sailboat design ideas

[frank smith]

Originally Posted by yipster

that is the waterline not the bottom, but seriously; on calm water and budget a flatbottom sharpie with swing keel is doable
http://www.proaxis.com/~boblark/bw2_main.htm

No question it can be done in a sharpie , Bolgers SA29 comes close.
But you could go bigger in the same length. Dont think 6'4" works
well for the whole length , but that depend on what kind of sailing
you want from it .

[apex1]

Originally Posted by shipwreck

Is it possible to have a flushdeck sailboat at 30ft with 6ft.4 inch headroom and have a deeper draft so the hull won't catch so much wind and look clumsy........

Hi Richard. Thanks for speaking english. Yes, i live in Potsdam. The lakes here are not deep. What would you say is the deepest draught a sailboat can have in this region? 1.25 meters or 1m ? Thanks.

answer

Originally Posted by apex1

Deepest possible should be around 1,5m, deepest sensible 1m, even that´s a lot, because there are quite many shallow regions. The Oder is sometimes below 1m during summer (just as a example).

Proposals?

[Fanie]

I would consider a catamaran with fatter hulls to provide shallow draft and with a keel, If the draft can be made for 300mm and the keels 200mm you are at 500mm. The fatter hulls would make small depth differences when heeling. More space than a mono etc etc. You can also have your headroom then.

[frank smith]

A nice house boat with a lug sail and lee boards would be nice .
what a fun boat it could be with a large poop deck and a pilot house .
It would be very stable ,like a church .

[sharpii2]

You can always go with a deep 'V' hull and a long straight keel.

I did that with my 35 ft final project boat. The cabin was a raised deck and there was only about two feet of clearance between the deck and the boom. It was intended as a live aboard in colder climes. It was very similar to a 'cowhorn' which was its inspiration, though it was much lighter.

To work the rig, you had to work from below through hatches. Not an ideal situation. Also, the rig was a low aspect ratio gaff cutter with a balanced jib for a staysail.

In real life, it would be bulky, somewhat clumsy, but emenently seaworthy. And probably not a slow as one might expect. But certtainly no high performance boat.

The sail area was relatively small but adequate and the outer jib was attached to a bowsprit. It would either be roller reefing or it would have a downhaul, so it could be struck without having to go forward.

The long keel had generous area which would have helped to prevent it from blowing all over the mooring when at anchored. the draft was 4.75 ft.

It seems like you are willing to put up with a huge amount of inconvenience and expense to get full headroom. There are cheaper ways to do this.

Bolger pioneered the 'slot cabin' concept where the cabin has an open slot in its top to provide standing and walking room aboard a 24 ft decked over sharpie. A fabric would close the slot, or any part of it to complete the shelter.

Another option is a pop up cabin top, where the cabin sides, in part or in full, are fabric and the cabin top is rigid. It is raised only when the boat isn't sailing. This was used on trailer sailors during the '70's.

Both of these options work on extremely light and easy to trailer boats that are under 30 ft.

These are the directions I would go, if I wasn't planing on living aboard.

[frank smith]

sharpii2 ,interesting sounding boat , got a pics .

[oralpiskin]

hi,
ı have a project work to do, and ı must use series64 method to find effective horse power but ı no know about this method...how can ı find about series64 method?

[apex1]

Originally Posted by oralpiskin

hi,
ı have a project work to do, and ı must use series64 method to find effective horse power but ı no know about this method...how can ı find about series64 method?

Sure not here!

Contact "urisvan" through PM, he may help you at ITU.

Or use the search function above to find a answer here. Series 64 was handled several times.

[sharpii2]

Originally Posted by frank smith

sharpii2 ,interesting sounding boat , got a pics .

Hi Frank.

Here are the original concept sketches. They show the hull and mast but not the rig. The rig is a gaff cutter with a balanced jib staysail and an ordinary outer jib.

[sharpii2]

Originally Posted by shipwreck

Good idea to start with the intended use and go from there. This boat would be used in not so deep and shallow lake region in Germany, outside Berlin. My main purpose is to be able to sleep comfortably for a night or two and be able to sail very short distances. The sailboat can not be too big because i only have so much room in my backyard! 30ft is max. Thanks.

