Z40 Roadster (Its a sailboat, not a car)

[Inquisitor]

Good Reading (continued)

passed away also but here a very good article on cat hull shape from malcolm tennant http://www.catamarans.com/news/2006/04/CatComparison.asp
of the net now but if you havent allready seen it have a look at freds calculator zip

I read the first document. A couple of years back, I momentarily flirted with the idea of building planing hull for the Z40 Roadster. I had seen some pictures of Yves Parlier’s “Médiatis Région Aquitaine” I was pretty excited about it and why not... catamaran, biplane rig and FAST! I finally decided against it when I read the details of how hard it is to sail. Definitely put it out of the single handing concept... and I'd have to live with the harsher ride of the planing hulls.

The software, I'll have to get my home computer cranked up with some Java on it and see that. From what I could read, it looks like it may be very helpful.

Thanks yipster!

 

[tom28571]

Cat/Tri religion - Many prefer tri's, I just prefer cats.

I can definitely imagine a tri being easier to launch/trailer. F39 comes to mind. However the single hull is narrower than my Mac 26 and I find it more like camping. Yes it has more room than a single cat hull, but the cat hulls are for guests, children and eventually grand children… They’ll just have to rough it! But they can rough it SEPERATELY. Also with all the articulations of the alma arms makes for one hell of a mess trying to put a full width bridge deck on it. With anything less than canvas ala pop-up camper.

I'd rather spend the day assembling it and living on it (maybe years) than deploying in minutes and HAVING to live with the smallness of the tri.


Vaporware... promise everything, convince them its real... and deliver when we damn well please! The Microsoft motto.
Beside, maybe I get buidling and you'll have to come down and help sand some glass with me. Yeah... right!


Do you have any references? I'd really like to follow up on that. Maybe they'll convince me it sails like...

Thanks Tom.

I think there are other factors relating to room in each of these different boats to consider but ultimately personal preference will play a large part. I am not firmly in either camp but have had more experience with tris. One unorthodox type of tri is the Pacific Banca although it is more of a motorboat.
http://www.stockphotography.co.uk/store/Zoom.aspx?prodid=13395

I gave up trying to make one boat do all things some time ago and now have about 7 or 8 boats around here and still have only a small part of possibilities covered.

The only place that I remember definitely seeing a sail rig similar to yours was in an AYRS (Amateur Yacht Research Society) publication about 25 years ago. There have been others but they escape my recall. I can understand why you need a rig that is mounted on the cat hulls to avoid structural problems with mounting on the expanding center part of the hull. Probably I would choose an unstayed mast with no jib on each hull, other than a light air foresail, but that is only a guess.

Actually, I may get over to Lake Lanier or Allatoona in October but hate sanding -- passionately.

 

[Inquisitor]

... but hate sanding -- passionately.

Its always good to have a passion in life.

 

[yipster]

not a job application but....

wondering for years now if the pasion would be more bearable in a airconditioned moonsuit

 

[Robjl]

Well you asked for it...

Inquisitor,
Have read through your thread and have the following thoughts in no particular order.
Your dingy scantlings will need to be equal to the fwd sections of your hulls to take the pounding it will get! Also unless you have a watertight seal around the gun'l the dingy will fill with water, maybe a drain ?? I don't think it's a good idea.
For a proper seaworthy cruising yacht I think you have to be able to drop the sails, all of them, not in a flat calm but at sea with 30 knots plus blowing. Your idea to roll the main around the "mast" is problematic, first I can imagine the mast, what 45 - 55' to be a bit of a wet noodle. Second, trying to roll it up in 20 knots will be nigh impossible, it must be about 7" in diameter? I have enough trouble rolling a similar sized genoa on a 2" diameter foil (using a ST44 winch) the loads on your furling line will be significant.
All headsail reefer/furlers have a return halyard (on the size you are talking about) dingy & trailer sailers are a bit different but outside my knowledge. I agree the cat is preferable to the tri, mainly for the size you get in the hulls.
I note your hulls are 4' wide yet you say the beds are doubles, this means the beds must extend into the bridge deck. I think that a watertight gasket joint is a big ask, real big task, I don't think I could do it on a one-off and guarantee the result.
Have you allowed for the significant battery capacity you will need to power your electric motors. How about solar panels, the dam things are heavy too, I'd also be wary of positioning the props in the centre, rather than well aft, my gut tells me that you will need both props pushing if you expect to motor anywhere in a straight line.
Mast pivot points, the loads there will be enormous, how do you propose to make the swivel?
Sheeting the leeward genoa I don't see as a problem, on most points of sail it won't see the wind.
I've done a little racing and know that once you get up close in the lee of a similar size rig there is little wind. I see this as a problem for your rig.
You mention the construction, my advice, finish it before you try to go cruising, I know your case is a bit different as you can "take it home" to work on it, but never the less I'd get the essentials done and not try to sail a half finished product.
I also couldn't work out how your two hulls at 4' wide and the bridgedeck could fit in the space you describe. I could imagine significant craning being needed to assemble it.
Second, the mould you describe making for the bottom of the hulls, (as I understand it) will need to be much more substantial than you describe, including framing, triangulated to be absolutely rigid, I've made frames like this and can attest to how substantial they need to be.
I also see problems with the torsion in the bridgedeck as the hulls try to twist it, especially as the roof of the structure isn't (or is it?) structural. Your task in getting all these bits to fit/de-mount and seal and transfer load will be quite a task.

