1991 Thompson Cutlass 195

magna83

Cadet
Joined
May 26, 2011
Messages
8
1991 Thompson Cutlass 195 with 5.7l Alpa 1. Well got sucked into a boat project. Thought my neighbor was giving me one heck of a deal. We both live on the lake and he bought the boat brand new. Kept it on enclosed dry lift and took really good care of the boat. He has not used the boat the last couple years. Decided to sell for $1000 with roll off trailer. Started the boat on muffs in driveway ran fine, checked dipstick, etc. Even had an certified mechanic (friend) there it checking out. There was a small soft spot in the floor just in front of the motor. Well took it to the lake last Sunday for the first time. Well after the warme engined was introduced to the cold water there was instant brownish foam all over the intake. Yep. Incorrect winterization that did not show while on the muffs. Should have done a lake test. So pulled motor on Monday and it is currently at the machine shop getting fixed. It was an as is sale and boat is definitly worth fixing. Pulled carpet back and removed the deck from just infront of the gas tank to the back of the boat. The stringers are in fairly good shape considering the lower 7/8 of the stringers were already fiberglassed on the majority of the boat. Since Monday, I have been reading endlessly on the forum in the shadows. I have a couple questions:

1. The peanut butter, is that ment to be used to hold the stringers in place and then tab after that? I also read somewhere that they used PL or liquid nail first then peanut buttered the 90 degree (boat to stringer) seam, and finally tabbed with fiberglass.

2. I just left a place talking about fiberglass. They even gave me enough to do some of the tabbing for free. Now this is the question as it conflicts with some of what I read. They told me after I installed the new Marine 3/4 plywood that I need to lay the resin/hardner mix on the entire bare wood, lay cloth only on the seams (for 2-3 layers on seams only) and only resin/hardner on the unseamed wood for all layers. They told me that the fiberglass adds strength which is not needed because of the wood and the stringers. Can someone please shed some light.
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,929
Re: 1991 Thompson Cutlass 195

Welcome to iBoats!

1. The peanut butter, is that ment to be used to hold the stringers in place and then tab after that? I also read somewhere that they used PL or liquid nail first then peanut buttered the 90 degree (boat to stringer) seam, and finally tabbed with fiberglass. You can use either. I prefer PL. It is used to keep the Stringer off the HULL and developing "HARD SPOTS" which can cause cracking when the hull flexes. PB IS used for Filleting all of the edges of the stringers, Transom, and edges of the deck.

2. I just left a place talking about fiberglass. They even gave me enough to do some of the tabbing for free. Now this is the question as it conflicts with some of what I read. They told me after I installed the new Marine 3/4 plywood that I need to lay the resin/hardner mix on the entire bare wood, lay cloth only on the seams (for 2-3 layers on seams only) and only resin/hardner on the unseamed wood for all layers. They told me that the fiberglass adds strength which is not needed because of the wood and the stringers. Can someone please shed some light.
Couple of things here. While Marine Grade plywood IS the best ply to use, there ARE GRADES of it as well and some of the Lower grades of Marine Grade are not THAT much better than using regular Ext. Grade Fir Plywood. So unless you want to spend the Extra cash for Marine Grade it is NOT absoutely necessary to do so. Second, they are ABSOLUTELY incorrect about how to coat the wood, unless the resin they gave you is Epoxy resin. With Epoxy no mat is required only Fiberglass cloth to span the seams.

If it is Polyester resin you absolutely must use CSM mat with it. Without the CSM it will harden and crack and allow water to penetrate into the wood. I have attached drawings on how I recommend you fabricate Transoms, Stringers and Decks. You are FREE to do as you wish, this is just how I recommend doing it and these are based on using Ext. Grade Fir Plywood.

(Click the pics to enlarge)
StringerLayupAndInstallation.JPG ----------------MakingDeck.jpg ----------TransomBuild.jpg
 

magna83

Cadet
Joined
May 26, 2011
Messages
8
Re: 1991 Thompson Cutlass 195

The plywood is Marine AB Grade Fir about $80 a sheet.

PL seems like it would be easier to use.

They suggested Epoxy resin only. So in that case, just to confirm, using the csm on the seams per your photo should be acceptable. I am looking to gelcoat the floor. They did not tell me the cost difference between the Epoxy and polyster. It just seems like it would be a lot easier to not install the matt over the entire floor.

Also, is it acceptable to use stainless steel screws to fasten the deck. If it is, would you put the mat over the heads as well.
 

Yacht Dr.

Vice Admiral
Joined
Feb 26, 2005
Messages
5,581
Re: 1991 Thompson Cutlass 195

Welcome to iBoats!

1. The peanut butter, is that ment to be used to hold the stringers in place and then tab after that? I also read somewhere that they used PL or liquid nail first then peanut buttered the 90 degree (boat to stringer) seam, and finally tabbed with fiberglass. You can use either. I prefer PL. It is used to keep the Stringer off the HULL and developing "HARD SPOTS" which can cause cracking when the hull flexes. PB IS used for Filleting all of the edges of the stringers, Transom, and edges of the deck.

