Z40 Roadster (Its a sailboat, not a car)

[Inquisitor]

Software

I thought I’d give a list of software I’ve used so far in my development for the other budding marine architect wannabes.

Microsoft Excel – is the only one I had to pay for so far. However, for doing trade studies and analysis I find it’s hard to beat. There are products out there… some of which I have used and like. MathCad being one of note. But Excel came with one of my computers, and I use it quite often on any number of other things.

FreeShip / DelftShip Free
DelftShip Free LINK

I got quite proficient with this piece of software. For designing the actual hull shape I found it extremely easy to use. It has the ability to analyze for hydrostatics and resistance. Most of the resistance analysis is based on theory for canoes, but hey… a catamaran hull looks oddly like a canoe. There will be a little interference drag since there are two of them, and the analysis is only really accurate up to the hull speed of the boat. After that, I have not really found anything that even claims to be able to analyze a light weight catamaran above hull speed, yet we know many production and racing catamarans far exceed their hull speed.

Also, the software will print or plot your stations for creating your hull molds. I’ve included a kayak that I designed and am currently building for the Admiral. She’s only 90 lbs dripping wet, so I custom designed it for her body weight so it would be more efficient and lighter for her to paddle…

In my early attempts, I tried to build and design the entire catamaran using this software. However, after the specialized features of the software to build nice hull forms, I found it to be extremely tedious to build even simple bulkheads, much less topsides and structure. At one time I even built the spiral staircases at the rear of the catamaran hulls. It took me close to twenty hours just for the stairs. So, now days, I just export the DXF 3D Mesh of the hull bottom ONLY to the next program.

Google SketchUp
Google SketchUp LINK

Damn! What a program! In my field, I cut my teeth on the likes of Unigraphics, Patran and Catia on high powered (for their day) workstations by Sun and Silicon Graphics. I even tried using AutoCAD in several of its versions for goofing off at home. And none of them can hold a candle to the shear ease of use and speed of SketchUp on a decently modern PC. Back in the 80’s and 90’s we never allowed ourselves to even dream about rotating a shaded, translucent, shadowed, perspectived 3D model by simply dragging a mouse. We typed in the three rotation angles and waited nearly a minute for a simple panel filled image. Cussed a little bit and then entered three more angles. On SketchUp creating geometry is simple and intuitive. I can put the program down and return to it months later and pick it up immediately. Any other product, I end up having a re-learning curve. Building models is a joy. The renderings are a little simplistic… hey, but you can turn them immediately. Getting data and sizes is a snap for the spread sheets. For the graphic artists out there, there are huge libraries of free objects that can be incorporated into your models Google SketchUp Warehouse LINK. Hey, I’ve got Lara Croft modeling on my boat! Basically, I can’t say enough about this program.

FEA
For detailed structural analysis, there is a numerical analysis method called FEA (Finite Element Analysis) or FEM (Finite Element Method). For a very simplistic description of FEA, it is a method of dividing up a model of your boat (in our case) into thousands or even millions of little squares and blocks. You tell the software where to apply forces to the model and then you let the program churn all this input data and it spits out deflections and stresses of the model. In our professions, whole PhD’s are about one tiny aspect of enhancement to one little element. It is an extremely deep subject. The simple act of changing the models “material” characteristics from what is called an isotropic material (aluminum, stainless steel are examples) to an orthotropic material (fiberglass or carbon epoxy) adds another order of complexity and pitfalls.

Knowing, that I would not want to be responsible for “trying” to create a “cook book” to allow even an engineer with a BS degree to create a VALID model, gives me a good understanding of why Marine Architects are leery about giving me a “cook book” on boat design.

POV-Ray Photorealistic Rendering
POV-Ray LINK
The rest of this is solely about how to get the photorealistic images and videos I’ve included so far. It’s not really beneficial to the design… except in wetting the appetite.
To create a world for your boat and to get the really good photorealistic images you need POV-Ray. POV-Ray is a program/scripting language for generating the images. The images can also be created based on changing time and thus eventually converted to a video. POV-Ray has an extremely steep learning curve and even though I’ve used it for at least five years, I’m not sure; I’d call myself even proficient at it. Fortunately it has lots of examples and you can get the rudiments fairly quickly. Polishing the image with all the effects can be a career in itself. Also, there is a large forum that has been helpful to me in the past.

