Bulkhead - What's Your Opinion?

[jibes138]

Screws in Fiberglass

By the way screwing directly into fiberglass is a very poor practice and provides almost zero joint strength. A proper method is to embed an insert at the time of molding and then the screw is fastened to the insert. Otherwise it should be a through hole with appropriate load spreading backing plates or at the very least large washers. Inserts molded in this way have large enough surface area to spread the load of the fastener but more importantly have enough strengh in the material to support the concentrated loads of the threads themselves. Notice how easy it is to strip a thread with a wood screw in fiberglass yet builders use this method all the time, too expensive to do it right. I just replaced an anchor locker hinge on my O'Day and where i expected to find it through bolted it was just screwed in with wood screws to the deck. Usually this practice is limited to decorative trim and non load bearing stuff but picture an anchor locker cover open in a howling wind, a ton of force is applied to the large flat surface of the cover with a large bending moment on the screws holding it to the boat. I'm surprised the screws haven't ripped out and the cover blown away.

 

[John]

By the way screwing directly into fiberglass is a very poor practice and provides almost zero joint strength. A proper method is to embed an insert at the time of molding and then the screw is fastened to the insert. Otherwise it should be a through hole with appropriate load spreading backing plates or at the very least large washers.

I was thinking of running machine screws through it and using a t-nut on the other end - plus 5200 or liquid nail. I know 5200 is not good in most uses since it is such a strong bonding agent, and it would make it very difficult to remove this bulkhead if it needed it again. But I'm figuring that if done right, and if the deck penetrations are kept sealed properly, then I'll never have to remove this bulkhead again.

Also, on the C36, this bulkhead is in 2 parts. The inside (towards the centerline of the boat) is the main, wide part to which the chain plate is attached. This is the part I'll be removing. Then there is a narrower part, maybe 2.5 feet wide, that goes all the way to the hull. There is nothing structural joining these two together - the joint is only covered by a little trim strip. What I'm thinking of doing here is fabricating a 1/4" stainless steel strap and bolting these two parts together with that. Then I'd route out the back of a piece of teak 1x3 and cover it with that.

 

[sailingdog]

Counting on never having to remove it again is generally a losing proposition on a boat.

I was thinking of running machine screws through it and using a t-nut on the other end - plus 5200 or liquid nail. I know 5200 is not good in most uses since it is such a strong bonding agent, and it would make it very difficult to remove this bulkhead if it needed it again. But I'm figuring that if done right, and if the deck penetrations are kept sealed properly, then I'll never have to remove this bulkhead again.

Also, on the C36, this bulkhead is in 2 parts. The inside (towards the centerline of the boat) is the main, wide part to which the chain plate is attached. This is the part I'll be removing. Then there is a narrower part, maybe 2.5 feet wide, that goes all the way to the hull. There is nothing structural joining these two together - the joint is only covered by a little trim strip. What I'm thinking of doing here is fabricating a 1/4" stainless steel strap and bolting these two parts together with that. Then I'd route out the back of a piece of teak 1x3 and cover it with that.

 

[newly anonymous]

if it were my boat...

...I'd glass the bulkhead and replace the standing rigging. I'd also inspect the chainplates very closely before deciding to re-use them.

Conventional wisdom recommends replacing standing rigging every ten years. There are a lot of wingnuts out there who will tell you that they've gone thirty years on their current rigging without any problems. This is usually because they're still running the original sails that came with the boat.

 

[Harvestamm]

Bulkheads

John

I had a similar problem when I decided to rehab my 1982 Mac 25 I purchased. I went back and forth as you are doing but decided that replacing them is the best choice. Instead of going through the cost of trying to located and purchase new buldhead from MacGregor I decided to save the money and build them myself. I removed each of the bulkheads and traced them over new 1/2" oak plywood. I then used a combination of a jig saw and Roto saw to shape the new bulkheads. Sanded, stained and varished them. They came out looking much better than what the manufacture had originally installed.

You can see of of the pictures of the bulkheads at the following link. http://forums.macgregor.sailboatowners.com/album.php?albumid=349

Hope this helps and good luck with your rehab project.

Art

 

[John]

chain plate

...I'd glass the bulkhead and replace the standing rigging. I'd also inspect the chainplates very closely before deciding to re-use them.]

What should I look for in inspecting the chain plate? Bear in mind, this boat is only eleven years old. (I've pretty much decided to go ahead and change the standing rigging.)

 

[Prime Time]

Been there and done it

My Mirage 27 had rotten bulkheads due to 2 problems prior to my purchase and restoration. Improper bedding of the chain plates allowing water to enter and rot the chain plate attachment areas, and standing water that had entered the boat while in storage, rotting out the bottom of the bulkhead. Take a look at my web page, were I describe the project.

