Adding through hull fittings to cold molded hull

[chergui]

I have decided to put a water cooled engine in my cold molded sailboat and replace the air cooled engine. The only problem is that I need two more holes in the hull, for the exhaust and intake. I'm going to get the guys in the yard where I'm hauled out to do it but I'd like to know for myself what the right way to go about doing this is. I'm a bit concerned about the hull getting damaged during this. What type of drill bits are you supposed to use on a cold molded hull, with the combination of wood and epoxy?

The hull could be quite thick also, I'm not exactly sure. The hull near the deck is close to 2 inches thick. I'm not sure if it thins out lower down, I haven't bought the plans yet from the designer. Is there anything I should be aware of or watch for before doing this? They guy at the yard I'm hauled out at is a wooden boat guy and seems quite knowledable and didn't think it was a big deal. Should I even go for it or just stick to an air cooled engine?

Jon

[Dan McCosh]

There isn''t any problem drilling a hole in a cold-molded hull, any more than putting the same hole in a fiberglass or wood hull. The lack of seams should mean that there isn't any problem with placement either. I don't understand how a cold-molded hull can be two ins. thick, however, That would be approprate for maybe a boat 150-200 ft. long. Is it actually glued veneers (cold molded), or something laid on existing planking?

[Buddy]

Same here, I'm assuming ( careful now) air cooled means 8-10 horse power, and that sounds like 20-25 feet and that sounds like 5/8 to 3/4 inch thick cold molded hull. Are you including a sheer clamp in that 2" measurement. That would be about right. A regular hardware store 1 1/2" (?) $5 hole saw will do the trick. I would examine the cutout and finger epoxy into any interply voids exposed in the edges of the cutout. There on in, just like any other boat. If below waterline, you ought to glue in a proper wood block to bed the thru hull into and secure the seacock. Drawings will come with the parts.

[Elco's]

They should use a "backing block". They should use a ball valve instead of a gate valve. Have them seal the open hole cut with epoxy before bedding the thru-hull.

[NormMessinger]

I agree with the above but go with your local guy. You say he is quite knowledgable AND he can see ezakally what your boat will require. The idea of a 2" thick hull only confuses us.

[chergui]

Thanks for the comments. The boat is 24' long. I mentioned the thickness of the hull because it is thicker than you would think for a 24' boat and thought it may be a bit trickier, although it doesn't sound like it. My 2" is an estimate.. I should properly measure it. I currently have a 4HP air cooled engine in the boat. Here is a pic of the boat:

http://www3.telus.net/chergui/Jeannette/jeannette.jpg

Edit: I should add that the boat was properly cold molded. As far as I know, it has 3 layers of of western red cedar all applied in different directions. One horizontal, one vertical, and one at about a 45 degree angle. I also have a sample of what each layer was made of. It just seems very thick at the deck and I would be surprised if the entire hull is that thick. But that would mean that there are more layers above the waterline and closer to the deck level than below. I don't know all the details of cold molded construction.

[ 08-03-2004, 05:50 PM: Message edited by: chergui ]

[Paul Pless]

What a pretty boat.

[imported_Steven Bauer]

What's wrong with the aircooled engine?

Oh yeah, nice boat! :D

Steven

[chergui]

Thanks for the compliments. The boat is a gem, I just got it a couple of months ago. There is nothing wrong with an air cooled engine except that it gets hot in the cabin and I have to attach the exhaust stack every time. I'm replacing the engine because the boat had a variable pitch prop and the engine was fixed speed. The vp system wasn't working properly and so we tried to fix it. It's turned out that for quite a few reasons I've decided to get rid of the vp system and replace with a gearbox and fixed prop. Because the engine is fixed speed, it needs to go also. So I've been trying to decide between two engines, one water the other air cooled (I posted in another thread about small diesel engines). I'm leaning towards another air cooled engine again now (with proper throttle control) just because it is lighter, easier to install, smaller, etc. I had been told by many people to go with a water cooled engine if I could. But the little air cooled engine is just simpler. Both have advantages and disadvantages though.

[John B]

I'll just add to Dan and Buddy's comments.
when you hole saw the hole drill it part way through from both sides so you don't get any breakout.

[Bob Smalser]

Wow...I sure love the boat....what is the design?

Lotsa ways to drill the holes without breaking out any wood...backer block...pilot hole guiding half-depth holes from both directions...etc.

But the important thing to me is to seal those hole edges thoroughly with epoxy. I usually drill oversize, fill with thickened epoxy, and then drill again...in addition to using a good sealant on the fitting.

[imported_Steven Bauer]

Is this the boat Gert was looking at a few months ago?

http://www3.telus.net/chergui/Jeannette/jeannette.jpg

No, I guess not.