But first you need to get your model converted from SketchUp to POV-Ray. You’ll need to learn about Plug-Ins for SketchUp. You can download the translator plug-in between these two programs here…

SU2POV3 Translator LINK

Scroll down and look for the program su2pov3.zip. You can download it, unzip and follow the directions to install it into SketchUp. Once done, you’ll be able to export your model. It creates an input file for POV-Ray in basically the same orientation as when you pressed the option in SketchUp. This will save you a lot of time just getting POV-Ray to show it.

Where Google SketchUp can create several images of your model per second as you rotate it with the mouse, POV-Ray image generation is extremely time consuming. Some of the images I’ve included here took nearly 4 hours to generate. The 720P video I have generating will take over a month running non-stop on four different CPUs. You’ve got to want it real bad to go through the headaches.

POV-Ray ONLY creates the images for a video… it just creates a bunch of bitmaps. You then have to combine them to create the video. I have found one way, but I’m not real happy with it. If anyone happens to know a better way, please let me know.

Creating the AVI Video
Bitmaps to AVI Translator LINK
This program allows you to gather the bitmaps into a Windows AVI file. It works, but has a couple of bugs, but it’s very nice of the developer to let us have it for free… besides the bugs can be circumvented to create your AVI video.

Creating the mp4 Video.
AVI to MP4 Translator LINK
There are many programs that can transcode one video format to another. Most seem to have fees and have rather complex settings that I’ve not spent the time to understand. However, I have found one that has no settings and does a pretty good job. Basically this compresses the avi file down to one that is small enough for YouTube or can also be burned to a DVD to be played in a standard DVD player. At some point, I’ll need to go through that learning curve. I’m not real happy with the quality. Apparently, in some of these transcoders you can modify the settings to improve quality at the expense of size. That would be beneficial for the DVD version. You’ve got plenty of room on those for your little demo.

For instance the AVI file for the low-resolution video came out to be 1.5Gig and after translation it was 46 Meg. The 720p video will be 10.4Gig and over 330 Meg when it’s finished.

That’s about it for tools… so far... Good Luck

 

[Inquisitor]

Back to the Z40 Roadster Design

In this installment, I want to discuss milestones.

I imagine under ideal conditions that this project would normally take quite a few years for a single person (with occasional help) to complete, I am concerned about having the staying power to finish. Therefore, I want to have some milestones that can return rewards.

What I mean is… Since the Roadster has to be modular to allow it to be trailered, I can design and build it in stages that may get me into the water faster…

1. Build the hull exteriors and interior structure to support the mast and cross beams.
2. Build the cross beams.
3. Build the masts and booms
4. Build dagger boards and rudders
5. Build a net based bridge deck.
6. Incorporate all standing and running rigging.
7. Get sails.

Get it in the water! Have a 4000 lb racer.

8. Build hull interiors
9. Build bridge deck while sailing the basic hulls.
10. Finish off pieces while enjoying it.

If I'm not mistaken, more time is spent in the interior than the major structure. I might get the boat in the water in half the time.

If I were to get into the island racing scene, I could sail to the destination with the full structure and then offload the bridge deck and other major components onto the pier, string up the net based bridge deck and run it in a ~5000 lb configuration. After the race, re-attach the bridge deck and parts, entertain in the evening and sail on to the next destination… just a vision of Nirvana for me.

 

[yipster]

Inquisitor, the pop-up bridgehouse, weight, is an idea and so is richard woods popdown bridgehouse floor, keep thinking

sure many consider trailerability a must but i think a 40 ft cat is over the top, ability of taking it apart is atractive tho
than there is launching, one than might even think of, weight, suspended hulls
drawing from the top down as we amatuers do -and i belive even god must have been one- take the A frame
not a racer but interesting, doubt anybody ever gave thought tho f.e. to balljoint strenghts or flex

i miss a link to your fea prog and would be liberal with free resin. if you can calculate infusion laminate strenght, great
call me nuts but i'm checking those new harder -low priced- polyurethane foams you can now actually screw into
dont save on hull i know but maybe it makes a fair sandwich

in time my ideas keep changing some but a nice bigger live aboard cat, that stuck
rite now however i have to stop myself buying a used delta wing i saw for $400 and build a small proa to race you

 

[Inquisitor]

Hull Fabrication

In this installment, I wanted to discuss some of the logic and design ideas behind the hulls. Attached you’ll find an image of a single hull. After fulfilling exterior dimensions and scantlings and using the bottom hull design from DelftShip, almost all design decisions are influenced by reducing cost, minimizing tooling and reducing waste.

