Wet Deck Core At Mast Step

[Karl13265]

Just came in from the boat after discovering what appears to be a wet deck core under the mast step. Removed the trim on the compression post and all is fine there.

Realize the question has been asked before but do I remove the deck section around the mast step, replace the bad core and then re-install the deck.

If so I'd like to know best practises before I start.

 

[Manny]

Here's what I did

1) removed Mast, found cause of water intrusion - old dried up shrunken caulking.
2) removed compression post inside cabin to inspect and to remove bolts for mast step
3) using small circular saw (a ryobi cordless) cut mast step area off. I drilled a hole first to determine thickness of deck.
4) removed soggy core from area, also removed a small amount under the remaining deck.
5) built up area with alternating matt and roving - cut pieces oversized so they would fit under the area I cleared out under deck.
6) used lots of epoxy to replace the top of deck that I cut out - drilled extra holes to ensure even coverage (lots of excess oozed out)
7) sanded, painted, sanded some more, painted some more, etc
8) replace mast
9) went sailing

 

[Karl13265]

Thanks for the reply Manny, you've answered my questions before and between you and Ed Scheneck (spelling) all has worked out.

Source of my water was a hole cut throught the deck and covered by a grommet where the antenna cable and line for the Datamaster Wind instrument wires were fed.

I didn't have to remove the compression post to get at the maststep bolts as only two went in through the coachroof (port side) the other two starboard side just seemed to go through the decking and at some point in time seem to have been seated in a bedded nut or plate under the deck.

My plan is to use a large Dremel (like) tool I have to cut the deck with a cutting wheel. I've used it on fiberglas before and it works great. The speed is adjustable and allows really good control of the line of cut. It also cuts a very narrow fine line which allows for less loss of fiberglas and less work when it comes to filling and sanding the void between the cut out portion and the remainder of the deck.

Second portion of the plan now that you've shown me what I'm up against is to use Corsil to fill the largest portion of the under deck void and then the remainder with roving and cloth. Corsil is nice to work with because I can fillet the edge to fit under the remainder of the edge of the deck and then as you mentioned cut oversize pieces of roving and cloth to do the remainder.

I'm also thinking about bedding a stainless plate under the deck right under the mast step, after I've drilled and tapped it to accept the four deck step bolts. That way I avoid the through bolts into the coach roof that could again cause a leak and that for my money don't add anymore stability to the step than my plate idea would.

Also thinking very seriously about filling in the large through hole and grommet affair in favour of a much smaller one that is more easily sealed, since I only have the two wires running through it.

Next steps are as you described, cloth the cut portion of the deck, after much epoxy below, sand, fill, sand, fill, sand you get the picture and finally paint and if necessary paint again.

Your thoughts and observation are much appreciated, snow is now going here, I'm tasked at work as the Provincial (State) River Watch Coordinator and am running out of time if all goes well to launch and sell the boat to go bigger.

 

[Ed Schenck]

Yes, thanks Manny. You did a super job and the pictures and explanation are excellent. I am wondering though if I will find the side decks on my H37C to be too thick to use your method. Wouldn't your way be very expensive if I find a one inch gap between the deck and the inner liner?

 

[Karl13265]

Morning Ed

Any comments on the modification to Manny method that I'm proposing.

 

[Manny]

I was a bit tired when I put in my reply last night, so I condensed some of the items. The hardest part of the whole thing was removing the compression post. The post on my 27 has teak trim all around. I had to find all the bungs and remove quite a few screws to get the trim off. Once I did that it made it easier to find the screws that fastened it to the bulkhead. I had to take some trim pieces off of the bulkhead to get all the screws out. I then needed to purchase a floor jack (i think that's what they are called) to lift the ceiling liner enough to get the post out - I gave myself a black eye doing that but one or two centimeters more and it could have been worse- always wear safety glasses!!!!!!
The aluminum step on mine was held by three bolts that were covered by the compression post - it came from the factory like that. If you are going to make the repair I would recommend through bolting, not embedding a plate and threading. The cabin liner (at least on mine) is pretty thick, I wanted to couple the repair to the liner as best as possible.
I'm not familiar with Corsil so I don't know if it is a good choice but if it is rated to handle a lot of compression I guess it would be okay.

