New Design for a 17' Daysailer/Racer

[brett]

Here is a roughie I just knocked up. I used a form of another boat I built scaled and teased a little. Plenty wrong with it at this point but you get the idea. I don't plan on doing anymore with it unless somebody decides to pay me. Afterall I'm entitled to make a living...

Being in the camp that has already designed, built and owned a sportsboat, I'm in the Kiss crowd. Big sails, Clean and simple layout and less mistakes. Ass. Pole hidden under the deck through the centreline. The only canting equipment on the boat. I personally wouldn't rule out Traps on this.

Brett
PS Tas. AMC. (assuming?)

[TaSSie_deVil]

Brett,

Not bad at all for a quick rescaling job. I can see a few similarities between my design and yours; namely the flared side decks, generally KISS arrangement (ignoring the canting keel idea), somewhat dinghy-like profile etc.

You assumed correctly, I do go to the AMC... hence the name.

Cheers,
T

[brett]

Originally Posted by TaSSie_deVil

Brett,
You assumed correctly, I do go to the AMC... hence the name.

Cheers,
T

Was there myself a few years back...

KISS is a really good idea when it is applied properly.For instance, using a self tending jib on this boat is important. Maximizing RM created by the two crew(who don't want trapezes) by providing maximum width carbon racks with seat backs for comfort is another simple idea when considering only two people handling a 17-18' high performance keelboat. A spin trough ahead of the forestay for ease of spin launching is a simple solution to better handling. A squarehead main could be a simple solution to improving gust response w/o a complicated rig.
But taking away at least 1/3rd of the potential RM of this boat in the name of simplicity is a false economy sentencing the hapless owner and one crew to many lackluster days on the water carrying around lead that is not paying it's own way. 33%!!!!!

[Paul B]

Originally Posted by brett

Here is a roughie I just knocked up. I used a form of another boat I built scaled and teased a little. Plenty wrong with it at this point but you get the idea. I don't plan on doing anymore with it unless somebody decides to pay me. Afterall I'm entitled to make a living...

Being in the camp that has already designed, built and owned a sportsboat, I'm in the Kiss crowd. Big sails, Clean and simple layout and less mistakes. Ass. Pole hidden under the deck through the centreline. The only canting equipment on the boat. I personally wouldn't rule out Traps on this.

Brett
PS Tas. AMC. (assuming?)

Really nice. Really, really nice. Not a scaled down K6, but I think it is a better type.

Of course you should expect payment for doing real work. However, I know many design offices "knock up" just this sort of thing quite often to show what they can do, with no particular client hooked. I doubt it pays off more than rarely. It is nice to see how people approach various problems. There's one office in the UK who has a website that shows a lot of proposals, maybe 5 to 10x the number of designs actually built. It is entertaining to look at.

Care to share what software you used to do this?

Now if only the non-KISS expert will stop posting the same platitudes over and over, and will actually address the real engineering problems with his proposal, maybe some of the KISS group might be swayed.

Or not.

[BrettM]

Originally Posted by Paul B

Really nice. Really, really nice. Not a scaled down K6, but I think it is a better type.

Of course you should expect payment for doing real work. However, I know many design offices "knock up" just this sort of thing quite often to show what they can do, with no particular client hooked. I doubt it pays off more than rarely. It is nice to see how people approach various problems. There's one office in the UK who has a website that shows a lot of proposals, maybe 5 to 10x the number of designs actually built. It is entertaining to look at.

Care to share what software you used to do this?

.

Never Seen a k6 here in OZ so no influences there. I did have a quick look on the net though.

It always make me laugh when I see a web site of some designer that has many impressive rendered images passed off as completed designs but no photos of actual boats. I believe that the only reason one would do this is if you don't have any work.

Hull was done in Maxsurf then transfered to Rhino for the cockpit and deck. Quickly Rendered using the standard Rhino render engine.

As for the RM's of different systems I might (if I have time) run some numbers on the above hull to see how some of the claims in this thread might stack up.

Brett

All of this bunch are very nice boats. Congratulations all.

Tassie Devil, I can't claim to be a designer but one thing about your hull - would the sharp chines aft be a problem when heeled? I mean it's not a dinghy, so she must heel and that heel will turn your flat U-shape into a Vee shape (more wsa, less dynamic lift etc) won't it? Isn't that why Rockets and Thompsons have very rounded sections, which turn elliptical or curved with heel? Even downwind today you're heeled under assy if there's any breeze, aren't you?

