Re-coring the Cockpit locker lids on a 10M

[Dave Cole]

My locker lids are getting noticeably soft in the center.   

There were some hairline cracks in the fiberglass and I am sure some water migrated into the core.

I know this has been done before.   I need some advice on whether this is a good plan or not.

My plan is to make temporary covers and remove the lids and take them back to my shop.

I'm thinking of working from the backside/bottom and cutting out the coring.  

Then grinding and sanding to clean fiberglass and then setting a new plywood core in epoxy with some thickener mixed in.

Let that cure and then put glass cloth/epoxy over that and blend it into the existing underlid surface.

What am I missing?

Is there a better way?

What is the thickness of the existing coring?   Is it balsa or plywood?

Thanks,

Dave

10M #26

[George DuBose]

There's a new material called Coosa, it is made in the US. It is a very hard rigid foam, very light and waterproof. I used 4" strips to build a ledge to support the cutout of the cabin sole. I had the occasion to whack it with a hammer and it didn't dent at all.

https://coosacomposites.com/

I would think of using that rather than plywood.

George/Skylark

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[Peter McGowan]

Sounds like a great plan!  W/R/T Coosa the big plus is that it’s the last time you or anyone will need to do it, because water has a hard time penetrating that stuff.  It’s lighter than plywood, but heavier than balsa, takes forever for water to get into it and even afterwards it won’t rot.  It’s got a good amount of glass to it, so gloves and mask for sure, even moving boards around with bare hands will be irritating (not unlike that pink house insulation you find in old homes) Not sure what’s coring your lids but I wouldn’t want mine to be any heavier, when I let them free drop it on occasion I know that the hinges are not happy about it.  If my lids were plywood, I’d consider replacing with Coosa because it’s so much lighter and forgiving on the hinges (and likelyhood of future stress cracks).  if they were balsa I’d have to consider whether the extra weight and expense of avoidance (an 8x4 sheet of Coosa is not cheap) is worth them outlasting me.  

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[Dave Cole]

I looked into buying several sheets of Coosa board pre pandemic and it was over $250 a sheet even if I drove to a warehouse location which was hours away.  Most of it was shipping fees to the warehouse.  Its an attractive product but hard to get at the time.  Perhaps Ill inquire again and see what they say.  Who knows, maybe they have a stocking distributor within a few hours now.  Back then it was a special order.

Thanks,  Dave

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[Jonathan Boright]

Would you recommend Coosa for a transom? Or a cockpit sole? (Yes, I’m doing both of those now). How does it do for shear strength?  The water resistance is certainly a plus…

Jon

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[Dave Cole]

As I recall, its stronger than marine plywood in every way.

But find their website.  I think they compare it to Plywood.  For me, the big thing was transportation costs.  I think the sheets themselves were about 50% more than marine plywood at the time.   But that was before it left the factory.

Dave

10M #26

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[Al Taylor]

When we’re talking about cockpit laz covers, how much strength does one really need? I can see the need for stiffness of plywood over balsa, but spending that much money on Coosa to make it bullet proof seems out of proportion to the rest of the boat. 

Just my $0.02.

On Jun 5, 2024, at 7:50 PM, Dave Cole <dave...@gmail.com> wrote:



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[Guy Johnson]

I re-cored my locker lids with 3/8" divinycell foam. From the inside I removed the wet Balsa core and cleaned everything up. On the OEM lids the hinge bolts went through the balsa core, you'll want to build up solid glass in that area. 

When you begin laminating, apply a layer of epoxy and let it partially cure before continuing. I used a single layer of 1708 bi-axial on the inside and vacuum bagged everything together. 

letting that first layer of epoxy tack up prevents it from being pulled through the lid by the vacuum. 

Guy

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To: pearso...@googlegroups.com <pearso...@googlegroups.com>
Subject: Re: [pearson ] Re-coring the Cockpit locker lids on a 10M

 

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[Dave Cole]

Vacuum bagging...good idea.  

Do you recall where you bought the foam from?

