Not another one sheet boat

[flo-mo]

Little Sailor

LOA: 7' 1.5"
Beam: 44"
Displacement: 200 lbs

[Peerie Maa]

Interesting, but you should work out the LcB, 'cos it looks as though that may turn out to be too far aft.

[brucehallman]

I think this is a very clever boat! Looking at the displacement curve in Free!ship it seems to have a fine LcB. Also, I feared that the twist in the bilge panel looked too steep, but a 'develop-ability check' is Free!ship for those panels looks good too.

[Lewisboater]

I think you might find that where you have to put the seat/thwart to properly balance the boat would be too far aft for comfort except for someone with very short legs. Move it forward so your knees don't interfere with rowing and us old folks can stretch them out a bit and the bow will sink significantly...probably more than you want. Put every full panel on a different layer (probably already is) and assign thickness and weight to your panels. Then make a box, assign it a layer, thickness and weight to say 180 lbs and put it in the mix. Align the LCB and the CG (from the hydrostatics at the bottom) by tilting the model and shifting the waterline...I think you will see what I mean.

[Woxbox]

I wouldn't want a thwart in a little boat like that. I'd much prefer to toss in a few boat cushions so I could sit or recline wherever was best at the moment sailing and rowing. The balance could always be right.

[Lewisboater]

even without the thwart I think there isn't enough support (buoyancy) for an adult far enough forward to keep the waterlines even near as shown... I would like to see what the lines look like with the weights in the right places. Look at the curve of areas...nearly half of the boat's submerged area is in the aft 2 ft and displacement is volume surrounded by skin area. To equalize the displacement to the lines show you would pretty much have to sit at the 2' 4" mark +/_ or the nose is going to sink...perhaps rather drastically. The LCB is right at around 2' 3 or 4" or slightly forward of the Lcf and you could probably get away with the centerline of your shoulders/hips being an inch or two forward of that but not much more before the nose starts trimming down. Move another 3 or 4 inches forward and I think you would see some significant trim issues crop up.

[Woxbox]

I don't know guys. Looks like a baby Open 40 to me. Could be the steroid answer to all those Puddle Duck Racers out there. Twin rudders and a tall bendy mast and you're ready to fly.

[brucehallman]

even without the thwart I think there isn't enough support (buoyancy) for an adult far enough forward to keep the waterlines even near as shown... I would like to see what the lines look like with the weights in the right places.

Here is the boat rotated forward to what I think would be the actual trim with a person aboard. LcF is at 3 ft 2 inches, in a 7 foot boat. Not perfect, but good enough. (Considering this boat is constrained by the "1 sheet" rule, damn good I think.) And, I was just attempting to get these developed panels to layout on a 4x8 sheet, and found it to be FAR from easy. Kudos to flo-mo for being very clever with that panel layout, I am impressed!

[Lewisboater]

That waterline looks more accurate but you should be looking at the LCB rather than the LCF I think (the LCB will always want to line up directly under the CG and the boat will trim to do it) ...and that is nearer 3 ft 10-11 inches if I read the lines right. I think you could shift that back a bit and lift the chin somewhat. That looks pretty OK but it might have some steering and tracking issues...especially in wakes. I realize that keeping it a 1 sheeter...does impose a lot of constraints and is the dominant factor in the design. If only that chin could be trimmed a bit and that volume moved aft a foot or so but I expect it wouldn't fit so nicely onto that sheet of ply.

[Peerie Maa]

That waterline looks more accurate but you should be looking at the LCB rather than the LCF I think (the LCB will always want to line up directly under the CG and the boat will trim to do it) ...and that is nearer 3 ft 10-11 inches if I read the lines right. I think you could shift that back a bit and lift the chin somewhat. That looks pretty OK but it might have some steering and tracking issues...especially in wakes. I realize that keeping it a 1 sheeter...does impose a lot of constraints and is the dominant factor in the design. If only that chin could be trimmed a bit and that volume moved aft a foot or so but I expect it wouldn't fit so nicely onto that sheet of ply.

True that you need to consider the LcB as the location of the LcG. If there is a discrepancy the boat will trim about the LcF, but that is the only function of the LcF, it is the pivot point.
I would round the chin, an angular forefoot like that one will be difficult to build, works OK in virtual reality, but as soon as you try to skin it with something as stiff as ply you will fail.

[Lewisboater]

Actually (boy...I sure am sounding like the bad guy here...) in the model he does have it rounded off...looks better too.

[brucehallman]

Actually (boy...I sure am sounding like the bad guy here...) in the model he does have it rounded off...looks better too.

The round off of the "chin" (in side view) has near zero effect on the longitudinal buoyancy curve because the bow is so pointy in plan view. The wood expended achieving a pointy bow might be better spent being used as a squared off bow transom. A bow transom would be needed to achieve more buoyancy forward.

[flo-mo]

Thank you for your interest for and your thoughts about this little design. In my opinion a one sheet boat is more like a caricature of a boat and not much more than a water-toy. The design process is just fun for me and if someone likes the result - all the better. I played a bit with Free!ship and added a sail.


sailplan

[htom]

It's a wee catboat! I suggest "Kitten" as the name.

[flo-mo]

Good eye Woxbox

[schoonerpacket]

I don't know guys. Looks like a baby Open 40 to me. Could be the steroid answer to all those Puddle Duck Racers out there. Twin rudders and a tall bendy mast and you're ready to fly.

Not until she can hold three people

[Woxbox]

Actually, with one adult she'd probably be lower on her lines than an Open 40 ready to race. But as a youth training boat, it could be a great platform.

[Daniel Noyes]

I was thinking Cat boat too, we have on old class at the Anisquam called the Fish class cat originally built by Montgomerys boat yard about 1930, very similar hard chine hull just built to 15' vs 8'... how about a barndoor rudder and a small sprit or gaf sail!

[Daniel Noyes]

Actually, with one adult she'd probably be lower on her lines than an Open 40 ready to race. But as a youth training boat, it could be a great platform.

could be an interesting sailing class, single sheet racer! hull or hulls must be built from a single sheet of ply, then mabey agree on a set sail area... or not!

[Woxbox]

could be an interesting sailing class, single sheet racer! hull or hulls must be built from a single sheet of ply, then mabey agree on a set sail area... or not!

Yep. The modern-minded could make an Open 40 of it, the traditionalists could do a mini sandbagger. Which would be faster?

[Daniel Noyes]

good question... this may require some experimentation...

I really could see a fleet of 10-12 of these things on a local lake, done up like traditional cat boats, and all going to weather just after the start of a race!

Thanks for sharing Flo nice little hull, it will sail great and looks like lots of fun.

[brucehallman]

I think this is my favorite one sheet rowboat: It has the advantage of being stable enough to stand up in, and uses virtually the entire sheet of plywood.

http://koti.kapsi.fi/hvartial/oss_sam/oss_sam.htm

[Tony_C]

Flo-Mo

You are king of the OSB - love your site!

[flo-mo]

[Daniel Noyes]

How about a cross thwart for rowing and to allow the sailor to sit astride it like a sliding seat on a international canoe and shift his weight toward the center in light air and out to the rail in a puff, the other option is side decks wide enough to get your weight almost centered, sitting down on the floor then hopping up to sit on the rail in a gust could make for exhausting sailing.

We sit astride the thwart in the Alpha


and I sit on the deck sailing my cat skiff

[flo-mo]

Makeover with Rhino:

Hull made of one sheet of plywood (4 mm x 250 cm x 122 cm).
A second sheet needed for the interior.

[flo-mo]

[flo-mo]

[dwr9]

Looks great flo-mo. Doug