Low-speed sailboat hull

I will do that, as soon as I'm a bit free from my studies. Any way to make tacking easier except for raising the boom higher? Tacking might be quite frequent in our local conditions (narrow lakes, unpredictable wind shifts), so scrunching under boom every time might get irritating.

 

maybe you'll think it's strange, but I think a very different solution.
10 feet long
4.6 feet beam
1.5 feet draft
displacement 0, 233 tons
construct is simple with two layers of plywood, because the longitudinal curvature is minimal.
no centreboard
the mast amidships, with a large mainsail, small jib and gennaker, everything inside the length of the boat.
the two people on board behind, amidships, with the necessary space

 

Remember the two requirements are that the boat must weigh under 35kgs and must go on a car roof

Richard Woods

 

The biggest criticism I can think of is that the thwart, which supports the dagger board case, is too far forward to be used as a rowing thwart, with one person on board.

The bow will end up deeply immersed, making it nearly impossible to stay on course.

An unconventional solution to this problem would be to un-ship the rudder and row the boat stern first.

As unsightly and undignified as this might be, it could actually work.

The Northumberland cobbles were rowed this way.

They had a very deep forefoot and very shallow stern, balanced with a very deep rudder.

They did not track well when rowed bow first, despite the large deep rudder. So the rudder was un-shipped and the boat was rowed stern first. This was especially useful when coming ashore in a breaking surf.

The bow not only split the the waves, but also had the most drag, so the boat was easy to keep pointed into the waves.

With two people on board, the thwart may be two far aft.

Maybe it will be best to forget using it at all. Then it can extend across the tops of the gunwales, leaving more leg room under it.

The rowing arrangement does not have to be all that efficient to be effective. Far better to have the oar locks too high, in relation to the rower, than too low. With them too high, you might have to use shorter oars, which will be lighter and less hard on the shoulders.

I'd make the aft air box straight across, with its height level with the gunwales. This would make the boat much more stable when flooded.
You could also row, sitting on a boat cushion, or stack of them.

No matter what you design, it will not please everybody. We all have different design philosophies and different values.

 

It's a conspiracy. We all swore a Satanic oath to give you reams of contradictory advice, just for the lulz.

 

raise the boom up and go with a loose footed sail. you do not need a yoke on the end of the boom either, just use a "snoter", a lenght of rope lashing the end of the boom to the mast. you can even lower the low point of the sail on the mast, ducking under the boom is not a problem with the boom up high, you just have to duck or "sweep" under the loose foot of the sail.

the clue is attached low on the mast, and the boom attaches 3 to 4 ft higher up on the mast. than you only have to duck under the fabric lower edge. that will give you more head room and make moving back and fourth under the sail easier.

You might consider going to a scow design to get more width, it has somewhat more drag, but the extra width will give you more room inside without the extra length.

 

yes, but i remember also 2 people and the beers that they will keep in the bilge

 

Thank you for your idea, but there is no way I could fit under my weight limit with such hull. Also, a keel like this doesn't make sense in boat as small as mine. It would make beaching impossible, launching - complicated, and lots of trouble in shallow water. The CLR would be very far back... The only rig I can think of to compensate for this is massive jib with mast set aft, just in front of transom.
As for layering plywood... There is no thinner than 4mm plywood available here, and 4mm is enough as it is.
I appreciate your idea, but this is way over in another direction...

That is an interesting consideration I haven't thought of. I did calculations now to check. With two persons onboard in rowing arrangement the LCB moves 60cm back, and the transom is submerged about 1/3 of it's height. Here is a screenshot of how it would look:



So basically yes, this is an issue. Boat won't take water on, but I doubt rowing will be very effective.

With one person onboard, the LCB, in fact, stays amidships. And, with lighter displacement, neither transom nor stem is below water.

So, with one person, it is completely okay. But with two, the boat will end up as in this screenshot. Which is, of course, bad. Only that I don't know what can I do about it. In my latest hull update I made today, I widened transom somewhat, but there is not enough buoyancy aft to allow weight shift so great. To compensate for it, I'd have widen transom even more, move rocker aft, make the boat heavier as a result, and in the end, ruin it's potential when sailing.

