Trailerable Multihulls

Discussion in 'Multihulls' started by JCD, Mar 4, 2008.

  1. JCD
    Joined: Jul 2006
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    JCD Follow the Bubbles!

    Hello Phil...

    I included a top view, but as you have already noted, it is covered by the cockpit (yellow). I will try to produce some other pics for you so that it can be clearer. I apologize.


    Dislike has been noted and this now makes the second time attention is drawn to it. I will definitely look at it further.


    This is an excellent idea. As soon as I get a chance, I will try to lay this out and see what kind of lower and upper body clearances will be resulting. My initial thought with the current layout was to set it so that a face to face encounter can occur. I would want to lay it out so the bench seat is inboard to reduce wave pounding vibrations, but that may have to change if I am to protect the waterline outboard. This is a great idea. Thanks.


    You have a way with words...but accurate and I agree. You reach the forward seat by "walking" over the aft seat because a "jump" with so low a clearance may break your neck. But again...the inconvenience is there.


    All true and if it is possible to do it, it shall be done. I have to lay it out and see how it will feel in there since lower body room is extremely limited that far forward.

    Yes...the middle is the cockpit, but it has not had the inboard side extended to accommodate the cuddy so it is a little deceiving. Right now it is 2.5' wide and when it is extended it will be 3.25' wide, or thereabouts.

    I did not post the model because there was still some work I was trying to complete and you didn't say if you had FreeShip. I guess you do, so I will try to post it tonight when I clean up the final work I've been incorporating.

    Thanks
    J:cool:
     
  2. catsketcher
    Joined: Mar 2006
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    catsketcher Senior Member

    get rid of the centre cockpit

    Hello JCD

    I would get rid of the centre cockpit rather than fiddle. A few cats have centre cockpits in the hulls. Malcolm Tennant had a bamboo bomber called Tanui or something similar with a centre cockpit but it has not taken off as an idea. Indeed I would suggest getting rid of the cockpit from the hulls.

    A bloke I knew got the hulls for a Turrisimo 9 cheaply - it had capsized and was a wreck. He decided to get rid of the cockpits from the hulls as he wanted more interior room. He had a huge cockpit anyway between the hulls. It worked really well. In a cruising boat you don't need to be hanging over the side like you do in a small racer and the feeling of being securely tucked in by the large 4 foot wide hulls is very reassuring.

    You lose a cockpit whilst trailering but this is not that much of an issue. You still sleep on the boat but just don't lunch on it as easily. My little 6 metre cat has solid floors and a large cockpit that feels very secure. It has a huge amount of room for a 6 metre cat and no cockpit in the hulls.

    have a look at www.foldingcats.com

    cheers

    Phil
     
  3. JCD
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    JCD Follow the Bubbles!

    Ahoy there Phil,

    The hull pits are a necessary evil or conversely, the necessary extra room, that is required in order for the cuddy to slide into the hulls. I have seen the sliding system but not a system where the cuddy fits into a neat secure package into the hulls. I have also looked at folding systems that fold up and down and yours is the first I have seen fold diagonally.

    This cockpit area in the hulls can have a nice dodger, which I haven't thought about yet, and it would provide a very nice floor area of over 24sq.ft. when deployed. Navigation will be from the cuddy, so the hull pits will just be one more place to hang out with solid deck since forward and aft of the cuddy will all be netting.

    I would like for you to come back to this once the design has evolved a bit further and offer your renewed opinion then. I know it is hard to visualize it at this point, but failing to "paint a picture" is a shortcoming I will overcome with a little more time.


    I agree completetely. The cuddy will be 6.25'L x 6.5'W and it also will be securely tucked between the hulls. Again, I have failed to provide good visualization, but that will change soon.


    Actually, this is the oppossite. While trailering, I will not lose the cuddy cockpit, but will lose the hull pits when the cuddy is slid into place. This also will become clearer, or at least as clear as it is in my head until I can get it translated to something visual. I think you will be impressed.


    I looked at the cat. Very, very nice. Amazing how you opened up the back of the hull to get that huge berth in there. Actually, I had given this some thought with the initial layout I had in mind, but I changed the layout. I was going to extend it inboard all the way to the hull width getting another foot in each hull up high.

    I am saddened that you have had to put much of these initiatives aside due to unforseen or uncontrolled circumstances. I hope everything works out as you have planned and I wish you GODspeed and a quick rebound. On a similar note, we also had to put the brakes on our lives very abruptly, but like your cause, family being the most noble of reasons, we did it and have no regrets. Look for the silver lining in everything gloomy and understand that sometimes you need to change some things and slow down to gain a new perspective and get that ummmpphhh to gather momentum.

