Bond new floor to hull

I've put a new plywood deck in my 18 foot fibreglass boat, and I'm looking for information on the most effective way to bond the edges to the fibreglass hull in order to prevent leakage. What kind of cloth should I use, and how many layers. I also plan on coating the entire floor with epoxy, can I just apply directly to the wood, or must I use cloth?

Re: Bond new floor to hull

Dunromin said:

I've put a new plywood deck in my 18 foot fibreglass boat, and I'm looking for information on the most effective way to bond the edges to the fibreglass hull in order to prevent leakage. What kind of cloth should I use, and how many layers. I also plan on coating the entire floor with epoxy, can I just apply directly to the wood, or must I use cloth?

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I would recommend just using CSM and polyester resin to seal the deck plywood and you can use one layer of 1708 and resin to tab it into the hull? The polyester resin is fine and much cheaper than the epoxy.

What method did you use to seal the underside of the plywood?

If you still choose to go with epoxy then you are correct about sealing the plywood. You can just coat it and you're fine. To tab in the sides to the hull a layer of say 17 oz biax (no mat needed) will be fine.

Re: Bond new floor to hull

You do not have to use epoxy unless you choose too. It is much more expensive than polyester resin. Here is how I recommend installing a deck. I recommend using Unwaxed Polyester Laminating Resin, 1.5 oz CSM (Chopped Strand Mat) and 1708 Biaxial Cloth. 1/2", 5/8" or 3/4" Marine Grade Ply wood. You can use MDO Plywood, or a good grade of Ext. Grade Plywood. Costs will be a factor. www.uscomposites.com is a good online source for materials.


(click the pic to enlarge)

Re: Bond new floor to hull

Thanks Cadwelder, I used System 3 S1 sealer.

Re: Bond new floor to hull

Thanks Woodonglass, my ignorance on these matters is about to become apparent, first, regarding bonding deck to hull, is one layer of 1708 Biaxial cloth sufficiently strong, or should I use more, and secondly, am I correct in assuming that CSM is to be mixed with the resin before applying to deck?
How is resin applied, with roller or brush, and how many coats?

Re: Bond new floor to hull

I mentioned in another thread, once you break into 1708 (or any cloth), you can easily tear off any exposed fibers, say due to wear on the deck which will make it worse in the longer run.
If you lay CSM on top of 1708 it would protect it better from potential damage.

Re: Bond new floor to hull

CSM is short for Chopped Strand Mat. After tabbing the deck to the hull with the 1708 you will then overlay the entire deck extending beyond your 1708 tabs with CSM and wet it out with the poly resin. Once I got to the CSM, I found it was easiest to pour the resin onto the deck and spread it with a plastic squeegee (auto body filler spreader, a big one) and then roll out any bubbles with a roller. You only want to mix enough resin to cover the area you are working. Others may have better ideas.

Re: Bond new floor to hull

1708 is a Biaxial Woven Cloth that has 8oz of CSM sewn to it's back side. One layer of it is sufficient for the topside of your deck. It is SUPER strong stuff. The CSM comes in 38" and 50" widths and is sold by the yard (36"). It is NOT mixed with the resin but is layed down in layers and then saturated with the resin like coostv described. You should coat the plywood with the resin first. If not it will suck up the resin and you will get dry spots in the CSM and a bad bond. You'll need 3-5 gallons of resin to do the top and bottom sides of your deck. The final layer of CSM is debatable in my opinion but can be applied if you want. My drawing shows how I recommend buildinig a deck. It's your boat so you can do it how you want.

Re: Bond new floor to hull

Dunromin said:

I've put a new plywood deck in my 18 foot fibreglass boat, and I'm looking for information on the most effective way to bond the edges to the fibreglass hull in order to prevent leakage. What kind of cloth should I use, and how many layers. I also plan on coating the entire floor with epoxy, can I just apply directly to the wood, or must I use cloth?

Click to expand...

Here is how I do decks ..

Material Schedule :

1 layer of1.5 oz mat strips along the deck seam
1 layer of 1708 strips along the deck seam
1 layer of 1.5 oz over entire deck and seam

Polyester resin

Application :

Pre-cut Everything before you start.

Pre-coat the wood with resin as already mentioned above. * this is step is required * .

Apply resin to the deck seams.. then apply the strips of mat and 1708.
Apply resin to the deck .. put down your 1.5 oz mat on the deck ( this is not one Big piece.. but smaller manageable sizes ) . Resin coat the 1.5 oz mat until its fully saturated.

I use a regular paint roller to apply glass in larger sized areas such as this .

Now you want to use epoxy .. that's fine ..

3 layers of 1.5 oz mat should do on the seams .. then coat your deck until it stops absorbing. ( might be a lot of epoxy depending on what kind of wood you used ).

Good luck and put some pics up for our viewing pleasure

YD.

Re: Bond new floor to hull

Yacht Dr. said:

Now you want to use epoxy .. that's fine ..

3 layers of 1.5 oz mat should do on the seams .. then coat your deck until it stops absorbing. ( might be a lot of epoxy depending on what kind of wood you used ).

Good luck and put some pics up for our viewing pleasure

YD.

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"The random pattern of the CSM works to hold resin suspended throughout the fiber. This makes it more watertight by helping to prevent dry areas and it will help to hold resin on to vertical surfaces. It also helps to localize fracturing in polyester resin or prevent it alltogether. Epoxy has these qualities by nature in the resin alone, therefore CSM is not needed in most instances. When coating with epoxy it is generally accepted that light and medium weight cloth is all that is needed. Epoxy is also stronger and less likely to fracture when mixed correctly and is more watertight. That is why you can build stronger, lighter parts out of epoxy and cloth. " EZMOBEE

Quote is from an earlier post by another respected iBoater!!! I think the use of Mat with epoxy is a waste of money. Fiberglass cloth would be a much better choice when using epoxy.

Re: Bond new floor to hull

Yacht Dr. said:

Here is how I do decks ..

Material Schedule :

1 layer of1.5 oz mat strips along the deck seam
1 layer of 1708 strips along the deck seam
1 layer of 1.5 oz over entire deck and seam

Polyester resin

Application :

Pre-cut Everything before you start.

Pre-coat the wood with resin as already mentioned above. * this is step is required * .

Apply resin to the deck seams.. then apply the strips of mat and 1708.
Apply resin to the deck .. put down your 1.5 oz mat on the deck ( this is not one Big piece.. but smaller manageable sizes ) . Resin coat the 1.5 oz mat until its fully saturated.

I use a regular paint roller to apply glass in larger sized areas such as this .

Now you want to use epoxy .. that's fine ..

3 layers of 1.5 oz mat should do on the seams .. then coat your deck until it stops absorbing. ( might be a lot of epoxy depending on what kind of wood you used ).

Good luck and put some pics up for our viewing pleasure

YD.

Click to expand...

Their you go thinking again.

Re: Bond new floor to hull

No doubt

YD.