Bolgeresque Noodle

It is my understanding that the box keel represents a very good portion of the boats displacement , 50% to 75% .

Having the weights carried by this submersed shape helps get rid of displacement waves , I think like the SES boats .

Weather a "better" shape than the simple one used by Atkin could be done today is a good question , but the Atkin were EZ to build and did seem to work.

The Austrains seemed to stick 75% of the displacement in their boats , and claimed 50% better fuel consumption and far, far less wake generation.

The Atkin box keel and reverse V deadrise plans come with the usual designers cautions , build it "MY WAY" or you will be sorry.

I can well understand the advantage in a power boat ,up to a certain speed ratio, but am less convinced the box keel is a great sailboat idea.
As a flatish bottom and lee boards , Dutch style, would retain the EZ trailer or beachable option. So the main plus might be the extra cabin hight , easily handeled with lifting a companionway.

FF

 

Well...here is the latest on the Noodle. I dumped the box keel as too much trouble. I couldn't get the displacement down to a decent towing weight. The picture shows a displacement of 10850 lbs in salt water drawing 21" without appendages. Reducing the draft to 19.5 gets me to 9570 lbs. Total height from external keel line to crown is 7 ft so headroom should be about 6.25 ft. There is a lot of windage with the vertical topsides but the slope of the cabin sides and crown should help a bit. I look for about 24"-27" draft with a small center keel and bilge keels with retractable boards for most of the LR. The design is more conventional...Bummer...but getting the box keel to work just doesn't justify the benefits. Getting the Bilge keels and center keel even and flat for and aft would allow for fairly level beaching/bottom resting... provided you have a fairly level bottom to rest on. Trailer weight should be somewhere around 8000 lbs in lightship form (only about 30% of stores and no water ballast). It should make for a decent camper on the trailer too.

Steve

 

The plumb ends are what's not allowing both reasonable towing weight and midship depth. You may prefer the 30 ft waterline for more room or more speed, but it would help tremedously if you could get the ballast lower. As it is, beaching would require a flattish underbody, but on a thrity foot waterline that flattish underbody is higher up (and so is the cabin roof).
Most significantly, while the current design has good form stability (and as it appears, self-righting attributes), in stronger winds she won't carry much sail on the wind even though she might have length enough to get some real speed if she could just hold the sails up.
You could gain a lot of depth (maybe 6") by shortening the waterline by 6 ft or so. Room inside is relative to displacement anyway unless you raise the cabin higher, which will cause the boat to sail on its mooring and to have excessive leeway when close-hauled.
Otherwise, the midship deadrise looks very correct for the beam. Not enough lateral plane without a centerboard or leeboards (there's an idea), but just right for driving it up on a beach or a trailer. A bit deeper would be good.

A.

 

Keep the plumb bow but bring the forefoot and the stern out of the water for more overhang and keep the rocker flat at these points. As the boat picks up speed and heels the waterline should increase. The boat will lose some directional stability, but a skeg on the run forward and the aft end of the hull (useful for prop placement and rudder support) will counteract this. Nice boat tho!

Andy

 

heres a (very) rough idea of what i mean but minus the skegs...

 

ah the forum is calling my pics 'invalid' - will try again later

Andy

 

The thing that matters is to keep displacement out of the ends in order to deepen the middle. The hard chine will dig in when heeled, which as you say will add speed. I liked the deadrise hull too, similar to Chesapeke designs such as skipjacks. You can beach a boat like that. It needs a lateral plane, lacking the full keel. Leeboards would be ideal, or bilge keels (which would level the boat when beached).
Skipjacks had some twist on their bottoms with maybe 12 degrees deadrise at the transom, 10 at the midship, and an increasing twist ending at 45 degrees at the bow.
Aesthetically, a plumb bow overhung is not my favorite, but it's subjective I guess. A raked bow means a twist in the plumb sides, true, but the foredeck would (could) be wider as well as the upper cabin forward.

A.

 

heres those quickies....

 

I adjusted the rocker a smidge...angle the bows a hair more and added a tad more deadrise. The result is a displacement of 4 tons @ 19.5 in for the hull alone. Appendages would push the draft to 3-3.5 ft...still reasonable for gunkholing. With 1000 lbs of water ballast and supplying just prior to launch I should be able to have an over the road trailer weight of about 3.35 tons or about 7500 lbs. This is decent I feel. Your pictures show a flat bottom...if it has enough rocker to keep the ends out of the water you will have a heck of a time sleeping...all that water slapping against the flat bottom. It would also pound most of the time...unless it was sailed on it's ear. I had thought to ameliorate that a bit with the box keel but it added too much displacement and I wouldn't be able to sink it to its lines properly.

Steve

 

The flat bottom doesn't need to be sailed heeled all that much to present a V to the oncoming waves. But without introducing more twist into the keelplanks up forward, a shallow V hull will pound more as the lower planks 'level off' with moderate heeling. The traditional way to stop the slapping at anchor was to hang fenders under the bow and stern sections... I should add that these drawings were for illustration purposes only!

Andy

 

Water Ballast

Steve,

Your design has me intrigued so your have to excuse if I keep popping up with ideas.

Here is a midsection idea that keeps th box keel, but combines it with a multi-chine hull for some major room for water ballast. The height of the cabin sole and/or the depth of the box could be adjusted as required for desired draft, displacement and ballast ratio.

This section is drawn with two feet of draft. The cabin sole is 3" below DWL. The width of the box at midsection is 2' including the centerboard box. I did a rough hull in Freeship at 30' LOA, 27' DWL and 8' BWL. The displacement came in at 4.506 tonnes 2.745 tonnes of displacement for water. That leaves 3945 lbs for hull and pax and stores. I haven't even tried to calculate what a 30' hull is going to weigh. I think there is room to coax thing around a bit. I'm not sure if your diplacement concern is solely for trailering reasons or general performance reasons too.

I like the split in the ballast tanks because it give some lateral displacement from the hull centerline and would help to reduce freesurface effects in the tanks.

 

......

 

Hmmmmmmmm...... . . . . . . . .

 

Beachable and trailerable...

Bilge keels are such a good idea, but they might dig in, causing some real problems due to lack of tide to raise the boat. On inland water, a soft sandy or muddy bottom might trap the keels, and then what?
The box keel has some benefits after all, especially if wide enough-- say, three feet. It is important to remember that a box keel with water ballast is subtractable from the midship area in calculations of trailer weight.
This should ( if I'm reading the parameters right) be a practical boat able to go anywhere without the need for Travelifts or hassle, inland, nearshore ocean cruising, rivers, tidal estuaries, etc.
I can imagine an air compressor run off of the engine to evacate the water ballast, lightening the boat for hauling out by trailer.
The bottom of the box keel could be a steel shoe for some ballast and for grounding and sliding over rocks that grip.
The alternative is a fully retractable centerboard or leeboards and a dory type bottom, or double chine with a flat bottom at least 3 ft wide.
Water ballast is necessary, even as much as one thrid the entire displacement (say, 3000# to the trailer weight of 6000#). This provides the necessary stability with shallow draft along with the moderate deadrise.
Maybe a 30" draft, 26 ft waterline (but almost kissing the water up to the knuckle). I think the box keel, in eliminating the need for a centerboard, is a heck of a good comprimise all things considered. There is something really appealing in a boat one can live aboard easing into places where only small boats can go, without anxiety.

A.