    Now...for an update. JCD has been busy! I have put together a list, which is attached of everything that has been designed into the accommodations. It is extensive and in my mind "proper" for offshore needs. Nothing else except food, ocean and trailer is required. I cannot and will not be able to fit anything else. All wall cabinets in the head/berth/galley are modular for the lake or inshore sailor that does not require them or care to use them for those adventures so close to land.

    I am posting the current pictures without the cockpit...and they do not yet include the redraft of the bow seats to bench seats since I have not tested the idea as of yet. I have excluded the tanks beneath the berth etc. for best viewing.

    Picture 7 – Engine/Head/Berth. The yellow countertop (2’ x 1’) above the settee/potti beneath it will include a basin and will be on vertical tracks attached to the firewall so it can be folded up and out of the way. Hot/Cold water included. The berth locker and medicine cabinets can be one or the other or two of either and they are modular. The narrowest traverse distance at shoulder height is 2.4’ with both port and starboard cabinets in place. This is the shower “square” and it is no less than 2.4’ x 2.1’ if you choose to stand. All other dimensions remain as previously described.

    Picture 8 – Galley/Salon/Bow Lockers. The full width folding table will fit between the seats and will be folded up and out of the way. The galley cabinets (I took one out for best viewing) can be one or both and they are modular. The narrowest traverse distance at shoulder height is 2.6’ with both port and starboard cabinets in place. This is the galley “square” and it is no less than 2.2’ x 1.6’ if you choose to stand. All other dimensions remain as previously described.

    Picture 9 is the plan view for clarity. The berth is 6.5’ for dimensioning purposes.

    There it is. Any comments from any of the 2487 viewers :eek: and a handful of participants :) is encouraged and appreciated. Now I move to work on the exterior and hopefully finish up the scantlings while I'm still working out the sliding system in my head. That appears to be my block.:(

    Thanks
    J:cool:
     

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  4. JCD
    Joined: Jul 2006
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    JCD Follow the Bubbles!


    Tally Ho to all…

    This is the perfect example of making mistakes on paper and not “during” the build. This is also the perfect example for improving the design on paper and not “after” the build.

    For this design losing or gaining 1” or the same in volume is like losing 5’ or the same in volume for a 60 footer.

    A suggestion was provided and explored.
    Current Salon Condition:Foot room is 1.5’L x 1.5’W
    Backrest only on forward seat
    Traverse backrest at aft seat against either bulkhead
    Fixed seating for dedicated storage and refrigerated/ice box
    Seat height cannot be reduced below maximum waterline for water tight integrity
    Both sides of waterline protected even if holed between seats

    Design Change:Provide raised sole of .7’
    Traverse foot room can be increased to 1.77’ with raised sole
    Longitudinal foot room can be increased to 1.9’ by bulkhead setback combined with new sole height
    Interchangeable backrest can be placed on vertical tracks to be used on either forward or aft bulkheads of aft seat while able to be slid down to stow

    Negative results:Ice box/refrigerated volume reduced by .24’
    Dedicated storage volume reduced by .32’

    Positive results:Stowing back rest for either forward or aft sitting at aft seat can be incorporated without blocking entry to forward seat or preventing traverse backrest use at aft seat
    Foot room increased longitudinally by .4’
    Foot room increased traversal by .27’
    Possible further increase with higher sole and seat bulkhead offset
    Fixed seating for dedicated storage and ice/refrigerated box maintained
    Seat height for water tight integrity maintained
    Waterline protection not compromised

    Decision: Incorporate suggestion for the design

    Here is a picture of the improvement. Thanks.:D

    J:cool:
     

    Attached Files:

  5. JCD
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    JCD Follow the Bubbles!

    Whoops,

    I forgot to attach the one with the back support. It can interchange between facing forward or aft. It is approximately 1.5' wide and 1' high.

    J:cool:
     

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  6. Richard Atkin
    Joined: Jul 2007
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    Location: Wellington, New Zealand

    Richard Atkin atn_atkin@hotmail.com

    Hi again J.
    I still love the layout, no matter what anyone else says. I would still prefer a bit more room in the dining area, but it's getting to the stage now, where it's personal preference, rather than problematic.
    I know you are strict on keeping it to 27 feet, but I think sometimes a design has a specific optimum size, and it's not always good to over-restrict yourself. I learnt that with my own 'restricted' design, and so changed it to the size it always should have been.
    In your case, just adding ONE more foot (after cursing and pounding your fist and ripping your hair out), would make a massive, massive difference to the comfort, without a big difference to trailering.
    You say "just one more foot here, one more there...where does it end..."
    I say just one more foot, and end it there. :D
    I get the feeling you're going to disagree :D
    Another foot will allow each person to get a better body posture, with better lower-back support.
    Also, don't forget that 2 seats can form an extra bed, using a folding middle section. In your design it would be an ideal place to put a guest bed, with a curtain for privacy from the kitchen.

