PDA

View Full Version : Designs: Sketchbook feature



dredbob
06-29-2014, 10:53 PM
I haven't seen any other mention of this new feature, so I'd like to express my appreciation to the editors and to the two designers involved (McGowan & Schacht). This is reminiscent of the Bolger "Cartoons" in the old Small Boat Journal, which was one of the best and most popular sections of that magazine and I have high hopes that this Sketchbook will run in every issue of WB and become just as popular.

Seahawk, the initial design, is a nicely lean powerboat that takes ideas from a lot of sources and ties them into a well integrated and good looking boat that will serve a number of uses. The only change I'd make to it is to add a pipe frame aft that is the same height as the roof of the steering shelter to create a sort of "roof rack" so that a load of kayaks could be carried up there. This could also provide support for a cockpit sunshade or even a full tent for use when cruising.

And check out the trailer weight; only 1800 pounds. Not bad for a 30 foot long boat. This is a boat that you could easily trailer to Florida or other southern climes for some winter cruising.

Great job, guys. I hope to see more such well thought out designs in the future.

Bob

upchurchmr
06-29-2014, 11:11 PM
Did you include a link?
What publication are you talking about?

dredbob
06-30-2014, 01:44 PM
It's in the latest WB, #239, July/August 2014, page 94.

Here is a link to some "Bonus Content", but the complete article is in the magazine.

http://www.woodenboat.com/seahawk-0

upchurchmr
06-30-2014, 05:53 PM
Thanks

J.Madison
07-02-2014, 06:43 PM
I really like the idea. I hope some traditional construction techniques are represented in the designs.

Tom Lathrop
07-04-2014, 11:57 AM
I do not believe the 1800# trailer weight. Don't even think the completed boat without engine, fuel, water or any other supplies will come in at 1800#. Another issue I had with the client specification list is that it was so specific that there was very little actual designing latitude left to the "designers". Nice looking and interesting boat and general appearance is a close mirror of Hand's handsome boat. Specifics, not so much.

Plenty of material here for a good discussion. Anybody?

dredbob
07-04-2014, 09:15 PM
I should say that the 1800 pounds was the specified weight of the boat ready to trailer, but not including the weight of the trailer. To me that would be the weight of a mostly empty boat but with the outboard mounted.

Bob

Ian McColgin
07-05-2014, 08:38 AM
Like Tom, I'm a bit surprised at the predicted weight totally empty for trailer. She is a pretty stripped out boat but still . . .

One huge thing I did not understand from the sketchbook is how the long cabin trunk and central helm screen hatches work in reality. In the pictures, they appear to have been left on the dock.

I certainly understand wanting to use an engine one has at hand, but this does seem like a great deal more horsepower than the use calls for.

Tom Lathrop
07-05-2014, 09:22 AM
Bob, Ian,

I think there is a lot more here to discuss other than trailering weight. As Bob said, the accepted condition for trailing weight is as the boat is on the trailer on the way to launch, minus liquids and stores. I don't have the bottom hull lines of Hand's boat.

I wonder what happens to the CG from light load (helmsman only) up to max load with 11 people aboard. That is especially related to running upwind light vs downwind heavy in waves. A little cut away in the bow seems inadequate to handle that as does the much wider stern compared to Hand's boat.

There is more. I don't want to unjustly quibble about the design but WB did put it in the magazine for our interest and I find it very interesting.

PAR, Tad, Michael, others?

Ian McColgin
07-05-2014, 10:23 AM
I agree that the truely vast range of running weights - counting a full load of people and some supplies about doubles the claimed trailer weight - is one of the more interesting features. The claim is that she'll proceed loaded or light from displacement mode to a plane in a fairly level smooth fashion - no squat and jump. This could be if the lower speed planing surface is well spread fore and aft.

On the passenger side, I'm not one with the cabin concept at all. This may be more a matter of individual call but I'd have gone with a forward cuddy and then open launch design back to the helm which might as well go all the way back. For weather I'd have chosen a surry top with eisenglass curtains that can roll right down . . . It just seems like the center standing ally could get crowded at times, though one very good feature of the case is that when the guests are standing they are forced to the middle.

I'd be most interested in non-passenger use of the hull concept. Seems to me that if the hull really works well and economically in displacement mode and on a plane, laden and light, then it would be a most interesting and flexable motor cruiser for a small footprint minded snow bird.

TR
07-05-2014, 02:12 PM
I believe the USCG now says each passenger weighs 185 pounds, so displacement doubles as the day trippers come aboard. That is a big deal. And that's if the specified hull weight could be achieved, which I think is unlikely given the stated construction. 3/4" plywood is not really compatible with a D/L just under 40 (Lightship or trailer weight). Perhaps with a light cedar core and carbon skins. Light boats are possible but they are expensive to build, in both time(man hours) and materials.

And light boats are uncomfortable, I would guess that if this boat was built to weight, everyone would find her motion tiring (too quick and noisy) and she will be tippy and quick underfoot. This does not instill confidence. And as Tom mentions, the passenger load is well above the waterline, and her waterline is narrow so M is not that high. GM will get quite small when fully loaded, which can lead to some scary handling issues. Catamarans are really the answer to the low-drag, high-stability question.

The biggest question for me, and the first question for any commercial operation, is does she meet regulatory requirements? I don't know if she would meet USCG stability requirements for small passenger vessels. I'm pretty sure she would not meet Canadian Transport Canada (ISO CAT C) stability requirements for 10 passangers if her design weight and draft were achieved.

dredbob
07-05-2014, 02:58 PM
In regards to the open slot, they only mention a roll up canvas cover with battens. This would store aboard, but I think I'd want to give a lot of thought to coming up with a more secure, lockable solution, that would still be able to be stowed away somewhere on board.

I'm more amenable than Ian to the slot top cabin as a passenger space. I've spent enough time trying to avoid the sun as it reflects off the water and comes under a canopy top either early or late in the day. Though I think that the view out the windows would have to be good, as a good deal of the pleasure of being on the water is the view. It would also be good for avoiding the spray that is bound to be flying at the speeds that this boat would be capable of, especially with the mentioned 175 HP.

I'd be much more inclined to go with something in the 50 - 75 HP range, or even less; just enough to be easily able to get up and stay on plane at the maximum intended load. I'd be happy with max speeds in the teens; that's plenty fast enough. If the boat could indeed eliminate the "speed hump" between displacement mode and planing, it would be nice if there were a sweet spot for best fuel economy that gave a bit more than normal displacement speeds. I'd like to see the fuel usage curves.

Bob

Tom Lathrop
07-05-2014, 03:49 PM
Mr McGowan has designed some nice looking boats that apparently met their design goals so I am a bit surprised at this one. I thought LE BLANC, modified to meet the client’s goals would be a more appropriate starting point than Hand’s boat which has a completely different approach to trim than SEA HAWK. Hand”s BRONCHO has all engine, fuel and passenger weights concentrated well forward in one area and is not very adaptable to large changes in CG as SEA HAWK demands. The appearance is similar to BRONCHO as is McGowan’s SULIS design.

Looking at the listed scantlings, I would guess the trailering weight to be at least 1000# higher, not including the engine. I don’t mind the slot top and think it is a good solution some of the time. I would guess the 10 guests might not be enamored with their sitting positions with their view limited to looking out the other side of the boat. I concur with TAD that stability might be an issue and the guests had best stay in their seats.

I don’t mean to try tearing this boat apart and don’t suppose I have the credential for that anyway. Nevertheless, as a long time reader of WB and sometime designer of similar power boats, I do feel justified to make some comments.