1. Hulls below the waterline are symmetric about their own centerline and therefore the same for each hull. Pro – A single mold to make both hulls. Simplicity and cost reduction.
2. Topsides are symmetric about their centerline except in the bridge deck connection area and aft stairwells. Pro - Tooling simplicity and reuse – reduced cost.
3. Although the hulls below the waterline have 3D curves, the topsides are only 2D curves.
a. Con – aesthetics are not as good as some artist designs
b. Pro – almost no tooling.
c. Pro – maximized interior space.
d. Pro – wave piercing design

The process would go something like…
1. Build a male mold for the hulls below the waterline using the same techniques as the cedar strip kayak. This mold would basically be 40’ long, 4’ wide and 2’ tall. Almost all the 3D curves (of the entire boat) are in this mold.
2. Apply peal ply to the mold. (This is a thin nylon/poly cloth that when peeled off the laminate will leave the “perfect” surface for subsequent bonding or applying more laminate)
3. Layup a minimal thickness hull. This means something as thin as possible that can still be pulled off the mold once cured and maintain its shape with the aid of jigs.
4. Use tight weave, light aerial weight cloth (approximately 4 oz/yd^2) for the outer ply(s). This will be your outer surface.
5. Epoxy and cure.
6. Sand and fill while on the mold. Probably easier to do this at this stage than when it’s the full hull.
7. Pull part off the mold.
8. Using flat surfaces, build equally thin flat panels. These panels will make up the topsides. Laying up against good, flat, smooth tooling will result in practically no fairing and filling requirements. Apply peel ply to the top surface.
9. Epoxy and cure.
10. Create simple jigs using 2x4 wood framing with 1x2 strips bent to support the flat panels and bottom hull. Place the panels (topside) relative to the hull bottom.
11. Tape (fiberglass/epoxy) all the seems.
12. You should now have a minimum thickness shell of the entire hull/topsides. Basically the image below. It should be air tight if all seems are correctly taped.
13. Now lay up cloth and foam to meet scantlings, vacuum bag and introduce epoxy using resin infusion method.
14. Cure, remove bagging and jigs.

Basically, this is the hull ready for interior reinforcements, deck and staircase. With minimal sanding and filling, should be ready for primer and painting on the outside.

Anybody see any flaws, have any ideas or have experience with anything like this it this way?

Thanks for any help.

 

[Inquisitor]

FE, Resin Infusion... RACING!

keep thinking sure many consider trailerability a must but i think a 40 ft cat is over the top

I’ve been over in Europe quite a few times and I can just visualize the concept of a 40+ foot trailer on back of dually Ford F450 going over like a lead balloon. It certainly is not a friendly picture at the pump or on many of Europe’s roads. Here’s it’s not too bad… and out in the western US… scales seem to shrink.

i miss a link to your fea prog and would be liberal with free resin. if you can calculate infusion laminate strenght, great
call me nuts but i'm checking those new harder -low priced- polyurethane foams you can now actually screw into dont save on hull i know but maybe it makes a fair sandwich

F.E. – I haven’t decided on a FE code yet. There are many very impressive free ones out there. It’s just a matter of pain that you’re willing to go through to get them to fire up and then the learning curve. Most require Linux and even compiling the source code. Not for the faint of heart. One thing I’ll insist on is Orthotropic properties for the materials. Can’t model composite laminates accurately without them. Also, pre and post processing will be a challenge. I think you mentioned the one with AutoDesk Inventor. At the time I looked at it, it had some serious limitations, I couldn’t live with. However that was some time ago and if it is fully integrated, that could save a lot of time.

Here are a few candidates I’ve started looking at. Both have composite properties, dynamic and non-linear analysis ability and both are free.

http://adventure.sys.t.u-tokyo.ac.jp/
http://www.calculix.de/

Resin Infusion - At a very basic level, more resin actually makes a weaker laminate. At one company where I used to work, our labs did some extensive tests on fiber to resin ratios. The stiffest and strongest laminates were with a fiber weight percentage of 89%! We were using unidirectional pre-preg, autoclave cured carbon/epoxy laminates. But as long as the fibers are getting wetted out, theory says the same benefits will occur in any laminate. Resin Infusion is claiming 70% with far fewer and smaller voids than hand-layup. That should create a far stronger, stiffer and lighter structure. The links below show YouTube instructionals that can explain it with a video. The last link is for a Ferrier F-39 being built in you neck of the woods. I’d go visit him in a heart beat if I were close.

