Trailerable Multihulls

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

  1. JCD
    Joined: Jul 2006
    Posts: 359
    Likes: 3, Points: 0, Legacy Rep: 36
    Location: Coney

    JCD Follow the Bubbles!

    Hello Meanz Beanz,

    You will get no argument from me. I don't know how many hours I spent running that design through my head while contemplating to replicate that form for trailering. Truly a work of art engineered to function. Remarkable indeed. Simplicity. Pop top and pop bottom. Who could have imagined? I still don't have that drop floor straight in my head.

    The reason I havent already bounced on that form is because I would like the hulls to remain upright so that the hulls can be used as a "camper home" if an individual decides to move to different sites without having to acquire lodging or purchase a motor home to replace the already available accommodations. Yes, it's important for the owner to know that an offshore getaway is possible by design, but more importantly, he/she may want the financial savings from trailering their accommodations into camp grounds and lake areas which can quickly add up for someone constantly traveling to different continental shorelines or inland lakes. Florida last week, Michigan next week, California real soon and Canada in the very near future.

    It is so difficult for me to process the amount of livable and comfortable space that can be incorporated into designs. That kind of work takes serious imagination and years and years of trial and error on the board.

    Nope...no argument from me. Hopefully, I'll be able to develop an "offshore trailerable catamaran" that will live up to the high standards set by these accomplished designers.

    So far, it's just a thought and some dooodling brought on by the fact that no one has claimed a catamaran design that is both trailerable and designed as offshore capable. I could be missing something and maybe they have given thought and found that it isn't feasible for one reason or another or the market may not demand it. I don't know, but I do believe that a market exists and given enough thought and dynamic engineering like that Sango, it will eventually happen.

    Thanks
    J:cool:
     
  2. JCD
    Joined: Jul 2006
    Posts: 359
    Likes: 3, Points: 0, Legacy Rep: 36
    Location: Coney

    JCD Follow the Bubbles!

    Hello Petros,

    Thanks for looking. I've just recently began to think about it and decided to research and see if there was a "trailerable offshore rated catamaran" and the more I looked, the less I found. Now, I'm on a mission and it is becoming more and more difficult with every idea.

    I also believe it is a great idea for many reasons. Lets face it, a category A or B cruiser will purchase the biggest and most comfortable cat he can afford for those ratings and that will probably be a lot of $$, but the design will be "waterlocked".

    No? Want to put it on the hard or dockside? Then you must pay through the teeth. Want to travel from Florida to Hawaii? Would you rather drive to California in 3 days at 50mph living on the boat, maybe launching at a couple of national park lakes on the way, without paying for lodging, and then shove off to Hawaii and know the design is offshore capable or, would you rather spend 2 weeks on a "waterlocked" inshore route, to pay $600.00 to cross the Panama canal to then head to Hawaii? I can drive to Canada in 3 days and launch in the Great Lakes in 1 day. How long will it take the "waterlocked" vessel?

    Personally, in comparison to purchasing costs and operating costs of waterlocked rated catamarans, I think costs are going to be a lot closer to nothing than they will be to little. Yes, you are absolutely right that comfort is essential and I have included that in my thinking right from the onset.

    Man, you don't even need a driveway or a yard. Law allows you to park your vehicle with trailer in the street for up to 3 days before you have to move it, well, at least in 99% of the USA, and it only becomes a nuisance when "the neighbor" gets uncomfortable due to jealousy and complains to the community board or police, but it isn't unlawful.

    My first thought was 27'. Then I looked at the smallest "I" would find comfortable and that was 24'. Then it finally dawned on me the first mate may want to be part of the adventure, so I went to 26'. I may still jump to 27' before all is said and done.

    Hmmm, I agree to everything except, the light and simple folding mechanism. Thus far, (and I admit I haven't dedicated my full attention to it), it has been really difficult trying to get the beams to fit their desined purpose and I fear that this could be the "make or break" part of the design. It is very difficult with all those "connective and hinging" points and all I can think of is how easy they appear to be able to fail. Gotta keep working on it.

    For me, 28' would be very nice indeed, 24' would be a bit small with the first mate and reduced payload. Right now, I have the design at 26' Loa with 17' Boa. Center to center she measures 13' and her hull bm is at 4'. Trailering, I'm looking to stay under 8.5' but no less than 8'. No permits required at either width. Trailer height for most parkways is the maximum allowed for school buses which is 9.5', I may not make that, but, if I keep it below 13.5', I will not need permits or special detours from major routes to get where I'm going.