Hey Doug, the canter could be fun, but it's like having dirty big racks or a big genoa - some people like them for the extra pace, others don't like the hassle. You can be innovative and not be into canting keels; for example, I haven't got much interest in them because if I want a fast boat I don't want ANY lead.....

249, seems to me that a canting keel designed and installed properly should not be a "hassle"
in any way. It's thirty year old technology for crying out loud! This is a relatively new application and does require the use of new technology(kFOIL or fixed wings) but the result is a fairly high performance ,reliable, easy to sail boat perfectly suited to just two people-and I want one......!

[BrettM]

OK, I ran some numbers on the hull (using Hydromax)posted in the above pics. I came up with conditions that I believe are reasonable estimates and carried these through the entire analysis. For camparative purposes the basic boat weight/vcg has remained constant except for the crew a,d bulb positions.

I have simplified the report to save me some time. For those who don't know, multiplying the GZ values with displacements will give the RM value. Area 0-30 is the area under the GZ curve to 30 deg and is effectively the righting energy across the sailing range.

Principal Particulars
LOA 5.5m
Beam OA 2.2
Beam WL 1.3 (Approx)

Lightship (Unballasted) 200 kg 0.4m above base
100 kgBulb 1.5m below base
2 persons & effects @ 90 kg VCG 1.0m , TCG 1.2m (on gunwale)
Total Displacement 480 kg
LCG was adjusted to give a reasonable initial trim.

Standard Condition as above
GZ0 0.450
GZ30 0.699
Gzmax 0.747 @ 42.3 DEG
Area 0-30 18.095 MDEG

Canted Keel Condition ie bulb moved 55 deg to TCG 1.23m VCG –0.86
GZ0 0.706
GZ30 0.853
Gzmax 0.859 @ 36.1 DEG
Area 0-30 20.689 MDEG

Standard Condition, crew moved outwards 1m on trapezes
GZ0 0.825
GZ30 1.022
Gzmax 1.034 @ 36.8 DEG
Area 0-30 28.829 MDEG



Standard Condition as above but with 3 crew
Total displacement 570 kg
GZ0 0.568
GZ30 0.740
Gzmax 0.759 @ 42.3 DEG
Area 0-30 20.409 MDEG

To get RM you need to multiply GZ x displacement ie 480 kg for the 2 person conditions and 570 for the 3 person.


Have Fun!
Brett

edited, 3 person RM 0=30 (oops didn't change the value from the 2 person value)

Thanks Brett! Seems a canting keel adds a whole lot of power to carry sail compared to the two person fixed keel and it seems it would pay to keep it relatively flat maybe 15-20 degrees..

[BrettM]

Principal Particulars
LOA 5.5m
Beam OA 2.2
Beam WL 1.3 (Approx)

Lightship (Unballasted) 200 kg 0.4m above base
100 kgBulb 1.5m below base
2 persons & effects @ 90 kg VCG 1.0m , TCG 1.2m (on gunwale)
Total Displacement 480 kg

Standard Condition as above
GZ0 0.450
GZ30 0.751
Gzmax 0.814 @ 43 DEG
Area 0-30 18.928 MDEG

Canted Keel Condition ie bulb moved 55 deg to TCG 1.23m VCG –0.86
GZ0 0.706
GZ30 0.905
Gzmax 0.921 @ 37 DEG
Area 0-30 25.238 MDEG

Standard Condition - 1 crew moved outwards 1m on trapezes
GZ0 0.638
GZ30 0.913
Gzmax .953 @ 38 DEG
Area 0-30 24.297 MDEG


Standard Condition - 2 crew moved outwards 1m on trapezes
GZ0 0.825
GZ30 1.075
Gzmax 1.097 @ 38 DEG
Area 0-30 29.666 MDEG

Standard Condition – with 2 crew on wings Max beam now 3.5m
GZ0 0.694
GZ30 0.961
Gzmax .995 @ 40 DEG
Area 0-30 25.907 MDEG



Standard Condition as above but with 3 crew
GZ0 0.568
GZ30 0.794
Gzmax 0.820 @ 38 DEG
Area 0-30 21.235 MDEG

To get RM you need to multiply GZ x displacement ie 480 kg for the 2 person conditions and 570 for the 3 person.

