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Cockpit floor support replacement

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ckroll
1st Mate

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50 Posts

Initially Posted - 08/23/2010 : 06:31:52

Hey guys. A buddy and me bought an 81' C25 to restore and are looking for tips on this one particular item. Over the years water has gotten between the cockpit floor and the aft ceiling and thus has rotted away the wood supports within. No cracks but it's quite squishy so we are looking to shore it up. Our thought was to cut out the ceiling from below to access the rotted wood and close it back up with a wood ceiling and associated supports.

So my question to the group is have any of you gone through this repair and if so, what success/failure stories can you provide for guidance? We know there are other issues that we need to address as the root cause of this problem as well. Thanks in advance!

Edited by - on

pastmember
Master Marine Consultant

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2402 Posts

Response Posted - 08/23/2010 : 11:24:06

There was a thread years ago, it was terrifying. Basically cut out the top, replace the core and glass the top back down. I think a lot of teak sole grates have been sold over the years rather that tackle this one.

Edited by - on

skrenz
Captain

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USA
351 Posts

Response Posted - 08/23/2010 : 15:41:52

I would not undertake this job from the bottom up as you are describing for two reasons: First the wood in the floor, now rotted, is designed to act as a type of monocoque construction where two skins are separated by a non compressible layer. The key to this type of construction, besides the interior layer not be compressible, is that the two skins need to adhere to the inner layer. FRP (Fiberglass Reinforced Plastic) is weak in flexural strength. The inner plywood layer provides the flexural strength. If you just remove the rotted plywood and do not bond the replacement back to BOTH skins, you will not have solved the problem.
Second, working over your head on your back, ESPECIALLY WITH FIBERGLASS, is a sort of never ending purgatory. You don't want to do that.

Much better would be to work from the top down. At least you have gravity on your side. Open up the floor and see just how much of the plywood is damaged. If you're lucky, you may only have to remove some of it. What ever you remove, TIGHTLY replace with new plywood of the same thickness and epoxy it down onto the fiberglass on the bottom.

What remains is to re-fiberglass the new cockpit sole. And the problem here is probably getting the non-skid right. Luckily, you have several options available to you. There are sold pattern mats that can get pushed into the uncured gelcoat to reproduce the pattern. You don't really need to match the existing because you can redo the whole floor. Also, there are aftermarket rubber type deck materials that are glued down, etc.

Do not attempt this job yourself unless you feel comfortable working with FRP. You can learn and the most important job is following directions. As I said above, the final finish of the replaced cockpit sole is the thing you want to work out how to do first. The rest will just be a lot of work.

Edited by - on

Happy D
Admiral

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921 Posts

Response Posted - 08/23/2010 : 18:27:16

http://members.csinet.net/dhapp/cockpit/cockpit.html

You can always replace the core with 1/4" marine grade doug fir and epoxy the original skin back on top. You just have to bevel both sides of the cut and lay fiberglass tape in the bevel and paint the sole.
I opted to use 3/8" okoume, but 1/4" doug fir is the original core material.

Edited by - Happy D on 08/23/2010 18:30:49

GaryB
Master Marine Consultant

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USA
4304 Posts

Response Posted - 08/23/2010 : 19:48:27

If I ever have to do this project I'm going to use one the these products so I never have to worry about rotted wood again.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=1593&familyName=Penske+Board&history=l3zmixo1%7Cother%7CfreeText%7EFiberglass%252CCore.Materials%5Epage%7EGRID

http://nida-core.com/english/products_nida.htm

http://www.coosacomposites.com/

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Stinkpotter
Master Marine Consultant

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Djibouti
9081 Posts

Response Posted - 08/23/2010 : 20:42:19

Every deck, cabin top, cabin side, and bulkhead on my Eastern is a 3/4" Nida Core polymer honeycomb / fiberglass sandwich. It's so solid you'd think you were on a battleship (except maybe for the planing part

). The transom is three layers of the stuff. Even though it's lighter than plywood, it just might work on a sailboat, too.

Edited by - on

Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 08/23/2010 : 21:31:49

Are you certain that this is core rot? The fordeck on my C22 was soft. I drilled some exploratory holes from underneath and it turned out that the core was solid but had come unglued from the top layer of fiberglass. I drilled holes from underneath up into the void and pumped in epoxy using a grease gun. I corked up the holes and then placed sandbags on the deck to compress the fiberglass to the core. Solid as a rock. Put MarineTex in the holes inside the cabin and all done. The advantage to working from inside is that it is easier to hide the repair. If it turns out that you core is good and you go this route I can provide more details about what epoxy to use and how to pump it in to the void area.

If it turns out to be rot I suggest you carefully check out the rest of the boat for rot. If it is extensive you may want to reconsider this project boat.

