How to fiberglass a deck and foam a hull

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oops!

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A very common thing that we get asked on iboats ...is how to glass a deck and foam a hull.

I typed this answer for another thread, but decided it needed its own search easy thread for future reference.

When glassing a deck after it has been cut and fitted to the hull.

What you are looking to do is to encapsulate the plywood deck with glass.....on the bottom...and on the top, with more layers of glass on the top for wear.

The minimum you want on the top of your deck is 8oz. of glass. I use 2 layers of 1.5 csm, and a 6 oz woven. This gives me 9 oz on the deck with a smooth surface.
The tabbing is done with one 6-8 inch layer of 1708.

If you are adding a ski locker or any other under deck storage.....cut the holes out before you install the deck.

To properly do the deck......sand your wood (both sides).....and vacuum it off. Mix some unwaxed resin at 1.5 % mekp or even at 1% (70 deg) and wet out the underside of the deck and all edges.....wet it out good. .....wait till its tacky and starting to cure. Then mix some resin at the proper 2% cat rate and 4 % wax....and glass a layer of 1.5 oz. to the bottom of the deck.....let cure.
Dont worry about glassing the edges.

Thats the under side of the deck......done.....you can paint that if you wish, just for extra protection.....make sure you use a primer over the waxed resin. most people don't bother painting.

Now it is time to prep the hull for glassing.......grind (rough and scuff) the area where the hull will meet the deck, and about 9 inches higher.....all around the hull....(kinda like a bath tub ring) all you want to do here is grind off the top layer of resin on the hull to get to the surface glass. This can be done quick....and don't go very far into the glass at all....just the top layer of old resin.

Now vacuum the hull thoroughly......and clean with acetone.......don't just wipe it with a damp rag....but liberally wipe the area with lots of acetone.....your intent is to wash the area. !

Its time to screw your deck down.......mark the stringer and frame locations using a chalk line......this is where your screws will go.......lay down the deck....and pre drill the holes.....
fill the holes with a good amount of 3m 5200.,,,,,and screw down the deck. wipe off the excess 5200.

Now that your deck is all screwed down, its time to cut the fibreglass. don't worry about the deck hull gap right now....we will deal with that in a second.
cut your first layer of csm so it will cover the deck and go up the side of the hull 4 inches. and another one slightly larger so it will cover the same area but 6 inches up the hull.
then cut the exact same size of 6 oz woven roving.

For proper tabbing, use 1708 bi axe...cut several strips 8 inches wide....(you may also choose to use double tabbing by cutting another strip 12 inches wide and double tab the hull)
when you cut the 1708.....cut it going with the weave of the fabric. not across it......this will give you a frayed top edge that is just a real pain in the azz !
Cut enough strips to go all the way around the perimeter of the deck.
(usually you will have enough scraps from cutting the stringer glass to do this)

If you choose to go with double tabbing.....make sure that your second, larger layer of csm and the final 6 oz woven will cover the second larger 1708 tab.

Now that the glass and the tabbing is cut, lets deal with the gap around the edge of the deck and hull joint.
Some people use pl premium for this.....I don't like it because of the full 48 hour cure time before you can glass over it.....and I would rather have fibreglass between the hull and the deck....so I use peanut butter.
Mix up some peanut butter....and fill the gap, making sure that you don't have any sharp ridges, and that there are no dips in the gap.
If you get a dip......just wait till the peanut butter stiffens (starts to cure) and go over it again.

If the job is really rough.....wait till it cures, and grind it smooth.....You will have to vacuum and acetone the hull again.

If you wish.....you can leave small "gaps" at the transom area through to the bilge only.....This is so any deck water can drain to the bilge.....Do not leave gaps any where where you are going to foam.

This is the point where you foam the hull

Foaming the hull
If you wish to foam the hull using a totally water proof method.....so the foam will not ever get wet or water logged...read this link....
http://forums.iboats.com/showthread.php?t=234392 go to page 167....post 4158

This method covers usage of conventional pour in foam...
With a large hole saw......cut 2 rows of holes in each area that you wish to foam. (usually the area under the deck between the outer stringer and the upper gunwale). From back to front, the holes should be 10 inches apart. one row....near the side of the hull......the next row......4 inches away from the stringer.....keep all the cut out pieces.

