Mike Kajan Yacht Designs

Kajan · 01-04-2010, 07:33 AM

Quote:

Originally Posted by YachtNews

I actually love the aesthethics of the "golden nugget" minus the hull windows, that is the only thing I do not like about her. "Too close to a wedding cake?" Come on Karjan! She looks nothing like "Wedge Too" so she looks nothing like one!

The 25-meter axe-bow: wouldn't that be a pretty wet ride with an axe-bow for such a 'small boat'? I think Axe-bows work pretty well with considerably larger yachts. That's just my take on it.

Thanks, YachtNews! I wanted the hull windows to add to the elongated feel of the design, hence the stretched design of the windows, I felt that had the windows been taller, the overall appearance would have been a taller yacht.

I also wanted to design windows not too often seen that would also work with the hull design in general.

And yes, you’re probably right regarding the axe bow concept on a 25m boat.
I thought it would be interesting if perhaps a fellow YF member could shed some light on the matter.

I’m aware of the discussion held some two years ago regarding the axe bow, in the “Axe Bow / Enlarged Ship Study” thread, and I must say, it’s fantastic to see the knowledge and experience fellow members possess.

It would have been interesting if the minimum requirements regarding length, width and height of the hull, if there are any, could have been included in this discussion or is it simply a question of how wet you want to get?

Makes you wonder if there is a way of putting together a formula or chart of some kind with all the aspects such as desired speed, fuel ratio, wave height, pitch, risk of nose-diving, deflecting spray… you enter the inputs and out comes a curve or a chart with recommendations. Neat!

I mean, when is it best to go with a conventional, axe, wave piercing, bulbous or even Lars’ integrated bulbous bow, or is this just common knowledge among N/A’s, from a pure hydrodynamic point of view, all fancy above the waterline design aside?

I guess both Lars/AMG and Palmer Johnson with the latest PJ170 are on to something.

Cheers!
/Mike

Kajan · 01-05-2010, 08:32 AM

If you manage to keep the deck less wet with a less extreme bow, I guess there are other ways to get it wet.
You would probably have to keep it dry when under way but that way the jacuzzi bottom could double as a sky light.

Henning · 01-05-2010, 10:09 AM

Even without water in it, a jacuzzi is a lot of weight to put up on the bow. Also, there is no advantage to using that bow form on a planing hull boat.

Kajan · 01-05-2010, 12:55 PM

Quote:

Originally Posted by Henning

Even without water in it, a jacuzzi is a lot of weight to put up on the bow. Also, there is no advantage to using that bow form on a planing hull boat.

A typical 4 person Jacuzzi has a dry weight of about 200Kg including pumps and nozzles.
If built in carbon fiber you could probably knock some 50Kg off that weight plus the fact that you’re removing some material from the superstructure.

The net weight increase would probably be less then 100Kg = average weight of a healthy Swede.

I’m not totally convinced that it would have any serious negative effect on a 25m boat.

Regarding the lesser advantage of this particular bow, well I assume there are YF members more suited then me to take you up on that.
I wonder where builders like Mulder, Wally, Pinasse to mention a few, gets the idea that it has an advantage? Or is it simply a design trend?

Yacht News · 01-05-2010, 01:01 PM

Quote:

Originally Posted by Henning

Even without water in it, a jacuzzi is a lot of weight to put up on the bow. Also, there is no advantage to using that bow form on a planing hull boat.

Also, no water would stay in the Jacuzzi, not on a 25-meter boat unless the boat ploughed into a wave

Having it located on the bow you probably could never use the jac while underway only if your sitting at anchor or alongside or something.

Yacht News · 01-05-2010, 01:05 PM

Quote:

Originally Posted by Kajan

And yes, you’re probably right regarding the axe bow concept on a 25m boat.
I thought it would be interesting if perhaps a fellow YF member could shed some light on the matter.

I’m aware of the discussion held some two years ago regarding the axe bow, in the “Axe Bow / Enlarged Ship Study” thread, and I must say, it’s fantastic to see the knowledge and experience fellow members possess.

It would have been interesting if the minimum requirements regarding length, width and height of the hull, if there are any, could have been included in this discussion or is it simply a question of how wet you want to get?

Makes you wonder if there is a way of putting together a formula or chart of some kind with all the aspects such as desired speed, fuel ratio, wave height, pitch, risk of nose-diving, deflecting spray… you enter the inputs and out comes a curve or a chart with recommendations. Neat!

Cheers!
/Mike

Maybe if you could get ahold of info on "Predator's" tenders or interview the crew who drives them maybe you could get an idea. As far as I remember the tenders share a similar bow design to the mother boat (Predator).

Kajan · 01-05-2010, 01:14 PM

Quote:

Originally Posted by YachtNews

Also, no water would stay in the Jacuzzi, not on a 25-meter boat unless the boat ploughed into a wave

Having it located on the bow you probably could never use the jac while underway only if your sitting at anchor or alongside or something.

Quite right YachtNews, which is why I mentioned the part of keeping it dry while underway, in the post

Yacht News · 01-05-2010, 01:16 PM

Quote:

Originally Posted by Kajan

Quite right YachtNews, which is why I mentioned the part of keeping it dry while on the way, in the post

Sorry, didn't see that part, I'm busy back and forth scouring for news.

Kajan · 01-05-2010, 01:22 PM

Quote:

Originally Posted by YachtNews

Sorry, didn't see that part, I'm busy back and forth scouring for news.

No worries, mate

I'm new at this and I appreciate some healthy and hopefully constructive feed back.

Henning · 01-05-2010, 02:45 PM

Quote:

Originally Posted by Kajan

I wonder where builders like Mulder, Wally, Pinasse to mention a few, gets the idea that it has an advantage? Or is it simply a design trend?

What Mulder has a plumb bow?

As a design trend, it is one on high speed displacement boats with a narrow WL length to beam ratio. On a planing hull boat, there is no operational advantage especially if there is any flare in the deadrise.

K1W1 · 01-05-2010, 02:53 PM

Quote:

Originally Posted by YachtNews

Maybe if you could get ahold of info on "Predator's" tenders or interview the crew who drives them maybe you could get an idea. As far as I remember the tenders share a similar bow design to the mother boat (Predator).

I am sure the guy who built them - Jan Meyer would be only too happy to tell you all about them.

Kajan · 01-05-2010, 02:56 PM

Quote:

Originally Posted by Henning

What Mulder has a plumb bow?

As a design trend, it is one on high speed displacement boats with a narrow WL length to beam ratio. On a planing hull boat, there is no operational advantage especially if there is any flare in the deadrise.

Have a look at the Mulder Favorite 1400.