18ft trailerable yacht

[stubby]

Hi,

I am designing an 18'6" dinghy. I want it to be a cruiser racer, able to be single handed, but also have the ability to be fast when racing with 2 or 3 people. I have got the general lines, but I am struggling with the rest. As it needs to be easy to handle on and off the trailer, I want a centreboard that swings back into the hull, so to get sufficient righting moment, I think the centreboard needs to be steel. I also think I will have some form of ballast down the centreline of the boat on the inside.. As of now I have drawn a mast of approx 25ft, fractionally rigged, with one set of spreaders. I have a 2'6"ft bowsprit with a roller furling headsail on it, then directly off the bow I have, a stay that can be taken off, and put back on for a smaller headsail, and a storm jib. I also have a fully battened main.

Jordan

[stubby]

Ohh and I'm only new to this design stuff so constructive criticism would be appreciated.

[stubby]

And the lines plan
Note: the bottom is a flat ply panel which is why it looks like there is an extra chine, in the top view.

[bistros]

If you can succeed to meet all your design criteria, you may have a winner that will be amazingly popular.

The cold hard reality is that every boat is a collection of compromises. Sometimes you exceed some of your requirements, but usually at the expense of missing others.

The sportboat arena is active, and one of the popular homebuild options out there today is the i550 - basically dead on target for your needs, except it incorporates a retractable keel instead of centerboard. Since they were trying to answer the same questions as you, perhaps an in-depth look at their answer might be worthwhile.

From first glance, your rig seems like it might be a bit overcomplicated - although the multiple forestay option and various jib/genny options give you flexibility for conditions. The currently popular way to address this is with a retractable sprit that allows an asymmetrical spinnaker, and a single roller furling jib/genoa on the boat's bow.

Best of luck!

--
Bill

[Cheesy]

Originally Posted by bistros

If you can succeed to meet all your design criteria, you may have a winner that will be amazingly popular.

The cold hard reality is that every boat is a collection of compromises. Sometimes you exceed some of your requirements, but usually at the expense of missing others.

The sportboat arena is active, and one of the popular homebuild options out there today is the i550 - basically dead on target for your needs, except it incorporates a retractable keel instead of centerboard. Since they were trying to answer the same questions as you, perhaps an in-depth look at their answer might be worthwhile.

From first glance, your rig seems like it might be a bit overcomplicated - although the multiple forestay option and various jib/genny options give you flexibility for conditions. The currently popular way to address this is with a retractable sprit that allows an asymmetrical spinnaker, and a single roller furling jib/genoa on the boat's bow.

Best of luck!

--
Bill

Most of the small sport boats in NZ at least dont even use a furler, just the retractable prod with a dirty big asymmetrical. At the moment the faster boats have also gone the light weight relativley small rig way as opposed to a large sail plan and large bulb

[bistros]

Originally Posted by Cheesy

Most of the small sport boats in NZ at least dont even use a furler, just the retractable prod with a dirty big asymmetrical. At the moment the faster boats have also gone the light weight relativley small rig way as opposed to a large sail plan and large bulb

It's really hard to evaluate the design priorities of someone else, especially based on a couple sentences on a forum. I'd agree that light and simple are really important - especially in a boat that will be trailered and moved about.

I'd certainly not discount a retractable keel - better hydrodynamics, better weight placement and just about as easy to deal with as a steel plate centerboard. With a proper trailer that allows bulb-up trailing, I much rather have the keel than a heavy plate centerboard.

The sportboat fleet at my club is certainly growing, while most other wet-sailed boats are declining.

--
Bill

[Cheesy]

I guess another consequence of the lighter boat/ smaller rig is the ease of stepping the mast and rigging etc On the Shaw 650 we used to use the main halyard to lift the keel.

The i550 does look like it might almost fit the bill here but for some people half the fun is in designing the boat as well

[stubby]

For me, the think is designing my own boat, as I want to do Naval Architecture in uni. And as I am homeschooling, I don't do VCE, instead I got strait to the uni, with designs and try show them I deserve to be in the course.

I did have a friend say he would go for a retractable keel, so I'll draw it up with that and see how it looks. The way I see it with the second stay, is it allows more sails for different conditions, so having this could be advantageous while single handing it. Again with the furler, I want that for the single handed aspect, as I want to stay off the bow as much as possible(I want to be on the boat not behind it floating away). The bowsprit will allow a bigger Genoa for light conditions, and it has the "cool factor", but I have considered a retractable one from that for the genny.

[stubby]

Also I have looked at the i550 but its all speed, and I don't think it would be any good for single handing, I tried to keep my boat beamy, but with a sharp entrance for upwind performance. I'll also draw it up with only a retractable bowsprit and see how it looks.

[raw]

whilst not wanting to damp your enthusiam, you are better off impressing the uni's with your math's, physics and english abilities than a bunch of pencil drawings.

Naval architecture is 95% about calculations. The drawing part you can pick up. Study hard.

[stubby]

Yes I appreciate that, but I also enjoy designing my own boats, and I like the challenge of it.

[Munter]

Good luck with your project. I used to want to train as a naval architect but decided not to after working in the marine industry for months before uni began. I realised that unless I was particularly lucky (or talented), I was probably going to end up designing power/military vessels instead of the sailboats and skiffs I was interested in. It was this realisation that made me reconsider and study a different field of engineering instead. Sail is still the preferred hobby but it is now completely separate to my work.

[stubby]

I have seen bowsprits that don't retract into the boat, but instead fold round the side. My question is how is this done, as I believe it would free up space in the cabin, and it could be pulled to windward a bit to make the genny mare effective. Also I think I will put the mast in a turnbuckle(I think thats what its called), this will make it easier to put up for me as I'm only 16 and not exactly large, but also for other people. But also I will be able to lower it with ease to go under low bridges, I particularly want this because my probable launching place has a low bridge.

[stubby]

OK, I have drawn it with a drop keel it seem ok, but it has to be positioned just behind the cabin entrance. So I took the bowsprit off and move the jib onto the bow, so now that makes it further back, luckily this has put the where the CE should be right over the keel.

[stubby]

BUT, I'm thinking to create room in the cabin I don't want the genny pole stowing inside it, so I think a genny pole that swings round the side would work best. BUT I don't know do they do that so would someone know how they do that?