Recoring 23 Partial Pop-Top With Foam or Other Synthetic?

[sreidvt]

My boat is a somewhat rare 1974 O'Day 23 partial pop-top. I haven't yet pulled off the upper fiberglass skin of the poptop (which also holds the hatch slider of course) but I think some of the core wood underneath may be rotten. Is there a synthetic material (maybe some type of foam) that I can use to re-core this? If so, I want to order ASAP because I'll be working on the boat next week while a friend of mine is here. I know Precision and some other makers now use synthetic core. Anyone know what the material is and where to get it?

Thanks in advance for any ideas. Thankfully the deck all seems to be solid.

 

[Ron20324]

Defender has something like you are talking about. Jamestown Distributers.

 

[sreidvt]

Thanks very much. I'll check that out. Also, what about Starboard (the material).

 

[justsomeguy]

what about Starboard

Getting something to stick to it would be a trick. I think you'd have to punch many holes in it to create any kind of cohesive laminate.

 

[sreidvt]

OK, thanks. I can't get to the boat now to check core thickness. I imagine it would be similar to cabin top core thickness for similar boats. Anyone got a guess as to the thickness? Did O'Day have a standard for this in the 1970s? Maybe I should call Rudy?

 

[sreidvt]

Rudy to the rescue! He said that back then they actually may have cored the pop-top with 1/2" but that 3/8" synthetic is probably plenty strong. Now to choose a material from Jamestown and get it here in time.

Any other thoughts on this welcome.

 

[sreidvt]

Ended up with this: https://www.jamestowndistributors.com/userportal/product.do?process=checkout&part=28288

Thanks for the Jamestown idea.

 

[Brian S]

I think divinylcell is a current coring material in new boats. Pretty sure the Left Coast Dart was divinylcell cored, and resin infused, with key load backing done with G10 board, no wood in the structure.

I don't think Starboard is an appropriate coring material, or a backing material. First, it's heavier than a foam core (which is the purpose of cored material: Increase strength kinda like an I beam, but using lighter weight material than building a thick solid glass layup) and second because Starboard is high molecular weight polyethylene, to which stuff doesn't stick well, and thirdly, because Starboard under load will creep and flow.

Now, keep in mind I am not a marine architect or a materials engineer, or even structural engineer. But this is my understanding over time from what I've read here and there.

 

[sreidvt]

The divinylcell I ordered from Jamestown arrived and it looks promising. Thanks again for the help folks.

 

[sreidvt]

The Divinylcell ended up being perfect. When we peeled the upper FB skin off each "side section" of the poptop we were surprised to find that O'Day (in 1974 no less) had actually used foam coring. Specifically, there was foam coring running along each edge and then a center channel of wavy fiberglass walls (rather than solid fiberglass) in each mid-section. No wood at all except for the ends of these side sections where the support poles attach.

It seems obvious, and this was really interesting to me, that some engineer had really worked on making this poptop strong but as light as possible (since it is raised in place by hand). We didn't open up the middle section of the poptop (which the hatch slides over) -- because it was fine as is -- but I'll bet that it too was foam cored. Impressed the heck out of me, actually. The foam coring on the right side had gotten wet from water intrusion so we replaced all of that. The foam on the left side was dry and solid in most places so we only replaced some of that. The boat is forty-three years old and yet the foam there was still in good shape...

3/8" Divinylcell was exactly the right thickness and was able to curve slightly to fit the needed contour. Great stuff and worked perfectly. I know there aren't many poptop 23s out there but I post all this in case someone else needs to do this repair. It's also interesting to know that O'Day was using foam coring, when needed, that far back.

https://www.jamestowndistributors.com/userportal/show_product.do?pid=1586

 

[GDayYall]

Interesting! Thanks for the update! Surprised to hear that about your boat. All of the core in my 1974 O'day 23 is 3/8" balsa. Would be interesting to know what month your boat was made. Mine was in May, I think.

 

[sreidvt]

Interesting! Thanks for the update! Surprised to hear that about your boat. All of the core in my 1974 O'day 23 is 3/8" balsa. Would be interesting to know what month your boat was made. Mine was in May, I think.

I'll take a look at the serial number and maybe someone can tell me if I can get the date from there. Have you done work with the core of your pop-top?

