seacast

[jonesg]

I'm prepping to seacast , it would cost $600 to use , has anyone tried using a plywood core with seacast on each side.
I can't think why it wouldn't work, pour the seacast in and push the ply transom down into it, maybe wet the ply with resin first, then pour more seacast over it and work the air pockets out.
With a coupla 1/4inch square sticks glued on either side of the ply it would ensure it stays centered as its pushed down into the resin.

The transom 'pocket' is approx 1 3/4 inch wide, if I use 3/4 ply that should translate to a $300 saving in seacast.

any reason why will this might not work?

 

[Stoutcat]

Re: seacast

Hi Jonesg,

From Seacast:

Q: Do I have to have an inner skin
and cap on my transom when I
am using Seacast??
A: Yes. Seacast??s strength is
dependent on being sandwiched in
fiberglass skin. It is a core material.​

Alan

 

[NoKlu]

Re: seacast

I'm no expert but I don't see why It wouldn't work as long as you could be sure there were no air pockets in the seacast. I'm not sure how thick seacast is and how well it flows. If it was thick enough ,you could pour the seacast, place spacers in, push the core ply in between the spacers, but not far enough down so it lands on the bottom, fill it almost to the top with seacast then pull the spacers out and top it off. That would make the seacast comletely envelope the ply. I think leaving the spacers in would greatly reduce the strength of the seacast and transom.The conditions in Stoucat's post would still be met. Great Idea and Question. If it works I'm sure a few guy's would be thanking you for being the guinea pig.

 

[salty87]

Re: seacast

i'd run that question by them. i'm sure they've heard it before. there's also some stuff about seacast being formulated to bond to fiberglass. could be an expensive, time consuming gamble.

 

[TheWoodCrafter]

Re: seacast

Seeme like a good idea to me.
Seacast can be bought formulated thin or thick.
I would think the thin formulation would be the way to go.
It would run in faster with less chance of any voids.
I also think the ply would have to be suspended in the Seacast
all the way around, since you can't really bond the ply to anything.
You would not want it fitting tight to the bottom or the sides (at the ends).
That would have to fill with seacast.
The trick would be holding it in place during the pour.
Might work.

 

[wca_tim]

Re: seacast

seacast is realy tough stuff, I'm pretty sure that the facvt they talk about it being a core material is that it is subject to crazing on the surface when it is the only surface, crazing is the mechanism by which cracks form in plastics.

In terms of strength, the thick formulation will be stronger and it flows plenty well enough to pour into a transom from my memory (I used it to do al aluminum boat transom 8 or 10 years ago).

In terms of strength, it is far stronger than wood - it's fiberglass reinforced plastic... I had some left over after I filled the void where the wood was in my transom and so poured it onto a piece of visqueen and let it harden. The next day out of curiosity, I put the 1 1/2 foot circle between across two concrete blocks and couldn't break it with an 18 pound maul... not unexpected, fully cured, fiberglass reinforced poly(ester/styrene) resin is tough stuff...

I believe that you can thin it slightly with styrene (styrene reacts and becomes part of the plastic... DON'T use any solvent!).

I wouldn't hesitate to use it again.

 

[jonesg]

Re: seacast

Seeme like a good idea to me.
Seacast can be bought formulated thin or thick.
I would think the thin formulation would be the way to go.
It would run in faster with less chance of any voids.
I also think the ply would have to be suspended in the Seacast
all the way around, since you can't really bond the ply to anything.
You would not want it fitting tight to the bottom or the sides (at the ends).
That would have to fill with seacast.
The trick would be holding it in place during the pour.
Might work.

Keeping the ply centered during the pour can be done with 1/4 inch vertical stringers, a couple on each side of the plywood. We woud obviously make a few dry runs to get the sequence down before mixing the resin up.

the only problem I can think of is the ply is 'relatively' soft between 2 hard layers of seacast, it might cause the resin to crack around the outboard bolts when the bolts are tightened.
maybe not.

My plan is to mix the resin, apply some to the ply to wet it for good bond THEN add the fiber to the bucket and pour half into transom, push the ply down into it and add the rest of the seacast on top, smacking the outside with blocks of wood to settle it. Bevel the bottom edge of the ply so it can penetrate the seacast and help it with a mallet.

I think a masonry bag can be used to inject the seacast down each side of the ply, I've done brick pointing work with a bag and they work great for injecting mortar. Or a heavy plastic bag, fill with resin, snip a corner, slide it into the cavity and wring it out.

The ply wouldn't reach all the way across or all the way to the bottom of the transom. But it would reach to the top, that way we know its at the correct depth.

I bought a hoist last nite and pulled the engine today, cut a 6 inch section off the top of the transom with the sawzall , potting soil comes to mind.
Is there an easier way to cut the top glass off?

The middle section was slow cutting, then I realised I sliced thru the brass drain tube for the self bailer.

anyone see the 3 stooges doing plumbing work?
"Hey moe, no wonder theres no water in these pipes, they're full of wires"
nyuk nyuk

 

[TheWoodCrafter]

Re: seacast

If you are worried about the ply compressing you could estimate where your holes would end up and bore some 2" holes in the ply first. Then seacast the area separately to fill in the holes. I did something similar to this with my splash well drains.
I used a cut-off wheel on the fiberglass. A sawsall is a little rough on the fiberglass structure and glass stands.
Good idea with the masonry bag.

 

[Stoutcat]

Re: seacast

If it's not encased, I'd be worried about it cracking...

