Sampan Lee Hull?

I'm sure some of you have seen this before. I don't think it was ever built. The designer claims he used a Sampan hull shape for the lee hull.

What was he trying to accomplish with this and did he pick a reasonable hull design? This seems like a planing hull and has plenty of rocker. It also looks like the freeboard could be extended vertically to create quite a bit of internal volume.

How would this perform unloaded & loaded?

Do any other designers use this approach?

 

I feel that the hull is closer to a scow rather than a sampan.
I suppose it is good for shallow water and max load capacity for length.
I would expect when in a hurry, it would be noisy and to slam, with that blunt bow.
It would be slower in a light wind as the wetted area would be more than other hull types.
For the a little more work you could use a similar hull style as the out-rigger.
Having said this, who really cares. It you like it, go for it.

Do others use this hull style, sure: http://www.grandpasarchive.com/boatplans/sail/16-ft-sailing-scow.pdf

Regards AlanX

 

Hello Mr. Alan

Thank you for your kind reply.

I also got the impression it was more of a scow.

I like the shallow water handling and maximum load for length traits. That must be why I liked this design. It's also a simple hull shape and shouldn't be overwhelming for a home builder. I agree with you about noise and slamming. Could those characteristics be mitigated on this hull? The bottom appears to be a curved flat panel with a straight centerline keel. Do you think this is so, or do you think it has a shallow-V chine to it?

You mention that for a little more work it would be possible to make the lee hull similar to the outrigger. What kind of hull is the outrigger. You can obviously tell from this image, but I cannot. If the lee hull was made that way, would it preserve it's shallow water handling and max load for length traits, or would the performance be completely different?

 

I found a link to Michael Schacht describing the original concept: Herbie the Volkscruiser Proa https://proafile.com/forums/viewthread/382/

I don't think the hull has any chance of planing, on account of waterplane loading being too high because the flare is all well above the waterline and the part of the hull that is in the water is quite narrow. The link above does not offer a frontal view, but from the views that Schact does offer, I think the cross section resembles this: Proa File | The Camel: a sailing cargo proa https://proafile.com/multihull-boats/article/the-camel-a-sailing-cargo-proa

 

Yes, Michael Schact. I'm not familiar with his portfolio.

I did find some hull images in the thread you shared.

 

From what I’ve seen Michael Schact isn’t a designer, he’s a “concept artist”

 

Wow, it is nothing like what I thought!
Basically a dory with a "sleeping???" accommodation and/or a deck on top.
@tmz, if you were to build this, how big were you thinking?

For me that Proa forum was a nice find.

If I was designing Herbie3 I would have less inverted rocker on the top of the deck section and more rocker on the bottom of the deck section.
The double ended oar rudder(?) does not work for me. How does it steer?

Regards AlanX

 

Yeah, the inverted rocker on top makes no sense, since the design is already aerodynamically dirty. I would rather have the safety of a flat deck, beneath my feet, while handling sails.

BTW, it doesn't steer. That was the main critcism in the original thread. I think he was planning to steer with the sheets. The combined kick-up rudder-daggers, that the Harry's use, would be a huge improvement.

BTW, I was thinking about using this hull shape with a cat, because of the shallow water and heavy load handling characteristics. I was also planning to significantly incease the freeboard, to make the accommodations more spacious.

You may laugh at this; but, I'm trying to design a beachable, live-aboard, sailing "ferry," with cargo and ATV storage on the bridgedeck. Yup, I can imagine a use-case for this.

You're going to laugh again, 50'.

I know this is unorthodox; and I don't mean to drag anyone along against their will; but, if you're enjoying the ride welcome aboard

 

Michael Schact is a good guy, but this design is not good. The rudders would be damaged in heavy seas as there is a spar projecting towards the bow. The blunt ends will cause huge drag when going to windward in any sea

 

A 50' catamaran is a BIG job for a first up.
Why not something smaller to start, say 24' (or less).
It's still pretty big (big enough to sit inside and sleep in) and would be 1/8 the cost and time.
If it works and you like it, then you can go BIG.

About 17 years ago, I built a plywood 23 ft bare bones open sharpie, working weekends it took 14 months from plywood to the water and cost A$6500 all up.


Today I think I could build it in 3 months but the cost would be would be double. Just to give you and idea of the scale of the job.

By the way, my hull is very similar to your hull but without the extended deck.

Regards AlanX

 

I had a play with the design,
Imported the design into QCAD, 1 pixel equal 1 cm:

The design is about 2 m deep and 11.1 m LOA (10.1 m LWL). Displacement about 2.7 t.
Estimated the hull thickness (12 mm plywood) and designed 12 mm plywood ring frames based on 500 mm centres:


I have the dummy standing on a floor between the bottom frames.
I would probably crown the deck/ceiling an extra 100 mm for more head room.
The shelf height at 109 cm is a bit high, should be reduced (14 cm) to 95 cm.
That would increase the head room above the shelf to 102 cm, just right for sitting up in bed.

Regards AlanX