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Old 07-07-2017, 19:29   #1
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Tips needed for core 2 part foam injection

I have a cored area that runs between the cabin and the edge of the boat for about 15 feet . It seems to be soft to walk on. I was thinking of trying to stiffen it up by drilling a few holes through some boards and right through the deck and through some boards on the top of the deck also.
I plan on removing the top boards so I can drill series of holes roughly 8 inches apart so I can fit the nozzle of an epoxy foam system that comes in two tanks. I'm hoping to inject enough foam so the deck starts to bulge a little. Then put the top boards back on the bolts coming up through the deck and cranking them down so the boards sandwich the deck to squeeze the epoxy horizontally inside the deck into any cavities created by the rotting core.
I don't know how long it takes this stuff to harden so I'm going to get out my stop watch and play with it before I attempt something so time sensitive.
I figure there should be enough relief holes on the ends and edges, so it doesn't blow the boat out of the water. Has anyone got any experience using 2 part epoxy foam injection?
I'd like to hear anyones ideas on this whether you're experienced or not.
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Old 07-07-2017, 20:58   #2
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Re: Tips needed for core 2 part foam injection

Quote:
I'd like to hear anyones ideas on this whether you're experienced or not.
Well, you've come to the right place for that sorta feedback!

I'm not at all familiar with epoxy foam.... in fact, never before heard the term, so no help there. But I have used 2 part polyurethane foam in between a liner and the hull to stiffen up a section that was oil-canning (following advice from the boats designers, Sparkman and Stevens). It worked just like they said it would, but it made one hell of a mess in the process... and that stuff is bloody hard to get off of a gel coat finish! This was on clean and dry FRP surfaces, not nasty damp voids full of rotten balsa.

So, my inexperienced view is that you have bugger all chance of a good outcome with your scheme, and it will make a mess that will make you rue the day you thought this scheme up. The only realistic repair is to remove one skin, usually the top, dig out the rot, clean up carefully andreplace the core with fresh stuff, pot in epoxy and replace the skin. If you are not too fussed about aesthetics (and if you are seriously considering your proposal you likely ain't) this isn't a difficult process, and it WILL give you a sound deck when you are done.

I know what I would do (because I've done it!).

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Old 07-07-2017, 21:29   #3
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Re: Tips needed for core 2 part foam injection

I have repaired a large section of spongy deck by doing what you said about drilling holes and injecting resin. Yes, tap with a hammer and mark the soft, hollow sounding spots or area and drill small holes about 6 to 8 inches apart and inject into those holes.
What I did different was to wipe the marked sections with baby oil ( to prevent any resin that overflows to stick to the non-skid deck surfaces ), then used a medium sized plastic syringe filled with regular polyester fiberglass resin with catalyst and thinned a little with acetone for better flow and injected inside those holes. Don't remember if any eruptions came from nearby holes but fed in as much as each hole would take and went back to the holes that had swallowed the mix and were not overfilled.
That expanding foam I don't think would soak into the mushy balsa wood or plywood voids and may expand too much or too little in places and make a mess on deck because it is hard to control.
Twenty years later still good as when first done. Putty fill the small holes, done !.
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Old 07-07-2017, 21:41   #4
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Re: Tips needed for core 2 part foam injection

You really made me stand back and now I think I'm going to re-think this. I still have lots of time so i'm going to take it slow. I'll see what other ideas show up . I really appreciate the heads up.
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Old 07-07-2017, 21:45   #5
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Re: Tips needed for core 2 part foam injection

Sounds like you had success with the resin injection. I like the hammer tapping and the lubing up the deck surface. Great Ideas , Thanks
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Old 08-07-2017, 08:17   #6
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Re: Tips needed for core 2 part foam injection

Try Injectadeck, Injectadeck | The soft boat deck repair. a friend used with success on some soft areas on a Gulfstar 44. Deck was rock hard after repair. Haven't tried it myself but intend to.
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Old 08-07-2017, 09:27   #7
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Re: Tips needed for core 2 part foam injection

imho if you're thinking of using thinned epoxy read this article, maybe do some more research, and spend a few days letting it all sink in.