Here is a good resource: [url="http://www.rotdoctor.com/"]Rot Doctor[/url]

Edited by - on

ckroll
1st Mate

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50 Posts

Response Posted - 08/24/2010 : 05:49:11

Thanks for the advice and we will be considering all options for this repair. It does appear that the softness runs pretty much the length of the cockpit and that a top down approach may be the best option. Appearance can be addressed easily with some topical remedies (rubber or wood mat, etc). As for other issues with this boat, it has plenty. We knew this going in and did a pretty thorough inspection. Replacing the bulkheads, adding keel bolts and fixing this issue appear to the be the major jobs. We paid nearly nothing for this boat and have plenty of time. Looking forward to this project and the finished results.

Thanks again and I'm sure I'll be back here again looking for more advice. I'll also post our findings and remedy when complete.

Edited by - ckroll on 08/24/2010 05:50:05

calden
Navigator

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USA
194 Posts

Response Posted - 08/25/2010 : 06:52:57

Yet another vote for recoring from the top. I fixed a San Juan 21 cabin top from the bottom and it was punishment. Lying on my back, angle grinder overheard gyroscoping overheard to it's own peculiar sense of gravity, clouds of glass particles flying every which way, fully dressed in painter's plastic suit, gloves, goggles, breather in hot summer weather, ear splitting noise, etc. etc. And that's with a LOT more wiggle room than you're going to have should you choose to do this.

It was truly not fun and a lot more work that way.

CarlPr

Edited by - on

Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 08/25/2010 : 08:19:47

I've seen re-coring done from the bottom, but don't think that's the best way to do it. You can't do it that way and use the best material for the job. You can do it if you use plywood. The best material to use is the foam coring material. It is very light weight, easy to cut to fit the space, and, after you saturate it with resin, it becomes virtually solid fiberglass. The finished product is very strong, and will not absorb moisture in the future. It isn't the worst job in the world, but it's one that you don't want to have to do again, if the new plywood becomes saturated and soft again.

Edited by - on

ckroll
1st Mate

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50 Posts

Response Posted - 08/25/2010 : 09:43:05

After discussing this with my friend, reading these comments and finding some good "how to" information, the top down method does appear to be really the only feasible way to approach this repair. We'll document well and will gladly provide a knowledge transfer to all who are interested.

Edited by - on

cshaw
Captain

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USA
460 Posts

Response Posted - 04/12/2011 : 12:06:41

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by ckroll
 After discussing this with my friend, reading these comments and finding some good "how to" information, the top down method does appear to be really the only feasible way to approach this repair. We'll document well and will gladly provide a knowledge transfer to all who are interested.
<hr height="1" noshade id="quote"></blockquote id="quote">
I looked for any posts you made on documenting your cockpit repair, but could not find them? I am planning on doing the top down approach and re-using the current cockpit sole, hoping to simply scrape out the rotted sole plywood and replace with new or the plastic honeycomb stuff. Can you please point me at any documentation you were able to put together on how you did it and any lessons learned?

Thanks!
Chuck

Edited by - on

ckroll
1st Mate

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Response Posted - 04/12/2011 : 13:05:11

If only I were as organized as I had planned on being when I posted that :-). The repair job was actually not that big of a deal for us.

I first supported the under side of the floor with a floor jack and a 6' 4x4.

I then used a 4 1/2 wet/tile saw to make the long cuts (about 2" off each side) and a grinder in the corners. I would however suggest that if you have a dremmel to use that in the corners in lieu of a grinder. Probably easier to keep steady and less likely to cause damage if the grinder runs on you.

Once cut the pulling of the core is obvious and I simply used a hand chisel to scrape any remaining wood from the skin (top and bottom). Keep in mind that some of the old wood will be "permanently" attached to the skins. You can try to get some of this off but be careful not to puncture.

As the core we used some plastic sheets that we roughed up with sandpaper, steel brushes and a wallpaper stripper.

My biggest warning is this (and I just posted something to this affect today): be VERY careful with the epoxy as you may not really be aware of what has touched it and subsequently other parts of our boat. There were two of us laying the epoxy and glass strips and my feeling is that was the issue (not enough room for two 6' dudes). We could have also taken some protective measures to cover the benches, et al but didn't and now we have a cosmetic mess.

Once again, sorry for the lack of documentation but we just got in the groove and never stopped to take notes. I will also add that we used the West Marine Fiberglass Boat Repair and Maint manual as our guide. It has EVERYTHING you need to do this project.

I hope this helps but if not please feel free to contact me directly.

Edited by - on

cshaw
Captain

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USA
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Response Posted - 04/12/2011 : 13:44:02

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by ckroll
 I first supported the under side of the floor with a floor jack and a 6' 4x4.

Once cut the pulling of the core is obvious and I simply used a hand chisel to scrape any remaining wood from the skin (top and bottom). Keep in mind that some of the old wood will be "permanently" attached to the skins. You can try to get some of this off but be careful not to puncture.

As the core we used some plastic sheets that we roughed up with sandpaper, steel brushes and a wallpaper stripper.
<hr height="1" noshade id="quote"></blockquote id="quote">
Great info, thanks! Got a few followup questions if you don't mind...