Starting at the deepest part of the hull (usually the back).....pour in your foam through the hole near the side of the hull, let the foam run down and pool near the stringer and let expand.....then wait....give it 5 mins each time you pour it in...let it expand like it should. the holes near the stringer should have foam expanding out the top. pour in more foam into the same hole till it expands from the hole near the side of the boat..
repeat this process till your hull is foamed. both sides. Make sure the foam has properly expanded out the top of the holes, so there are no air voids under the deck (in the foamed areas).
After all the foam is poured in.....wait a full hour till the foam has properly expanded and cured.

Now we have to replace the wood in the cut out holes....
Take a utility knife and cut the top off the foam that has expanded out of the holes.

Take one of the cut out pieces of deck you kept..... re insert it back into the hole saw (with out the drill bit in the saw) and using 40 grit sticky back sand paper.....stick the sand paper to the wood in the hole saw, re insert it into the drill ....and sand the foam till you get to the depth of the deck. quickly check your work by placing a cut out back in the hole....a little too low is ok....high is not. make sure its flush with the deck. Do this to all the holes.

As before, mix up some resin at 1.5 % and liberally coat the edges of the cut outs....on the deck and the cut out parts. let cure till tacky.

While that is tacking........
Mix up some peanut butter.....catylize the resin first 1.5.....add your milled fibres, cabosil and glass bubbles...and mix that all together and coat the edges of the holes in your deck liberally with peanut butter....replace the cut outs and make sure the peanut butter squishes out the edges....If you have sanded the foam too far, and the insert too deep, just take a putty knife and add more peanut butter on top of the cut out till the deck is flat. repeat till all holes are filled to deck height.

At this time......I should mention, that you can do it another way......forgoing the top row of holes, and using the gap between the deck and hull to pour in your foam. this will save you the time of drilling the row of holes closes to the side of the hull, however it means that you must remove the excess foam between the gap so that you have proper contact to the hull and deck for the peanut butter......this can be done with a sawzall. But its time consuming to do properly.....You still need the row of expansion holes nearest the stringer....So its your call.

Time to glass the deck.

Now again,....using 1.5% unwaxed resin.

Wet out the whole top deck, front to back......saturate the wood....wet it out good, use lots of resin.......as before.....let it get almost cured...tacky, but not hard. (make sure you test the resin at the front part of the deck.....forget about the back part ...you started wetting out at the front...so that is where you will start glassing....the back will be semi cured by the time you get there).

If you are not going to gel-coat the deck....but just lay a carpet over raw glass. use waxed resin at the usual 2% cat rate, 4 % wax......if you are going to add another layer of anything over the raw glass...like gel-coat or dura deck.....ect....use unwaxed resin...
Again.......use waxed resin only if this is the last layer of glass that will contact the air (or carpet).
Everything else....use unwaxed. (if you change your mind later....and decide to gelcoat....the top layer of wax MUST be ground off).

Now....here is where it gets tricky.....Take a piece of plastic, big enough to move around on.....and lay it over the wet resin....but leave your area that you are working on first open and uncovered. This plastic is so your clothes don't stick to the deck when you are glassing and to lay the dry rolls of fibreglass in front of your knees when you are doing the deck.

Take the first layer of 1.5 oz csm. and glass only the area you can reach....you want to glass up the sides of the hull so wet it out over the tacky resin, and glass the deck and up the side of the hull minimum 4 inches. glass right over the tacky peanut butter you layed for the hull deck joint....if you did this properly...there will be no sharp edges or ridges to contend with.
this is your first layer and first bond......so get as much air out with your resin roller as you can.
Leave the rest of the glass rolled up in front of your knees ...so you can just unroll the glass like a carpet as you move farther down the hull.

One of the basics of glassing is to just use enough resin to fully saturate the glass, but not have so much that there is excess......With resin, remember...less is more
Since you are doing multiple layers at once.....you can use more resin in the second wet out stage....(after you have resin coated the wood till tack, and are wetting out for the first layer of csm).
After the section you are working on is glassed with csm, it is now time to tab the hull deck joint.
Take your pre cut 1708 8 inch wide strips and lay them half on the deck and half way up the wall of the hull.....glass them in.
If you chose to go with double tabbing....glass the larger pieces of 1708 now......go a little higher up the hull and lower on the deck.

Next.....take the larger second layer of csm, and lay that over the area.....and glass that in including over the tabbing...and higher up the wall....This is all done wet on wet.....so a good chemical bond is formed.
Now take the final layer of 6 oz woven roving....just lay it over everything. and using your resin roller....glass that in.....the 6 oz needs very little resin. to soak in...so it will usually drink any excess resin that was left over from the previous layers..

