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Old 20-10-2011, 12:08   #16
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

I was mostly interested in the use on fiberglass boats on the bows of our catamaran to protect against a log in the water from cracking the fiberglass and starting leaks that would sink a boat out in the open ocean. I was hopeing it would help to get a boat to shore before it sank even if it was weeks to get to a marina for hallout. States like Washington have started banning copper bottom paint and folks are looking for other products to take it's place. I know in locations like San Diago have divers who scrub boat bottoms weekly even with copper bottom paint and it quickly wears off, this stuff might last a lot longer when scrubed weekly.
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Old 20-10-2011, 12:09   #17
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

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I actually think this is great. This may convince others that an old wood boat can be saved without the nasty fiberglassing the hull.
This is my concern with coating wood hulls. It's common knowledge that coating a wood hull increases the chances of dry rot. But I see that 717 has done both inside and out which seals the wood from any new invasion of the fungus.

That's a lot different then what's being shown on the Youtube. Sealing both sides, the wood becomes the core material. And just hopefully no fresh water gets in there. Maybe it would be good to treat the wood with an antimicrobial before the overlay.

I use to have a 1965 38' Pacemaker (13 tons of wood and motors) and the biggest problems I had were the vertical seams along the stem and transom, not so much the lower hull. So saving a wooden boat is more complex then just coating the bottom.
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Old 20-10-2011, 12:16   #18
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

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I was mostly interested in the use on fiberglass boats on the bows of our catamaran to protect against a log in the water from cracking the fiberglass and starting leaks that would sink a boat out in the open ocean. I was hopeing it would help to get a boat to shore before it sank even if it was weeks to get to a marina for hallout. States like Washington have started banning copper bottom paint and folks are looking for other products to take it's place. I know in locations like San Diago have divers who scrub boat bottoms weekly even with copper bottom paint and it quickly wears off, this stuff might last a lot longer when scrubed weekly.
For fiberglass you might consider using Kevlar cloth. It would work about the same as polyurea but just a different application. It can't be sanded so it has to be faired in and coated with a layer of glass then faired to finish. Very common for boats up her in the Puget Sound.
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Old 20-10-2011, 18:17   #19
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

I spent some decent time redoing my old boat and a lot of thought and thinking went in before the doing.
I can tell the polyurea spray is a superior idea from the standpoint of time, personal effort expended and product quality and final results.

With a wooden boat you can coat the outside, but if you do nothing with the inside then the rain will come along and rot it out.

If you took a wood hull and completely exposed the interior framing with good access, did required structural repairs, thoroughly cleaned the interior likely by pressure washing, scrubbing with detergent, etc..., might need to pull out the machinery and fuel tanks to expose the spaces.
Let it thoroughly dry out completely.
Then you could EASILY spray the interior hull and exterior hull and expect a fully sealed and rot proof and very strong boat.

You could even using cardboard boxes form up interior flotation spaces on a large wood power boat and I think make it unsinkable. The wood hull itself floats and mostly the large fuel tanks will provide lift (6 lbs fuel per gallon versus 8 lbs per gallon of water means you got 2 lbs flotation. So if you had a 300 gallon full tank of fuel, you have around 600 lbs floatation in a full tank, much more if empty) You need to overcome the weight of the machinery and other metal gear on the boat, perhaps about 3000 lbs of flotation needed. What I mean is watertight bulkheads, divide the boat up into about 4 or 5 compartments, each compartment will have to have a bilge pump. Also you can design in closed totally sealed compartments. My boat has a lot of bilge space between framing that is mostly just air and nothing else is there. All of this could become builtin flotation chambers.

Even a heavy keel sailboat could benefit from watertight compartments to limit flooding taking the whole boat down.
With that it might be impractical to consider.

But if you can keep the hull from cracking open then it just wont sink. If you pop off hoses or get swamped in a fierce storm well, it might go down.
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Old 20-10-2011, 19:48   #20
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

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For fiberglass you might consider using Kevlar cloth. It would work about the same as polyurea but just a different application. It can't be sanded so it has to be faired in and coated with a layer of glass then faired to finish. Very common for boats up her in the Puget Sound.
So your saying for the outside of my catamaran bows over the jellcoat put Kevlar cloth? and how thick to make it leak free after a crash into floatsome? Instead of something like a bottom paint doing the job ? If this material finished looks like a truck bed sprayed on liner or smoother it would be almost like bottom paint in texture and look and provide crash protection too I would say it's a safety product. I bet it also would be noise reduction too sence it absorbes shock of explosions. Looking at the U-Tube of aluminium jetboats that were painted on there bottoms to prevented scratches when driven over rockie river bars and no scratches. It would make worring about scraping a fiberglass boat on rocks No Problem. I bet it would stop blistering of fiberglass and water intrusion into hull locations like rudders.
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Old 20-10-2011, 20:54   #21
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

Your Gemini 105 isn't going to be very tolerant of extra weight and the uneven surface applications shown would very likely make it into a sailing pig. It might be a good idea, but if it's not you'll have a very tough time returning your boat to good condition.

