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#34592 - 06/25/04 08:42 PM Re: Designing the next F14 ***** [Re: Darryl_Barrett]  
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South Australia
It's not a bad thumb of rule that on a cat you keep the spinnaker just a few sq ft smaller than your working sail area
Remember that unlike cars "more horse power" does not always make a boat go faster. You still have to be able to control all the power (and through a wide range of conditions as well)
Darryl

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#34593 - 06/25/04 08:47 PM Re: Designing the next F14 [Re: Wouter]  
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What are you doing up at this time of night WOUTER (in Holland) did you get my email?? and the attachment??.
I'm sure that Berny will answer, but I think he is running over 140 sq ft of main sail on the 430. It is a little large for my liking but it all seems to work fairly well on his cat.
Darryl

#34594 - 06/25/04 09:10 PM Re: Designing the next F14 [Re: Darryl_Barrett]  
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Wouter Offline
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Wouter  Offline
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North-West Europe


I just spoke to Greg Goodall who is here in NL and after that I dug out my boat that was underneath 300 mm of sand. We had a big storm going over our coastline for the last 2.5 days and I feared my boat got damaged. The hulls are okay but I fear the trampoline has been stretched to its extreme. There was 200 mm of sand on it and as it had rained as well it was waterlogged. Dry sand is given as 1600 kg /m^3. I calculate that some 1.91*1.81* 0,20 * 1600 = 1087 kg !!! was lying on my trampoline. I took it off very carefully. The Trampoline is hard now as all the elasticity has gone and it almost behaves like a hard plate shaped to a 3D shape. I hope it either resumes it manufactured shape over the next couple of days as platics sometimes do or else that I can get it within acceptable parameters again by pulling on some tension strings. Else I'll have a problem for the coming event I'm organising.

Will read your mail now !

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#34595 - 06/26/04 01:37 AM Re: Designing the next F14 [Re: Wouter]  
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Berny Offline
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Quote


Okay I'll bite ; how much sail area is on your 430 ?

Wouter


My previous quote gives a clue
Bern

Oh, I should also have said the boat's presently uni-rigged

Attached Files
34751-430@crsc7.jpg (455 downloads)
#34596 - 07/05/04 04:27 PM Re: Designing the next F14 [Re: Berny]  
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Where are you up to with this Brian? I note discussion has stalled. Did you get the help you needed?
Bern

#34597 - 07/15/04 02:52 PM Re: Designing the next F14 [Re: Berny]  
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Here's the profile drawing of the "Freestyle 14". It's taken three drafts to get to this point. If you have difficulty seeing the measuring lines, here's some points of reference:
The transom is 1' tall, the tallest section of the hull is 2'6" tall. Along the bottom is 14' with the curve of the bow accounting for the extra 3".
Freestyle 14 profile view

No cross-sections just yet. I need to get some side-walk chalk and a long timber batten to help me figure out some things. Such are my tools



G-Cat 5.7M #583 (sail # currently 100) in Bradenton, FL Hobie 14T
#34598 - 07/27/04 11:54 AM Re: Designing the next F14 [Re: Sycho15]  
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jollyrodgers Offline
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maui
Hello,
you originally asked about rocker. It's a very important curve. Yours looks allitle flat forward and maybe too curved in the last 18"...or did you invent a most superior rocker?
It would be cool if there were a data base of the various rocker curves of existing cats. A data base of the rest of their features like mast height, hull volume would be good too. Guessing that the Texel guys must has some of this data to create their #s.
it's just that a visual curve is good as a spark to the imagination. Maybe if we posted pictures of the side of our hulls we could vectorize the profiles and get the rocker curves.

Because we use alot of it, i would shape the hulls from styro to test different hulls.
the whole project is for those with free time and money to play with.
have fun with it.

#34599 - 08/04/04 03:16 PM Re: Designing the next F14 [Re: jollyrodgers]  
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I would certainly appreciate some help with the rocker design. Some measurements off a board boat would be helpful. Here's how they would be useful:

Length of waterline of boat measured.
On a flat surface: set the boat so the bow and stern of equal height above the surface and measure that height, as well as what part of the hull is in contact with the ground.