Cheers.

 

[Inquisitor]

Not out for the count... yet...

... but I've definitely been pummeled!

I never really expected to win converts or line up orders. But I did hope that I would get exactly this kind of response. Someone without an ax to grind or a pencil to sharpen. Someone who has experience and is willing to share it in a construtive manner.

Thanks Robjl

 

[Inquisitor]

Getting right back up on that horse...

I'll start with some of the easy questions/concerns.

For a proper seaworthy cruising yacht I think you have to be able to drop the sails, all of them, not in a flat calm but at sea with 30 knots plus blowing. Your idea to roll the main around the "mast" is problematic, first I can imagine the mast, what 45 - 55' to be a bit of a wet noodle. Second, trying to roll it up in 20 knots will be nigh impossible, it must be about 7" in diameter? I have enough trouble rolling a similar sized genoa on a 2" diameter foil (using a ST44 winch) the loads on your furling line will be significant.
All headsail reefer/furlers have a return halyard (on the size you are talking about) dingy & trailer sailers are a bit different but outside my knowledge.

OK... I need the halyards. My original concept was just to reduce the lines coming aft to the cockpits. I have a question... :?: Are there any issues about leaving the free end of the halyards tied off, on the masts? I'd like to leave them there. Under almost any normal conditions, they'll never be needed anyway. I guess only when something goes wrong with furling them... and they have to come down NOW.

The masts are semi-wing masts. Did some rough calculations and they currently look to have a section of approximately 6” x 18”. Deflections will be minimized even if it requires carbon fiber. No wet noodles here. So if furling is required while the sails are sheeted in, there will be some high torques required on the furlers. :?: Is there some situation that the sails have to be furled while under load... or can they always be "into the wind" and thus not take as much load to furl?

Have you allowed for the significant battery capacity you will need to power your electric motors. How about solar panels, the dam things are heavy too, I'd also be wary of positioning the props in the centre, rather than well aft, my gut tells me that you will need both props pushing if you expect to motor anywhere in a straight line. .

I have not done any electrical load analyses. But, yes, I have accounted for lots of batteries. At the moment, the motors I currently have picked out are 36 Volt and I was planning on four banks of three and thus have WAG’d it to be 1200 lbs of batteries. I also plan on a large amount of solar cells to be supported on the hard bimini and two generators with fuel supplies. The weights of all those items have been accounted for in the 8500 lbs estimate.

Mast pivot points, the loads there will be enormous, how do you propose to make the swivel? .

One of my earlier posts shows a joint on a wing mast of a similar sized catamaran. I believe it is made of aluminum. After I do a detailed analysis, I’ll know how beefy it needs to be or if I need to go to stainless. I do expect the loads to be very high for the two bottom joints as well as the mast head joint. The main loading condition will not be the sail loads but, actually the torque of the two hulls going over waves... one supported aft and the other supported at the bow... trying to twist the boat about its transverse axis.

I've done a little racing and know that once you get up close in the lee of a similar size rig there is little wind. I see this as a problem for your rig.

I new there were going to be some issues with shadowing... I guess I always rationalized that a standard fore/aft double masted boat has similar shadowing issues just on different points of sail. Maybe that was an oversimpification. I think I’m going to have to make a model (wood one, not computer) and work some things out first.

More to come that needs some pictures...
Dingy issues
Hull Widths / Joints / Seals
Hull mold
Trailering / Craning / Where the hell are all the pieces going to go?

 

[Inquisitor]

One Ringy Dingy...

I can't say the dingy issue was fully formed, but here is where I was heading...

My basic thoughts were (1) I don't like towing one (2) don't like the big thing hanging off davits. (3) Concerned about wave piercing hulls in big seas. (4) want that extra reserve buoyancy.

:idea: Make it work for a living... Stick it under up front, under the bridgedeck!

(1) - Yes, I did rationalize that the scantlings would need to be nearly equivalent to a 40' long monohull. I did not actually go through the analysis to see what kind of weight penalty that would have.

