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Just recently acquired a 1974 O’Day 20 that needs some interior work. The v berth plywood appears to be original but is seriously degraded and needs to be replaced. There are screws down the middle of the plywood pieces. However, the plywood doesn’t appear to be screwed where it meets the hull. It looks it might be secured to the hull with epoxy.
I am worried that just “yarding” on these will damage the interior hull surface.
I would love to hear from folks who know more than I do on this.
Thanks,
Randy

Hey Randy welcome to our play house
Given the age of your boat I am sure poly was used and not epoxy. But it really does make any difference for what you will be doing. Do you have a multi tool? If not I would go get one but there are other tools for the job. Do you have a 4.5 inch grinder?
You need to cut the glass tabbing right next to the hull and pull all that old wood out. After that is done we will move on to the next step.

Thank you. I greatly appreciate the guidance on this.
I do not have this tool but getting one is not a problem. Let me see if I understand. There are fiberglass tabs on the hull holding up the plywood. My task is to use the grinder tool to cut through these tabs, so that I can remove the plywood. Am I close?

When strips of fiberglass is used to join things together it is called tabbing or tabs. So you are correct you need to cut the glass loose from the hull and remove the wood. When you put new material back in you will tab it back in with glass just like you took out. Before putting things back together you will need to sand off any old tabs and rough up the area you will be glassing back to.

Not to contradict, but you may be able to save the old glass tabbing. Do not remove anything that is good to start.

Just remove the rotten crap.

If you have cleats that support the deck; leave them because otherwise you have to add them back to support the new deck.

Also, it gets pretty easy to blow thru and put a hole in the hull when you start cutting close.

In many situations, the edge of the old deck can be left and then a new cleat bonded to it. I would cut out the old crap all the way to 2" away from the hull and inside bulkheads to see if I could use any of that for the new deck.

A small bit of rotten deck can be removed and replaced with epoxy fillers, so if a bit of rot remains behind; don't worry about it. If it is so loose is pulls off; get rid of it.

Cut it all out with 2" remaining.

If the question mark wood is strong; leave it.

When you get it cut out; report back on the condition and pictures. Try to tell is what the hull edge is like when you can reach in there.

Use a multi tool or a 4" skilsaw set really close to the deck thickness. It may be hard to fit it in, so the multi tool is really essential. I only use a carbide head on them.

Fuzz is giving you a lot of good advice. I'd just not be in a rush to cut out the old tabbing because it might be globs of poly filler that are still strong and a shit ton of work to remove.

Here is a picture of how u may end up fixing it.

Orange is the old boat cut to 2" away with glass tabbing or poly fill edges under.

Yellow is a new plywood cleat epoxied to the edge. You would replace any rotten orange wood with fillers. Green is the new deck. The other side can probably be done the same way or easily removed and the new deck glued back down onto the bulkheads or cleats.

Boatside can be a noghtmare to remove all the old tabbing and not hole the hull and get the new deck to lay down in the right spot and then remove paint for tabbing the new deck back down..

Like Fuzz stated, use a multitool, even the cheap ones here, have been holding up very well for me and I use all 3 of mine all the time. The money is spent on keeping sharp blades. They are NOT fast but will do an exceptionally clean job of getting all the old wood followed with an angler grinder and a sanding disk.
https://www.harborfreight.com/search?q=multitool

I don't think you will want to leave any of that old plywood in there. It's cracking and coming apart all the way to the edge where your hand is.

You two have been very helpful. I am off to buy a multitool. I will report back on progress. Thank you!

Follow the “leave two inches” advice. Not to leave 2” of wood in the repair, but so you can easily measure and test fit the replacement wood.

Also keep in mind that many of our small boats will require you to use several smaller pieces to replace that berth. Most sailboats under 27’ are built with the cap going on last. Basically they build the hull and interior before the deck cap is laid up. It can be tricky to make sure it all fits if you don’t have the 2” lip to hold all your pieces in place.

Start off leaving the 2". If it seems easy to remove and after you have templates made for repair pieces; you can decide then to cut it all away. You may realize it is jist too much trouble if well adhered. Otoh, if it is barely on, make cardboard templates early. Much easier to make a cardboard template now...

Very good advice to make a template before removing the old stuff. If you do cut everything out lay the multi-tool blade flat against the hull to make the cuts. You will not risk cutting into the hull that way and you will have less glass left to grind off.
On a side note my first sailing experiences were in an O'Day 20 so it brings back some memories.