For example: A Prindle 19 has about 18'9" of waterline. If the bow and stern were each 2" off the ground, the section of the hull touching the ground would be 8' from the stern.
(The above example was total random guesstimation, but information in that format would be helpful to me.)

Or... if you can use some sort of board or chalk-line... make a line from the bottom of the bow to the bottom of the stern, and measure the deepest part of the hull and it's location relative to the stern.


G-Cat 5.7M #583 (sail # currently 100) in Bradenton, FL Hobie 14T
#34600 - 09/28/04 08:03 PM Re: Wanna help design the next F14? [Re: Darryl_Barrett]  
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beddoe Offline
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Hey,
The best thing to do if you really want to design a boat is look at what makes other boats so good. Is the Flyer really that much better than Goodall and Boyer's mach4 or is it just that all the quick guys Like Ashby and Bags sail flyers. One of the most successfull cats of the last two decades in australian quick cats would have to be the taipan 4.9. Still considered by some as the bees knees. It's greatest point was matching aesthetics with speed and balance, and for the time it came out it was miles ahead of the pack. If you look closely at a taipan you will notice that the butt end resembles very much a mosquito, which boyer was still building at the time of inception. and the front looks a mighty lot like an early A class. The reason they didn't just scale down an A class is that there isn't enough bouyancy for two people with the A hull.

You must remember to take into account things like change in bouyancy when looking at other designs for inspiration. If you down scale a Flyer hull, which seems like a good idea, keap in mind this amount of bouyancy was made to hold up one bloke and 76kg of boat. Not a whole heap in my book, seeing as I build 3500kg bluewater cruising cats. If you down scale something like a Flyer or another A you will lose bouyancy, and the hulls will dig in more unless you're a midget or a pygmy, no offence to m's and p's.

Don't jump in the deep end with this, talk to lots of people about this. People who know what they're talking about. If you can get a hold of guys who have built prototypes before talk to them about what went wrong and then don't add that to your design. prototypes take time. The first AHPC F18 capricorn took about 12 months to make it to the water.

One thing you might like to know. A guy buy the name of Russell Denholm who has won every class in the Taipan classes, 5.7, 4.9sloop, 4.9cat, the only other to do so was Glenn Ashby. Russell has built an A class catamaran that from a birds eye view looks like a foil. the widest part of the hull being just forward of the front beam. It was much quicker than any of the top A boys on their Flyers bot the thing couldn't turn. This problem will be solved with the next prototype to be finished soon. You may also have to do this yourself. Maybe 2 or 3. Remember also, you dagger boards should sit equal with the draft of your mainsail. Meaning the deepest part of the main. Papertigers have altered their center of effort over time using foil rake, to mave the COE back as masts became rakier and rakier.

You will need to keap everything in mind. Keap looking at other boats of all sizes for ideas though. You may have to name it after the huge number of boats you stole ideas from.

Beddoe(wookie)

#34601 - 11/27/04 01:11 PM Re: Wanna help design the next F14? [Re: beddoe]  
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Sycho15 Offline
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Here is the latest-and-greatest attempt at the profile view of the Freestyle 14 catamaran. I've been to a few regattas lately and sailed on a couple spinnaker boats and have been taking notes on their hull designs. [note: this picture is not exactly level]

[Linked Image]

Comments and critiques would be greatly appreciated!


G-Cat 5.7M #583 (sail # currently 100) in Bradenton, FL Hobie 14T
#34602 - 11/27/04 10:13 PM Re: Wanna help design the next F14? [Re: Sycho15]  
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Conrad Q Offline
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Alberta, Canada
The 2'6" deep hull is way too deep. THe Tornado is only about 24" deep, and you are only going to be hauling 1 person and a 150 lb boat. At one time, I had 800 lbs of crew on my 360lb T and was out in big wind, and had a problem smacking beams on 3' waves then, but you should not with 350 lbs total. You need to be careful with the volume up front. I did not do that on an A that I built (it had the max width nearly straight from the front to the 9 ft mark), and the hulls were real prone to go nose down so had to cut the bottoms off and spread them a bit. Then the next bottom was too fat up front... both great (if expensive) learning experiences. So that is 2 mistakes I will not have to make next time You will likely also want a bit of rocker on the front of the hull so that it will turn easier, like in the first 2 ft. I honestly beleive that the extreme rocker that you have on the back of your hull will cause you to go slow, by making the hulls drag along too much water. Go take a long look at a T which is a superbly designed boat, even though old. Plus take a look at the Flyer if you can find one. The back half of the hulls are a nearly flat line: meaning all the rocker curve is near the middle of the boat. My personal opinion is that the straight rocker on the back sections are required for good speed, and my next A-cat will have that trait.

