what fiberglass materials to use for transom replacement?

72cheyenne

Seaman Apprentice
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May 29, 2010
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Hey fellas, looking at doing my first transom replacement. I kind of know the process and am descent with fiberglass but never did a boat. I am wondering how much poly resin, what type of cloth and other items I may need to replace the transom boards back in on my 16' nordic crestliner runabout? Any help would be appreciated.
Thanks
Nigel
 

Cadwelder

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Re: what fiberglass materials to use for transom replacement?

Marine grade plywood (there are other choices) and polyester resin. CSM and 1708 are the materials of choice here on the forums. For your transom only, I'd guess three gallons.
 

oops!

Supreme Mariner
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Oct 18, 2007
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Re: what fiberglass materials to use for transom replacement?

ok....here we go.


as far as plywood marine grade is allways the best....but is not allways avalable locally.
exterior grade plywood is allmost the same as marine, the big thing you want is the glue.....it needs to be waterproof....this is found in the exterior grade (not osb).

i have found that at least one peice of 1 inch thick, works fantastic for flatness.
you will need to make up the thickness of your transom however you can.
1x1 inch plus 1 x 3/4 inch....ect

you will need 2 gals of resin...minimum
i suggest standard unwaxed polyester.

8 yards of 1.5 oz csm
3 yards of 1708 biax
a small bucket of milled fibers...(powder)
small bucket of 1/4 inch short strand.
1 can of acetone
1/2 liter MEKP

as far as tools...
you need several mixing sticks.
i prefer a egg mixer on a drill.
a mekp mixing cup...(plastic shot glass)
a few ice cream pails (i like proper measuring buckets)
your fuzzy roller with several rollers
fiberglass resin roller
several bondo spreaders.

there ya go
cheers
oops
 

72cheyenne

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May 29, 2010
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Re: what fiberglass materials to use for transom replacement?

thanks guys for the info, I will be using a piece of 3/4" acx plywood and laminate it together with a 1/2" piece. Now should i Completely coat the wood transom with fiberglass before installing?
Thanks
 

72cheyenne

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May 29, 2010
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Re: what fiberglass materials to use for transom replacement?

also where is a good place and/or website to get the supplies from?
Thanks
NIgel
 

TruckDrivingFool

Lieutenant Commander
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Re: what fiberglass materials to use for transom replacement?

I and many others have use uscomposites but depending on where you are shipping can add up. I'm just about done with mine (roughly 77"x25") and had many of the same questions. So far I've about 4.5 gals of resin but this my first time doing FG so I would say my waste is about 3/4 to a gal. Plus I had a redo on making my lamination, so I'd guess it about 3 gallons of resin. and I've go through 4yrds of 1708 and not sure on the csm (due to the remake). If you go through US Comp I will warn on the hardener if you use the plastic shot glass that comes with it, read the cc measurement and not the ounce as they suggest in their pamphlet. I've been using 5cc per pint and 10cc per quart and getting 20 minutes before it kicks in the pot.
 

DeepBlue2010

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Re: what fiberglass materials to use for transom replacement?

Here is some info to help you catalyzing your resin
A) 1 cc = 1 milliliters (So you can just replace cc by ml in your calculations as I did below)
B) 1 US fluid ounce = 29.57 milliliters
@ 1% catalyst/resin ratio
You need about 0.3 milliliters of MEKP per ounce
For a pint (16 ounces) you need (16*0.3) = 4.8 ML ~ 5 ML ~ 5 CC
If you choose to increase your catalyzing ratio to 1.5 for instance, you just repeat the calculations (it will be 0.44 milliliters per ounce in this case). Be sure to read the recommended ratio on the resin you buy. Stay closer to the lower range; it will give you more time to work without compromising the curing process.
 

oops!

Supreme Mariner
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Oct 18, 2007
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Re: what fiberglass materials to use for transom replacement?

@ 1% catalyst/resin ratio


If you choose to increase your catalyzing ratio to 1.5 for instance, you just repeat the calculations (it will be 0.44 milliliters per ounce in this case). Be sure to read the recommended ratio on the resin you buy. Stay closer to the lower range; it will give you more time to work without compromising the curing process.

sorry.....this is incorrect.

the correct ratio of mekp to resin (ANY POLY RESIN) is 1.7-2.5 %

some of the mekp manufacturers claim you only need 1% resin to mekp ratio........this is a very weak mix and will crack.

i use 2% on every thing...including gellcoat.....it is very safe and strong.

if you need more working time.......ask for a ddm, instead of a mekp. the ratio for a ddm is still 1.7-2.5%
 

TruckDrivingFool

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Re: what fiberglass materials to use for transom replacement?

Not to hi-jack but,

oops! - That means I should think about upping my mekp to at least 7.5cc per pint and 15cc per quart. Correct?
 

oops!

Supreme Mariner
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Re: what fiberglass materials to use for transom replacement?

Not to hi-jack but,

oops! - That means I should think about upping my mekp to at least 7.5cc per pint and 15cc per quart. Correct?

sorry bud i work in metric.

try using that system....its much easyer.

for 100 ml......you use 2 ml of mekp.
for 500 ml you use 10 ml of mekp.
for 1000 ml you use 20 ml....

really simple
 

TruckDrivingFool

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Re: what fiberglass materials to use for transom replacement?

2 per 100 easy enough I'll give it a try thanks.
 

72cheyenne

Seaman Apprentice
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May 29, 2010
Messages
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Re: what fiberglass materials to use for transom replacement?

well thanks a lot guys for the mixing info and all other info. It really helps a lot. I will be starting a new thread within the next few days on the work where I'm sure I will have more questions. Thanks again, it's very appreciated
Nigel
 

DeepBlue2010

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Re: what fiberglass materials to use for transom replacement?

oops, as always, I appreciate your input and recommendation. Just to clarify, I wasn?t suggesting any specific mixing ratio.
Be sure to read the recommended ratio on the resin you buy. Stay closer to the lower range; it will give you more time to work without compromising the curing process.
Which is the same as you did with your suggested ratio (1.7%-2.5%) catalized @ 2%.
I choose 1% simply because it is the simplest example for the calculations and you can easily apply the same methods using any percentage. However, I didn?t know that 1% is not an acceptable ratio even if it was recommended by the factory. I am glad I read your post before I start mixing for my boat. Thanks
 
Joined
Aug 2, 2011
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Re: what fiberglass materials to use for transom replacement?

MEKP = Methyl Ethyl Ketone Peroxide and according to Florida's hazardous waste management guide for Fiber-Reinforced Plastics it "May be explosive" Can cause blindness and affects the central nervous system....among other things....I understand lots of things can be dangerous, but this MEKP sounds extremely dangerous 8O !!!
 

kahuna123

Senior Chief Petty Officer
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Jun 2, 2011
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Re: what fiberglass materials to use for transom replacement?

you mix it at down here at 2 in 90 degrees at 90% humid and you'll be throwing away hot buckets. 1.5 is more than enough. If you live in that Tampa Bay Area you are welcome to bring it over and we will have it done in a day. You supply the materials. If not PM me and I will walk you through it.
 

winston596

Cadet
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Jun 5, 2011
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Re: what fiberglass materials to use for transom replacement?

Not to hyjack the post by why poly resin instead of epoxy resin?
 

Woodonglass

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Re: what fiberglass materials to use for transom replacement?

That's what the boat is MADE out of. Epoxy will work, but at twice the cost. No NEED to use it, but you can if you want.
 
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