Hull Shape as Keel

[Fanie]

Sorry guys, for some reason my e-mail does not respond when someone post to a subscribed topic...

Thanks oldsailor, I have actually seen a few boats beside the link to Richard's Janus that have flat bottoms... probably from Richards designs too. The trimaran I built for testing a few things with have a round bottom... and is terrible to walk on. Given enough power those flat bottoms may well plane

Cp..I will investigate. Mine is over at 0.6799... whatever that means... boat ends not full enough.

I have actually have everything roughly worked out, from fluids to storage to fishing tackle and berthing, so this is the third time I'm changing it quite a bit. Not the end though, probably will change a couple of times again.

You all have to keep in mind, this is a holiday vehicle. Couple of times a year we go fishing somewhere, throw a bunch of stuff together and we're off. Probably won't be going to the sea every time, but for when we do it must be 100%.

The stuff we take are basic - food, drink, tackle. No pot plants and no growing tomatoes (he-he waterworld), so everything is simple. There may be times the wives would join us on the occasional trip, so it mustn't be so bare and rough that they won't enjoy it either... small microwave with inverter, couple of solars, gas stove. Simple, neat, functional, safe and comfortable and of course so it won't fall over

Also. I have no sailing vessel experience... with power boating I'm ok, but it's different since they use less funny names for things and there's less things to trim and fiddle with Patience, I'm getting there. Have to find out how things work, from sails to winches to clamcleats to...

Good luck

Thanks Richard, at times I feel like I need a miracle...

Anazingly, the guys in waterworld never seemed to have bad weater...

[Nordic Cat]

Fanie, the high Cp means that the ends are very full (the underwater part)

The better she sails, the more fun you will have, and if she is seaworthy, she might carry you out of that place when they start behaving like Uncle Bob up north

Keepup the hard work, you are getting there.

Regards

Alan

[Fanie]

Hi Alan,

What does it mean if you say the underwater part ends are very full ?

As for the boat, I'm beginning to dream about the blooming thing now, like when you sleep and you dream... Couple of things has to happen here before I can up and just build it, but she will be sea worthy. Who knows, we may end up fishing from it Oh, you can learn

[terhohalme]

Fanie, you can start here:

http://www.oneoceankayaks.com/smhydro/hydro.htm#loa

Not particularly for multihulls, but the parameters (and terms) are same.

[Spiv]

Originally Posted by Meanz Beanz

If you ever did manage to stick that bow fully underwater it would act as a bit of a plow once you over came the reserve buoyancy and it would contribute to pitchpoling.....

Originally Posted by Nordic Cat

I don't like the bows, same comment as MB above, also i would make the flare curve softer in the vertical part to avoid annoying wave slap.

Hi Fanie,
as stated by MB and Alan, having wide, flat decks can be dangerous.
Out there there is a wave that WILL get over any bow. If the bow is rounded or thin on top as well as below, It will slice through the wave and re-emerge.
It is good to have buoyancy in the bows, but more in the middle rather than up on top.
The other way to do this is to make the bows longer, but you cannot do that as the boat would be too long to tow.

[Fanie]

Hi Stefano,

The idea was that the decks are rounded on top so water would run off it. Flat flat decks would be a problem, even for me. I cannot widen the hulls more than what would be allowed on a trailer, so they are long and relative slim.

The hull keels are not flat in the front. They taper down towards the rear and downward so they would - that's the theory anyway - act as a foil that would force the bows up. Hulls don't burry when there's no movement. When there's movement the more the better the foils would work. If I have it wrong, someone should explain to me why not. Please and thank you

I'm not sure how it would contribute to pitch-polling, the whole water line length widens to full width above the waterline.

I can lengthen the bows, problem is not the towing. I don't have space to build a longer boat. I would love to build a 12M instead of a 10m, but I can only get a 10m in here.

[Fanie]

I admit the front would give a more bumpy ride, be like a cathedral hull VS a V hull. I haven't finished it yet, and I do consider what you guys offer as advice. Will play with it some more.

Keep critisizing - it helps.

Thanks.