Ed, I'm not sure if this method of repair would be to expensive for your chain plate project. I guess it depends how large of an area you are going to cut out. I can tell you it cost me less than $150 for the epoxy, glass, and floor jack (and I had a bunch of glass and epoxy left) I don't remember the thickness of the core on mine but I'm thinking it was about 3/4 inch - much thicker where the step area is raised. I had saved a piece of the old core but I cant find it. One thing I can say is that if your are doing large areas you are going to add a lot of weight, that may be a consideration.
This was actually pretty quick repair once the deck was cut off. I think it took me one or two afternoons to clear out the core, prep the surface, glass, and put the cabin top back on. It took longer to paint!

Manny

 

[rardiH36]

Manny:

Good post.

I don't have cabin top and side deck core issues (yet that I know of), but it's informative to read the posts for maybe my turn at core repair someday. Although differences exist between various Cherubini models, probably a lot is the same.

Questions: 1) Was the core material under your mast area plywood or balsa? 2) If plywood, was it decomposed, or still good would but delaminated between the plywood layers.

I ask because the cockpit sole under my pedestal when I bought my boat had gone "soft". The whole pedestal rocked back-and-forth. Repair was necessary. After removing the pedestal, etc, I removed the top skin much like you did for you mast area. Although the cut was straightforwarded, the top skin needed a lot of gradual pry bar coaxing to peel off. This difficulty because core material was plywood. No rot at all of the wood. The plywood was strongly attached to the top and bottom fiberglass layers. I had to use a wood chisel and a sander to get all off from the top and bottom skin fiberglasss. Too many years of water however had caused the glue between the layers of plywood to separate. If I had know the condition of the interior before I started the project, I might have gone at the repair differently. Such as drilling lots of 1 inch holes (in a pleasing geographic pattern) down to the bottom fiberglass layer (but not through). Try to dry out the wet core for a week or two under the low humidity California sun. After dry, flood all of the holes with epoxy. Wack for a while with a rubber hammer to promote flow of epoxy through layers and void spaces. Re-flood. Wack some more. Eventually fill the holes flush with the cockpit floor using thickened epoxy so as to stipple the surface to mimick the non-skid. Refinish/paint.

Thanks for info about the core material and condition you found on your boat.

regards,
rardi

 

[Karl13265]

Hello All
Thanks again for all the comments and advice. For Manny, Corsil (spelling?) is a blue rigid foam material use with figerglas construction. A friend built a tender for his boat from it last winter. The pattern was traced out on the foam and the pieces then clothed and epoxied together at the joints. From there cloth and epozy was cut and spread over the interior shell and susequently over the exterior of the hull and deck to form the boat. Deck and hull are double clothed at the joint and the whole issue then sanded smooth and then painted. Looks great, works even better. Strong stuff and very light so as not to add too much weight to the topsides. This is my first option, recoring with marine grade plywood or using your method of fiberglasing would be work great as well.

As to the mast step, as I say the two starboard side bolts were holding on with next to no thread and the two portside extending down through the coach roof didn't appear to be doing much either. They appeared to be more of an after thought than original to the boat. I'll let this issue play out as we progress with the rebuild.

I'll check the posts each day until I start the project for any more tidbits of wisdom to be gleaned. Again thanks to all from me, still in the snow in eastern Canada while my first mate prepares to leave for Washington D.C. for a week. Maybe if i'm lucky she'll come back with a new boat.

 

[Manny]

Rardi,

I feel your pain. I too have a cockpit floor with a soggy core. Originally I thought the floor was just fiberglass that was a bit thin and flexing when weight was applied. This winter I went to open up a small crack to repair along the one of the channels on the edge of the floor only to have my dremel pop straight through and start spitting out soggy wood. I couldn't tell if it was ply or balsa. I can tell you when the temps dropped below freezing the cockpit floor turned hard as a rock! My pedestal was solid - no flex at all!!!
I "temporarily" added support with an oak 2x4 under the floor from port to starboard under the floor just in front of the pedestal guard. I screwed and epoxied it into the wooden wall on port quarter-berth and the plywood bulkhead in the starboard lazarette. I also reinforced the plywood bulkhead with scrap oak. I had to grab my car's jack to slightly force the 2x4 into position because the center of the floor had a little sag. I then liberally painted the oak with epoxy for added protection.
At least for now I am going to try the method you mention about drilling holes and filling with epoxy. I wanted to try and do that this winter but the weather never seemed to cooperate with my schedule. A dock mate had the same issue with a different manufacturers boat and cut out the floor and repaired.
Oh yeah, the wood under the mast step was definitely balsa (in the little squares) and definitely very soggy. Most of it stayed together but I had a few pieces disintegrate when I tried to remove it.