Fuzz wrote: ↑Sat Nov 27, 2021 4:18 pm If you do cut everything out lay the multi-tool blade flat against the hull to make the cuts. You will not risk cutting into the hull that way and you will have less glass left to grind off.

Fuzz and I may disagree on the danger of cutting into the hull using this method. The hull will curve sharply below the berth. Typically at a rate that is much steeper than above the berth. The berth can be thought of as sitting at the apex of the chine (as much as the oday can be thought of as having a chine.

If you’re thinking ahead you will realize that this means that you have the same problem cutting from the bottom to the top as you would cutting from the top to the bottom. The solution seems to be cutting half way in each direction. I helped do this on a boat recently and we had to leave about a quarter inch from the hull in the first cut. Once removed we took several more passes with the saw blade to get as close ass possible. Final passes were sanding to remove residual and prep. It was a lot of work. On the plus side we didn’t have any gouges to fixe other than the ones created by the first attempts to get it in one pass.

Blah blah blah… be careful and you’ll be fine. Nothing you do is unfixable. Lots of pics as some of us really like to build vicariously.

Thank you for your thoughtful responses to this question. Here is the plan:
1. Buy a multitool.
2. Use cardboard to make a template before I cut anything
3. Use the tool to cut the plywood about two inches from the hull.
4. Remove the cut plywood
5. Examine what I have. Take pics and see what the panel of experts think

I have sailed a small 14’ boat much of my life (my dad made it from popular mechanics plans in our garage in the mid-sixties.) But this is my first real sailboat and greatly appreciate the wisdom of this group.
Randy

Randy Michaelis wrote: ↑Sat Nov 27, 2021 8:57 pm Thank you for your thoughtful responses to this question. Here is the plan:
1. Buy a multitool.
2. Use cardboard to make a template before I cut anything
3. Use the tool to cut the plywood about two inches from the hull.
4. Remove the cut plywood
5. Examine what I have. Take pics and see what the panel of experts think

I have sailed a small 14’ boat much of my life (my dad made it from popular mechanics plans in our garage in the mid-sixties.) But this is my first real sailboat and greatly appreciate the wisdom of this group.
Randy

Real good plan..

Step two. Make a template is now complete. See pics
Next step will be cutting.
Stay tuned

Another tool that is handy is a 4" circular saw. I bought an el cheapo at Menards for $47 about 3 years ago with a carbide blade. It cuts much faster than the multi tool, but can't get into nooks and crannies or up to the hull edge. If you are hating the multi tool; make sure it is a decent one. I have used like 10 Harbor Freight multis diring my build and could have gotten a good one. I always use carbide blades which they don't sell good ones or any at HF and I get those from woodworking shops. The 4" circ saw will love to cut through the boat, so if you use it or any circ saw; set the blade depth low to avoid cutting through the boat and end the cuts naturally and ise the oscillating tool to finish the cuts.

I hate gving the circ saw advice because it is a dangerous tool for people with experience and can be tricky to use in small places and with curves. But it will speed the job and save the carbide oscillating bit.

Also, did you remove the vinyl liner? I see a lot of rot up toward the bow and I'd like to see behind the liner.

The 70s had a lot of boats with balsa cores and before you put any money or much time in; need to make sure the hullsides are not rotten balsa cores.

Whether you like it or not; this needs thorough inspection behind the liner with some pictures and prodding. If the hull is all loose after you remove the vinyl; a good chance you have rotten core. If so, everything changes, but hopefully O Day just stayed with frp in the 70s.

See blue..

I have used like 10 Harbor Freight multis diring my build and could have gotten a good one. I always use carbide blades which they don't sell good ones or any at HF and I get those from woodworking shops.

A lot of times people burn through electric tools because they try to force them to do the job faster than they are made to. It dulls the blades and burns up the motor. The wood cutting blades will get the gullet full of sawdust and stop cutting so the blade needs to keep moving to keep the gullets clear. A circular blade does this for you, the multi-tool does not and needs to be moved so the area of the blade doing the cutting can clear it's gullets. When I started using my two cheapos from Harbor Freight (got the single speed free cause I spent more than $50.00 and the variable-speed I got on sale for less than $20.00) I was thinking the half moon blades I was using were getting dull to fast till I started using a rocking motion to keep the gullets cleared and they last a lot longer and cut faster without burning the wood. Don't force the tool to cut, just slight pressure and keep where the blade cuts moving.

To keep from getting to close to the hull, the first cut, use a 2X4 as a guide for the blade. The plywood looks like it is already coming apart so it may not take to much to cut it, it may just fall apart as you try to cut it. If that is the case you may be able to use a sturdy putty knife, board for a guide and tap the knife through a little at a time. Dried out, delaminated plywood is easy to cut through.