Thinking about the question as it has became much modified, (a lake only about one meter deep) I came up with this idea. Here, for your entertainment, I submit the following proposal. It is the shortest, smallest, cheapest solution I can come up with. The cabin has the space of a typical jail cell. I figure that if a man can spend the rest of his life in a space this small, he can certainly spend a few weeks in it.

A 20 ft (6.12 m) by 8 ft (2.44) scow, rigged as a gaff cutter, with an aft cabin and a long fixed keel. (See attachments below.)

I thought of a scow for three reasons:

1.) It provides the most initial stability of all the mono hull types. With the high cabin, the rig is going to have to be high to clear it. And that means the Center of Area (CA) is going to have to be high as well.
2.) The hull can be narrow enough to provide legal trailering ability (at least in the USA), and
3.) The construction of the hull and fitting it out can be immensely simplified

I thought that an aft cabin arrangement should be considered even though it complicates the steering system, makes auxiliary power more difficult, and has the cabin entrance facing the wind while at anchor.

I thought mainly of the helmsman being able to see where he is going without having to be perched high up in the air. I also thought of the aft cabin as interesting aerodynamically. It kind of acts as a mizzen on a yawl that is never struck. While at anchor, it will help the boat behave itself. It will also give the bow a certain amount of upwind proclivity while adrift. This could help make getting underway somewhat easier, as the boat won’t charge downwind down wind once all sail is struck.

The long keel is somewhat a product of the aft cabin. The aft cabin makes some kind of retractable rudder somewhat complicated and difficult to set up. With a fixed keel, the rudder can be fixed as well. I also had trouble coming up with a leeboard system that would be able to SAIL in one meter of water and not just FLOAT in it. With the leeboard system I originally thought of, the boards would pivot only on the fore and aft plane and both would be down at the same time. In one meter of water, the lee side board would be touching the bottom much of the time.

The long, fixed keel cures this dramatically. The all up draft at full displacement is less than two thirds of a meter and that’s with the boat sitting dead upright. As the boat heels the draft will be somewhat less. This is one of the very rare occasions where a long keel is actually superior, despite its massive wetted area and general upwind inefficiency. Tacking in this boat will really be a series of glorified close reaches. But it will make upwind progress in very shallow water. Something that probably cannot be said with certainty with any other arrangement with a hull with this much windage.

The odd gaff cutter rig is a product of the high aft cabin and the long keel. The sail area of the main sail can be shortened quite quickly by dropping the peek. One of the jibs can also be hauled down quickly as well (both would have down hauls). Thus, sail area can be substantially reduced in very short order without tying a single reef. With one of the jibs down, the other can be back winded to force the bow through the wind when changing tacks, which will make this operation much more reliable.

Interestingly, the vertical CA is not much lower than it would be if the main were jib headed. The mast would be only about three feet taller as well. But the horizontal CA would be too far forward (which it may be as is, already) requiring an even longer boom and/or a deeper fore keel as well. With an S/D of nearly 17, I think the sail area is within reason.

With the amidship cockpit, the mast could possibly be stepped without a crane or tabernacle by one person. With a forward cabin, a tabernacle would almost certainly be needed to make this possible. Also, on a hot summer day, the open doorway facing the wind may be much appreciated.

The two biggest flies in this ointment are how to provide cheap auxiliary power and how to reef and strike the sail with the boom so high up in the air.

The auxiliary power would be an outboard engine which would be mounted in the cockpit with the lower unit protruding through the hull in a well near the keel. Dealing with exhaust fumes provides a vexing problem. I have thought of a PVC pipe behind the exhaust port (if it is above the water) with some kind of fan to suck the fumes in and blow them out over the side. Certainly not my favorite arrangement, but it may work.

So far, I have not thought of a solution for the high boom. But at least there will be few worries about being smacked in the head by the boom J.

This boat may not win any races, but it may certainly turn a few heads. :- And as it makes progress to windward, despite its enormous bulk, it may turn even more.