Through hulls on passagemakers ???

I am in the pre-planning stage for either building refurbishing an ~50' steel (or possibly wood) hull passagemaker. This boat must be seaworthy and safe. I would like to have as few through hull fittings as possible and would love your insight and comments as to how to design, locate and care for those through hulls that are necessary. Which ones are necessary and are my concerns about the safety issues involved fact or myth. Thanks!

 

Keep all thru hulls in the engine room.

engineroom is enclosed in watertight bulkheads.

Service thru hull valves at every haul out. .

 

I know Micheal might disagree with me but a proper seachest is the way to go, espacially in steel boat of that size..
Google for sea chest to see some drawings (ingnore all those fancy wood coffins). Most drawing are for ships and quite different designs.
For a boat I'd recommend one, a generous size, with a removable grill bottom, a coarse strainer above it, next Seacocks on the sides and on top a bolted hatch. The hatch hight above the waterline and you can clean the chest completely afloat. After each seacock a separate fine strainer..
BR Teddy

 

A sea chest for intake is the way to go. Then make all the outlets above the waterline.

 

Dont want your black or grey water thru hull above waterline .

Equipment that pulls alot of water while in harbor like AC , refrigeration should be stand alone thru hulls with strainers. It is these harbour house service intakes that clog with trash fastest.

On a steel boat , its best to sandblast, epoxy prime, then line the waterline discharge thru hull stem pipes with plastic or GRP pipe to keep "old Age" rust bleeds from soiling your boot top.

 

Love the sea chest idea. The idea is for dry stack and inner keel cooling so all i would have attached to sea chest would be air condition, water maker and fire suppression/deck wash pump. I would prefer above WL discharges (possibly with below WL extension to be attached for stints at port). Will that work? Comments?

 

I would prefer above WL discharges (possibly with below WL extension to be attached for stints at port). Will that work? Comments?

If you live in an area where ice is common , the above the WL toilet discharge will require either white toilet paper , or a crowbar long enough to break the ice daily.

FF

 

Sure we will do short stints in the ice, but i as a Southern boy that has been in the NW for a number of years.

 

I've seen some nice manifold arrangements. One larger sized pipe leading to a larger can shaped manifold and filter with the 2ndary feeds individually valved from the sides. With an easily removed cover which can even be clear polycarbonate then you can see the strainer. The whole arrangement is well below the waterline and to clean the filter you turn off the main sea cock. To rod out the pipe you jam a rubber extension hose into the riser and turn the valve on and use a broom handle.

 

That surely another viable idea. The ones i've looked at so far arefashioned as a square tube, rising vertically from the hull. The one i like best looks to be about 12" by 12" and rises from the hull above the water line. atached to the side are the thru(chests) appearing as a manifold that are below the water line. The acrylic to is on top. There is no seacock at the bottom, because it would have to be very large to flow enough water for all the inlets. Being above the waterline, it can be cleaned in calm seas.

 

Those sorts of arrangements are called stand pipes.

On larger vessels the engine room is so low that you cannot sensibly take the sea chest, or standpipe above the waterline. Remembering that the pipe cross sectional area goes up relative to the square of the radius you don't really need such a big seacock at the base of a manifold. Sea chests are large to allow partial blockage from growth and also to carry a large strainer that doesn't need cleaning between haulouts.

 

i like the seacock idea. I spoke with a man with a Nordhavn 62 and his seacheat is connected to the hull via two larger seacocks with hoses that travel up the the seacock. He has what sounds like a modified sewer snake to "route" the hoses out occasionally or dislodge the occsional jam. I have asked him if his is taken above WL, but have not recieved the answer as yet. His boat is very expensive his boat sees many blue miles. He likes the set up. He said these are the only deep through hulls he has on his boat. Others are either just above of just below waterline. Another Nordhavn owner, that had no chest, had over 30 thru hulls. Any one of his low ones would max out both of his bilge pumps, even if they would pump at the rated capacity. Which to you think sleep better?

 

Concur. Seachest in a watertite compartment as Michael suggests. Include in seachest fittings for high pressure air and high pressure water. Blowing the seachest clear of debris is a time and effort saver, and can save your life. Trying to prime the fire pump during a fire and discovering a mudded up seachest, is an avoidable disaster if you can blow it out.

 

Once again...its the harbour use " house service " equipment like , refer and AC that pickup garbage. Keep these services separate and your main engine intakes will always be clean.
In main engine intakes I only pickup anchor weed. To avoid this weed knock the grass clump off the anchor while tha boat is in reverse.

 

"Another Nordhavn owner, that had no chest, had over 30 thru hulls. Any one of his low ones would max out both of his bilge pumps, even if they would pump at the rated capacity. Which to you think sleep better?"

Sure would take a mighty bilge pump if a 12x12 sea chest started leaking!

Not sure even a fire boat would have the pumping capacity.

Sleep well!

FF