sea chests vs. though hulls

[Bertramp]

I looked at a Striker at one point to purchase. It, like all other Strikers, had a sea chest as a water source for cooling the engines, generator and I assume anything else that needed a raw water source.

What are the benefits (if any) of this setup as compared to though hulls ?

If they are a better system, why have other manufacturers not adopted this system ?

 

[Genesis]

Fewer hull penetrations, more fair running surface.

Downsides include it as a weak point in the hull structure.

 

[Bertramp]

that word is "through" .... sorry (fat fingers)

 

[SKYCHENEY]

We had a 49' Gulfstar MY with a factory molded in fiberglass sea chest. It was not a weak point. In fact, the way it was engineered into the aft section of the keel actually added to the structural integrity of the boat. It drew water in on each side of the keel and then up through one large SS strainer and then into the individual "through hull" type ball valves for each hose that needed to be fed. It worked great and I had no complaints after running that boat for 10 years.

Maybe the Striker setup is different, but my experience was a good one.

 

[Genesis]

I guess "potential" is probably called for in that "Weak point".

I'm sure it can be done right... and quite honestly, I don't see much of a downside if it IS done right. The only real issue I can think of offhand is cleanout access and how that would be handled, as if nasty stuff got growing in there you have to have a way to get to it to clear it.

 

[SKYCHENEY]

Yes, cleanout is a bit of a problem. When we were in Lake Gunterville for over a year, we did have some zebra muscle growth in the chest. The only good way to take care of it was to pull the inlet covers on either side of the keel and reach up in there and scrape em out. It originally had some antifouling paint in there, but we had not known that and neglected to paint in there when the bottom was painted. Had we kept up on it, it may have not been an issue.

 

[jim rosenthal]

Hines-Farley Offshore Yachts use seachests. Sonny Hines is hands-down the most fanatical and picky builder of sportfishing yachts in the world. They are so robust that they undoubtedly stiffen the bottom.
Upsides are less drag. Downsides are more expense, harder to keep from fouling, harder to clean out, and at least theoretically a limit on how many seawater sources that can be accommodated. Practically speaking I think this is not an issue.
My guess is the added expense and trouble don't make it worth it.

I had a Striker. I thought it was a terrible boat- LOTS of things wrong with it and not much right. I would not have another Striker as a gift. I'd rather pay for a Hatteras or any other quality GRP boat.

I think most commercial craft and military vessels use seachests, by the way.

 

[Nonchalant1]

I thought that the big idea of an intake seachest was that it's highest point is above the waterline, so it can't sink the boat. It constantly stays full of water so you can pull water through it from outside the boat, but if a break happens in a line inside, it'll only drain the little bit of water in the line and won't pull any from outside. If a break in an inside line happens from a throughhull, it can run until the boat sinks.

Doug Shuman

 

[jim rosenthal]

Doug, you may be right in theory, but I recall the Hines-Farley clearly, and I don't think the highest point in the chest was above the waterline. I think they did it to minimize drag on the bottom. You're right, though, if the highest point were above the loaded waterline a leak in the top of the chest would not sink the boat. And leaking through-hulls can and do sink boats.

 

[Tom Ipock]

I also owned a 49 Gulfstar with the sea chest. I thought it was a wonderful idea. My Hatt has nine intake thru hulls in the bottom vs one? Other than the beautiful wood work in the GS and the sea chest concept, nothing else on the GS stands in the same neighborhood with the Hatt.
Tom

 

[Nonchalant1]

Hatteras uses seachests for the opposite - to get water out of the boat. There are 4 seachests on my boat that are the water output for more than a dozen outlet pipes. The idea is to have a large diameter chest that's a foot or so above the waterline on the inside, and an inch above the waterline on the outside, so water exits cleanly without staining the outside of the boat but the high point is still far above the waterline. The exit just above the waterline should also keep critters from growing in the seachest because it always empties after it is used.

 

[spartonboat1]

I thought I saw an article in Passagemaker regarding a series of 50' or so boats that were produced by Alexander on the west coast and they had a nice picture of a common seachest about 1 1/2 to 3' in height with multiple output/withdrawal points. It had a robust looking plate on the top attached with sturdy looking fasteners, maybe cap screws...can't remember, tool lazy to find the past issue.

 

[GaryNW]

Doug,
Intake seachests need to be flooded as you do not want pumps to be sucking air at startup. Sizing of the seachest and grate open area must also take into account total gpm as you don't want one pump to starve others. I have done two designs. One was a fireboat with a 1800 gpm (100 psi) pump. We used a 2'x2' seachest and used the hull cutout as the grate (couple of hours drilling 3/8" holes!). We just could not see trying to find an in-line strainer with the required capability. The other was a 58' seiner that had 5", 4" and 2" pumps and several other users. Here we used (2) approx 2'x2' chests, one on either side of the engine stringers. Grates were 3/8" bronze plate. The seachests allowed a nice flat surface on which to mount the sea valves and pumps. Also allows for much more straight-forward plumbing. Helps a lot to be able to use off the shelf 90's and such when you are routing 5" IPS in a very busy engine room! Chests were big enuf inside to mount slabs of zinc and paint with antifouling at haulouts.
Gary
p.s.- both boats were frp