Thanks,

Dave

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[Guy Johnson]

Jamestown distributors 

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[darin doherty]

I just did the starboard side.  I definitely recommend divinycell.  The mistake I made was going with 1/2 in instead of 3/8 in.  I had to carve some out to thin the thickness where it sits on the frame below. 

You don't need plywood or cossa board.  It will make you seat heavy with no real benefits.  The divinycell or balsa are plenty strong.  Just add a couple of stiffining ribs.  I am 280 and can jump on mine. 

Also, I went from the underside, not the top.  I did have to use some weight to remove the cupping of the top side of the seat when laminating the cell board. 
No vacuum bagging, just polyester and a roller.

Good luck.  It really wasn't too bad.

Darin
P10 #108.  Charis

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[Al Taylor]



Guy, can you say more about your vacuum bag set up? How do you get the laz lid in a bag?

[Al Taylor]



Guy, can you say more about your vacuum bag set up?

[Guy Johnson]

The bag is a big sheet of nylon bagging material that is sealed on the edges with special sealing tape. The lid is put inside the bag and then sealed.  When bagging the bag needs to conform to both sides of the cockpit locker lid. 

Jamestown sells everything you need. Harbor Freight has cheap vacuum pumps. 

Guy

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[Dave Cole]

Have you tried this with cheap poly sheeting?

Seems like it should work.

Dave

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[Al Taylor]

I would think regular poly would stretch and break at sharp corners. The nylon reinforcement would prevent that like ripstop. 

Fiberglass Supply Depot looks like a good source too and I’ve found great prices there on some other basic supplies. 

On Jun 7, 2024, at 9:34 AM, Dave Cole <dave...@gmail.com> wrote:



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[Dave Cole]

If I leave plenty of extra poly beyond the edges, I would think that would prevent tearing.  There is no reason for the "bag" to be tight.  Sort of like vacuum bagged food aways has a margin of plastic.

I may rig something up and try it out.

I have a vacuum pump, tubing, etc.

Dave.  

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[Guy Johnson]

It can work with Poly sheeting too. It's easy to underestimate the clamping force of vacuum bagging until you've done it for the first time. Also smoothing the peel-ply and air venting layer is easier with the vacuum sheeting than it is with poly sheeting. Any wrinkle in the peel ply will fill with resin and require sanding. If you get everything smooth on the interior surface of the lid, you're all done. 

Guy

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[Dave Cole]

Did you have any issues with the lid becoming twisted during the recore process?

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[Guy Johnson]

No problems with the lid changing shape. Since I bagged the entire lid calming force was equal in all directions and the lid maintained it's original shape. 

Guy

Puffin 10M #6

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[Dave Cole]

Excellent!

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[Dave Cole]

I have the lids off my cockpit lockers and I cut out the inner liner on one of the lids to find the balsa sopping wet.  

It's amazing that so much water can get into a cored panel.

The core is indeed 3/8" of an inch thick and it is across the entire lid surface, and even under the hinge screw holes as Guy mentioned.  

I have some 1708 Biaxial fabric and plan on putting one layer over the cored area as Guy made that work.  

But I think I will end up with several layers under the hinge mounting areas as I am not going to put coring in that area.  

I have just over 1 1/2 gallons of Epoxy on hand.    

But I'm thinking that 1 1/2 gallons of Epoxy might not quite be enough?  

How much epoxy did you guys use to redo your lids?  

What do you think?

Thanks,

Dave

10M #26

[Guy Johnson]

1.5 gallons is more than enough epoxy for the job. 

 1708 Biaxial fabric and plan on putting one layer over the cored area as Guy made that work.  

But I think I will end up with several layers under the hinge mounting areas as I am not going to put coring in that area. 

That approach worked well for me. Remember to let a layer of epoxy tack up on the inside of the lid, then finish adding your layers. I had some epoxy bleed through the top of the lid on my first one. 

Guy

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[Dave Cole]

Great.

Thanks!

Dave

10M #26

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[Guy Johnson]

One more thought the hinge area of the cover needs to be thinner than the cored area to avoid hitting the raised lip that surrounds the locker.

Also, I beveled the edge of the core material along the outboard side near the hinges.  

Guy

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[Dave Cole]

Resend since I hit the size limit.