Now.....move your plastic back...and work on the next area you were just kneeling on...and repeat the process unrolling the fibreglass each time till you are all the way to the transom.
Watch out that you don't glass your self into a corner....and have the plan for glassing in your head before you start...

If you have left a hole for drainage in the peanut butter....just make sure that the hole is not glassed over.
if you have a ski locker, glass over the hole in the deck over the locker....but no need to resin coat the class that will be removed....just cut the glass after you have reached a full cure from the resin.

If you do have any major air bumps in the cured glass......the top can be quickly ground off after its cured......but don't grind down to the wood, or you will be glassing again....just grind off the bump.

That's it.......you are done. Beer time.

As you can see....this job will take a full day. it can be broken up into sections....after the deck is foamed...or after the peanut butter is added to the gap around the edges...I like to do it all at once, because of the good chemical bond you get.

cheers
oops
 
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zopperman

Lieutenant Commander
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Re: How to frbreglass a deck and foam a hull.

Re: How to frbreglass a deck and foam a hull.

How to frbreglass a deck and foam a hull

What's frbreglass :p

Just messing with ya, oops. This would have saved me so much time on my project!! Well said and easy to follow instructions. :D
 

oops!

Supreme Mariner
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Re: How to frbreglass a deck and foam a hull.

Re: How to frbreglass a deck and foam a hull.

What's frbreglass :p

it is a composite material made from inter woven glass fibres and resin.......it is used to replace reevits ! :D
 

GT1000000

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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

To the Moderators,
Please, don't take this the wrong way,I do not want to overstep my bounds, but...
This is a really great step by step guide and I think it should be added to the fiberglass how to's sticky, because before long it will have disappeared deep into the forum and no one will remember it or find it and it will have to be re-written.
Thanks for not screaming at me or throwing rocks...:redface:
GT1M
 

zopperman

Lieutenant Commander
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Messages
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

To the Moderators,
Please, don't take this the wrong way,I do not want to overstep my bounds, but...
This is a really great step by step guide and I think it should be added to the fiberglass how to's sticky, because before long it will have disappeared deep into the forum and no one will remember it or find it and it will have to be re-written.
Thanks for not screaming at me or throwing rocks...:redface:
GT1M

Second
 

oops!

Supreme Mariner
Joined
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

bumping for comparison to alum boat above link

to all future iboaters that see the above post by jasoutside......we are in currently in a fun debate about fibreglass and aluminium boats.....

however, the steps outlined are correct for a fibreglass boat
 

jaybeava

Seaman Apprentice
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Messages
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

Hello all! First off I just wanted to say thank you for the great info. This is always my first stop for everything and the info you provide is the best on the web.
On to my question... Oops, you mentioned " To properly do the deck......sand your wood (both sides).....and vacuum it off. Mix some unwaxed resin at 1.5 % mekp or even at 1% (70 deg) and wet out the underside of the deck and all edges.....wet it out good. .....wait till its tacky and starting to cure. Then mix some resin at the proper 2% cat rate and 4 % wax....and glass a layer of 1.5 oz. to the bottom of the deck.....let cure. Dont worry about glassing the edges."

Can you explain mekp, cat rate, and differences/advantages:confused: between wax resin and non wax? I am not sure what exactly to purchase and how to mix. Would standard polyester "Boaters Resin" get me started? I do have some basics in aviation composites but its been a while.

Thanks for the help
 

oops!

Supreme Mariner
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Messages
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

hi buddy.......welcome to iboats.

boaters resin is just fine.....in fact....just about any poly fiberglassing resin will be strong enough.

you need to add some stuff to the resin to make it hard......or to make it do what it is supposed to.
just pouring it out of the pail and waiting till it gets hard is not enough.....it wont ever work.
you need to add a catylist.
Methyl Ethel Ketone Peroxide or MEKP for short.

MEKP is added to the amount of resin that you are going to use....
lets say you want to use a quart.....you need to add some MEKP to the resin......but how much?
this is called the cat rate. (Catylization ratio)

studies have shown that MEKP added to resin give the basic user the best results at 1.7-2.5% of resin.
Studies have also shown that 1% MEKP is very strong.....the problem is that .09% is really weak !. so to measure that minuscule amount. you need to be a chemist. as some of the MEKP sticks to the side of the material you are using to pour it into. (kinda like getting that last drop out of a beer can.....lol)
using the imperial method to measure how much MEKP going into......is a freekin headache !!!!....you need a slide rule.
i use the metric system.....1 ltr is close enough to a quart.....one lieter is 1000 ml of resin. (a beer can is 355 ml).
so if you want to mix at 2% you use 20 ml of MEKP......20 mil is about half a shot glass...or half an ounce.


