Restore /refit of my 1988/89 26D

[OverEasy]

In general:
Indexing the layer weaves relative to each other will result in a more uniform load distribution for the new surface.
Laying them in the same weave orientation doesn’t give you as much load path distribution

Any opportunity to provide a bonded separation distance between fiber layers gives a significant boost in rigidity which is why foam core panels are so advantageous on a strength to weight ratio assessment.

[kenfyoozed]

Does the mat between the woven fabric provide enough separation?

[OverEasy]

Thicker works better as long as the separation material is rigid…. Like foam core or balsa or honeycomb.

Part of the reason is skin load shedding

Think of an I-beam… the top and bottom are in tension and compression while the middle web keeps them separated.
No web would be a two level strap and kind wimpy…. Start with a pair of strips 4 inches wide by 1/8 inch thick….it’s not gonna hold much of a load if simply supported at each end of say a 4 foot length….but Add a web of a say 2 inches tall and it becomes quite rigid…make the web 4 inches tall and the rigidity becomes significantly stronger.

Same applies to fiberglass composite core construction…. Two thin layers of sheet fiberglass are kinda wimpy…. Add a 1/4 inch foam core bonded to the sheets (one on top the other on the bottom) and it becomes fairly rigid…. Increase the thickness of the core and the rigidity becomes significantly more rigid. The foam by itself is rather wimpy but if it can provide a good separation between the sheets is where the strength is gained.

There are several good sources that go into the process whereby this occurs but now isn’t the place to do that without boring everyone to tears…..l

Suffice to say that the more separation between the top and bottom fiberglass sheet layers with a well bonded core the stronger it gets.

[kenfyoozed]

Overeasy.... that's for the explanation. Thats makes sense. Which has opened an idea for me.... I'll get to in a moment....

So the starboard roof went under surgery today. The core was completely trashed.



The deterioration seems to extend further midship than I thought or hoped.



The section I cut out had to be removed so I'm ok with that. What I don't want is to have to cut more out but I may be forced. Also while on the issue of core material there is none on either side of the front hatch. This is looking into that section. Top is the deck and the bottom is the ceiling liner and nothing in between,



I feel this area truly needs more strength as you can hear the fiberglass creaking if you walk on it now.The only way to add core is to cut more out from up above and slide core, most likely plywood strips with repair putty into the voids. Or the next great idea i have is I could drill a grid pattern and inject a foam material that would expand and fill the voids. I like this idea as its minimally invasive to the overall structure. At this point in for a penny.....

I have decided to also overlay the entire top of the boat with a layer of 1808 and 1708 when I am finished with these repairs.

[OverEasy]

Just an extra reiteration….For any core to work requires it to be properly bonded to the upper and lower sheets….it can’t just “rest” in the void space…. That poses the challenge with using expanding foam….

It could take a bit of R&D but it might be possible to clean the interior surfaces…(messy)…of any wax compounds on the surfaces.
Then apply resin to those cleaned surfaces just prior to foam injection…hmmm
You’d need to set up a set of surrogates to test whether it would work and how it would functionally bond.
Expanding foam requires the gases that do the expanding have the volatiles outgas…if that doesn’t happen the foam won’t form properly and may actually ‘eat’ itself…. And not form proper foam…it would also be a relatively weak foam but that’s where the R&D comes in…

Another process once the interior surfaces are clean of dirt and waxes another technique it insertion of thin foam strips wetted with slow curing resin between the sheet surfaces ….then use additional very thin resin to fill any residual void spaces….bonding it all together into one structure.

[kenfyoozed]

I ran across this.

https://youtu.be/tBGKiZquNWk



Using 8lb pour foam. Ive used this type of pour foam to insulate a boiler so I am familiar with it. It could make quite a mess if the area that's poured is not sealed, which my boat does not seem to be. I really do not want to open up more of the deck but it seems I may have no choice.

[kenfyoozed]

After a better look at he deck and cabin ceiling liner it seems the port side does not have the same void as the starboard side did. It appears the starboard side void is roughly 1/4" and the liner and and deck were not mated properly at the factory. This doesn't surprise me as the deck joint had no sealant from the factory as well. It appears that on the port side the bottom of the deck rest on the top of the liner, and this isn't true on the starboard side which is why there is an issue. I think the deck needs the liner to have the full strength. So the voids on the starboard side will need to be filled. Just got to come up with a way.

And need some marine plywood to repair the rotten damage, and it seems no one in my area has anything to offer.

[OverEasy]

Hi Kenfyoozed!