(2) - In concept (if not in actual design... yet) it would also be...

(a) - Self bailing so that any seas that get into it would quickly be let out.
(b) - Full foam volume to assure un sinkable.
(c) - Self righting.

:?: IF all this could be realized... is there still some other issues that might make this undesirable or un-safe?

Here are some more images to help visualize.

 

[Robjl]

Furling your main(s)

There's no problem cleating the halyard to the mast, you could use a small winch and let the whole lot rotate. So long as the sail is rolling above the winch and rope tail it would be fine. But why would you want to rotate the whole mast, why not copy one of the in-mast or in-boom furling systems, as I see it you would solve several problems.
One; the sail would be much easier to furl and reef, two; the problems of swivelling the whole mast (whatever shape the mast is) disappear, three; you can use currently tried and proven furling gear (though the in-boom type will present some problems with the large rake on your mast), four; if the mast needs spreaders it is not a problem, six; VHF radio antenna can be on top of the mast where it belongs and likewise you have a spot for a radar dome and deck lights, maybe a GSM mobile phone antenna on top of the mast too, also a Tricolor on top of the mast where you get best visibility, and nearly forgot the wind gear as well.
I always allow the sail to luff or flag to furl it, the loads on the gear are just too great to furl under load.
I wouldn't call into the wind "not much load" maybe it's relative? but in 25knots my 45 square metre genoa (flagging) needs a winch to furl it....maybe I'm gettin' old.
Your dingy: I'm not a hull designer... but... you have wave piercing bows on your hulls but the aft sections appear flat, she'll go like a cut cat off the wind in flat seas but I think it will hobby horse at sea. Also I'd be concerned about your reserve buoyancy (the dingy). It looks too low to my eye. I think it will pound and negate all the features of your wave piercing fwd sections.
You said you were "Concerned about wave piercing hulls in big seas" isn't that what they are for?
Regards.

 

[yipster]

"Concerned about wave piercing hulls in big seas" isn't that what they are for?

in bigger seas a naccelle wont do and i can see that concern
in my motorsailor ladybird skeches, see my gallery, i sharpened the pencil on incat, still sizing down
a closer view of ladybirds nacelle at http://www.boatdesign.net/forums/attachment.php?attachmentid=15095&d=1185625951

 

[Robjl]

Trying to get my head around it,

Have a look at:
http://www.boatdesign.net/forums/boa...-new-post.html
This is a proposed rig with a similar headsail setup to yours, I can't work out with yours how (or why) you have come up with this configuration. Why two masts not one? Why two rigs side by side? Why not a conventional rig? it would certainly be more likely to work and be cheaper and easier.
Also, have you worked out the detail of your hulls to bridgedeck joint/seal and the method of dropping your roof and the method of making that area waterproof in both positions?
Regards

 

[Inquisitor]

I'm glad someone is curious. I was beginning to wonder if anyone wanted to see the labor of love take shape OR at least the train wreck waiting to happen. Heaven forbid that someone might actually want to save me from my folly...

...so thank you Robjl.

Well, you’ve definitely nailed the areas that bother me the most…

In this installment, I’ll start with the “waterproof” joint. There will be a lot of them! Between floor panels, between the floor and hulls, between roof panels and between roof and topsides. I’m starting with the premise that just about any modern car has door seals that can take driving rain at well over a hundred mph. And most… keep out the rain. Well... one of my car’s doesn’t but that’s an entirely different story... its a Dodge. Unfortunately, they are not made to take several tons of green water coming over the bow or hammering the bottom of the bridge deck.

Hopefully, the words will make sense...

The bridge deck floor will be made of panels approximately 10’ long x 2’ wide x 2” thick. The 10’ running longitudinal is the basic spacing of the cross beams from hull to hull. The beams will be designed to take all the primary loading of the boat. In other words… if the beams and hulls are mounted together and the masts rigged, we’re structurally ready to go sailing. Any structural contribution of the bridge deck will be redundant. The 2’ width is to permit the panels to be picked up by two people and to fit into the hulls for transport. The 2” thick is a WAG!

The attached picture shows what I’m WAGGING on a joint between two floor panels. The male portion will have silicone rubber sheeting to take the compression loading pressing the two panels together without squeaking. I would expect that this would be enough to eliminate most leaking if the two mating surfaces were perfect. However, like modern car doors, that use hollow gaskets, I have surgical tubing in the joint to eliminate any of the last possible leaks. Since the tubing is completely enclosed it will not take any direct strikes of green water… only the dribbles.

 

[yipster]

Why two masts not one? Why two rigs side by side? Why not a conventional rig?
it would certainly be more likely to work and be cheaper and easier.