If it were me building this hull, with only 14 ft to work with, I would make a high aspect ratio mainsail, using the 26 foot Carbon fibre mast as quoted. I would make the sail a square top main with about a 5.5 ft chord that would continue for a good distance up the mast and then taper to 2 ft square top. I would put a circular traveler on it, and put the rear beam about 1'8" from the rear of the hulls, so that you can have atleast a 1'4" arm on the tillers. If you use a 6 inch chord wingmast with the pivot about 2 inches from the front of the mast, the center of your main beam would be about 5'7" from the center of the rear beam if you put the traveler on top of your rear beam. Personally I would make the hulls about 13 or 14 inches wide at the top in a tapered shape similar to the T at the middle and then taper to about 10 inches wide at the transom. I am also now a big fan of the tapered top on the front of a hull that Bill Roberts pioneered, leaving the thickest part of the hull in the middle. The Taipan 4.9 does this a bit on the very front of its hull, too, and that is a great little boat.

Maybe if I remember this thread while at home, I will draft up something that I would consider way better than what you designed and post it. It only takes about an hour now after having done so many versions of the A-Cat.

#34603 - 11/28/04 12:29 AM Re: Wanna help design the next F14? [Re: Conrad Q]  
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I think the 14 needs to be re-thought and radical (especialy if it is someone else's time and money?)
I would try deep hulls so the boat is less prone to hobby horsing (short shallow hulls will be a disaster in this regard, even though there may be strong arguments to support planing hulls)
This could be countered with a mast well aft and large rudders, no centerboards. While twitchy and not easy to "get rolling" the boat would tack and drive really well. A cable type traveller "track" for the mainsheet from rudder gudgeon to rudder gudgeon? I believe that in the real world of chop-whenever-it-blows any, the extra wetted surface of narrow deep hulls would pay off in fore-aft stability (not "shaking the wind out the sails")
Mast aft also reduces pitch poling off the wind. While the moment produced is unchanged (center of effort is still acting at same height) the mast weight and inertia are further aft which effects the countering moment and response time.
Maybe a longitudinal center beam from fore to aft crossbeams with multiple mast ball mounting holes and multiple shroud plate mountings at the hull fabrication stage would be reasonably cheap to do, and you could learn a lot fast. Maybe you could do without a hooter pole, a savings in itself? if the mast was way back.

#34604 - 11/28/04 01:44 AM Re: Wanna help design the next F14? [Re: davidtilley]  
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Are either of you familiar with the Formula 14 class specs? We've got 14'3" of waterline to play with, and 300 sq.ft. of sail. Running without the reacher isn't even being considered, especially after the H14Ms showing at Spring Fever 2004.

In the picture, the mast is shown with no rake because it was easier to draw it that way; it will be raked back a bit. The mainsail area is ~140sq.ft. The reacher will likely be the same.

The hull rocker more closely resembles the AHCP Capricorn and a few other F18s I've looked at. I only have 14'3" to work with, so I can't have the long clean straight lines they get. I have that steep rocker in the back so I can really leverage myself off the stern of the boat to keep the bows up without too much bouyancy fighting against me.

I haven't done cross-sections yet, but the hulls will have a high Cp, with the volume down very low. The bows will curve back together at the top, with pretty much no flat deck ahead of the mast beam. The reason for the tall bows is to allow me to create this curved section without compromising the shape, and to give me the extra "stuff it" ability in heavy air while carrying the reacher. It shouldn't add much weight at all, and the extra windage should be minimized by the curved shape.

On the off-chance you didn't notice, clicking on the picture takes you to a much larger version.