Alan

 

[jonesg]

Re: seacast

If you are worried about the ply compressing you could estimate where your holes would end up and bore some 2" holes in the ply first. Then seacast the area separately to fill in the holes. I did something similar to this with my splash well drains.
I used a cut-off wheel on the fiberglass. A sawsall is a little rough on the fiberglass structure and glass stands.
Good idea with the masonry bag.

good ideas, off to depot to get a grinder and steel cutoff disk.

 

[mnessman]

Re: seacast

What I was planning on doing is replacing my transom with ply then on the outer edges using the seacast to help fill any voids that the plywood didnt fill all the way. And I would also use it to level off the top. By using glass on the plywood also it would allow for the seacast to bond to the wood. This way will save alot of money and still have a strong transom...

 

[jonesg]

Re: seacast

the only thing is,
the more wood you use, the less room to get the seacast in.
its a conundrum.

someone mentioned seacast being a core material,
all laminating resins are. They all need capping off.

 

[mnessman]

Re: seacast

yes that is true but I am only looking at a small amount of seacast to use such as 1-2 gallons, and I think that by thinning it out as prevously mentioned that it will be able to flow between the wood and the edges of the transom. It would be alot like using a resin mixture to make fillets when doing stringers. The wood would be the strenght of the transom with the seacast helping to fill the sides so that there are not any gaps between the wood and the side of the boat.

 

[jonesg]

Re: seacast

The issue to watch in that case is ; as you pour it in ...it pours out the bottom into the bilge.

we know the water got in the transom someplace ... one approach is to fill the cavity with water and see where the leaks are, or pour acetone in there.
External leaks are simple, duct tape will block those, the bilge leaks need looking at beforehand. Anyway, thats our plan.

Theres some videos on Youtube showing this issue.

 

[Stoutcat]

Re: seacast

Hi,

I keep going back to the manufacturer to see what they say...

Seacast? is a composite core material that must be sandwitched in between fiberglass or aluminum.
Seacast? come in a bucket with premix resin, BPO catalyst, and premeasured reinforcement. The safest way to catalyze Seacast? is to use BPO as it will not cause blindness. Seacast? is formulated to be a core material. You must sanwitch Seacast? in between fiberglass or aluminum.​

Typos aside, I think the company is pretty clear.

Before I strayed from their instructions, I'd want to test first.

JonesG... Can you post some pics of the project?



Alan

 

[jonesg]

Re: seacast

will do 're the pics, just started cutting the top off last nite, used a grinder with diamond masonry disk, like a knife in hot butter.!
The mush goes all the way to the top.

They also sandwich iseacast with ply, theres a video on youtube of a guy peeling it off after the resin tripped off, he waxed it first.

see here

http://www.youtube.com/watch?v=mLtcszWP2VU

 

[jonesg]

Re: seacast

Hi,

I keep going back to the manufacturer to see what they say...

Seacast? is a composite core material that must be sandwitched in between fiberglass or aluminum.
Seacast? come in a bucket with premix resin, BPO catalyst, and premeasured reinforcement. The safest way to catalyze Seacast? is to use BPO as it will not cause blindness. Seacast? is formulated to be a core material. You must sanwitch Seacast? in between fiberglass or aluminum.​

Typos aside, I think the company is pretty clear.
Alan

Read the hazmat warning ! ,

http://www.msdshazcom.com/WEB_DOCS/ARCHIVE/WCD00014/WCD0145B.HTM

It WILL cause blindness, its a peroxide, commercial bleach ( I think thats what it means). The principle quality is its a low temp catalyst, good for deep molding work.
Its hard to find, it doesn't work with regular poly resin unless the resin is promoted, so I gave up trying to do it myself.

 

[Stoutcat]

Re: seacast

Hi Jonesg,

Nasty warning!



But I wouldn't give up just yet. When used as directed by seacast, I bet it will be fine.

And if that proves to be not your cup of tea... This forum is loaded with posts from other folks who have other solutions.

Alan

 

[wca_tim]

Re: seacast

um... that msds sheet is perhaps a little overblown... if you don't think so, download and read some of the ones for products that are under your kitchen sink...

benzoyl peroxide, one of the most common organic peroxides, is approved by the fda for use on skin... I use many others routinely. with reasonable precaution they are no big deal. don't drink bleach, don't pour hot coffee on yourself, and so on...

this stuff is no more toxic then many of the paints and solvents that we all use on a regular basis... wear long pants, long sleeves, gloves and a carbon filter mask with fresh cartridges... no worries.. of and don't do it in a closed garage with no ventilation... especially not with a kerosene heater...

in all seriousness, just follow the instructions and you'll be just fine.

 

[j_martin]

Re: seacast

Why are you mixing systems? SeaCast is a Monolithic (all the same) core material. It's main claim is that it replaces wood, is stronger, and will not ever have a problem with absorbed water. Putting a wood block in the middle of it negates those characteristics.

If you're going to use wood, use wood. It can be in several pieces as long as the laminated system has good design strength. If you use wood, use a good laminating/layup resin. Rot Doctor's LL resin is durned expensive, but it is really nice to work with and has some amazing properties to it, both in the wet state, and cured.

Either way, cleaning out the original hole is critical. Any wood clinging to the fiberglass sides or bottom will cause the new lamination to eventually fail at that point for lack of adhesion. From what I've heard, SeaCast is less forgiving in that area, and many fail because of the preparation shortcoming.

Here's a link to the bass boat orthoscopic transom project. It's a whole different boat now, even had to relearn how to drive it.

http://forums.screamandfly.com/forums/showthread.php?t=159482&highlight=wet+transom

hope it helps
John