this is also compounded by the fact that properly mixing that little amount, is very difficult, and most of the resin in the pail has little or no MEKP in the resin.

by adjusting how much MEKP you add and stir in well....you can make the resin last longer in the pot or shorter.
this will give you a longer time to work with the resin before it turns to jelly...then almost instantly it will get hard.
it takes about 15 minits for a pail of resin to turn to jelly approximately 15 minits at 2% added MEKP.....or a cat rate of 2%.

some times we mix cold......1.5 % (long working time...20 minits) or hot....2.5% cat rate (caytilization ratio)....(5 mins working time)

when mixing mekp into resin, dont guess......measure !....there are many places to get metric system measuring devices.....if you cant find any....pm me and ill send you some....

to properly mix resin and MEKP. you need to really stir it well. just swishing it around a jar with a stick is not good enough !......you need to really mix it.....scrape the sides of the jar and the bottom.

i personally use an egg beater attachment in a drill.
 

oops!

Supreme Mariner
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

in doing any job....research is king.

the link in my sig covers anything you need to know about fiberglassing in the first 16 pages...it is a really good read.
if you read all the posts....pay particular attention to ones from a guy called ondarvr....he is one of north america top resin/gellcoat experts.

after reading the first few pages....you will feel like you have all you need to do your project sucessfully !
cheers
oops
 

oops!

Supreme Mariner
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

sorry....it was very late last night when i typed that and i forgot about the wax/unwax question.

waxed resin is a finishing resin.
and is used on the very top layer only...not in a laminating application.....
wax also is used as a mold release when they make a boat......
they wax a mold.....then they spray gellcoat into the mold. (gellcoat is basicly a pigmented poly resin).
the wax will not allow any thing to stick to it...so when the boat is finished in the mold.....the hull will pop out of the mold.....if they did not use wax......the hull would just bond to the mold. and the whole thing, hull and mold would be garbage.
for this reason......waxed resin is never used in a laminating application

ok...let me explain....

first off.....there is a heat issue of curing resin.
when a glassing job is done.....sometimes we add several layers of fiberglass to the resin....when the resin cures...it gets really hot.
if it gets too hot....the resin will cook and become brittle. so several layers of resin application may be needed.
you will need to let the resin cure enough that the heat comes out of the resin before you can add another layer.

now dont panic here.....you can do several layers before you have so much resin that it will cook....you can do six layers of csm...or three layers of 1708 before you need to worry.

as well.....if you are using thickened resin (on iboats forums we call thickened resin peanut butter). depending on how much you use to fill a wide gap....you will need to let it semi cure before you add layers of fiberglass to it....sometimes you really need to add gobs of thickened resin to an area....the bigger the gob.....the more heat it will build up on cure.

second......wax is a release agent

if we used a wax resin for the first layer.....and let cure.....then we tried to add another layer over top....the second layer could not bond to the first one....it would easily pull off....(remember wax is a release agent that stops resin from bonding)

you might be asking .....why use waxed resin at all?....what's the point?

well ...two major reasons....the major reason is that air inhibits (slows or stops) the cure of resin.
unwaxed resin will remain sticky on top for several days to weeks.
this is because the top layer is not fully cured due to air.

the second reason is that resin is not totally 100% water proof....small water molecules may get thru the resin and fiberglass lay up over a long period of time.....so wax is added to the resin.
when the resin cures...the wax in it will come to the surface and form a barrier between the resin and air...it increases the water proofing of resin and it also cures hard and non sticky in just a few short minits.

wax is sometimes called and sold as "airdry"

you can purchase un waxed or waxed resin....and as mentioned....you can also just purchase "airdry" and add your own wax.
was is added just like MEKP and mixed very thoroughly in to the resin....
wax is added between 3 and 5% of the resin amount.

personally... i never buy waxed resin.....i buy airdry and add it to the unwaxed resin.
this stops any potential mix up of products during laminating
 

ShellBack89

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Messages
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

Opps,

Thanks for the great information. Between you, Wood and Frisco I "almost" feel confident enough to tackle my Sea Ray and with GT1M rooting me on, I just might "Git R' Dun". Thanks again!:D

SB89
 

jaybeava

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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

Thanks for the info! I am starting to gain some confidence in tackling this deck/foam project. Where would I find the wax resin used at the manufacturer? Don't want to run into any surprises :) Do you typically use wax on your last flooring layer or is it not as critical?