G-Cat 5.7M #583 (sail # currently 100) in Bradenton, FL Hobie 14T
#34605 - 11/28/04 01:19 PM Re: Wanna help design the next F14? [Re: Sycho15]  
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Concerning the rake aft of the knuckle:
The water only knows its relative speed to the hull. Therefore if the rake here is steeper than other boats of comparable speed, who have it figured out, it will be draggy (want to detach, but can't) Bernouli says the decrease in velocity must cause an increase in pressure, so the water slows to fill the hole, and its surface climbs to correspond with the increase in pressure. Now if the boat is past its hull speed, the former bow wave or trough may be back here, and so what happens then?
Personally, I theorise that rocker has no place in a short fast boat, and turning ability has to be achieved by other means. (ref previous poster) This leads to a canoe stern below waterline at keel-line elevation(bottom of boat) and a wedge shape in plan at deck elevation ( no reverse taper to stern, but taperd all the way to the bow from stern). If you can accept dxf or dwg files, I will send you an iso of one I worked out. Basicly a minimum drag at keeline, transitioning to min waveform at waterline. (Built a 1:10 model of hull form and then got side tracked)

#34606 - 11/29/04 01:26 AM Re: Wanna help design the next F14? [Re: davidtilley]  
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ABC Offline
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Canberra, Australia
Hi guys,

Sorry to jump in on your topic, just came across it and had a few thoughts.

Perhaps you should be looking at other high performance short boats like the Moth. As you're dealing with a very short hull length and a conceivably very high power to weight ratio, perhaps there is potential to have quite a flat bottom (in terms of rocker) that is only very narrow in width (ie 150mm) that has a flat bottomed planing area?

Two Moths strapped together with a nice big powerful rig on them is a very interesting prospect indeed. Pity they're only 11ft long.


Taipan 4.9 AUS129 AlphabetSoup
#34607 - 11/30/04 07:28 PM Re: Wanna help design the next F14? [Re: ABC]  
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#34608 - 11/30/04 08:10 PM Re: Wanna help design the next F14? [Re: Darryl_Barrett]  
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#34609 - 11/30/04 09:01 PM Re: Wanna help design the next F14? [Re: Darryl_Barrett]  
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ABC Offline
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Yep, ok. feeling pretty dumb about now will do some more research before posting next time so I know what I'm talking about.

Looks like a great little boat Darryl, rake the mast a little, and whack a kite on the front and lock the feet in some footstraps down the back and off we go!

Sorry if I'm igniting the spinnaker debate again but 14ft is probably the right size for single handed with kite - get a bit intimidated by my Taipan with kite solo (with my crew its not too bad).

Have fun guys! I'll pop in from time to time and see how things are going.

Andy.


Taipan 4.9 AUS129 AlphabetSoup
#34610 - 11/30/04 09:42 PM Re: Wanna help design the next F14? [Re: ABC]  
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If you notice on one of the photos there is a little black cylindrical fitting of delrin in the middle of the front beam in front of the mast base! thats the supporting base for the carbon spinnaker pole (which is standard -thats why it is an F14!!). There wasn't any wind whatsoever on Saturday the 27th of November (when the shots were taken) so not only did we not sail but it seemed a little premature to rig up the spinnaker?

#34611 - 11/30/04 11:36 PM Re: Wanna help design the next F14? [Re: Darryl_Barrett]  
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Bradenton, FL
Very nice boat Darryl! Have you tested it much yet?

To the person comparing a Tornado to the F14, especially regarding the bow height, please remember that you have two men almost 20' from the bow of that boat which gives you a whole lot more leverage than a single person only 14' away. Especially considering the F14 is aimed at lighter crews. The heavier guys would likely be on an I17. We'd like to see the F14 class be able to cater to women and children as well as the rest of us, and are designing accordingly. I'm doing everything I can think of to keep this little boat of mine from ever wanting to pitchpole.

Shouldn't the Capricorn be slower than other boats in it's class, as it also has a lot of rocker in the stern while many other boats in it's class don't. Instead, it's kicking butt and taking names. However... I'm working on a drawing that will reduce the aft rocker to 6" instead of 12" by having the deck drop by 6" after the rear beam... I'll be posting a new drawing tomorrow (Wednesday)


G-Cat 5.7M #583 (sail # currently 100) in Bradenton, FL Hobie 14T
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