Transom plywood is rotten, on inboard mercruiser 1990 thompson cutlass 190

[WOEISMEIGOTTA470]

No Title

Duuuuuuuude!!! This thread is giving me MAJOR flashbacks of what I had dealt with on my Thompson. Our boats are so similar, and the pictures you're posting are haunting me!! :faint2:
That motor does look pretty fresh so, at least you have that going for you! I'm also really jealous of that gantry lift your using. I found that Thompson left a lot of air pockets (voids) in their fiberglass layups, especially around stringers. Stay positive my friend cause at the end of all this, you'll have a much better constructed hull that will far outlast what came out of the factory, especially if you follow the advice from the 'Ol (not so dumb) Okie!

One more thing...

So THIS is why they call it a DOGHOUSE! :lol: Cute pup!

 

[ChizelSpiel7]

You are not kidding on the voids. The fiberglass on the transom is really uneven to the point that in some areas, it was not even glued to the wood.

 

[ChizelSpiel7]

So i called a couple of local marine shops here in san antonio for 1708 fiberglass to repair the cut i made into the fiberglass transom. They referred me to a company called restex. Called them and they told me they sale the stuff in rolls and resins in gallons. So they referred me to a place called Plastic Supply. They sale resin and fiberglass to them, and in turn they sale it in smaller quantaties. So they tell me that the 1708 is called ComboMat and its the same thing? Is that right? They have it for $2.95 per linear ft. And the polyster resin is $7.50 a pint. Is this also the same fiberglass and resiin i'm going to coat the wood for the transom, tabbing, stringers and decking to the hull? Reason i ask, is maybe i should by a larger amount if i'm going to be using it besides fixing the area that i cut into the fiberglass on the transom.

 

[JASinIL2006]

Polyester resin from U.S. C omposites is $30 a gallon plus shipping (cheaper if you buy 5 gallon buckets). Your HD stuff will be $60 a gallon, won't be as fresh and likely has surfacing wax in it.

50" wide 1708 will cost 8.50 a lineal yard.

If you're going to be doing a transom, stringers, deck and all the tabbing, etc. that goes along with those, you'll spend a small fortune more using HD supplies.

 

[WOEISMEIGOTTA470]

Looked through your demolition photos again for self amusement :lol:. Gotta love how those engine mounts, they only slapped one layer of roving over the top, no protection at all on the back or sides!! My original transom plywood layup had rusted steel staples sandwiching them together. The inside CSM skin peeled off very easily, and the top edges of all the wood was left bare, only painted.
Also that tiny 2" tall center stringer is also kinda weird, on mine it was 'glassed so poorly that as soon as I made the cuts along the seams, the fiberglass "cap" lifted off with no effort at all. Luckily the wood was somehow still in-tact, and with a bit of sanding and lots of cleaning w/ acetone re-'glassed the entire length successfully. Actually most my stringers were alright. I ended up doing a partial stringer replacement, and full bulkhead, transom, and deck replacement (w/ exception of the bow). Even though I didn't replace most my stringers, they all got re-wrapped in new 1708.

Also read that your I/O gimbal housing was silicone'd around the seams? Mine was too, thought it was a previous owner fix, or maybe it was factory... lol wouldn't surprise me :facepalm:.

 

[ChizelSpiel7]

Polyester resin from U.S. C omposites is $30 a gallon plus shipping (cheaper if you buy 5 gallon buckets). Your HD stuff will be $60 a gallon, won't be as fresh and likely has surfacing wax in it.

50" wide 1708 will cost 8.50 a lineal yard.

If you're going to be doing a transom, stringers, deck and all the tabbing, etc. that goes along with those, you'll spend a small fortune more using HD supplies.

So, i should at least get a gallon of polyester resin for transom,stringers, deck and all tabbing? What are hd supplies. Pardon my ignorance. I'm lost to all this type of work. And is ComboMat basically 1708?

 

[DeepBlue2010]

I would say No. All search results of this term (ComboMat) came up with this description

"E-Glass Woven Roving Combo Mat is a complex mat made by stitching together woven roving and a layer of distributed chopped strands"


1708 is not woven

"[SIZE=-1][SIZE=-1]Contains double bias(17oz) stitched at 45degrees
along with one layer of 3/4oz mat."

With that said, you can tell for yourself when you go there. If it is woven, it is not 1708. If the fabric consists of two layers stitched at 45degrees (+45 & -45) with CSM at the bottom, it is 1708.

While are there, don't listen to the "expert" salesman who tells you they are the same or even better. He is a salesman who wants to make a sale. 1708 is takes less resin for the same strength compared to woven[/SIZE][/SIZE]

 

[ChizelSpiel7]

Looked through your demolition photos again for self amusement :lol:. Gotta love how those engine mounts, they only slapped one layer of roving over the top, no protection at all on the back or sides!!

How should i go about reinforcing the engine mounts. Tab the ends with wood and fiberglass?

 

[ChizelSpiel7]

I would say No. All search results of this term (ComboMat) came up with this description

"E-Glass Woven Roving Combo Mat is a complex mat made by stitching together woven roving and a layer of distributed chopped strands"


1708 is not woven

"[SIZE=-1][SIZE=-1]Contains double bias(17oz) stitched at 45degrees
along with one layer of 3/4oz mat."

With that said, you can tell for yourself when you go there. If it is woven, it is not 1708. If the fabric consists of two layers stitched at 45degrees (+45 & -45) with CSM at the bottom, it is 1708.