    My design has this function, as shown in the pic.

    Oh, one more thing.....there is nothing more annoying than having to look under something to see what you're doing on or above the stove. Even if the visual intrusion is only partial, it's still bloody annoying (speaking from camping experience). You might want to bevel the cuddy and hull pits to avoid this.

    I am looking forward to seeing the internal layout of the cuddy and the other hull. Great work J. As I said earlier, if you can master the sliding system, I think your design will be fantastic.
     

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  7. Richard Atkin
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    Richard Atkin atn_atkin@hotmail.com

    You might not need another foot...maybe just another 6 inches
     
  8. catsketcher
    Joined: Mar 2006
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    catsketcher Senior Member

    Design spiral

    Hello again,

    My thought are still the same but I put them up here in reference to the design spiral. What are the initial parameters this design is fulfilling?

    If comfort is one then the cuddy is severely compromising this aspect. I like the idea of a covered area in the middle of the boat. My design for my 7 metre version has a covered area (fabric covering) aft of the mast. But try as I might - and I have spent hours and hours looking at my prototype (and living on it too) and with a pencil I can't see how a permanent cuddy can be worth its weight and inconvenience. You get much more usable voume by having two normal cabins -one each hull- and getting rid of the cuddy.

    So my advice is to go normal - do the expanding trailer thing with three beams. Have a fabric dodger and get heaps more volume in the hulls and don't lose any on deck as the dodger performs the same job as the cuddy.

    A few things about folding - (I have done more then a few experiments and have built a cat that does fold)

    What works on paper or in the computer may not work in real life - One example - there are huge rotational forces (torques) that present themselves when folding. Think of it this way. If you are in front of the boat and look backwards towards it the decks will want to rotate inwards. This is because the centre of gravity of the boat is under the mast but each hulls CG is on the centreline. So there is are two torques that balance out.(I know it is a little more complex but that is the easy version) This means when the cat folds the mechanism must deal with huge binding forces. Most folding mechanisms are designed to be strong when expanded but they must resist the rotational forces all the time during folding. I think this is one reason sliding beams don't work well. Getting halfway folded and then having your system bind up happened to me the first time. It wasn't fun on a 6m prototype with my strong brother and a few friends to get it back. A 26 footer would have done us in - remember the square cube rule.

    For a big boat I would go the expanding trailer with three beams and solid floors. This normal engineering. Again I would caution going down the innovative road without a huge amount of time up your sleeve. I had been involved in multis for about 20 years before I started drawing my own little folder. I had a huge library, I had worked for a really good boatbuilder, built two large multis and still got hit by a few curve balls. I still wonder if it was a good thing that I made my design. It has cost me greatly in both time and money and has not returned a cent. Go the proven route - don't go looking for trouble so that you can solve problems. They will come to you anyway.

    One thing I would like all boat people to remember. You will have fun out there on many different boats. There is not one nirvana ship that will make the difference between having fun and not. Humans are really adaptable. I can cruise a kayak, a small folder or a 50 foot cat. All let me do different things. Don't think that one special boat will be the gateway to something amazing. It is probably better to spend effort and time taming your expectations rather than doodling.

    cheers

    Phil Thompson
     
  9. masalai
    Joined: Oct 2007
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    masalai masalai

    I may also throw an unexpected spanner in the works, but... I was reviewing my options - Bob Oram designs, - and took a quick look at the 29ft Islander, and knew what was puzzling me... The "Fast cruising" cats seem to have a beam that is 2/3rds (0.66) of the loa - additional stability (carries more sail), deck space etc...

    Ponder that aspect... Why have a cat if it leans as much as a mono? and goes just as slow... - I cannot consider a boom/main but step the mast a BIT aft to about midships then add sails from the bows to masthead (a-la hitchhiker) then 2 more from abeam of where the mast was - use only the leeward sails and reduce your personal handling stress.

    For your current plan, think of box girders for strength, hinging midships with an inverted U slotting over this and going along most of the box-girder to pins near the hulls to lock all in place and cover the hinges so they won't pinch parts of the crews anatomy (eouch)...
     
  10. JCD
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    JCD Follow the Bubbles!

    Hello Richard,

    Thanks. Yup...personal preference. The increase and backrest incorporated is enough improvement for that small space. No need to go bigger.


    No more length unless an overwhelming condition arises.


    Guests can sleep in the other hull...any more thna that can sleep in the hull pits. It is a design for 1 or 2 for offshore work and possible +1 or 2 for everything else. Everybody else can watch the trailer and sleep in the car.;)


    No can do. It will take having to shift the whole cockpit back or a portion of it and then seating space will be lost or reduced in the berth which I consider essential.