A few years ago I tried an "environmentally friendly" bottom paint that wasn't effective, and it was an expensive mistake. I ended up having to dive on the boat (or hire divers) every few weeks, and I wasted my labor and money. Fortunately I was able to paint over with a conventional bottom paint the next year without a total stripping job.

Polyurea is tough stuff and you might never be able to remove it. Might kill your enjoyment of the boat along with its resale value. Are you ready to bet the value of your boat on an experiment?
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Old 20-10-2011, 21:13   #22
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

At this time I'm on freah water and other than a little seasonal scum on our bottom we are not concerned about bigger critters growing on our hull. I haven't found out what the weight of a coating would be, but question is does it float on it's own unlike a copper paint.

Sorry for your experiment on bottom paint, what type of bottom paint works on your boat now.
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Old 20-10-2011, 21:52   #23
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

Not intending to hijack the topic of this thread, but to answer your question -- Now I use Pettit Hydrocoat. I find it very effective against hard growth and so-so on slime. It's a water-based multi-season ablative and half the price of some other paints. If you shop well and wait for the Spring rebate (they've offered one the past two years) you get it under $100/gallon. It's also good on inflatables (I use it on a RIB that's in the water full-time) and seems to hold up well. I give the boat one coat a year with the second on the leading edge of the centerboard and bows.
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Old 20-10-2011, 22:50   #24
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

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Not intending to hijack the topic of this thread, but to answer your question -- Now I use Pettit Hydrocoat. I find it very effective against hard growth and so-so on slime. It's a water-based multi-season ablative and half the price of some other paints. If you shop well and wait for the Spring rebate (they've offered one the past two years) you get it under $100/gallon. It's also good on inflatables (I use it on a RIB that's in the water full-time) and seems to hold up well. I give the boat one coat a year with the second on the leading edge of the centerboard and bows.
So how many gal. does it take each year ?+ $100.00 It must wear off quickly ?

Sorry from straying but I still haven't found how much the Polyurea is a gallon and cost is a deciding factor on anything that floats.
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Old 21-10-2011, 04:50   #25
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

I bet you can grind off polyurea with very very coarse grit on a sander. I think it would be tough to do but not impossible.
it is resistant to abrasion not impervious.
When I ground off my old bottom paint, I got some stick on sheets for a floor sander 24 grit from the Home Depot. These were made for sanding oak floors. I cut them in circles and used them on a 5 inch disk Porter Cable sander. It cut quick!

I also think polyurea will be lighter than a coat of resin and kevlar cloth.

Adding thickness to the hull at 1/8 inch is not doing much. it will slightly increase the displacement and the boat will sit about where it is or perhaps higher. A wood boat will rise a little due to the wood being drier and lighter. I think my boat rose an inch after coating with the permaflex.
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Old 21-10-2011, 05:26   #26
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Re: Dragon Shield Polyurea Coating for Hull Strengthening

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So how many gal. does it take each year ?+ $100.00 It must wear off quickly ?

Sorry from straying but I still haven't found how much the Polyurea is a gallon and cost is a deciding factor on anything that floats.
It takes a little over a gallon of bottom paint for my 39 foot tri (one coat plus one extra on the leading surfaces and bows). Your boat would be less than a gallon. It wears off but not quickly.

Getting back on the topic of this thread -- does anyone know whether bottom paint adheres to the Polyurea?
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Old 22-10-2011, 07:31   #27
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any info on the price....also can it be rolled on?
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Old 22-10-2011, 09:39   #28
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

I think it is a 2 part like epoxy and sprayed on but don't quote me. I saw the sprayer with 2 cans going to the sprayer to mix.
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Old 22-10-2011, 20:29   #29
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Polyurea coating/ lining is derived from the reaction product of a polyisocyanate component and an amine-terminated resin blend. It is a two part spray on mixture that is heated to about 200 F. While the formulations vary somewhat it typically cures in a few seconds.
Tough stuff, we use it at work to rehab process piping.
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Old 22-10-2011, 22:07   #30
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Re: Dragon Shield Polyurea Coating for Hull Strenghtening

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Polyurea coating/ lining is derived from the reaction product of a polyisocyanate component and an amine-terminated resin blend. It is a two part spray on mixture that is heated to about 200 F. While the formulations vary somewhat it typically cures in a few seconds.
Tough stuff, we use it at work to rehab process piping.
Sence you use this product and seam to know something about it would you use it to help protect your sailboat bottom from abuce, to keep the boat floating if floatsome hit the hull or rubbing on rocks and cracked the fiberglass.
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