A couple of months ago I drilled about 25 1/8" holes in the cockpit sole, and about 75 holes in the quarterberth overhead to allow the water to drain out onto some absorbant stuff laying in the quarterberth. I had been hoping to simply tape over the holes on the bottom after it had drained and dried out and fill the dry rotted core with "Git-Rot", but there just was not enough core material left in there, so I will be doing the same approach as you did... (with the seats, etc masked off!!! <grin>)

Did not think of supporting the inside... very good idea with the jack! I will also plan to put a lot of weight on top of the cockpit sole when I put it back down to squish it all out level if I can.....

About how thick was the fiberglass cockpit sole that you pulled up? (will help me have the right dremmel cutting tool for the corners)

About how thick was the core material that had rotted out? (looking to find out what thickness material I need to get for the "new" core)

What type of "plastic sheets" did you use for your new core material? (and where did you get it?)

Finally, you said you used epoxy to glue things back together. Just to make sure, you really did use epoxy rather than polyester resin, right? And did you have to use any filler material or cloth to fill stuff in?

Many Thanks!!

Chuck

Edited by - on

ckroll
1st Mate

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50 Posts

Response Posted - 04/13/2011 : 05:44:59

We used cinder blocks in big trash bags along the edges and center for the same reason you noted above.

If I remember correctly, the skin was probably between ¼ and 3/8 in thick and the core about 3/8 as well. I apologize for not knowing the exact measurements but when I cut the skin I set the depth shallow at first and kept lowering it until I hit the wood (which since it was rotted was obvious). Probably ended up making the cuts ½ in plus deep.

We used two sheets of (about) 1/8 in plastic. Wish I could tell you what kind and where to get it but my friend obtained it from his father in-law who in turn got it from the company he works for. They use it for fabrication and he was the one who suggested that we use it in lieu of wood.

My apology on the terms and the lack of using the correct ones. We used the resin and hardener available from West Marine as specified in the repair guide. And yes, we did use the Epoxy Resin (WM 105 I think) and the Hardener. Also used the filler per guidance in the repair manual. Note: USE A MASK!! That filler is super light and floats everywhere. I can assume that it’s not a good thing breath it in. Same goes when cutting and sanding the skins. Lots of very fine debris in the air (close your hatch if possible).

Regarding the mixing of the resin and hardener, I would suggest using the pumps as they measure the exact amounts needed and it’s a lot neater. Also, only mix in little amounts if you use the quick curing mix. I did not realize what “quick” really meant but discovered during my first mix that it really does mean QUICK!. Creates a lot of heat too if mixed in a large batch left to cure. You should go ahead and buy a lot of small plastic cups and spatulas for mixing.

If you cant find the manual, send me an e to ckroll at s1defense dot com. It is a must.

I hope this helps!

Edited by - on

cshaw
Captain

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USA
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Response Posted - 04/13/2011 : 06:46:00

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by ckroll
 I hope this helps!
<hr height="1" noshade id="quote"></blockquote id="quote">
Thanks!!! Yes it does! The older I get the more I like to go to school on the experiences of others!!! <grin>. I have a lot better idea of what to expect now!

Cheers!

Chuck

Edited by - on

Steve Milby
Past Commodore

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5902 Posts

Response Posted - 04/13/2011 : 07:15:48

Chuck, the West Brothers System has a book that explains how to do re-coring, and I suggest you get a copy. You should also consider discarding the original skin and replacing it with a new skin of fiberglass cloth and resin. The reason is that, when you're done, you'll have to paint over it, and that will ruin the non-skid, so, you'll have to add non-skid material to the paint. By the time you do that, you will have completely lost the "original-ness" of the surface. By resurfacing it with a new skin, I think you'll have a much more durable surface, and it will look at least as good as if you use the old skin.

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cshaw
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USA
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Response Posted - 04/13/2011 : 08:40:24

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Steve Milby
 Chuck, the West Brothers System has a book that explains how to do re-coring, and I suggest you get a copy. <hr height="1" noshade id="quote"></blockquote id="quote">
Good suggestions Steve! I think I am going to wait to see what condition the floor comes out in before deciding on whether to try and re-use it or not. My initial plan was to simply paint the area around the saw kerf after re-filling it.

I have use the West System extensively thru the years on lots of boat and telescope projects, and I really like it and the info they have also!

Thanks for the inputs guys!!!!

Chuck

Edited by - on

ckroll
1st Mate

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Response Posted - 04/15/2011 : 05:25:50

Forgot about this reference to a project like this. Not sure it covers any more than we've discussed or in the guides suggested but you can never have too much info IMO.

http://members.csinet.net/dhapp/cockpit/cockpit.html

Edited by - on

cshaw
Captain

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USA
460 Posts

Response Posted - 04/15/2011 : 10:43:46

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by ckroll
 Forgot about this reference to a project like this. Not sure it covers any more than we've discussed or in the guides suggested but you can never have too much info IMO.
<hr height="1" noshade id="quote"></blockquote id="quote">
Thanks!!! That is a GREAT website. My project list for Confetti just got a LOT longer!!!! <grin>

Chuck

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