Resin Infusion Links
http://www.youtube.com/watch?v=-efttvlRbO8&feature=related
http://www.youtube.com/watch?v=Moh9WQ2ZnTo&feature=related
http://www.youtube.com/watch?v=eXF1F_HxozM
http://www.gurit.com/product.asp?section=0001000100080010&itemTitle=Infusion+Resin
http://www.fram.nl/workshop/fram.htm

Racing – YOUR ON!

 

[yipster]

send you a p.m. and mentioned a smooth trouble free build or something along those lines here is there webcam
but seriously yes i check. there is a harry proa here too i like to visit but i'm still thinking cat

 

[Inquisitor]

send you a p.m. and mentioned a smooth trouble free build or something along those lines here is there webcam
but seriously yes i check. there is a harry proa here too i like to visit but i'm still thinking cat

Yeah! I like to know when I'm coming or going!

 

[Inquisitor]

Hull Shape

In this installment, I would really like some input… not that I wouldn’t like input for any aspect that you question or just want to know more… but this one, I’m a fish out of water.

I used DELFTship. And I know… I’ve read it many times on this forum. It doesn’t make me a designer.

I have read and re-read and studied and contemplated Larsson & Eliasson’s, “Principles of Yacht Design”

I have thoroughly studied MikeD’s, Hull Speed thread.
http://www.boatdesign.net/forums/boat-design/hull-speed-1220.html
His seemed to have been a comprehensive Internet search and basically said that nearly all the verbiage on the Internet was either naive or wrong and had details to justify that opinion! I wish I had been fortunate enough to have known him. Knowledgeable, helpful, yet stern in his assessment. Perfect mentor! Sounds like he was a great guy!

I studied any image I could get my hands on, on the Internet… Gunboat 48, Moxie 37, Lightspeed 32. Basically, I’ve studied them till I’m blue in the face. Then I stirred in some common sense based on basic Physics and a little aerodynamics. So here goes…

First, I noted that all of the modern designs had rounded bottoms and the bow was almost tangent to the water surface. The first two images show these two observations.

Second, when I opened the new DELFTship model, I instantly ignored the default geometry and started adding my own… here are my basic changes:

1) The stations are circles. (Front half of hull) See DELFTshipFront.png. Knowing that a sphere holds the most volume using the least surface area. And a cylinder, is the closest cousin between a catamaran hull and a sphere. That this station shape should have the least surface area, holding the most volume. This should reduce surface drag. Also, since the water is displaced in a radial direction with no tendency to shear and mix, I would assume I would reduce turbulent flow.
2) Getting the gist of MikeD’s thread… I gather that catamaran hulls can comfortably exceed their “classic hull speed” (1.34*sqrt(Length)) because their bow wave is smaller due to their length to beam ratio. Gathering that reducing bow wave size is a major plus explains why all these modern designs have such a shallow entry.
3) I’ve gone one step further. I’ve used a modified symmetric NACA supercritical airfoil shape for the side view of the submerged half. The theory being that this will maintain the water in a more laminar flow for a greater percentage of the hull.

Now the hard part, that I’m a little thick on…

From L&E “PYD”,
The transverse stability is what it is. Hull shape of a catamaran isn’t going to change it… much. The 23’ beam defines it!

However, longitudinal stability and especially longitudinal dynamic damping are a mystery to me. I understand the concept, but how to determine if I have enough is the problem? The only data point I’ve heard is that the old Wharram configuration of hulls (basically symmetric front to back) have “bad” damping since the rocking forces are the same at each end. I’m assuming with my fine bow and broad stern, that I’ll have “pretty good” dynamic damping? Am I smoking the right material?

What else should I consider?

Anyway can anyone enlighten me?... or maybe just point me to some reading material?

Thanks!!

 

[Mezaire]

Hey Inquisitor,

I am definately no expert on multihull hull shapes but I do know a bit about rigs, mroe to the point, what works and what doesn't.

I like the concept of your rig but I see two big issues.

1. You said you had mains that furled around the masts. This will only work for sails that are all the way in or out, not as an effective reefing system. The reason for this is that sails have depth vertically aswell as horizontally. When you try to half-furl or reef your mains you will get terrible and highly inefficient shapes just when you want efficient flat shapes. Also have you thought about what will happen to the main halyard when you furl?
You could fix this in 2 ways. the easiest would be to simply go back to fully battened mains on battern cars and lazy jacks. This is a treid and true cuising multi method because it works!!! Yhe other way would be to have a swivel top and bottom of the main luff.