Sailingmountie,

Thanks for the info on Corsil, sounds interesting. I wonder how well it would handle the loads of a mast on top of it. Maybe your friend has a scrap piece he can give you to try some testing - maybe gently drive over it with your car to see if it flattens out.
You should head down to D.C. with your first mate and take a short ride over to Annapolis - maybe you can hitch a ride on a sailboat!!!

Manny

 

[Karl13265]

Manny
I'll try the vehicle test or better still just ask my friend as to what the Corsil properties actually are.
As to the trip to D.C. with the first mate, that's a no can do. Don't know if you've seen any of the flood situation in Fargo, ND but I have the potential for a similar problem here at home. Due to this, I'm not allowed leave from March 1 to May 31 each year, unfortunately I coordinate our program.
I'm trying to convince the mate to take a day off from her meetings to rent a car a car and head to Harve de Grace to look at a couple of boats. We'd like to move up to a 37.6 - 40 Hunter.

Thanks again for the info.

 

[rardiH36]

Manny:

Thanks for the info that the core around the mast step was balsa.

Regarding when you tapped into your cockpit floor it "spit out soggy wood": This is very different than my situation where the wood was still in good shape. I would think that if the core is too far gone, then a complete peel-away of the top skin and rebuilding the interior with new wood (or other material) will be the best route. I found a post that I made about 1.5 years ago when somebody else was looking for another owner's experience with cockpit sole repair. Might contain something of use:

Dear Sailtip: I did repair this past summer the cockpit sole section under/around the pedestal of my 1980 Cherubini H36. The core was a mosaic of individual plywood squares. The plywood itself was not rotted and was still firmly attached to the upper and lower fiberglass skins. But probably because of years of H20 ingress, the glue holding the plywood layers together had failed. Took several hours with a sharp wood chisel/hammer and then an orbital sander/grinder to get the all plywood off of the fiberglass. I'm a newbie to sailboat maintenance, so best to make your own assessment about the following which is how I went about my repair. I'm sure that others have better methods, but maybe you can find some nuggets of info that might help. I don't know if the Cherubini 37 cockpit sole is constructed similar to the Cherubini 36. On my 36, after removing the pedestal and other mounted hardware from the sole, I used a cutting bit on my dremel tool to neatly cut around the top layer of fiberglass at the interface of the non-skid and smooth surface. Then I was able to peel off the top section... (didn't come off easy). Cutting out the bottom from the limited space underneath the cockpit floor seemed just too difficult. I removed all the old plywood core and roughed up the new mating surfaces. I put duct tape over the holes into which the pedestal and grab rail bolts went, both on the top and bottom skins. Maybe not necessary, but from underneath, I attached several long/straight 2x4's using deck screws through the wood into the lower fiberglass skin. I did this to bring the lower skin to a reasonably flat condition since the pedestal and steering sheaves are mounted in this area. I cut off the portion of the screws that protruded up through the fiberglass. Later, after the epoxy work had been completed, from the bottom I was able remove the screws and then the 2x4's. I drilled lots of 1/2" holes in the replacement wood. Then I flooded the bottom with West Systems epoxy and layed in the new wood. Pressed it down until epoxy oozed up through the holes. Then flooded over the wood with more epoxy. Then brushed a layer of epoxy to the underside of the top skin to wet it. Then layed and centered the top skin on. Jiggled it around for a while so the epoxy would flow and adhere. An issue was deciding how much epoxy was needed to flood the space so that all plywood/fiberglass would be mated everywhere, but that lots epoxy wouldn't ooze out. The fact that the boat was not completely level also complicated. I put heavy stuff on the top skin to keep it compressed and level on the new core. After the expoxy had set up, but was not yet rock hard, I shaved back the high spots that had oozed out. I found that having some epoxy filled syringes on hand was useful to neatly fill the gaps where epoxy had not filled to the top. Since the orignal cut to remove the top was at the smooth/non-skid interface, and with careful shaving the excess epoxy, and sanding with a small block, and with two-part polyurethane paint to finish it all off, the repair is not readily noticeable. One item that I would vary if I ever do this repair again (hope not), is that I should have made the core area around the pedestal maybe about 1/8" thicker than at the edges of the repair area. After a rain or washdown, I have noted a small 1/16" deep puddle in the center around part of the pedestal base. If the center thickness had been bowed up a bit, the water would run off and into the cockpit drain. regards, Rardi

