting their "WEST System" epoxy products. Outside the US of A polyester or vinyl ester resins would be almost exclusively used repairing fiberglass boats.

[mitiempo]

Originally Posted by pcmm

One of the nice things about 1708 is the mat stabilizes the biaxial. I've used just biaxial AND 1708 and I find biaxial by itself moves and can distort easily. The mat in 1708 makes the biaxial less "squirrely" at the beginning, making placement an shaping a bit easier. Both are great products!

I agree. I have used 1708 for many small repairs as well as glassing bulkheads in. I wet it out on a sheet of ply covered with plastic and place it on wet. Never had a problem wetting it out with West epoxy.

The op is re-coring a portion of the deck. He doesn't need the ultimate strength so much as he needs to build the glass up to the same thickness as the original.
1708 will add thickness fairly fast and will surely be stronger than what Dufour used in 1983.