2. I just left a place talking about fiberglass. They even gave me enough to do some of the tabbing for free. Now this is the question as it conflicts with some of what I read. They told me after I installed the new Marine 3/4 plywood that I need to lay the resin/hardner mix on the entire bare wood, lay cloth only on the seams (for 2-3 layers on seams only) and only resin/hardner on the unseamed wood for all layers. They told me that the fiberglass adds strength which is not needed because of the wood and the stringers. Can someone please shed some light.
Couple of things here. While Marine Grade plywood IS the best ply to use, there ARE GRADES of it as well and some of the Lower grades of Marine Grade are not THAT much better than using regular Ext. Grade Fir Plywood. So unless you want to spend the Extra cash for Marine Grade it is NOT absoutely necessary to do so. Second, they are ABSOLUTELY incorrect about how to coat the wood, unless the resin they gave you is Epoxy resin. With Epoxy no mat is required only Fiberglass cloth to span the seams.

If it is Polyester resin you absolutely must use CSM mat with it. With the CSM it will harden and crack and allow water to penetrate into the wood. I have attached drawings on how I recommend you fabricate Transoms, Stringers and Decks. You are FREE to do as you wish, this is just how I recommend doing it and these are based on using Ext. Grade Fir Plywood.

(Click the pics to enlarge)
View attachment 97431View attachment 97429View attachment 97430

hmmm..

The plywood is Marine AB Grade Fir about $80 a sheet.

PL seems like it would be easier to use.

They suggested Epoxy resin only. So in that case, just to confirm, using the csm on the seams per your photo should be acceptable. I am looking to gelcoat the floor. They did not tell me the cost difference between the Epoxy and polyster. It just seems like it would be a lot easier to not install the matt over the entire floor.

Also, is it acceptable to use stainless steel screws to fasten the deck. If it is, would you put the mat over the heads as well.

Your not going to gel the Floor if you went with epoxy ..

You can..will countersink the screws .. You can fill the screw heads with Clay before you fiberglass over them ( just in case you need to Unscrew them ).

YD.

PS. This IS gettin a little Armchaired IMO ...
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,929
Re: 1991 Thompson Cutlass 195

The plywood is Marine AB Grade Fir about $80 a sheet.

PL seems like it would be easier to use.

They suggested Epoxy resin only. So in that case, just to confirm, using the csm on the seams per your photo should be acceptable. I am looking to gelcoat the floor. They did not tell me the cost difference between the Epoxy and polyster. It just seems like it would be a lot easier to not install the matt over the entire floor.

Also, is it acceptable to use stainless steel screws to fasten the deck. If it is, would you put the mat over the heads as well.

That's pretty good Plywood

PL or PB both are about the same I just like PL cuz it remains more flexible when fully cured.

They are Gunna recommend Epoxy because of the price. Your boat is MADE from polyester resin. If you want to Gelcoat the deck using Epoxy will make it a very tricky proposition. Gelcoat and epoxy are not readily compatible. You can get them to work together but you really have to have everything right. Even then it is prone to fail and NOT adhere very well. I would NOT recommend trying to Gelcoat over epoxy. The PRO's on here ALWAYS say NOT to do it. Also you WILL have to completely cover the deck with fiberglass cloth not mat if you use epoxy soooo either way you WILL be covering the entire deck with some kind mat or cloth regarless of the type of resin you use. Again, I recommend the Poly and mat

You don't have to use stainless. Regular Deck screws will be fine. You will be predrilling and sealing the holes and screws with resin so you won't have to worry about them getting loose or rusting out.
 

magna83

Cadet
Joined
May 26, 2011
Messages
8
Re: 1991 Thompson Cutlass 195

Where are you guys buying this stuff (poly resin, fiberglass, acetone) in bulk? I was at a marina store talking about the fiberglass. Called back and they wanted $136 for 1 gallon of epoxy resin. I see people listing $150 for 7 gallons. Must be the poly resin. Also what is biax 1708? The marina store wanted about $8 per yard for the fiberglass and did not recognize the 1708 number, he just said his fiberglass is the best stuff on the market. Heard that before. Is that just the part number of a certain manufacturer for 1.5 oz mat? I do not want carpet. So it sounds like the Poly with mat and gelcoat is the best way. Only the wood has been purchased at this time. I guess I am a little confused after reading so many different builds.

just read friscoboaters on his sea ray. Oh man. then started to think what I have gotten myself into.

Thanks for all the help.
 

magna83

Cadet
Joined
May 26, 2011
Messages
8
Re: 1991 Thompson Cutlass 195

oops my floor was 5/8" not 3/4" and no one has 5/8" marine board in town. What type of plywood is an acceptable alternative without spending $106 a sheet for Hydrotek.
 

ezmobee

Supreme Mariner
Joined
Mar 26, 2007
Messages
23,767
Re: 1991 Thompson Cutlass 195

I put a 3/4" deck in both my projects and am a big fan of the solidness. Some my feel it's overkill but I like it. The Arauco exterior ply from Lowes is a very nice product.
 

magna83

Cadet
Joined
May 26, 2011
Messages
8
Re: 1991 Thompson Cutlass 195

I did not have to remove the entire floor so I have to match the 5/8 floor thickness. I will check lowes for 5/8.
 
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