[chergui]

Hi Bob,

The boat was designed by Chuck Paine and is the Carol design. If you have been to the Port Townsend wooden boat festival in the last 6 years you have probably seen the boat before. You actually responded to my posting when I was contemplating whether I should buy a wooden boat or not. I followed up on that posting after I bought the boat. It contains all the details so I won't repeat it:
http://media5.hypernet.com/cgi- bin/UBB/ultimatebb.cgi?ubb=get_topic&f=6&t=001841&p= (http://media5.hypernet.com/cgi-bin/UBB/ultimatebb.cgi?ubb=get_topic&f=6&t=001841&p=)

Appreciate the advice everyone. By the way, what is a "North Sea" type exhaust? Someone told me to use that. And also, what do I do if the shaft does not line up with the flange on the gearbox? If I get this water cooled engine the shaft will be about 3 inches above the flange. If I push the engine back, it is buried underneath the cockpit and the drive shaft would be very short. I can't raise the engine much higher up because there isn't enough clearance. This is another reason I thought the air cooled engine would be easier. It is not as deep as the water cooled engine.

Jon

[ 08-04-2004, 02:39 AM: Message edited by: chergui ]

[Buddy]

By chance are you measuring the hull thickness at those bulwarks? Could it be that there are "ribs" and an inward sheathing on them to keep them light but stiff, all totaling 2" face to face but actually composed of 1/2" skins on 1" thick stiffeners? Seems a look at the drawings or a call to the designer could settle that without resorting to a drill bit. I just cannot believe a sailing yacht that size will have 2" of wood thickness throughout her hull. If "truly" cold molded from the customary 1/8" veneers, that would require eight layers to reach that thickness . You see 5 layers rarely, but I have never heard of more than that. Of course I haven't seen all there is to see.
Don't believe I've seen a prettier boat than your's though. Congratulations!

[chergui]

I measured the thickness at the bulwarks, right at the aft scuppers. My initial guess of 2" was actually off by quite a bit, it is actually 1 1/4" thick. There is some cloth around the bulwarks that I can see printed through in a couple of places. Maybe that could account for a bit. There are no ribs, I have pictures of it being built. However, it's hard to tell how many layers it is. Maybe I'll be able to tell once the through hull's are drilled. From inside the boat, the hull appears thicker at the foreward bulkhead also. I have a sample of one of the western red cedar strips used and it does appear to be 1/8" as you suggest.

[chergui]

Ok. I drilled the first hole for the exhaust and it was easy. The epoxy wasn't thickend when I applied it, but I put it on as thick as I could (which is not very thick) until the point it was running down. Most of the epoxy on the boat is fairly thin anyway though. I was going to wait until it had hardened before putting the through hull fitting in, but they just put the fitting in with the uncured epoxy, then sealed it all up with "Boat Life".

Bob, do you usually wait till the epoxy is cured or just add the fitting all at the same time or does it matter?

[Bob Smalser]

I'd drill it oversize....fill or line with unthickened epoxy gone over with a heat gun gently a bit to seep into the grain....then thickened epoxy....let cure...then redrill to the correct size. Use masking tape and modeling clay dams if necessary to hold the goo in there.

Then I further bed the fitting in poly sealant.

Just like I do with wood-core fiberglass boats....and also plywood boats.

A bit more trouble than just slathering goo on the fitting and stuffing it in there....but a whole lot more likely to not be one of the surveyor's bad news comments several decades hence.

[Buddy]

Its filling the end grain pores thats the trick. Most of the wood you see is flat or edge grain, and sure enough the epoxies pretty thin there. But on the end grain, living below the waterline with some pressure head at the bottom of the boat. If the water makes it past the boatlife ( good stuff by the way) the next thing it will encounter is a practically all end grain surface tunneling through your entire hull. Bob's approach is the bulletproof way and your time is cheap. Boatyards is not. The epoxy will cure under the boatlife, but doesn't sound like you have enough to offer any real secondary protection. I went a little further than Bob. I drill 1/8" holes around the perimeter of the big holes and inject thickened epoxy to make sure to get any interply voids as well as the oversize/epoxy/redrill tue size business. Is the boat already in the water? Maybe next haulout you can pull and do again.

[chergui]

Thanks guys. I don't like the way we did it either. The boats out of the water, I still need to do the intake hole and the parts are still trickling in anyway. I think I'll take the fitting out and re-do it. The wood doesn't look porous at all and I rubbed the epoxy in as much as I could. It may be fine as is but I'd like to actually see it dry. When you cram something in there with it uncured you don't really know what you wiped away.