 

[Jim]

Most Catalina 36 will fail in the same fashion. I know, I have one.

 

[yakman]

bulkhead repair

I own a 1985 26 foot oday with a starboard side leaking chainplate ,this ongoing problem an battle has compromised the integrity of the bulkhead. I have been advised at the yard that they can install a sheet fiberglass to remedy this problem and since it is glass they say that it will not happen again. I am uncertain as to the practicality of this as well as the cost. I do know that once the old is out it is just a matter of installing the new one whichever product I use.

I read here that a product called CPES can be used ,has anyone tried this tack? basicall I would be solidifying the bulkhead and possibly replacing it at another time.

 

[John]

I used this product when I replaced the bulkhead on my C36. It is a filler/sealer and it seems to work very well for that purpose. I am not at all sure it would actually strengthen an already-dry rotted plywood bulkhead. As for fiberglass - I don't know that it has the structural strength, although there is a synthetic product - I forget what it is - that can be used in place of plywood, supposedly.

Having replaced the bulkhead on my C 36, I think that if the integrity of the bulkhead is compromised, that it definitely should be replaced. I can't see that this would be any more difficult than it was in the case of our boat, since the mast had to be pulled for mine.

Yakman, if you go to the C36ia web site, look under "upgrades" in "articles" you will see what it involved for our boat. My opinion, which is far from an expert one, is that if it is compromised, replace it using a sheet of marine grade plywood and replace it, using a filler/sealer like CPES first.

 

[Hermit Scott]

What mainesail said about having catalina send you one that is cnc would make instalation much easier I would guess. A cnc cut bulkhead will make a professional looking repair easier since you won't have any gaps around the edges. Since they don't stock it, another option would be to ask for the 2D cad file. You can take that to a shop with a CNC router and they will knock it out for a couple of hundred dollars, probably in a day or two. A waterjet will also do the cutting if they know what they are doing. If not they will delaminate the plywood and end up buying you more.
It's probably an autocad file and if it is the file will most likely be a .dwg or .dxf. .dxf seems to be more easily transfered to older machines. Ask them to send you both if you go that route.

 

[John]

Not for Catalina

What mainesail said about having catalina send you one that is cnc would make instalation much easier I would guess. A cnc cut bulkhead will make a professional looking repair easier since you won't have any gaps around the edges. Since they don't stock it, another option would be to ask for the 2D cad file. You can take that to a shop with a CNC router and they will knock it out for a couple of hundred dollars, probably in a day or two. A waterjet will also do the cutting if they know what they are doing. If not they will delaminate the plywood and end up buying you more.
It's probably an autocad file and if it is the file will most likely be a .dwg or .dxf. .dxf seems to be more easily transfered to older machines. Ask them to send you both if you go that route.

We are not talking about a Catalina at this point, since my job has been finished. Catalina doesn't stock these bulkheads and had no suggestions as to how they could help with that. However, it was a simple matter to simply use the old one as a pattern, using a router with the appropriate bit as shown in my explanation on the C 36 web site.

I don't know about the ODay; maybe they do stock this bulkhead. It sounds to me that having a shop make up the bulkhead might be pretty expensive, but if you aren't set up in any way to do it yourself, maybe there would be no alternative.

Yakman - if you have any questions and want to ask more about my experience, please feel free to ask more either on or off list.

 

[Valentina]

Has anybody tried using STARBOARD or SEABOARD material for replacing bulkheads ?
I am talking about boats up to 26 ft long that do not have massive bulkheads.
Mine can be cut out of a piece that is 24x48 inches. I am thinking of using a 3/4 King Starboard material - "they" say- it's maintenance free material.
Any opinions on that ???
One thing I don't know about this material is how much it expands and contracts with temperature. Most likely, marine plywood is more temp. stable, but it rots....
Any thoughts are appreciated.
Thanks,
Alex

 

[Maine Sail]

Has anybody tried using STARBOARD or SEABOARD material for replacing bulkheads ?
I am talking about boats up to 26 ft long that do not have massive bulkheads.
Mine can be cut out of a piece that is 24x48 inches. I am thinking of using a 3/4 King Starboard material - "they" say- it's maintenance free material.
Any opinions on that ???
One thing I don't know about this material is how much it expands and contracts with temperature. Most likely, marine plywood is more temp. stable, but it rots....
Any thoughts are appreciated.
Thanks,
Alex

Starboard or competitors like Sea Board should not be used in structural applications as it is very, very flexible.

Another problem with it for bulkheads is that nothing will stick to it and it's nearly as slippery as Silicone. Even 5200 won't adhere well.. Most bulkheads are tabbed in place with fiberglass and you can't fiberglass to Starboard.