Adding a bulkhead to seal the engine compartment area/Altair

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thinwater
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Adding a bulkhead to seal the engine compartment area/Altair

Post by thinwater »

I have a lot of faith in the construction of the PDQ, and in her crash tanks and bulkheads. Still, questions come up.

Has anyone sealed the under-bunk compartments by adding a bulkhead, in order to provide more flotation? It seems simple, would add little weight, would cost little storage, and might be reassuring when you bump something in mid-ocean.
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by doubledutch »

Don't forget there are already sealed compartments behind the under berth area. Unfortunately in my experience these compartments somehow manage to take in water over time so I need to climb into the under berth compartment so that I can pump the water out of the "sealed" aft compartments. I would hesitate to build anything in that would interfere with this access.
I really don't think more flotation spaces are needed. There are two up front and two aft already. If you are still concerned you can always stuff flotation bladders into the compartments.
Henry
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by thinwater »

Yes, I am well aware of the crash tanks around the rudders. Nice design. No, I agree additional flotation is not essencial, but it would feel good mid-ocean.

What I suggest is a bulkhead at the forward end, with no top. Access under the bunks would not be unchanged. Yes, the crash tanks are good, but simple calculations show that a hole in the main portion of the hull would have you riding quite low and you would be hating life if a storm came along. I guess I wonder why a bulkhead was not glassed in at that location at the factory - the hamper/step at the foot of the bunk takes the same space but does not form a seal. If I had in-boards this would seem very important. Sail drives have been knocked out before. Do the LRCs have a bulkhead with a separte sump pump, or some other arrangement?

I hit a submerged log with another cat at 12 knots. We backtracked to look for the log and had great difficulty finding it. I did not blame the helmsman. We sheared the dagger board off cleanly, and it was solid mahogany. The log was 2' in diameter x 30' long, weighed more than a PDQ32, and would have caused signifigant damage to any boat. I'm sure that the mini-keel on the PDQ would have sustained major damage; it should come off without damage to the hull, but I don't think that is 100% certain. Impact forces, even with several feet of crushing, would reach 15-30,000 pounds, and locally much higher.

Another owner asked this question. I thought it deserved discussion.
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Where does the water come from?

Post by thinwater »

doubledutch wrote:Don't forget there are already sealed compartments behind the under berth area. Unfortunately in my experience these compartments somehow manage to take in water over time so I need to climb into the under berth compartment so that I can pump the water out of the "sealed" aft compartments. I would hesitate to build anything in that would interfere with this access.
I really don't think more flotation spaces are needed. There are two up front and two aft already. If you are still concerned you can always stuff flotation bladders into the compartments.
Henry
It's freshwater, so we are talking rain, not serious leaks. I've re-bedded everything in the area, so it is not hardware. I'm fairly sure it is inadequate scupper design on the stern hatches. I replaced the gaskets, but it didn't help much. I could add drains along the rear beam, but I don't like the idea of reducing flotation. Any ideas? I think we all have the same problem; a gallon of water every few months.
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by eepstein »

I get water in all four main watertight compartments, all fresh. an early posting mentions a few ways it can come in. James resealed the inspection ports and it helped some. I have a wet/dry vac with a long hose and check them every month or so. A guy I met a SSCA has a slightly larger custom cat and he says its common for him too. He actually floods the forward compartments when we rides out hurricane force winds in the Caribbean - thus would never want to seal them permanently.

Hope this helps.
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by thinwater »

I agree; sealing compartments seems like a clear mistake. the huricane example is just one part. I had a Hobie fly of a beach with bare poles!
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by mikeandrebecca »

eepstein wrote:A guy I met a SSCA has a slightly larger custom cat and he says its common for him too. He actually floods the forward compartments when we rides out hurricane force winds in the Caribbean - thus would never want to seal them permanently.
Could you please explain what you mean by this?
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by mikemak777 »

i think he means the guy fills the forward compartments with water to add weight to the bows to counter act the wind force to prevent being flipped backwards when riding out a hurricane or similar winds.
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by doubledutch »

Regarding water in existing aft flotation compartments - I have also checked and sealed all normal possible entry points but while I have less come in there is always some. I suspect some of it is as a result of day to night temperature changes and condensation. During the day the air expands and escapes where it can. With night time cooling and moisture the air returns and brings in a little water with it. By next morning the water has condensed and run to the bottom so the new days expanding air does not take it along. As this cycle repeats a few drops each day eventually do build up. We have seen this happen with sealed electrical panels on roof tops where moist air from cooling towers is present - in these cases we can drill a drain hole in the bottom of the panel - unfortunately not an option here.
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by mikeandrebecca »

mikemak777 wrote:i think he means the guy fills the forward compartments with water to add weight to the bows to counter act the wind force to prevent being flipped backwards when riding out a hurricane or similar winds.
Sorry if my questions seem stupid, but do you mean when lying to a para anchor, or do you mean when the boat is on the hard?
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by mikemak777 »

i've only heard of people doing it while in an anchorage riding out a storm where the bow faces the wind. if on the hard, i suppose one might use sandbags or something similar to add weight. i will have to plead ignorance, as i don't know anything about riding out a hurricane at sea with a para anchor....and i hope i never find myslef in that situation, but i don't think i would be putting water inside my boat. hopefully someone else can offer more experience in this regard.
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by mikeandrebecca »

I am asking partly due to some comments made by my marina owner. When on putting our boat on the hard for the winter, he asked how much our cat weighed. He told me that we routinely get very high winds during storms here and implied that there was some concern about it not being heavy enough. I think he may have been messing with us (we are newbies after all), but I don't know for sure. :?
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by eepstein »

I was talking about at anchor or on a mooring. I had a bad experience with a sea anchor once many years ago - but thats another story. On the hard I suppose winds could do damage - its pretty windy today :-(, but its the rocking horse effect on waves while at anchor where the wind catches under the hull and adds lift to a catamaran like a kite. Imagine 3' seas in an anchorage with 70+ knots of wind as the scenario. I only know of one catamaran owner who experienced it first hand and was okay. So from that stretch we come back to leaving inspection hatches the way the factory built it and buying a wet/dry vac. :D
Stay warm up there Mike - now that the snow realized its supposed to be farther north than DC.
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Re: Adding a bulkhead to seal the engine compartment area/Altair

Post by mikeandrebecca »

Thanks Eric! It's funny how little snow we have had. It snowed a few inches yesterday but I think it'll be gone in a day or so. We are dying to get our boat back in the water!!!

By the way, Drew's post on this subject now may have been partially inspired by my asking him about filling the flotation chambers with pop bottles to help in the event the area was holed. I posted about it yesterday on our blog:

http://www.zerotocruising.com/?p=4026

Mike
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Clearly, I made a mistake using the word "sealed" in my post

Post by thinwater »

All I was asking about was the addition of a bulkhead reaching from keel to the forward edge of the bunk. Basically, the engine compartment would be divided off from the rest of the hull, but the top opening would be just as it is now.

No, sealing a compartment is poor planning. We all agree.

No, filling a bow with water at when using a sea anchor is not good. The bow MUST rise to the waves, and the 32s have a slight weakness there already (the beam is very far forward), and what if you later decide to turn and run (chute fails, perhaps)? A bow full of water would be deadly.

BTW, another way these "sealed" compartments often get water is by sucking in water that is laying on top of the inspection port when it cools. Oil drums are very prone to this effect, and so oil drums are often stored tilted to prevent water from sitting on the head. On a boat, the alternative is to place the inspection hatch on an extended neck, to keep it above the water.
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