My continued thanks to everyone for their wisdom on my project. A couple of follow up questions for you.
My plan is to cut the plywood at about two inches from the hull. My plan is to start with my new multi-tool and go carefully. I like the recommendation that I use a two by four against the hull to keep a consistent space from the hull. I have also made a cardboard template of the space.
The questions:
1. It sounds like there is some concern about what might be lurking behind the vinyl in the far forward section. Would you recommend that I remove all the vinyl in the berth? Or just focus on on far forward section?
2. When I remove the plywood I will need to stand in the hull. It looks like it is full of a long pieces of styrofoam. I assume I will need to remove this so that I can work in there without a floor. Is that correct?
3. Do I save the styrofoam or should it be replaced? It looks okay but I am aware that it is almost 50 years old. Is there a better product I should use for this?
Sorry for all the questions but I have a few days off and I plan to get started on this phase.
Thanks again.
Randy

Randy good questions.

!. I would ramove the vinyl to check the quality of the wood underneath it. A heat gun is a good tool that will loosen the glue if you can not just pull it up.

2-3 Check to see if the styrofoam is dry and has no water absord by it. If no water save it in a dry location and put it back. It was used for upright flotation for the boat. If you want to go with a modern product you can pour the two part foam that is available in the store here. Call Joel to get how much you will need.

Wee I hope that helps some. Keep the questions coming, that is what the Forum is for.

Tom

Greetings panel of advisors.
I removed the plywood v-berth and took out the pieces of Styrofoam. I left a two inch piece of plywood on the perimeter.
I am confident in the plywood I left. Seems pretty weak to me.
What if I removed the remaining plywood and built braces that would support the berth from underneath? I have attached a photo of a pic I found online. What do you think?
Again, I am very appreciative of your wisdom as I proceed with this project.
Oh yes, one more question. What are cylindrical objects on the hull?
Randy

If you are sure the lip you left is solid it would make a good support for the new plywood. That is a pretty big area so I like the idea of the supports in the second picture. I have a hard time believing that foam will do anything for you so if it were me I would get rid of it. About the only thing I can think of those pieces of round glass might do is stiffen the hull in that area.

Those are stiffeners for the hull; perhaps for trailering?

The picture you found has one issue. Those spans look a bit much unless you plan 3/4" ply and 1/2" ply will sag some on the edges unless bonded with glass tapes.

You said, I am confident in the plywood and said it seems pretty weak, so hard to know what you mean. The main reason to keep is easy to add back new and easier to remove now if u want.

Decision time on it..

Let me try that again. I am not confident in the remaining plywood. Seems pretty weak.
Thanks
Randy

Randy Michaelis wrote: ↑Sat Dec 11, 2021 11:17 pm Let me try that again. I am not confident in the remaining plywood. Seems pretty weak.
Thanks
Randy

That being said I would break out the multi tool and then the grinder and get rid of that mess. You can always hot glue some cleats to the hull for supporting the new plywood till you glass it in.

What Fuzz said.

It is also wise to plan any storage under or pour foam for safety. Any boat destined for the ocean needs to consider flotation.

Using an angle finder can help you get cleats ripped off the saw to fit the deck better as well.

I would break out the multi tool and then the grinder and get rid of that mess.

Yes, finish the removal of all the weak stuff first. Can wonder about supporting what is going back in after you finish the removal.

Fuzz wrote: ↑Sun Dec 12, 2021 12:37 am

Randy Michaelis wrote: ↑Sat Dec 11, 2021 11:17 pm Let me try that again. I am not confident in the remaining plywood. Seems pretty weak.
Thanks
Randy

That being said I would break out the multi tool and then the grinder and get rid of that mess. You can always hot glue some cleats to the hull for supporting the new plywood till you glass it in.

Make the replacement pieces first. Then cut it out. It is much easier to ensure fit with that 2” shelf to help you out.

My approach:

I would leave what's left, use it as cleats for the new panels, add the new panels and glass them in from above. I' d make a rough template from cardboard and use a deck of cards taped along the edges of the template to get the shape about exactly right. I'd add a stiffener under the new panel athwartships but wouldn't bother tabbing frames into the hull. It made it this long without them. Not sure if you can get a full width piece into the berth so there may be an installation puzzle, solvable.

I suspect the only thing under the vinyl is exposed, rough glass. I'd rip it out and replace it with the same thing, sans mold.