On Thu, Jun 13, 2024, 1:51 PM Dave Cole <dave...@gmail.com> wrote:

It looks like the taper in the core starts about 3 inches from the hinge edge.  (See the picture).  The core at the hinges is about half thickness or about 3/16".   The core is very wet but its mostly intact.  Just not bonded to the skins well at all.  

I used a 6" drywall knife and a mallet to scrape the core off the top skin.  Its taken less than 45 min per lid to remove the inner skin and core.

Im using an oscillating multi tool with a carbide blade.  It slices right through the inner skin and doesnt make much dust.

I think Im going to use 3/8 marine plywood for the core, since I can get a sheet down the road.  Ill coat it in epoxy so it should be good for another 50 years.  😃

I can sand down the edge of the core so it blends into the thickened fiberglass at the hinge.   That way it will be a nice continuous surface to the hinge area.  

Without the wet core, these lids are very light.

Dave

10M #26

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[Guy Johnson]

If you're going to vacuum bag, you could vacuum the first coat of epoxy into the plywood. 

Guy

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[Dave Cole]

I re-cored both locker lids last weekend.

I vacuumed bagged them using things I already had.  Well, I did splurge for the 4 mil clear plastic, $10.

This works really well.

I had a refrigeration vacuum pump.   I had a manifold, so I created a Y using that so I could do both lids at the same time, and I simply taped the hoses into the corner of the folded plastic sheet.  One bag for each lid.

For tape, I used what is sold as Silo tape around here.  Silo, as in a Farmer's Silo.   It's some type of poly tape that sticks well to poly sheeting.   I know that Rural King sells it, not sure if Tractor Supply has it.

It must be about 4 mils thick and it worked well to create a nearly airtight bag around the lids.  

I used 1/2" marine plywood as the store was out of 3/8th.   I was concerned about it being too thick near the hinges,so after everything setup, I sanded off the flash and took them back to the boat to see if I had to modify anything.

It turns out the thickness of the plywood was fine but the screws and nuts for the hinges would interfere with the cockpit fiberglass.  So I used a 1" forstner bit to recess the nuts and washers on the inside of the lids, and then coated everything in epoxy.  So no exposed wood to suck up moisture.   

I was concerned that doing the vacuum bagging would be a lot of extra effort, but in hindsight, I think this is the easiest way to do this and get good results.

I first coated the inside of the lids and let that start to set up, then put in a layer of thickened epoxy to help fill any voids, then the plywood (which was already coated with epoxy) then a coating of epoxy, then the 1708 Biaxial cloth, then more epoxy.

The vacuum was applied and the bubbles came out of the epoxy.   I put a covid facemask around the vacuum hose end fitting so the plastic wouldn't be sucked into the hose.  I applied vacuum for a while, then released it and then repeated several more times every 20 min or so.   I think that helped suck more air out of the assembly.  

What is really nice about this process is that the sheet plastic pushes the cloth up against the inside of the lid and the plywood in a way that is impossible to do manually.  And of course the plywood and cloth are compressed as well against the inside of the lids.  The results are very smooth with few visible bubbles.  I will definitely do this again.

Great suggestion Guy, to vacuum bag these!  

Dave

10M #26  

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[Guy Johnson]

Dave;

Glad to hear it all worked out for you. I think you’ll be really happy with the results.

Guy

Puffin 10 M #6

On Jun 23, 2024, at 5:01 PM, Dave Cole <dave...@gmail.com> wrote:



<IMG_20240613_132221606.jpg>

Dave

10M #26

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[Dan Pfeiffer]

I have an asymmetric spinnaker for sale.  It has a sock and an ATN Tacker.  In like new condition.  Only used a few times.  It is a little long on the hoist for my 10M but not at all unmanageable.  Probably only keeps it from carrying to +90TWA (though I have done that too).  It is 47 feet on the luff and 39' 1" on the leech.  It would fit very nicely on a 10M tall rig or a P36 (same hoist) or any boat with about 45 to 47' hoist.  White with green.  I have the original documents from the order.  Was 5K new!!!

I am asking $1200.   See photos, ask questions

Dan Pfeiffer