Sorry I had to repost all this but I discovers a typo in my load conditions. All fixed now. Most numbers went up.

I think that this shows that the addition of a canting keel over a fixed one increases the GZ curve to approximately that that would be achieved by having one crew member on a trapeze. The canting Keel is slightly better in this respect than the addition of a third crew.

It is however not quite so good as the addition of wings/racks to and overall beam of 3.5m and is far behind the 2 person trapeze configuration.

In my opinion and using the facts above, a canting keel is not a cost effective or user friendly option (for this size yacht) against the additions of wings or a single trapeze.

If it were my boat twin trapezes and no lead in the keel would make it fly - but that's become a dinghy

Brett

Thanks for your work ,Brett. The facts show clearly that if you don't have a trapeze("customer" doesn't want one or two) and if your max beam is limited to around 8' the canting keel gives close to the RM of a three person boat at a substantially lighter weight and with JUST TWO PEOPLE! As I estimated in a previous post this extra power may cost around $1500US over the fixed keel but it meets the specs pretty well-and for me personally it would be well worth it. (of course the racks on my boat would have seat backs!-high comfort quotient)
With a properly designed system you have an easy to sail two person keelboat with a reliable ,quick, robust, retracting canting keel that doesn't talk back ,always shows up on time and takes minimal maintainance.And more than likely faster than any existing keelboat in ths size range.

[BrettM]

Doug,

What Customer? Have you taken a deposit for something? Perhaps you want to share some drawings/numbers of your design?

The numbers I put up show that if you start with a basic setup and decide that you want some more power, then a single trapeze, canting keel or an additional person will give approximately the same increase in RM. Bang for buck, the single trapeze is obviously at the top of the pile. Add a 2nd trapeze and you add a lot more.

On this size range boat, where the bulb weight in near to that of a moveable crew member it it simply does not pay its way. On a larger yacht or perhaps a radio controlled "toy" the tables are probably turned.

Unless one has a predetermined mindset, financial interest or loads of money to waste it is the wrong choice/reccomendation in this instance - period.

I sail a high performance sports yacht and can not see how it is such a good idea. I'm not biased, I'm merely selling fact. I'll let some others jump in and comment.

Brett

Brett, read the first post: the "customer" does not want any trapezes-not one, not two not any nor does he want a third crew-just two.
Hands down the canting keel fits the bill better than any other solution with those restrictions; your figures prove it irrefutably.
If you want to ignore the "customer's" restrictions then a foiling two person boat scaled up from a Moth might be best or an Aussie 18 or any number of currently available dinghies-BUT THAT IS NOT WHAT THE CUSTOMER WANTED.
And as I've said before this concept with a canting keel fills the bill perfectly-and as best as I can tell there is nothing like it on the market currently.
I love the concept-a two person boat with unmatched comfort and unmatched performance among keelboats in this size range.Easy to handle and big enough to take a couple of friends for a day sail.It's an exciting idea that would open up performance keelboat saling and racing to more people than ever before!

[BrettM]

Originally Posted by Cleve Motley

Anybody interested in considering a design for a new 17' daysailer/racer that's a balance between a dinghy and a sportboat? Here's the background:

I love the RS K6, and would like to see if the designers on this forum could translate a lot of the key features, performance, and looks of that design into a slightly smaller boat that two people could comfortably sail and race (as opposed to the three man crew of the K6).

Key criteria:

Light weight from state of the art materials
Lifting fin keel with bulb for stability
Kevlar glass/foam core/epoxy build
Light, blanced helm
Fast upwind
Quick to plane on a broad reach
Beautiful
Quickand easy to rig/unrig
Ergonomic cockpit design
Accessible to home builders
Carbon fiber mast and bow sprit

I'd be interested in building a prototype and seeing if it would attract any interest in my local waters (Santa Barbara). If nothing else, I'd like to build a boat that my wife and I could race on handicap that would be fun, fast, and pretty.

What do you guys think?

Thanks,
Cleve

Doug.
Can you please highlight the relevant sections in the first post saying that traps are out and canting keels are in? I do see a part about two crew members though so I'll give you that.

I do see cleve entertaining the idea a little later but only after your speech about how good your canting KFOil system is.