Also had a question on stringers... Since tearing into the aft decking on this Bayliner and removing the foam I noticed that the foam was pretty wet and mainly where the stringer and hull meet. Does this mean there is a good chance that the stringers need replacing? Besides drilling the stringer to get a core sample and sealing with 5200, is there another inspection method? I'm getting a bit worried as this might have opened up a whole new dimension. I'm working on this in my apartment parking lot (I miss my garage) and I'm not able to pull the engine if needed for stringer repair. Yet to find out about fwd engine mount (yikes) . I'm starting to dislike foam! Lol. Running into this makes me think that this probably a more common issue than most owners realize. Thanks again for your help.
 

oops!

Supreme Mariner
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

hi jay.

ok.....waxed resin is a top coat on the deck only.. and on the layer of glass on the under side of the deck.

any place where there will be nothing else on top of the fiberglass.

so if you want to gellcoat your deck.....dont use waxed resin.
again....i would buy un waxed.....and add the air dry when i mix the top layer.

but waxed resin can be bought at the same place that you buy laminating resin.

as far as your stringers......chances are they are glass over foam....that means....they dont have any wood to rot !.

start a thread on your restoration and we can answer all your questions.....and you will be on the water right away !

cheers
oops
 

krakatoa

Senior Chief Petty Officer
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

Hello There Fiberglass Man!:D What a topic, very very interesting since Im in my way to deck restoration on my 19 footer but I have a few DUH!!! question

1.CSM stand for......
2.The tabbing is done with one 6-8 inch layer of 1708 What is 1708?
3.For proper tabbing, use 1708 bi axe... this line stand for.....?
4.More or less, How many yards of fiberglass including the woven should I buy for a 19 footer Bow Rider?

And a last personal question.....

What you think about PVC 3/4 Panels for flooring a boat?

THANKS!forgo
 
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Woodonglass

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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

CSM - Chopped Strand Mat - First layer that goes down when using Polyester Resin. The styrene in the resin actually dissolves the strands in the mat and makes the mix stronger.

1708 is a Biaxial woven cloth meaning, the weave of a 17 oz cloth is done in both directions at a 45 degree angle which gives it greater strength and then finally 8 oz of CSM is sewn to the back of the cloth. Kinda one stop shopping.

Tabbing is the process of laying stips of the biaxial cloth on the deck and then up onto the sides of the hull to connect the two. 4 to 6 inches on the deck and 4 6 to inches on the sides of the hull.

Check the first link in my signature for some helpful drawings that should help you visualize the process. You should put one layer of CSM on the bottom of the deck and then 1,2, or 3 layers on the top.

For a materials list for your 19' boat my GUESS-TI-MATE would be you'll need a minimum of 5 -10 gallons of resin(you should always precoat the wood before laying the CSM and fill any voids in the edges of the wood to prevent air bubbles. After you precoat the wood, while it is still sticky and tacky you can lay the first layer of CSM and wet it out with resin. A fiber glass bubble roller really helps lay the glass down with out air bubbles) and 15-20 yds of CSM and I'd buy 30 ft of 1708 12" tape. (Precut strips of 1708).

Not sure of the availability of these products in Puerto Rico, but you can order them on line here... www.uscomposites.com
 

krakatoa

Senior Chief Petty Officer
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

Thanks for the info, BIG HELP!
 

Yacht Dr.

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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

The minimum you want on the top of your deck is 8oz. of glass. I use 2 layers of 1.5 csm, and a 6 oz woven. This gives me 9 oz on the deck with a smooth surface.
The tabbing is done with one 6-8 inch layer of 1708.

I just started to read this .. but had to say real quick ..

CSM is weight/Sq foot .. not yard.

So you have approx 27 oz of CSM ( if apples were apples ). :) Thus making your total ( by yard ) 35oz.

Unless I am missing something here ..

.... Continue reading ...

YD.
 

81 Checkmate

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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

Great write up! OOPS!

Just a quick question or two?

1. If you use a Poly resin, would the last coat require the wax to be added?
2. Do you lay the Tabing strips across the boat from side to side and over lapping each other, or do you lay it from Bow to Stern?
 

oops!

Supreme Mariner
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Re: How to fibreglass a deck and foam a hull.

Re: How to fibreglass a deck and foam a hull.

hi check mate....

yes....add wax to the last layer of resin, unless you are intending on gellcoating the deck....then no wax.

with poly resin or gellcoat.....the last layer that touches the open air, should have wax.

the tabbing strips....are just 6 to 8 inches wide.....they go across the hull deck joint....so bow to stern
 
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