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Roy M · 04-05-2009, 07:55

On a more positive note, the removal of the board offers the opportunity to inspect and clean the trunk interior, repair or replace the control lines for the board, and confirm if the board has developed a split which will increase the weight of the boat and diminish performance. You could, also, build another board beforehand and simply do a switchover.

At the moment, my plan for the replacement is to use some redwood or spruce 2X stock for the center core (which takes the heavy loading against the trunk at top and wherever it exits the trunk), and to use closed cell polyurethane foam sheeting for the fore and aft fairings. I'll add some graphite tow in the places it looks best, then cover everything with a couple layers of 6 ounce cloth in epoxy. If I'm feeling particularly crafty, I'll imbed some apitong pieces in the leading edge, as I did my present board, to limit the damage from hitting rocks or submarines. All submerged exterior surfaces then get graphite powder mixed into the last layers of epoxy, as well as several layers of glass tape on the leading edge. My hull bottoms and minikeel use the graphite powder and have never been damaged by occasional beaching (intentional, of course!).

Randy · 04-05-2009, 08:31

These centerboards are heavy as any of us who've had them out have experienced & trying to keep with the light is right principle I've thought about the issue, so I'll share some of my thoughts on a centerboard rebuild which I don't know are ideal.
I'd thought of using MDO which is a highly stable exterior plywood & vacuum bag the two 3/4" together using a slightly thickened epoxy for the core.
For a while I was thinking of a foam cored board with graphite fiber but it seemed like it'd take some good engineering to create the right safety margin. The lateral stresses are pretty high I'd imagine and losing the centerboard would be about as bad as losing the rudder

Roy M · 04-05-2009, 20:13

Randy, from Insidewoodworking.com:
MDO plywood is a form of overlaid plywood. What this means is that MDO plywood starts with a core of overlapping veneer, much like traditional veneer core plywood. But instead of having a surface veneer of finished woodgrain, MDO plywood features a surface layer of medium density fiber, much like MDF. The result is a sheet of plywood that can typically be used once for forming concrete.

I've used it for making forms for fiberglass parts, but, even with epoxy to seal it, I wouldn't even begin to consider it as a viable marine building material. It is largely compressed dust with no significant lateral strength, except the core, maybe, it isn't stable in water, and it weighs a ton.

Lumber stock has the highest stiffness for naturally light materials, graphite is great for specific areas of tension strength, and foam is super for lighter loading where stress isn't spot loaded. If I could locate very long soda straws, I would consider using them to build a centerboard, aligning them in the axis of the top and bottom, vertically. I hang out with some folks who play with these strange combinations of materials, then produce truly weird and wonderful solutions to engineering dilemmas. The balance between cost, ease of fabrication, and ability to repair the centerboard after episodes of acute abuse, in exotic locations, with onboard materials and tools, and of course, appropriate strength to weight ratios, had lead me to consider the proposed concept. Bob Dixon, a multihull god and far betterbuilder than I will ever be, gave me a foil section he had built using this method. Wow. I'm sold. As soon as I get a few other projects sufficiently completed (aft cabin interior remodel and hard dodger), I will build the new centerboard. It goes in when I next haul out, to paint the bottom and pull the stick for repainting, adding radar and other toys, including possible synthetic rigging. That won't happen for at least six months, though, so no pictures forthcoming. I will send some of the galley as it progresses. Right now, I'm making money, indicating that the economy is finally turning around in the boatbuilding world.

Randy · 05-05-2009, 08:10

I was actually thinking of the HDO variation & there are versions made specifically for marine grade applications. There is hardly any wood material that is more stable, it's used for tankage & ducting because of it's resistance to adverse effects of liquid/water or water vapor.
Refer to: http://www.plumcreek.com/Portals/0/d...ctInfo/MDO.pdf
It is certainly heavier than foam & in practice more dimensionally stable than solid stock. So for guys needing to deal with a centerboard issue I think it's worth looking at.
Again, with the right engineering which is out there somewhere a lightweight carbon fiber sandwich could be made. Without going overboard in our application as we aren't after a race (BMW/Oracle tri) boat.

Roy M · 05-05-2009, 21:08

Thanks, Randy. I checked the weights and they are basically the same for HDO and marine ply. I guess my point was, after having used plywood on my previous centerboards, and seen the consequences of the weight factor, both when the core is dry and wet, as opposed to foam core with a central wood element, I am clearly sold on the foam board. Initially lighter (easier to handle, displacing less water) and easier to effectively repair than plywood, I like the possibilities offered by the higher tech material. But the proof will be in the pudding. You won't be going wrong using your HDO. In fact, my rudder and skeg are made of a type of HDO called Finn-Form, each of the two 3/4" laminates contained 17 plys of solid birch and phenolic resin. They were die-straight and incredibly strong when installed, and remain so thirty-some years later. The first centerboard was also constructed using this material, but was incredibly heavy, and eventually absorbed water after hitting a variety of underwater hard thingies in its first years. Removing it was a real pain. I want to try a closed cell material now.

Randy · 06-05-2009, 06:58

It seems like water intrusion is a real issue with whatever material is used. Maybe not if built correctly. Foam is appealing to me but then I read about foam cored boats being saturated with water makes that idea less attractive. Also I read somewhere that vinylester is the most water resistant resin going but don't know that that is definitive.