That epoxy. Foam stuff looks to fit the bill…I’d still figure out how to wet coat the interior surfaces with resin first though.
I’ve use expanding epoxy foam for flotation and years later had the opportunity to disassembly the floatation chamber and found that the bottom where the liquid was poured onto was reasonably bonded but that bond was progressively worse the further up the chamber the foam rose. The interior surfaces were clean, dust and oil free and had been previously epoxy resin saturated and cured to preclude moisture from attacking/saturating the marine grade plywood that the chamber was made from.

But epoxy foam is pretty good stuff.
Strong, filling and water resistant.

If you can get a small bead of canned expanding foam to make a lower edge ‘dam’ to keep the epoxy foam stuff in place long enough for it to kick off that might be an option.
You might want to experiment with that crack fill foam roping that’s used in concrete work to see if it holds up to the epoxy resin or if it disappears.

Just thoughts…

Best Regards
Over Easy

[kenfyoozed]

Overeasy, thanks for the ideas, it got my mind rolling. I think what I may use instead of expanding foam is to use Total Boats polyester structural repair putty. I have used it the past when I bed the new 3/4plywood to the transom before I glassed over it. It was also pretty easy to use to make the fillets with. My idea is to drill a grid pattern, of about 2-4" and then inject this putty using refillable caulk tubes. The putty is more of a thickened paste than a putty so It should flow well from a battery powered caulk gun. To clean the areas I would flush the same holes and area with acetone or lacquer thinner to clean the voids as best as It could.

[OverEasy]

Hi Kenfyoozed!

What a brilliant idea!
Absolutely brilliant !

That way you get a good controlled infill and a good opportunity to bond with a relatively manageable process!
Great Idea!

Best Regards,
Over Easy

[kenfyoozed]

The more I think about it, the more I feel like the right thing to do is remove all the core on the cabin top. In doing so I will replace with coosa. This solves a lot of problems but makes the refit that much longer. I think I am going to replace the 1/4" original plywood core with 1/2" coosa. This way I can bond the liner and deck together. and make it once cohesive unit. To do so my next delima is to use epoxy or polyester. I prefer polyester to the quick working times over epoxy, especially going into the cooler months. Price wise Its about 10-15$ per gal in the amount I think I need at this point. I could also change fabrics from a dbm1708 to a db170 but that won't save much cost. A lot to think about....

[OverEasy]

Hi Kenfyoozed!

Coosa is a great choice.
You might want to look up the BoatWorksToday episodes for reference (if you want) where he used Coosa to repair his transom.
He had a LOT of rotten plywood to excavate!

The Coosa would allow you to get it into the slot gap areas and never degrade ever again.
The price is reasonable give its a true lifetime product.
I’d go with th longer working time option when it comes to what resin to use.
Your not in a rush and if it sets up earlier than you are then that’s heck to pay dealing with it!
I’ve made that boo-boo a time or two…once was fortunate enough to feel it happening and was able to pull it all apart before it set in the wrong position…another time I had to cut/grind/pry (& yes cry) it all out and start over from before the beginning.
I learned that a slow cure is generally a forgiving cure.
For complex assemblies I’ve found that using plastic tooth picks and a couple of preplanned holes can be of an advantage when dealing with complex shifty assemblies to keep them in place while they slow cure.

Coosa looks to be a nice product but I haven’t had any first hand experience with it.
If you go that route keep us all posted on how it goes for you.

Best Regards,
Over Easy

[kenfyoozed]

I have been watching, boat works today as well as sail life for a while now.

I removed half of the cabin deck and found a lot more rot. Than I was expecting. So it’s good that I will ahead and cut it all out. The problem I’m having now is I left about an inch of fiberglass all around the perimeter of the area I cut out. The plywood core extend past the area about another inch and it is tabbed in. Some areas I’ve been able to excavate all the plywood. But in other areas there’s no way I can remove the plywood that’s under the fiberglass. I have tried multiple tools and have found nothing that actually works. I am off to the hardware store to see if I can find something that may work. Or at least sparked an idea.

[kenfyoozed]

I found one of these wood chain saw disc and it did the trick.


I was only able to get about 1-1/2” inch under the fiberglass but that should be far enough.

Before:


After:



I’ll be adding two layers of coosa. First layer will be 1/2”. It will be thick enough th span the distance from the deck to the cabin liner. This will be set in some type of filler/ adhesive. The edge o that goes under the original fiberglass deck will get a rabbet cut into the edge allowing the edge to be thinner and reach further under the original plywood. Filling all the space available, making the entire area become one unit. Then another layer of 1/4” coosa will cover the area inside the original fiberglass edges. Then 2 layers of 1708 over top and all should be good.

[Be Free]

I've never even heard of one of those before. I don't know what I'd use it for but I do know I've got to have one!