Hi Robjl, there's a lot of controversy on bi rigs, without going into that now
i do figger the A rig to be cheaper and easier than a conventional rig on a cat

 

[Inquisitor]

Raising the House

Early versions of Z40 had a streamlined / rounded top more like a Fountaine Pejot.

My first feature transition of having a drop-top came about from several reasons.

1) This is highly subjective… but I have never seen a 40 foot cat with full standing head room on the bridge deck that looked nice… to me! They all look stubby. They only start looking good when they reach 50 to 60 feet.
2) For the helm station I lean towards wanting the best visibility. At first, I was enamored with having a raised helm… ala Lagoon 440. But that is obviously ten times harder to design if the bridge deck must be disassembled. Plus, having to move the boom even higher wasn’t desirable. After reading a good article on helm locations (I think in Practical Sailor) I settled on the aft location. The major problem sited with that location was the lack of visibility of the corners.
3) The easy one… I wanted to reduce windage and reduce the moment arm of the windage on the bridge deck for racing and/or rough seas.

Having a lowering top seemed to be the answer. Since it has to come apart anyway and has to be light, it didn’t seem all that complex to add the ability to raise and lower it.

Now, how to get the walls out of the way?

They have to fold up into the roof. And since the roof must seal against the base (with the wall removed) just above the topsides, the wall now must be strait vertical. The same seal that seals the roof to the topside when down, also seals the windows when up.

Since the window (walls) hinge into the roof the walls can no longer be rounded like the Fountaine Pejot. They have to be strait or the window panels will overlap and not fit up flush. So the bridge deck is rather square with rounded corners. As a side benefit, it has more room on the bridge deck. A third benefit, many of the panels can be made on same simple mold, whereas a round plan view would have resulted in every panel being different.

Mechanism wise. The roof will have 4 major lift points. Two at the stub mast steps. This can be a simple block and cable affair that pulls the roof up and once wedged at the top will help maintain location laterally. The second pair of lift points will be at the rear, just above one of the main cross beams.

Next installment… why two masts.

 

[Inquisitor]

Dual Masts

It all started because of a picture a long time ago. It happens to be a picture on page 146 of "Principles of Yacht Design" by Larsson and Eliasson. Basically, its just the comparison of a rod and an air foil and a factor of 30 between them. Basically any sail boat with a back stay and four shrouds and a standard mast (approximately 6" round) has more windage than THIRTY SIX air foil shaped masts with a 6" thickness!

Needless to say, I went through many different concepts to get rid of cables. I finally settled on this one... two masts, two furling headsails and two backstays all meeting at the top. This was to allow the masts to weathervane through 360 degrees for windage issues. Having two allows the masts to be lower, yet carry more sail than a single masted design and reduced stiffness and strength requirements. It allows many different reefing scenarios including having only one side fully deploy or diagonal sails deployed. Ought to be interesting, just playing with the different configurations to see what the pros and cons are.

With all said and done, between fewer cables, weathervaning masts and shorter masts, the windage should be approximately half of a conventional single mast design.

Having the masts stepped on the hulls eliminated a great deal of structural weight in the bridge deck. As a side benefit, it also frees up the space to be used more flexibly. Also, the configuration will help to stiffen the bridgedeck... especially in torsion.

Having the mast triangulated makes raising the masts as a pair almost trivial. For instance using the booms as lever arms and the anchor lasses (one in each hull) to raise, cranes are not needed. And there are no lateral cables required to keep a single mast from toppling over sideways while raising. Not that I can imagine the need arising, if windage and weight aloft needs to be reduced still more, it should be easy enough to lower the masts while at sea. All the rigging devices will still be on board.

Safety through redundancy is improved. A single backstay or foresail can be eliminated and the rig is still standing AND serviceable.

Weight aloft. The masts being shorter helps a great deal. The height of the weight centroid is lower and the material needed just for the length as well as the extra material needed to support the extra length is reduced. Also since I'm not trying to make the smallest diameter mast, the mast can be a larger airfoil size with far thinner walls. Wall buckling will likely become the driving design criteria instead of Euler column buckling as in a standard mast design. Preliminary design studies say the design can actually have less toppling moment than single mast design.

A down side - more complexity. But that includes more redundancy and smaller sails for easier handling... for when I'm older.

THE DOWN SIDE - EFFICIENCY. Yes! there will be more points of sail that shadowing occurs. That is a certainty. There will be more points of sail where nearness of other sails causes a reduction in sail efficiency. That is a certainty. However, that is just a reduction in efficiency. Enlarging the sails can correct that and throwing up another hundred square feet of sail to account for it sounds fairly easy and cheap. I'm not trying to fit into some racing standard, so efficiency is not an issue.

From the 60's - There's no substitute for cubic inches.