Nice to find another owner of a 1974 23'. What, if anything, have you done with your keel? I have not yet gotten this boat in the water but the CB apparently was still moving when I bought it in 2014 (after some keel work by the PO's boatyard).

 

[GDayYall]

I have not done work to the core of my pop-top, although I need to eventually. I have recored several locations on the deck and also under the mast. As for the keel - the PO of my boat had drilled through the keel and CB and put a SS bolt and nut through as a pivot pin. The CB would not go down when I first got the boat. I loosened the nut so the bolt could spin freely and it works fine now.

 

[Sunbird22358]

The CB would not go down when I first got the boat. I loosened the nut so the bolt could spin freely and it works fine now.

I suspect that the problem was that the original pivot was a plastic (or metal?) pin that was friction fit to the hole in the keel, the pin would have been just smaller diameter than the hole in the CB allowing it to pivot. When the previous owner changed to that bolt, It clamped the CB between the sides of the keel slot, he should have installed a bushing in the pivot hole of the CB that would be the diam. of the original pin and just long enough to be longer than the CB is thick. That way, when the bolt is tightened, it squeezes the bushing and allows the CB to pivot freely. Of course, the problem is that the original hole in the keel would then need to be reduced to the size of the bolt. Sounds like you fixed it OK, as long as a lock-nut was used <GRIN!> I'd hate to have that nut back off while I was sailing..... OOPS!
Anyway, that is how O'DAY set up the CB pivots on the smaller CB models, like my 1979 DS II (later models of the DS II had the CB pivot setup like the newer K/CB models with the pin held in by wedges).

 

[GDayYall]

as long as a lock-nut was used

Of course!

 

[sreidvt]

I have not done work to the core of my pop-top, although I need to eventually.

You may find that it is foam cored. I think they did this because the pop top is fairly large and, of course, has to be lifted by hand. So I think they really were trying to keep it as light as possible while still being strong. I wouldn't be surprised if it was the only part of the boat that was foam cored since everything else we lift or slide on that boat (outside) is solid fiberglass.

I don't think there are many 1974 23s out there so happy to hear more about your boat, pics, etc.

 

[sreidvt]

Would be interesting to know what month your boat was made. Mine was in May, I think.

My HIN ends in 0274. So, I believe that means it was made in February of 1974. It's also just beyond being hull 575 (of this model I assume) so I imagine they were busy cranking these out that winter. I was around for the New England winter of 1974 but I was only 8.

I believe this boat has spent its whole life in New England. I assume it was made in Mass. and I know it spent a long time in CT before I brought it to VT. In a lifetime, how many vehicles would a person own that were made in a state that borders one's own? Pretty cool.

What the rough production number of your boat?

 

[sreidvt]

While we are on the subject of coring...

GDayYall, I saw an older post from you that said the pure fiberglass on our boats comes in about 2" around the perimeter (before any core starts). If so, that means the toe rails on these boats are screwed into solid fiberglass, right?

If so, that is great news because I planned on rebedding all the deck fixtures next spring (or maybe even this fall) using the MaineSailor method (just as a preventative measure). But since I don't think any of them are leaking (the poptop was the only problem area and that's fixed now) it seems I may not need to do anything with the toe rails but sand and Cetol them.

Do I have that right?

Cheers,

 

[GDayYall]

Yes in my boat the toe rails are screwed into solid fiberglass.

My boat is a few months younger than yours then, with a HIN ending in 0574 for May '74. It is number 641 - so they were about 70 boats apart in the production line.

 

[sreidvt]

Yes in my boat the toe rails are screwed into solid fiberglass.

My boat is a few months younger than yours then, with a HIN ending in 0574 for May '74. It is number 641 - so they were about 70 boats apart in the production line.

Oustanding news about the toerails. In that case I will just sand and Cetol them until and unless I see some sign of them leaking into the bilge.

How do you like your 23? Any comments welcome. How quickly does it come about? Sailed on a friend's Compac 23 a couple years ago (shallow draft keel but no CB) and it just didn't like to tack. I am hoping the CB on the O'Day will make it much better in that respect.

I have not yet put mine in the water yet because finding time to work on it is a real challenge. Hopefully it will be ready for summer 2018. Have been sailing a Mirage 5.5.

Cheers,