Cockpit core repair

[gs11gk]

Hello everyone.
I'm in the middle of a project and looking for some guidance. I have a 1974 Pearson 30 that had some softness in the aft half of the cockpit sole. I took the plunge and cut out a section of the top skin to have a good look. I found wet balsa and some mush. I've since cut out more top skin and I'm trying to figure out how to repair it. As it stands now, I have a 2" ledge and I've removed all the balsa that I can.
So my questions are around how to lay the glass up. The boat had a 3/4" balsa core and the top skin laminate is 3/8" with a slight camber. I suspect that this was built up with a polyester resin. I have some 3/4" balsa that I've been trying to fit but its proven very difficult to wedge it under the remaining lip of the top skin. I don't have a good way to sand it down and the underside of the lip isn't so unform. I'm pretty frustrated with that- and then not sure the best way to build up the laminate. Using epoxy and 10 oz cloth, it would take a large number of layers. Fiberglass mat seems not conducive to epoxy and it will cost a small fortune to rebuild it that thickness with epoxy- I think.
So I am considering rebuilding the core with 1" balsa or corecell and thinking that I wouldn't need such a build up with epoxy and fabric. With that approach, I could have the same overall height as what is left of my cockpit. That would still leave me with the issue of fitting core under that lip but I could likely fill it with thickened epoxy.
I'm hoping someone with more experience than I can help point in the right direction.
Thanks.
David

 

[gs11gk]

Forgot to ask a secondary question. I suspect that the water may be coming through where those four bolts are holding down that cap underneath my tiller. There doesn't seem to be any core material left under that cap and there is a big mass of epoxy that I suspect was laid by a previous owner. Are those four bolts just to hold down the cover or are they structural. I'll probably want to rebed them- but want to be sure my rudder doesn't fall to the bottom of the lake!

 

[dlochner]

Take a look at this YouTube channel:

He did a complete record of his deck. Lots of good info there.

 

[gs11gk]

Thanks- I'll check that out as I'm also recoring areas around my life line stanchions. That is going much more smoothly than then cockpit. BoatworksToday also has some good information on recoring.

 

[gs11gk]

I just noticed you hail out of Fair Haven, NY. I grew up in Hannibal- know Fair Haven well. Small world!

 

[dlochner]

I just noticed you hail out of Fair Haven, NY. I grew up in Hannibal- know Fair Haven well. Small world!

yes, the world is much smaller and more connected than most folks think. There are several Pearson 30s in the marina here.

 

[Charlie Jones s/v Tehani]

I had to rebuild my cockpit floor also- I used a product called Kledgecell. worked well. And for work like this, epoxy is the ONLY way to go

 

[thinwater]

• If the bolts are a concern, just fill under there with thickened resin. No foam.
• the foam does not need to fit neatly. Fill in with resin and make sure it is well bonded underneath. Don't try to work one big sheet; cut it into as many pieces as you need for handling. This will NOT reduce strength. Just fill the gaps with putty and sand smooth.
• Use something heavier than 10 oz. cloth. I suggest 17-ounce biax with one layer of 6-ounce cloth for a finish. Stronger, cheaper, and faster. But you will only need ~ 2 layers for strength. Any more is just wasted weight.
  
• Use a roller at each step to get a good bond.

Have fun. Just did a similar foredeck section. Easy.

 

[gs11gk]

Thanks for the advice. I'll look into Kledgecell.

The latest idea is to take the 3/4" balsa pieces that I previously sanded down to about 06-0.70" and start filling in under the lip one block at a time using thickened epoxy and tapping them in as needed. It might take me some time but at least I'll have a process, provided I can figure out a way to do it neatly. How critical is it to entirely fill in under than lip? Maybe I am worrying too much about that.
Once I get under the lip filled in, then I can use the rest of the 3/4" balsa and glass in the original section/s that I cut out... or build it up new with 1708 (I think). I'm doing this in my slip, under the hot Texas sun so its a bit of a mental and physical challenge!
One way or the other, I need to get her back into sailing condition! This little project has become more daunting.
On the bolts, I need to figure out if they are just holding a decorative cap or if they are more meaningful. That's gonna mean crawling into the back of the boat with a flashlight and exploring. Joy. I'd hate to epoxy them in place and then need to remove them.

 

[gs11gk]

So having crawled back into the boat today, those four screws are nothing but a cover and source of leaks. The funny thing is that the cover doesn't move even when unscrewed and pried up. Its held in place by the rudder/tiller assembly.

I bought some balsa in both 1/2" and 1/4" to supplement my stock of 3/4". Half inch will go under that difficult lip. I will then fill the rest with 3/4", some of which has already been rough sanded to about 0.6-.07 to make a contour at the edges, but is still 3/4" in the middle. Then, the 1/4" balsa will be bonded to that 3/4" stock, making a 1" surface that I sand again for a contour. Finally, I intend to build up a 1/8" skin using two, possibly three layers of 1708 and West Systems epoxy. I'm not intending to use the old skin as I prefer to just start fresh.

That should get me the same top contour and provide a strong epoxy laminate.

Does that sound a reasonable approach?

 

[sailnoproblem]

I am not a fan of balsa. I have used devincell, and also a product called nida-core which is a vinyl honeycomb.
Both of which come in various thickness.