 

[Karl13265]

Manny

Got out to the boat yesterday and again today with the First Mate, did the deck cut out with my new Roto Zip that I bought at Home Depot. Works like a champ, a bit harder to work with than the Dremel but such is life.

Had to pry the deck loose from the core which was wet enough to ooze water as we scraped it away from the cabin liner. Got everything all cleaned out including some additional wet area under the fore deck, just as you had indicated.

Found two surprises, first that the port bolts that secured the step had been sheared off and that was the reason the step came away without taking out the compression post. Second that there is actually two cored areas. The first being between the outer deck and the inner core (this area is small and is roughly the same shape as the exterior raised gelcoat area extending port and starboard) and then the inner core between this small area and the interior coach roof. Both are now cut out and cleaned.

Will start sanding all areas tomorrow and then set up for Manny's alternating mat and roving fiberglas. Before fiberglassing, I'll be placing a dehumidifer over the cut out deck portion held off the roof by two pieces of straping, going to tent the dehumidifer with plastic and tap the plastic to the deck to allow for moisture only to be drawn from that area, that shoudl dry out the small area that I cleaned out under the foredeck prior to sealing with roving and epoxy.
Attached photos are green due to the winter cover still being in place. Still cool up here in the Great White North. Will let you know how the fiberglasing works out and send along the pix.

 

[sandpiper10471]

RE deck repairs:
It is best to set new core in a layer of saturated mat, same if bonding back the old top skin. Unfortunately, mat and epoxy are not compatible. Best to use vinylester resin (half the price of epoxy with almost the same characteristics and is compatible with all the usual fillers and mat) for this as it is more tenacious and waterproof than polyester.
Not all Hunters will be the same build schedule. Example, the side decks next to the cockpit on my 37C were cored with blocks of ply. That makes no sense to me. I hope the rest is balsa!
The mast step area is usually a sandwich of two plywood cores with three layers of glass. Foam does not have the compressive strength needed for this area. Use marine ply or hardwood. This is probably the most stressed area of the boat, next to keel vs. rock!
When rebonding the top skin it is essential to bevel the joint at about 14:1 and fill the resulting channel with laminates of glass. I like to use stitchmat for this - it is two directions of roving stiched together with a thin mat on the bottom. Because it is stitched and not held together with glue, it is compatible with polyester, vinylester and epoxy. VERY strong stuff. You use less mat which is heavy and resin rich without much strength. Its primary purpose is to bond adjoining layers of roving or cloth. If you just fill the gap with epoxy and cabosil or epoxy and chopped fiber, you have the strength of the bottom skin only and the joint will show through the finish after a short period of flexing and working.
Re drilling holes to dry method: Unless you are in the Atacama Desert or parts of Venezuela, the core just won't dry out in a month of Sundays. Take off the top skin, recore and go sailing!
Re cutting out the top laminate: I like to use an angle grinder with a small diamond blade. Easy to control and very quick. WEAR PROTECTIVE CLOTHING and that includes heavy gloves and long sleeves. Mask (not a cheap paper one) extremely important!

 

[Manny]

sailingmountie, your pictures of the core brings back memories. I am starting to itch again thinking about the fiberglass!
As far as drying the area you can also use liberal doses of acetone on the wood, it will displace the water and evaporate quickly (make sure you have adequate ventilation).
I tried to bevel the seams of the repair but nothing I had would grind through the glass. I have been keeping a close eye for any separation at the joints and there has not been any sign (and it's been a few years).

Manny

 

[sandpiper10471]

Glad you have had no problems with the cockpit repair. You saved yourself a lot of work! To grind the bevel I use an angle grinder with several discs of 20 or 40 grit 4" pads. Works well but it takes a lot of practice to get it even. But then that is what cabosil is for, right?