Thinning epoxy: Best practice for reducing the viscosity of WEST SYSTEM epoxy
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Old 08-07-2017, 09:34   #8
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Re: Tips needed for core 2 part foam injection

Like Jim mentioned, my experience is with polyurethane foam so the behavior is likely different. My experience was a small disaster and ultimately cost a lot of time to repair. The foam I used expanded too fast and blew the aft deck off my sailing canoe. As I saw the bulging begin I grabbed a large screwdriver and stabbed holes in the plywood to let the foam escape but it did not and so bulged the deck that I had to remove the bulged part, fair it, and glass it over. That part was relatively easy and the outcome was good. but in the long run polyurethane foam absorbs moisture and nearly doubled the weight of my small boat. the real time went into chipping out all the foam a couple of years later and replacing the aft deck. So while the epoxy foam may not absorb moisture the bulging is a feature I would avoid at all cost. As already suggested, peel off top layer, clean out the bad core, replace with non wood core (like coosa foam board) and replace a top skin. good luck. f
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Old 08-07-2017, 11:31   #9
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Re: Tips needed for core 2 part foam injection

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Originally Posted by tml View Post
Try Injectadeck, Injectadeck | The soft boat deck repair. a friend used with success on some soft areas on a Gulfstar 44. Deck was rock hard after repair. Haven't tried it myself but intend to.
TML
If this product works as reported it will save a lot of people a whole lot of work and could actually save some boats lives. Has anyone here actually used it?
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Old 08-07-2017, 11:50   #10
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Re: Tips needed for core 2 part foam injection

Inject-a-deck looks amazing and it needs wetness too . Bonus
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Old 08-07-2017, 12:02   #11
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Re: Tips needed for core 2 part foam injection

Yeah , I think thinning epoxy is something I know I would screw up for sure.
Thanks
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Old 08-07-2017, 12:13   #12
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Re: Tips needed for core 2 part foam injection

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Originally Posted by Rorzech View Post
...I'd like to hear anyones ideas on this...
Anything seems possible when you don't know what you're doing.

Decades ago there was a product sold that claimed to be the equivalent of "engine rebuild in a can." If it sounds too good to be true...well...
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Old 08-07-2017, 17:21   #13
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Re: Tips needed for core 2 part foam injection

I too have never heard of epoxy foam; turns out a quick search yields at least two manufacturers ProSet and Sicomin. Proset is a division of Gouegon Brothers, Sicomin might be a French company; both products look appropriate for the application.

That doesn't mean they are.

The problems with this approach are the same regardless of the magic bullet one uses for the 'fix'; any bond between the 2 skins is tenuous at best and is destined to fail, generally sooner rather than later.

Sure you can do it for a temporary repair, or an unscrupulous 'boat flipper' could use it to disguise a major problem, but a cored deck is a structural member of the overall system that is the boat's hull, and an 'epoxy-injected-into-rotten-wood' repair will not take the place of the designed scantlings of the original structure.

Not to mention the cost, the same quick search yields a (fairly unresearched) cost of about 300/cubic foot, compared to about 100-120/cu ft for 1" coosaboard...
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Old 20-02-2018, 19:25   #14
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Re: Tips needed for core 2 part foam injection

"Sure you can do it for a temporary repair, or an unscrupulous 'boat flipper' could use it to disguise a major problem, but a cored deck is a structural member of the overall system that is the boat's hull, and an 'epoxy-injected-into-rotten-wood' repair will not take the place of the designed scantlings of the original structure."

I'm not sure I agree. I replaced the foredeck and side decks of a 27' sailboat, using new balsa core and epoxy. It's a job I'd not do again, and is a vast amount of work. On the other hand, I know several boats that have used epoxy injection, and after 20+ years they seem solid as a rock. I wouldn't call that a temporary repair. It was also about 2% of the work compared to what I did. Aeromarine has an intriguing video on deck repair, in which they inject the space between the hull liner and deck underside with structural marine foam, then use epoxy injection from the top, into the rotten core. I bet that is as strong as the original deck, maybe stronger.
If the core is waterlogged and totally destroyed, I'd try injectadeck, which loves water.
Is it "as good" as replacing the original construction? Who knows. But when was the last time you saw a boat deck fail? (Me neither, never).
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Old 28-02-2018, 05:01   #15
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Re: Tips needed for core 2 part foam injection

I have to admit, the Injectadeck does sound pretty good. I have some repairs coming up soon to address soft decks. I was initially leaning toward cutting the skin out and re-core with CoreCell. However, I will be looking more into the injectadeck. I wish there was more feedback from actual users on the performance.

Maybe I can call the maker and ask a few questions. I will let you all know what I find out, but the descriptions of it sounds interesting. Either way I will take lots of photos and documents the repair and post it here.
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