faster backwards

[grob]

skippy

"the pointy bow won't prevent you from getting lift"

I agree, but I don't beleive the pointy hulls do it as efficiently as the aerofoil shaped ones.

[nero]

If I had the free money, I would have ordered plans from Shuttleworth two years ago. Unfortunantly, at that time I had no idea of what I wanted or what was a good cat. ... still am a bit unstable smile.

I also like the Dazcat 14m and 15 racer. Kurt Hughes has a few older designs that I flashed on earlier also. Hughes prices are tempting.

The light bulb hull allows larger feeling living space inside the hull. It has many disadvantages also.

A hull like this makes the boat a lot wider for a given distance between the hull center lines. So a thin hull cat with hulls set wider would be more stable.

The inside floor space is not as wide. The storage is either below the floors or above the dwl by 70 cm. There is not much space below the counter tops.

But it looks cool. And should ride the waves nicely.

thanks again everyone for the advice.

[brian eiland]

I continuosly marvel at the many french (and european cats) with those fat plum bows. I just returned from the miami show where almost every cat had those plum bows....plum bows and a straight-line sheer. Catamarans are already boxy looking on their own without adding to this uglyness with more boxy lines.

Is there some sort of competition to see how much accomodation one can fit into the shortest length vessel? No, I understand the desire to limit the overhang of the bow on the racing vessels, but certainly this shouldn't be extended to the cruising vessels.

And not only the plum bow, but the very fat ones at that!! Take a look at any of these fat bows plowing along, and then look at the gunboat cat bows. You don;t even have to tank test this to determine which is more efficient. The ONLY reasons for these fat bows might be the difficultly during manufacturing to glass the inside surface, and/or to provide extra bouyancy up front. At any rate the fat, plum bow shape is a very poor choice!!

And WET!!, look at that water level climb up the fat, plum, bows and where is all of that 'above-free-surface-water' going to end up.....spray over the trailing portions of the vessel!!

And please learn somthing from the Prout example, as well as many other double-ended monohulls....get them pitching ever so slightly, and it will esculate without sufficient dampening....and you will soon loose all drive from your sails due to the oscillations of the mast.

[Skippy]

grob: "I agree, but I don't beleive the pointy hulls [generate lift] as efficiently as the aerofoil shaped ones."

Grob, I think your point goes directly to the heart of the matter. What is it about the shape of a foil that generates lift? I'm not convinced that it's the blunt leading edge, because even a submarine hull is blunt, and as far as I know, that doesn't generate lift at all. What it has in common with foils is that it's submerged.

I can see that the flow into the bow of your hull will be from an angle rather from dead ahead, so it might be turbulent around a standard bow. But let me make one WAG here: Suppose you had an asymmetric hull designed for one tack only, maybe even a specific speed. I think the best bow would be a pointy shape turned into the water flow rather than straight ahead. In fact, if you look at the traditional proa hull, it looks a lot like that. Dealing with both tacks is certainly more difficult, and maybe some rounding helps. But I would be careful about taking the foil comparison too far.

[nero]

Breaking out the sander tomorrow. I will fair the lower bows out to a point ... looking from the deck down to the waterline.

From the side view I am content. The bow is not exactly plumb. It was generated from a sweep of the hull profile and then messaged into a fair line with the sides from a top and side view. The hugh bow wave riding up the front of the bow at present is spread out like a fan in front of the boat. Simular to what the game fishing boats on the east coast do.

If I can split that wave with a sharp axe edge ... a dull axe edge then the wave should disappear.

My motivation for a rounded front edge was to limit damage from collision. The 50 cm of foam will take most of the energy.

Unfortunantly, Marseille is being hit by snow and cold weather this week. Not sure when I will get the next no wind sunny day.

Also have a waterheater to replace. frown

[nero]

Okay here is the new photo of the sharpened bows. After looking at my model in TouchCAD, I realized that my designed bow fronts were some where in between the present and the first attempt.

Will test them soon to find out what the differences are.

[nero]

Photos doesn't represent the sharpness of the bow. It is has a 2 mm edge that goes up just below the bulge upper part.

[nero]

Tested the new bow this evening. The forward-flowing fountain bow wave is gone. Yehhhhh! the boat cuts well thru the waves.

Thanks everyone

[brian eiland]

Originally Posted by brian eiland

Take a look at any of these fat bows plowing along, and then look at the gunboat cat bows. You don;t even have to tank test this to determine which is more efficient. The ONLY reasons for these fat bows might be the difficultly during manufacturing to glass the inside surface, and/or to provide extra bouyancy up front. At any rate the fat, plum bow shape is a very poor choice!!

And WET!!, look at that water level climb up the fat, plum, bows and where is all of that 'above-free-surface-water' going to end up.....spray over the trailing portions of the vessel!!

Just happened across a few photo examples of fat bows.

Think about it, if one was looking to get this much bouyancy up front, then make this fat cross-section shape a flat plate, internal 'collision bulkhead', and then add a pretty flair shaped sacrificial bow piece onto the front of this bulkhead....maybe even some of the newer elastomer materials.