: Kris,

: First of all thanks for that nice modified wireframe model, it looks pretty
: cool. You beat me to the punch, I don't have time until this weekend. Very
: nice.

That's just a very quick 2D drawing done on top of your image.

: Just because I can't use KAPER to prove you are wrong does not mean that you
: are right.

I'm not making my arguments in relation to KAPER, or any numbers at all. What I'm saying it the same if we were living in mud huts and making these from twigs. A 3D flow simulation would be nice to see - but I think that would be serious overkill.

Since you have modeling capabilities - for the umpteenth time - slice your model into buttock lines (will have to be closely spaced so at least one falls the the problem area and can show it) - and also take slices from the waterplane down (also at small intervals). These will cover the two axis not described by your forms. Water is 3D, so you need to look at x, y, & Z sections to see this stuff (if you can't see it just looking at the hull form).

If you can export to some standard CAD format I could try to do it, since you seem to need me to provide some sort of computer derived evidence (and if I'm wrong - even better, right?).

: Or that I am for that matter. Your argument that a sharp chine
: leads to turbulence is not convincing to me. It is just your intuition..

No, it's not intuition at all. Water flowing over or across edges (not along them - which is fine) will create turbulence.

: If
: KAPER can't resolve it we need to find fluid dynamics software but frankly
: that is more than what I want to take on now.

Flipping your previous effort over and taking a garden hose to it might even show this.

: For pure speed you would indeed want a QCC type of shape.

Actually, the QCC is more of an all-arounder that happens to be pretty fast. It was designed as an efficient gear hauler with good manners, not as a racer. Look at some race kayaks and Surf Skis (and if you can't see the differences from a QCC 700 hull - then I'll know to stop discussing this stuff with you).

: BTW not all SOTs
: are created equal. MIne is the Wilderness Systems Freedom, one of the
: fastest ones around. It is relatively fast but I would have to do the
: compariaon again, it has been a while.

Many love(d) the Freedom, but I found the Tarpon 160 faster for me - and to have MUCH better handling. Also, despite what you are seeing when you look at images of it, the Freedom's hull is not formed the way yours is.

OK, so here I think we have major problem #1 - your choice of reference examples. Freedom is an OK SOT, but seems a poor example to use to design a narrow 19' SINK. Comparing your latest 19' footer to Anas and Nordy (excellent sea kayaks - I've paddled a Nordy (and an LV) briefly and used to own an older Pintail, close Anas cousin) will also lead you to limited and potentially erroneous assumptions. Have you paddles either of these?

: A sharp chine has some other advantages like cutting through waves without
: much pitch and tracking without much yaw.

The chine you have amidships that parallels the flow, sure - attribute whatever mythical powers to the edges you like And note I kept to that part as much as possible on the drawing). What I'm talking about are the terminations and how they turn across the flow.

: You don't bring in any convincing arguments other than your experience. I am
: really interested in the physics and modeling and would like to know how
: this works out mathematically not intuitively.

Not convincing to you, so apologies for my poor communication skills, but obvious to me (only question remaining for me being to what degree this impacts performance - and if at your skill/experience/intended use it even matters).

Mathematically? Intuitively? How about real world on water??? Experience and intuition are quite different things.

: Only my own, and a CD one time I believe the Extreme.

So there we have major problem #2 - you are essentially designing in a vacuum. You need to go and paddle as many different kayaks as you can, in whatever variety of conditions you can. Some with performance like you want, and others very different. Are there car designers who've only drive two cars (one of which they made)? Furniture designers who've only sat on two chairs (one of which they made)? Of course not. The only place you're likely to find a lot of people designing vehicles with little or no experience actually operating them, and doing some of it on proprietary in-house designed software, is one of the space agencies like NASA or ESA. Kayaks aren't rocket science.

On the theory side - have you at least read "Shape of the Canoe" by Winters?

: You may very well be right but you seem pretty religious about it.

I don't care if I'm "right", my interest is in the design. I simply see something that catches my eye as it does not look right to me (and have reasons why that are not merely "intuition") - and think I can either learning something myself and/or maybe getting you a better result because of it.

: The two
: different designs that we are talking about basically only differ in flare
: so how different can it be.

The flare should be unchanged! You're really not getting this. It's about cleaning up your lines - not altering the overall specs. LOOK at my drawing - it has the SAME flare. I took it straight off of your lines. Only the panels creating basically the same overall form are changed - so their joining/blending - is altered -and put more in line with the flow.

: If there are differences, each shape is
: probably better at something. Maybe I will build one your way too, in fact
: I would like to have one at my new workplace which is right on the water.

Well, now I'm jealous, as I'm currently without any workspace other than outside. Bet my water's warmer though!

What you done so far have looks really good - and is really impressive - except those crazy chines! *L* (maybe that's why I seem "religious" - or even care. That one thing is just not at the level of everything else).

All this stuff is for fun - and I certainly don't mean to lessen yours! I give you HUGE points for being original Henk - but the flip side of that is with almost no frame of reference, and using a program you created yourself, you really have little choice but to be original!

Something very cool in all of that - something I like about that almost clean slate approach - but it's not necessarily an effective way to design boats. There is so much information, so many good tools available, and so many great examples to reference, it makes little sense not to avail yourself of them (sorry, most are NOT mathematical - at least not technically speaking). I'm not really claiming any expertise in these areas either, and so I'm just sharing the same sort of advice I apply myself.

Kris

PS - Nothing personal in any of this, and I'm singling you out so much as I'm using this to kill time during a slow period at work.