While are there, don't listen to the "expert" salesman who tells you they are the same or even better. He is a salesman who wants to make a sale. 1708 is takes less resin for the same strength compared to woven[/SIZE][/SIZE]

Ok, i will insist on 1708. So approximately how many gallons of resin should i get and how many yards of 1708. And is there any other materials i need to buy for this project when i order or buy locally?

 

[Woodonglass]

Exactly what ALL are you going to be glassing? How much wood (approx. Sq ft) Transom, Stringers, Deck, Motor Mounts etc. If we know that we can give you a better estimate on Resin and Glass quantities. I looked up Plastic Supply in SA and I don't think they're gunna have 1708 based on what I'm reading and seeing on their website. The combo mat will work, BUT it's not as good as the 1708 biaxial fabric and will use more resin. NO MATTER WHAT the salesman tells you!!!!

 

[DeepBlue2010]

Some measurements would help answering the quantity question. You will need few more supplies though..

Some rollers to get all air pockets out of the laminate. I use the metal ones not the plastic and always clean them as fast as you can with acetone. I keep them a glass container filled with acetone while I am glassing

You will also need measuring cups 1 Quart and bigger

Very small measuring cups (in cc or ML) to measure the catalyst. Some only use drop bottles and measure it by drops (I can not get myself to do that yet but this is just me)

Scissors, Cutters (Keep in acetone)

A box or two latex gloves

few rolls of shop towels

good supply of mixing sticks from Home Depot

A good supply of chip brushes

a parchment paper roll would help. I cover a piece of ply with it and lay the fiber glass on it and get it wet with resin then I transfer the glass to its location. I do this only if am glassing a complex shape with curves and turns. I found the glass much easier to confirm to the shape this way

and, of course, all of your personal protection gear (respirator, chemical resistant gloves, eye protection, etc )

I am sure I am forgetting something still. It might come to me after I drink my coffee


Good luck to you man!

 

[WOEISMEIGOTTA470]

No Title

How should i go about reinforcing the engine mounts. Tab the ends with wood and fiberglass?

This is what I'd do for the engine mounts:
-Take Measurements (height from top of stringer, and centerline of engine mount brackets from transom face are most important)
-Carefully remove out old mounts
-Fabricate new mounts from wood, you can use the old mounts as a template for size of lumber, beveled cuts etc. Use solid or ply, but whatever it is don't use pressure treated lumber)
-Round off all sharp corners & edges
-Precoat new mounts in thinned out laminating resin and catalyze on the low side for slow kick; Lets that resin soak into the wood deep.
-Cover the entire mount in two layers of CSM, think wrapping it like a present.
-Glue new mounts to stringers and hull with PB.
-Tab Mount in with 1708.

See attached pictures w/ markups.
You can see I suggest shortening the mounts, which gives you access from front and back. I figured it gives you the most space in your bay, and also allows the option of through bolting the engine mounts with a washer and nut from underneath, rather than using lag bolts.

This is how I'd do it obviously just a suggestion, I'm sure others will comment on this.

 

[ChizelSpiel7]

Those are some good suggestions. Love the graphics! What program are you using to illustrate pictures. I kinda like the optional suggestion. Reinforce what is already there. Less work. Thank you for you're illustrations.

 

[ChizelSpiel7]

No Title

beveled the slit i made on transom today and took some pics of the stringers that need repair. I see now why the transom was put on in sections as well. Took some measurements too. The Floor was 23"x43" x2, Middle section of transom is 27"x33", Sides of transom is 22"x29" x2.. What type of wood should i use? Arauco plywood (i've read home depot and lowe's carrys it), Douglas fir plywood, AB grade exterior plywood, AC fir exterior plywood, white oak,mahogany, marine? Maybe use marine in the middle section and lower grade wood for everything else????

 

[Woodonglass]

Arauco is really good stuff. 7 ply and very few voids. If you can find it I'd use it.

 

[ChizelSpiel7]

Arauco is really good stuff. 7 ply and very few voids. If you can find it I'd use it.

I found some arauco. Waiting for them to call me back for prices. For the deck shoud i use plain ole 1/2 plywood?

Mccoy lumber has not called back. But found this place http://roddislumber.com/

Marine grade 3/4 $70.40 1/2 $45.86

Arauco 3/4 $54.40 1/2 $35.84

 

[JASinIL2006]

I use Arauco throughout and I was really impressed with it, especially for the price (just a tad more than plain exterior plywood and WAY cheaper than marine plywood). The extra plies and the lack of voids make it well worth the extra money.

I used 1/2" Arauco on my deck. If I were to do it over, I might have used 5/8" to get a bit more rigidity under pedestal seat bases. (No problems yet with the 1/2", but I worry it maybe should have been a bit beefier under the seats.)

 

[DeepBlue2010]

It is a trade-off. With a thin sheet (1/2 inch) you will need to beef it up with glass. At least you will need 17oz top and bottom to beef it up to take the load.traffic a typical deck expects. 3/4 is rigid enough on its own and only needs sealing which can be done with 1.5oz CSM from the bottom and top. Not to say you can't use 1708 from the top of you want to "tank it out" but you don't need to.

So your choice then on where you want to spend the money, wood or glass and resin. Personally, I will vote wood

 

[Woodonglass]

What's the span between stringers? What kind of seats? Pedestals?

 

[ChizelSpiel7]

What's the span between stringers? What kind of seats? Pedestals?

Floor on each side is 23"wide x 43" length. Seats are boxed with cushion next to motor on either side.