I thought about moving thwart forward, but then it would leave even less space for bow crew member when sailing, so that's a no-go.

Sharpii2, what would you suggest?

But there is the daggerboard box in the way, so the only option is to sit on top of it... And for that, a seat is needed.

I actually thought about sailing without boom, at least upwind. One of the reasons I chose standing lug over balanced. But for downwind sailing, I need boom anyway. So maybe I should have it easily removable and attachable. Like here. This would give best of both worlds.

As for "snoter" you suggested, if I understand correctly, the boom would have to go somewhat past the mast, like in balanced lug, right? Because this is exactly what I'd like to avoid - it would be best to have end of the boom in front of the mast at all times. Is there rope-only, no-jaw solution to this?

I'll consider your advice about boom crossing part of the sail.

As for scow... Well, thanks, but this is a major re-design... And scows have lots of wetted surface compared to other types of same displacement. Isn't that contradiction to the purpose of my boat?



For now, I tried my best with current boom arrangement. Raised it 5cm up, reduced boom rake from 5° to 3°, to compensate for sail area. Now both crew members would suffer about the same fate. It reduced sail area from 7.3 to 7.27, not significant. Do I need to add more headroom?



I could probably raise the whole sail more up towards the end of the mast, but I don't know how will it set. This puzzles me still. Please, take a look at the halyard which goes from mast top to the yard. It is attached to the point of the yard which is 40% of it's length.

But will the sail set like this, exactly? Or will the yard want to swing forward, moving CE forward too? I don't know how to predict the resulting halyard angle. All I know that halyard must be attached at that point on the yard. Please, can someone help me out on this one? I've asked this before numerous times on this thread, but no one gave any advice...

 

No it won't. It will pull forwards. You can easily mock that up right now with two broomsticks and a bit of string. And while you are about it try limbo dancing under the "boom" to see how much space you need. Put a sofa next to a wall to get the hull width

Don't worry too much about theoretical CofE that will move significantly depending on sail trim and crew position

RW

 

I actually thought about cutting out 1:10 size sail from paper, adding pencils as boom and yard, and then trying to "raise" it with string on some kind of stick to see if it sets like I want it to set. Thank you for suggestion, I'll try dancing with boom.

You see, why I'm not sure about where the yard is gonna end up, is my sad experience with balanced lug last summer. When I drew the rig in computer, it seemed right. When I actually tried setting it, the yard wanted to move forward, and thus I became short of mast length to set the sail properly. I'm afraid this might happen here too.

 

Parrel beads round the mast may help

RW

 

True. But will they permit dipping the yard from one side to another? At first, I thought I should simply run halyard through block on yard, then around the mast, and connect to the end of the yard, like in GIS:



But this arrangement won't permit dipping the yard. Then I thought that maybe I don't need to lash yard to mast altogether - it should run too far away when the sail is on the good tack.

SO, would parrel beads allow dipping the yard (by partially lowering and re-raising the sail)?

 

Rowing seating arrangment

So you got the seat right over the boat's Longitudinal Center of buoyancy.

Good.

I actually thought it was forward of that, but I was looking at the boat's entire plan view, rather than its waterline. Perhaps this is why I was deceived.

Now the boat will row well with just you on board. This is good in itself.

With two people on board, you can have the rower on the thwart, and the passenger seated on the bottom of the boat, with his/her back facing the rower. This will move the aggregate CG further forward and cause less of the transom to be immersed.

This may be the best you can do, given all the other design choices you already have made.

Boat design is not just about making such choices but prioritizing them as well.

This boat is supposed to be a good sailboat, with one or two crew, for light wind sailing, on small lakes.

It was never intended to be a good rowboat.

So if it drags its transom some and has shorter than optimal oars, it will still row adequately, which is really what I think you should be aiming for.

To make it a better rowboat may well spoil other qualities you have worked hard to put in the design.

 

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