 

[jssailem]

@gs11gk here is a great link to BoatToday.com series on repairing decks.
https://www.boatworkstoday.com/videos/fiberglass-core-replacement-part-1/
It is a challenge but with the right system your can accomplish the task.

 

[Charlie Jones s/v Tehani]

I am not a fan of balsa. I have used devincell, and also a product called nida-core which is a vinyl honeycomb.
Both of which come in various thickness.

agree- have in my boat repair work, replaced too much balsa- great til it fails,, then sucks

 

[jssailem]

The use of balsa in most boats is an engineering choice. Reduces top side weight. Top side weight is calculated along with keel weight and CG position to achieve a righting moment in the boat.

It is the engineering application of design that when you laye the boat on the rail in the big puffs the boat wants to stand back up and keep you dry.

Putting a heavy STRONG core i.e. plywood and solid fiberglass/resin, will affect the design CG. A little can be tolerated, a lot will change the CG of the boat and could impact a lot of things.

 

[BILLNPR]

You might look at Seacast. It is listed as a transom and runner repair for power boats. The product is basic fiberglass filler with large fiber which bond together. It would be easy to pour and the level with a plastic trowel or a 2x4 wrapped in seran or packing wrap so the mix does not stick to the 2x4.
www.ecowolfinc.com
www.transomrepair.net

 

[sailnoproblem]

The use of balsa in most boats is an engineering choice. Reduces top side weight. Top side weight is calculated along with keel weight and CG position to achieve a righting moment in the boat.

It is the engineering application of design that when you laye the boat on the rail in the big puffs the boat wants to stand back up and keep you dry.

Putting a heavy STRONG core i.e. plywood and solid fiberglass/resin, will affect the design CG. A little can be tolerated, a lot will change the CG of the boat and could impact a lot of things.

I agree with the weight. However with this repair I don't see much of a problem, it's the cockpit and a small area. Devincell I agree is heavy once saturated, but the Nida-core is lighter then balsa. Again this is the cockpit and a small area. I doubt any way the repair is done will have little to no affect on the CG. (But I am not a Navel Architect)

 

[jssailem]

Well keep it light and seal it well. Then go sailing. If you turtle you know you failed to seal it or it was too heavy, Or you just got unlucky and lost your keel.

As you say small pieces no problem.

 

[sailortype]

my recently retired boat was a P30... great boats.
I have a similar situation with my new old boat, an Ericson 35-2. I am currently recoring the side decks. I also have this overhang issue to deal with. I am using Nidacore for most of it but it is difficult to 'stuff under' the overhang. I am using 4" or so of 1/2" plywood for that part and will piece in Nidacore for the rest. I am installing it in say 16" sections and making templates with hard cardboard to get the shape right. To clean out the 'underneath' of the overhang, a strong piece of thin metal with a hooked end will get most of it out (kinda like the end of a file)... then I am using a length of 3\8 wood with some 40/60 grit tough sandpaper (floor sanding stuff works really well) either glued or stapled to it. Will make short work of any remaining balsa core. You definitely want plywood wherever there will be penetrations for deck hardware and these holes should be over-drilled and filled with epoxy before drilling the necessary correctly sized mounting holes. You do NOT want foam or honeycomb material under deck hardware.
Epoxy vs polyester... I have always been an epoxy proponent but trust me, if you use polyester correctly, it will be good for 75 years. You have to do some dismantling of these boats to understand the tenacity of this stuff. Epoxy is good, even better in some applications... but here, polyester works just fine. The problem you will have is the heat and kick speed.

 

[dlochner]

Epoxy vs polyester... I have always been an epoxy proponent but trust me, if you use polyester correctly, it will be good for 75 years. You have to do some dismantling of these boats to understand the tenacity of this stuff. Epoxy is good, even better in some applications... but here, polyester works just fine. The problem you will have is the heat and kick speed.

Epoxy has better mechanical bonding characteristics than polyester or vinyl ester resins, basically it is stickier to cured surfaces. Both epoxy and polyester resins do well when used for laminating so long as the fabric is compatible and the resins can chemically bond, i.e., before it completely cures. As @sailortype says, both will last a long time.

Take a look at the BoatworksToday.com (or his YouTube Channel) for more information. Andy uses both in the same repair, epoxy to stick everything down, polyester to laminate, and epoxy to fair, gelcoat or paint to finish. He also has a couple of videos on epoxy bonding to polyester, it is a common myth that you can't put polyester over epoxy.

If I were doing this repair, I think I'd used thickened epoxy to bed the core material and fill the gaps between the core. And then laminate with laminating polyester resin. Finally fairing with epoxy fairing compound.

On the final glass layer consider a light to medium weight mat. The advantage to mat is it can be sanded smooth without affecting the structural integrity. Hulls are often laid up with mat or chopped glass in the initial ) outside layer) to create a smooth surface and to eliminate print through from woven fabric.

 

[Displacesailor]

Use a product like Cooca Board or Divinycell H80 that is grid scored.
Save your money and use polyester or vinylester resin that will last as long as the rest of the boat.
below is a picture of my Cat 22 cockpit that was damaged by ice under the glass. I replaced the whole floor.