    Okay...stick around. I have been working hard to take it to the next level. The sliding system is becoming a real deceptive little mystery. It is really frustrating. I have been calculating inertia and moments to establish how stiff I will need to make it. I can't get the damn thought of the beams binding out of my head. I'll have to look at it further. I still have some ideas to air out.

    Update. I worked on extending the cockpit outboard and thought it was going to be more difficult but after some stretching and deleting and connecting...whala, a huge cockpit and high comfortable companionways. It is 6.25' L and 6.5'W and it doesn't include the space to the cuddy which is another 1.25' so this thing is huge. I attached a picutre.

    Upon closer inspection, this thing is very spacious and it has me thinking that maybe I should put some thinking into fully developing the space to make it comfortable and protected and excluding the cuddy altogether. I could raise it some more and get some air draft at the berth and the galley. Hmmm. The cuddy will add weight up high, windage etc. I don't know, I'll see.

    Thanks
    J:cool:
     

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  11. JCD
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    JCD Follow the Bubbles!

    I'll add an extra layup of glass at the stem and increase length by one millimeter okay?:D

    J:cool:
     
  12. JCD
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    JCD Follow the Bubbles!

    I appreciate that you keep it real. The design is suppossed to be the bare minimum that 1 or 2 minimalists can use to go offshore with a category B rating and be also readily available for use on the road. She must trailer fully road legal without permits, which is 8' wide. As of now, she will be the first that appears to show promise for the rating. She must fold (slide) easily and the mast must fold by mechanical action so that it can be done from the cockpit. There are a couple of other things that are more variable, but basically it is almost impossible or someone would have already done it.


    Woah...I extended the hull pit today and was thinking the same.


    See response above. How would you lay them out?


    I will definite explore this now because it is almost time to hit the cuddy.


    LOL...:D
    I will try to stay on the path and not look for trouble. I was thinking 4 solid overengineered beams. It's a small vessel and to be rated, so it has got to be stiffer than most.


    Thanks
    J:cool:
     
  13. JCD
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    JCD Follow the Bubbles!

    Hello Masalai,

    This is an unexpected pleasure.

    The design comes in at 62% but she is a cruiser and a little bit heavier but she meets the criteria for offshore category B. If you haven't, please look at the specifics on the thread so that you can see her results...on paper of course.

    I don't believe she will break any records, but I definitely don't think she will be slow. If you don't find the specifics, let me know and I'll post it again. Can you elaborate further on the rigging...you lost me where sails are abeam of the mast.

    Those boxes and hinges are going to be huge compared to the design size. The design criteria is for a sliding system but other systems including hinging may still be an option. I'm trying to design the beams at full displacement and that is pretty high at 2.594T at 17 feet.


    Thanks
    J:cool:
     
  14. masalai
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    masalai masalai

    Like the jibs/genoas to the bows but a second pair to replace the "area of the main" and move the centre of load further aft...

    Does the attached plan image make sense? - I have attempted to show the aft starboard jib/genoa as furled, and the other three deployed, for a breeze aft or about beam on, and the arrows, at the lower part of the image, represent apparent wind due to moving forward... This layout is my version, of the simpler John Hitch rig with just the two fore sails with a blade midships (not shown), I believe his concept would be "more friendly in a gust" as the spill is down pushing up not the reverse, flick the sheet and release from the cam-cleat to free up altogether... As wind force builds, ROLL-UP windward, then aft leeward then bow leeward then drop blade/storm for "barepoles"
     

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  15. catsketcher
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    catsketcher Senior Member

    The Hitch rig has hitches

    Hello Masalai

    I think that it is important to know that the Hitch rig suits the East coast of Australia if, and this is a big if, you cruise like John Hitch.

    In winter the southerlies blow you up the coast. If you have time you wait while the northerlies blow. As the summer comes the reverse is true. You wait out the southerlies while you run with the northerlies. I have cruised north 5 times and always have had to tack upwind when the wind doesn't do what you thought it would.

    You gotta have time to do this so usually a cruiser gets sick of waiting and cracks on into the wind for a day or two - more if they are far up north.

    I understand why John went this route for him but this rig would be hard to use on a small boat. Small boats like trailerable multis need to be nimble. We love sailing so close to shore I can count the oysters, short tacking in between the yachts instead of using the motor. I think it would be a travesty to lug a very hard to tack rig on a boat meant for exploring the niches and coves.

    Go the 3/4 normal rig. For me I am going to change Cats-paw's 16ft skiff mast and go a sliding gunter. I reduce the lift weight by about 45% and get the gust response of a flexy tip.

    cheers all

    Phil Thompson
     
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