replacing the deck on a 20 foot cc

TPG

Super Anarchist
Figured I'd run it by the gurus, transom and deck job on a 20 foot center console, gonna do a divinycell core deck. (Plywood where I need to reinforce) What do you guys feel the glass layup should be? Deck area is about 10 feet by 5 feet roughly. 2 sets of stringers per side about 2 feet in. Would like to do the deck as one piece, drop it in, glass it up the sides.

 
3/16" G10, beveled 2" around the edges and epoxied to the surrounding (also beveled) deck via layers of fiberglass tape starting with 4" width, then 3", then 2", then 1".

You'll be way ahead time- and strength-wise with the G10. Makes a lot less mess too. Only more expensive if your time is worth very little.

 

Raz'r

Super Anarchist
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De Nile
10'x5' G10?

I suppose if you're building a tank.

I'd check the gougeon magazine for similar projects. You will likely need enough glass for dent resistance that strength will be more than enough.

 

12 metre

Super Anarchist
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English Bay
10'x5' G10?

I suppose if you're building a tank.

I'd check the gougeon magazine for similar projects. You will likely need enough glass for dent resistance that strength will be more than enough.
I think (or hope) that tenders meant using G10 instead of plywood in the reinforcement areas.

Otherwise, I agree with Raz'r. Would end up way too heavy and is an inefficient use of G10. Also, good luck using G10 to if there is any deck camber.

Balsa is generally the preferred core material for decks - unless one plans on drilling a lot of holes in the deck and not potting them properly. Personally, I would avoid using PVC foam for the deck. Compared to balsa, no chance of rot - but higher probability of delam issues in the future.

If you do decide to go with foam, Corecell seems to be preferred.

 
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TPG

Super Anarchist
10'x5' G10?

I suppose if you're building a tank.

I'd check the gougeon magazine for similar projects. You will likely need enough glass for dent resistance that strength will be more than enough.
G10 would be insanely expensive and ridiculous. For backing plates its great, a sheet that big, good luck.

I assumed top skin would be the heavy side while the underside is just to improve flex resistance, reduce chance of rot (if balsa)

 

12 metre

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Actually, the inner and outer skins work in unison to resist bending. For example when someone is walking on the deck the outer skin goes into compression while the inner one goes into tension in bending. The core really does nothing other than keeping the skins from moving relative to each other, which is what happens when the core delaminates from the skins - which is why a springy deck is often a sign of possible delamination. Think of the stiffness of a stack of wood strips glued together vs a stack of unglued strips simply laying on top of each other.

For the transom, if outboards are attached, plywood or Coosa/Penske board seems to be used quite often

 
3/16" G10 is $18/sqft, 1/8" G10 is $13/sqft from McMaster and probably cheaper from other sources.

I'm assuming the deck is not a 10' x 5' rectangle.

You can lay up that much epoxy and glass at G10 strength, consistency, and finish levels for less than $13/sqft, counting time and materials? I cannot. I had to do this with a 1.5' x 5' strip of deck underneath my mast a year ago and have well over $25/sqft, considering time at $50/hr. Perhaps others are a lot faster than I am as an enthusiastic amateur.

But I agree that deck camber would have to be matched with segmented strips of G10, and if strength were critical as it was with my cambered application, maybe impossible.

 

12 metre

Super Anarchist
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I'm pretty certain 3/16" or 1/8" G10 will be less stiff than a 1/2" cored deck unless you install a grid of deck stringers to stiffen it.

You would have to use almost 1/2" G10 to get similar stiffness. A 12 sq ft piece of 1/2" G10 is over $500 at McMaster Carr - so a 150 sq ft section is gonna cost over $5,000.

Cost aside, G10 is just not the right material for a deck. You almost may as well pour a 1" reinforced concrete deck. There is a reason.almost every builder uses cored decks - and it's not just cost. It's just way too heavy to be used as a panel

 

TPG

Super Anarchist
Pretty sure the open 2-3 foot by 10 foot spans on G10 won't survive even being looked at either.