Roy M · 06-05-2009, 07:49

I guess, at a certain point, one needs to make a decision among the variety of available options, in order to move forward. Or, simply studying options might be a more viable strategy since no actual money has been spent and no one can find fault with failures that haven't yet occured. I've built two centerboards in thirty years, and will now craft a third, even more advanced than the second in design. I eagerly look forward to hearing of actual experimentation and results by others that may lead to improvements in design and fabrication and, especially, performance. I'll keep you folks informed as to my own experiences.

Maren · 06-05-2009, 09:36

Quote:

Originally Posted by Roy M

I eagerly look forward to hearing of actual experimentation and results by others that may lead to improvements in design and fabrication and, especially, performance. I'll keep you folks informed as to my own experiences.

Do, please.

In many ways, I think yours along with Cruzon, Rattle & Hum and Rikki-Tikki-Tavi as amonst the most advanced of the Searunners for differing reasons.

Roy M · 06-05-2009, 18:15

You are very kind, Maren. I hope we meet in some quiet harbor one day.

md7a · 07-05-2009, 21:50

Thanks to the excellent original drawings from John Marples, we just completed replacement of the centerboard on Blue Moon.

The old board had cracked along the trailing edge, swollen, and warped in a twist that made it nearly impossible to move or remove.

We followed the instructions from the Construction Manual and the design drawings, but took one shortcut - used the old board as a shape pattern.

We had some trouble with the split-vinyl-tubing pads on the old board: used to insulate against bumping in the trunk. We wound up removing them from the new board, but with an extra layer of glass cloth it seems tight enough for our purposes.

Has anyone had actual experience with the advanced-materials boards described above? I considered a pro-built board after reading about Farrier build projects, but in the end didn't have the money.

I've posted photos to the gallery.

Jmolan · 08-05-2009, 06:34

Hey everyone, just landed back from 6 weeks in the Sea of Cortez cruising. Had a great time, met a lot of great people, and all that. Maybe I will shoot a few Searunner related photos out.
The first shot is of "Sea Otter" a 37' Searunner in La Paz. The owner is SeaOtter Jim a great guy who has been there for 30 years or so. He sailed down on a Horstman, kicked around later on a 31', and eventually got Sea Otter from Jo Hudson, the guy who did all of Jim Brown's cartoon's.
The hard top was designed and built by Jim Brown himself as he spent many years borrowing the boat and cruising in the Sea of Cortez. Lot's of crazy stories about years in La Paz. Sea Otter Jim is an outboard mechanic and married a local gal and has a buitiful daughter.
The next few shot are of his overhead. He solved a problem I have on how to deal with a crumbling paint ceiling. He use 2" or so foam stuck to the top, then pulled a thick vinel and tacked it to the stringers, then covered the stringers with a thin hard wood strip. looks good and clean and way better than sanding a hundred small squares and painting upside down...

Next few shots ( I forgot the order) Are a home on a Rock of an Island that some US guy has that is surrounded by whale bones. I guess he stays 4 months a year.
One shot of me when we had outboard problems, it was 10 miles out from anchorage and I just threw the avon in the water and motored at 3.5 kts with a 3 H.P. motor....pretty nice to keep em light

We came into Puerto Escondido this way and the mono's were blown away that we did not ask for assistance....biggest problem was it was hard to turn left....:-)
Next couple shot are one of our favorite places. El Gato anchorage. Looked like we were in Southern Utah with all the red rocks. Fantastic places on the Baja..
Shots of the continous line furler drm on the Stbd. ama. Put it out there and get clean air when off the wind. I have used the drum on all my head sails now. Just roll tem up and drop em' and bag em'. attache another and roll it out. You can also so see the "softies" I use on everything that used to have shackles.
Then the classic last night of the cruise shot and the happy couple after 6 weeks of living in close qtrs together.....hahaha.

farotherside · 14-06-2009, 16:35

hey folks,

currently repairing my Searunner 37's deck, I've got the forwardmost six feet or so of deck of the middle hull open to the the elements, ready to be replaced tomorrow.

I was wondering though - what do you folks do for anchor management? Do you have a bow roller? How about chain/rode storage, do you do that in the bow, or use the storage lockers in the wings?

Care to post a photo of your bow, and/or suggestions on how best to trick out my bow, while I've got it open?

here's the "before" photo:

Roy M · 14-06-2009, 21:23

Here are a couple shots from my archive. I guess I better take some more and show them later

Randy · 14-06-2009, 21:39

The standard setup is an anchor well aft of the bow cleat to hold the chain & rode with anchor maybe setup on a roller to the side of the forestay. The anchor well is 10-12" deep in the top section of the sail locker & draining thru holes in the side of the hull. The aft end of the well is the bulkhead that the running forestay is attached to. I'm curious why the builder of your boat didn't set it up that way. Also big chocks that you can get substantial chafing gear like fire hose set up in is really useful.

During passages I disconnected the chain & anchor & they were stowed deep by the centerboard. Try to keep weight centered and down low. The boat will be happy for that (actually you will be cuz the ride will be better!).

Good luck Searunners are great boats & will take you anywhere.