If you are set with a furling main, have a look at Furlex genoa furling systems closely first.

2nd issue is that in anything over 15 knots of breeze the whole boat will be VERY wet!! My boss builmt a Crowther 28 cat and it was a hatches closed, full wet weather gear job on deck in any decent breeze!!!

Mez

 

[yipster]

good reading

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

 

[Inquisitor]

Baggy and Wet

Hey Inquisitor,

Hey Mezaire!

Thank you for taking the time to read my “War and Peace” and for giving me a heads up.

Issue 1a (sails with vertical depth) – I remember this crossing some brain cells at one time or another.

Thought 1a1 - At that time, I think, I read that high performance cats (a very broad generalization) were going toward very nearly flat sails. The reason being… that they almost always (end up) sailing into an apparent wind, even when the true wind is off the rear quarter.

Thought 1a2 – Just want to clarify – Single handing is (just) slightly more important to me than speed… ever so slightly. However, I knowingly sacrificed battens and a nice big roach. So I knowingly have less efficient sails. I increased the area to make up for lesser efficiency. Sorry, its must be an American thing… THERE IS NO SUBSTITUE FOR CUBIC INCHES! A Viper may be inefficient as compared to a Porsche, but it will… “Get’r done” none the less.

Thought 1a3 – You just made me realize that I had a flawed logic. I don’t have the opportunity to do much rough condition sailing!!! I’m always trying to eek out every last bit of energy out of the meager winds I get around here. I can count the number of times I’ve reefed on one hand. (Damn near had to go look up the word) So, I really wrapped around your, “just when you want efficient flat shapes”… and I realize now why… if its blowing like hell you need them even more efficient (to not turn the boat over)!

Thought 1a4 – I have this in my back pocket. How about a variable cross section mast? Let’s see if this makes sense without a picture (I usually need a picture). Say we have a simple triangle sail. Say the foot is 20’ long. If the sail was perfectly flat, at half the height, the chord would be 10’. Now, let’s say a real sail’s chord at this point is say 11’ to give it a belly. So the chord line it 10% longer than if it was flat. Well, if the circumference of the mast was 10% longer at the same height than at the foot’s location, then the mast would reef the sail perfectly. I might have to think about it… but you might be able to have it tad bigger… say a 11% longer circumference and it would cause the reefed sail to be even flatter than the full out sail. Does this make sense?

Issue 1b – (Halyards for the mains) I planned on running lots of stuff up (inside) the masts… wiring for electrical stuff up top. Even lines for lifting stuff - I plan on using the masts as a crane to help lift the panels off the trailer onto the boat. HOWEVER, I don’t plan on having halyards for the mains. I plan on the main sails being installed (one time) using the bolt rope and bolting the head grommet to the mast. I did plan on having down-hauls. Anyway, this solution appears to be simpler and better aerodynamically by using the bolt rope and not having cars, halyards and stuff. Oh, I do need extra long out-hauls instead of halyards.

Issue 2 (wetter) – lewisboats mentioned that also. Can you elaborate on that a little? I want to make sure I understand the problem before I address it. I assume you two mean that water will come over the bow more on this design than others.

Thought 2a – If the concern is because of the wave piercing hulls, I have the secondary buoyancy of the center mounted dingy to keep from burying bow.

Thought 2b – If the concern is because of the low slung bridge deck… When the roof is lowered and the Bimini is forward the seating area is still 5’ lower. I can stand in this area and “just” see over the bridge deck’s roofing. When the roof is lowered and the Bimin is pulled back and mounted to the stair railing the seating area is sheltered and the cockpits are now 5’ below this shelter and its easy enough to duck under the Bimini if green water comes shooting across the roofing. If the roof is up and the Bimini back the nearly everything is covered. It can sail in this position… just not hard-core. I’ve included pictures to illustrate these.

Like, I said, please help me understand the concern. I don’t want to miss something critical!

Thanks.

 

[Mezaire]

Hey again.

Your idea of variable chord masts sounds good in practice, but masts are engineered to take variable loads over their length. Varying the chord may make the mast bend in ways you just don't want, eg inverting.

http://www.almasts.com.au/components.html

Read the section on furling swivels.