And 1/2" divinycell/balsa core + enough glass to cover and permanently attach it is a bit less than $5000. I'm pretty sure any yard would do a deck replacement including fairing for way less than $5000.

Doing some reading and thinking I'm going to raise the deck approx 2".

3/4" or 1" nidacore, 2 layers of 1700 on top, 1 layer of 1700 on the underside. raise the stringers and deck edges with foam core by 1 1/4" (1708 multiple layers for the stringers over 1" heavy core material)

 
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Alcatraz5768

Super Anarchist
1" foam core layer out on the garage floor with a layer of 600gsm double bias and a layer of 600gsm biaxial to give 1200gsm quad finished. Roll the foam with a paint roller with epoxy, roll out the first glass layer, use a squeegee to add more resin, then add the second glass layer, roll with a ribbed roller. Get it all wet out, put a layer of peelply over it, and have a beer. In the morning very carefully turn it over with a couple of mates, and do the other side. Cut it to shape, drop it in, onto glue splooge and glass the perimeter with 4 narrowing layers of eb, covered with peelply, 2 weekends work.

Db, not eb, damn auto correct.

 
Obviously we've got crossed signals here someplace. I'm reading this as a recore job with the top skin being replaced. Keep the bottom skin in as-is. Add your divinylcell core. Reinforce the fitting areas with plywood (though I prefer 1/2" G10) instead of compressible core. And put the final skin of 1/8 or 3/16" G10 on top.

Or tell me to eff off. Which is fine, but I've done this on three sections of my boat already and will be doing a fourth this winter, and it works a treat.

Where did "150 square feet" come from? 10 x 5 = 50 in original post.

 

TPG

Super Anarchist
Obviously we've got crossed signals here someplace. I'm reading this as a recore job with the top skin being replaced. Keep the bottom skin in as-is. Add your divinylcell core. Reinforce the fitting areas with plywood (though I prefer 1/2" G10) instead of compressible core. And put the final skin of 1/8 or 3/16" G10 on top.

Or tell me to eff off. Which is fine, but I've done this on three sections of my boat already and will be doing a fourth this winter, and it works a treat.

Where did "150 square feet" come from? 10 x 5 = 50 in original post.
bottom skin gets cut out. doing a deck job on a cc involves just cutting it clean out of the boat.

Our recores over Divicell H80 is with 2x 1208

Doesn't 08 imply with mat on the bottom? Why with mat?

I think that's the same but we use grams per square meter as a measurement system and you guys don't know what a gram is.
600gm = 17oz :)

 
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TPG

Super Anarchist
Where did "150 square feet" come from? 10 x 5 = 50 in original post.
You are correct, I misread. I thought it was 10 x 15.
Well you're still right, G10 isn't the proper material for this application. Foam or balsa core (leaning towards foam) plus 2-3 layers of 1700 ontop, 1 or 2 on the bottom and call her good.

The expensive decision is epoxy or poly. <_<

 
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12 metre

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Doesn't 08 imply with mat on the bottom? Why with mat?
Yes. Some believe you get a better bond when glassing onto a different material (or fully cured surface for that matter) if the initial layer is mat. If laminating several layers at once on such a surface, only the first layer should be an "08". Aft that you could use 1200 or 1700.

My own experience from chisellng out old glass is that lams without glass tend to cleave off more easily. Mat seems much tougher to chisel out cleanly. This isn't necessarily proof that a mat layer bonds better, but I think may be the reasoning behind the logic.

 

12 metre

Super Anarchist
3,943
739
English Bay
Doesn't 08 imply with mat on the bottom? Why with mat?
Yes. Some believe you get a better bond when glassing onto a different material (or fully cured surface for that matter) if the initial layer is mat. If laminating several layers at once on such a surface, only the first layer should be an "08". Aft that you could use 1200 or 1700.

My own experience from chisellng out old glass is that lams without glass mat tend to cleave off more easily. Mat seems much tougher to chisel out cleanly. This isn't necessarily proof that a mat layer bonds better, but I think may be the reasoning behind the logic.
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