I didn't see the bridgedeck before, so yes that should be sufficient for protection.

Another point is sheeting angles on the headsails, which will be way to fine on the leeward jib for anything but upwind work. As much as it's nice to think high performance multis always sail on apparent, you still need to create an efficient shape at 90deg apparent.

As for no main Halyards, what happens if the main tears it self to shreds when your 100NM from the nearest point and it can't be furled??

Also, do you have backstays? If not, hot do you expect to achieve any sort of headstay tension?? If no backstays then inverting and breakage will happen!!

Also, if your mast rotates to furl, what is going to happen to all your ropes and electrical wires going up the mast?? It's hard enough to stop chafe on halyards on a Farrier Tri with a mast that rotates through 140deg!!

Mez

 

[tom28571]

I don't have much to add to the discussion but wondered about one thing. Have you done, or seen, a study of how a trimaran compares to a catamaran with the same goals? At first glance, a tri seems simpler, especially at the launch ramp. I could see the deckhouse expanding over the akas similar to slide outs on a camping vehicle. Structural integrity would be achieved in the normal way with no dependence on the deckhouse.

You have a most ambitious dream here. All in all, I am not sure it can be done to suit your desires with all the compromises that will crop up along the way, but have at it and we will watch and kibitz. One thing is certain. I have never been able to watch any of the boats I've built sail around and into a slip before I launched them.

There have been some examples of a sailing rig like yours but none caught on.

 

[Inquisitor]

Your idea of variable chord masts sounds good in practice, but masts are engineered to take variable loads over their length. Varying the chord may make the mast bend in ways you just don't want, eg inverting.

Considering, it was a 10 minute rectal extraction; I didn’t really expect it to be fully formed. However, I’m not doing an absolute minimum weight, cutting edge carbon fiber racing boat and most of the production boats I’ve ever seen use simple aluminum extrusions of constant cross section. They are not “designed” for variable loads over the length… they’re just oversized to take variable loads over the length. Although I have only done a cursory, first level strength, stiffness and buckling analysis on the masts, I don’t think it will be that big a deal to make them variable cross section. They’ll certainly be less complicated than an aircraft wing.

http://www.almasts.com.au/components.html
Read the section on furling swivels.

As for no main Halyards, what happens if the main tears it self to shreds when your 100NM from the nearest point and it can't be furled??

I wasn’t aware that any furling headsails have halyards. My 26 footer doesn’t. I do provision for being able to lower the masts while moving… however it was with the thought of going under bridges… not recovering a flogging main in gale conditions. I’ll have to give it some thought for both the head and mainsails. Having smaller, redundant sails eases my mind to some degree on that point anyway.

Another point is sheeting angles on the headsails, which will be way to fine on the leeward jib for anything but upwind work. As much as it's nice to think high performance multis always sail on apparent, you still need to create an efficient shape at 90deg apparent.

Actually, I’m designing and building something for my 26 foot monohull that will handle that very problem and several others quite nicely.

Also, do you have backstays? If not, hot do you expect to achieve any sort of headstay tension?? If no backstays then inverting and breakage will happen!!

Actually backstays are in described in the first posting and just about every picture shows them. They’re hard to see in the little thumbnail pictures.

Also, if your mast rotates to furl, what is going to happen to all your ropes and electrical wires going up the mast?? It's hard enough to stop chafe on halyards on a Farrier Tri with a mast that rotates through 140deg!!
Mez

See the picture below. Its a great idea! I wish I could claim it. The picture doesn't do it justice. It pivots for lowering/raising the mast and also rotates about 360 degrees for mast rotation. All lines go up the centerpoint and thus don't get wrapped around anything.

Again, thanks Mezaire, you've given me several things I need to think about some more.

 

[Inquisitor]

I don't have much to add to the discussion but wondered about one thing. Have you done, or seen, a study of how a trimaran compares to a catamaran with the same goals? At first glance, a tri seems simpler, especially at the launch ramp. I could see the deckhouse expanding over the akas similar to slide outs on a camping vehicle. Structural integrity would be achieved in the normal way with no dependence on the deckhouse.

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.

You have a most ambitious dream here. All in all, I am not sure it can be done to suit your desires with all the compromises that will crop up along the way, but have at it and we will watch and kibitz. One thing is certain. I have never been able to watch any of the boats I've built sail around and into a slip before I launched them.

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!

There have been some examples of a sailing rig like yours but none caught on.

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

Thanks Tom.