    I'm not giving up on the folding beams just yet. I think that it may be a necessary evil to design them with "expensive" materials to achieve desired results. The question then becomes whether the extra cost is worth the reduced weight or, if absolutely necessary to achieve the desired result, will the extra cost be worth future offset through future cost savings? It could be the beams may pay for themselves in one season of marina fees?

    I think you're right about the telescoping or demountable beams. This may still be a reality I may need to face and consider. With either, the design will have to be open deck because the hulls are 4' beam on each, unless the cuddy sits on the tubes, in which case the tubes must now rest on the hulls. This is a significant eyesore not to mention the windage both on the water and on the trailer. I would look to telescoping before demountable beams if the deck must be open and it must be considered.

    The intention right now is to overcome all of these design difficulties and get it drawn. I have a job from which I will be retiring early, so I have not considered going into any kind of production but, that isn't to say that it may not happen if the market has a high demand and someone wants to partner up to do it. Then I would look at it more seriously. Again, if the demand is high, I guess plans could be sold, but right now, if someone told me that they believe the idea is something they would like to translate into a tangible product, then I would be happy to give the plans away and assist any way I can to see this design born. As of right now, it is difficult enough trying to get any kind of collaboration from anybody and I find myself unable to draw from experience or ideas to overcome obstacles, so it is slow and painstaking.

    My initial thought for retirement was to design and build the Green Lantern. After thinking about this real hard and looking at all the benefits behind the concept, I am giving significant consideration to definitely building one for myself. The more I think about it, the more it outweighs the Green Lantern. The first mate has also expressed significant favoritism toward the trailerable because unlike me, she loves onland outdoors a lot more than offland outdoors and with the trailerable rated for offshore, we can share and do both.

    I'm attaching the first rough specifications and the beam and daggerboard concepts that I'm trying to air out of my head to see what I can come up with for the design. Peruse and offer your thoughts. I welcome them.

    Well...if you have any suggestions or ideas and you care to share...

    Thanks
    J:cool:
     

    Attached Files:

  3. Meanz Beanz
    Joined: Jun 2007
    Posts: 2,280
    Likes: 33, Points: 0, Legacy Rep: 585
    Location: Lower East ?

    Meanz Beanz Boom Doom Gloom Boom

    I believe that when the floats are up the ridge along the side takes some of the load off of the beams. It is in effect a mini bridge deck cruiser...

    R. Woods sells his plans online http://www.sailingcatamarans.com/sango.htm they are inexpensive really.

    Its a unique little cat, the design has a "pop- floor" giving bridge deck clearance with better headroom at anchor.

    Not too shabby in the speed department either.

    This is one called "Double Dutch" that has a more modern cabin styling and no step down at the rear of the hulls.
     

    Attached Files:

    Last edited: Mar 20, 2008
  4. Meanz Beanz
    Joined: Jun 2007
    Posts: 2,280
    Likes: 33, Points: 0, Legacy Rep: 585
    Location: Lower East ?

    Meanz Beanz Boom Doom Gloom Boom

    Does this help?
     

    Attached Files:

  5. Meanz Beanz
    Joined: Jun 2007
    Posts: 2,280
    Likes: 33, Points: 0, Legacy Rep: 585
    Location: Lower East ?

    Meanz Beanz Boom Doom Gloom Boom

    It sits on a gantry, you can put the hulls out and in place on the trailer. Not perfect but...?


    Depends what you call offshore, I'd do coastal work in a Sango but not ocean crossing, for that I would want to see 40'. I think your max practical limit for trailerabilty is 30'. That would be a beast to tow but doable and would result in a light (prolly fast) 30' with moderate accommodation (I reckon you will have to compromise here) I can see that a 30' "Sango" that is portable could have reasonable appeal even if you didn't want the trailerable feature on a regular basis.

    Good luck mulling it over, not a easy trick with all the inherent limitations of a legal road trailer.

    Cheers
    MBz
     
  6. JCD
    Joined: Jul 2006
    Posts: 359
    Likes: 3, Points: 0, Legacy Rep: 36
    Location: Coney

    JCD Follow the Bubbles!

    Hello Meanz Beanz...

    Thanks for all the info. Yes...the pictures were very helpful and thanks for wishing me luck with the mulling. Is that your bote?:)

    The gantry is okay...what's perfect anyway? Even if I pull it off and have the hulls on the trailer, I will still have to scale those hulls to get inside.

    I'm trying to stick to the generally accepted "qualified and scientific" belief about what "offshore" might be and even that appears to be a little murky and grey. Some say that huge righting moments is the measure, others say that its the huge length overall. Other say that Multis can never be offshore capable and attribute all the oceam crossings to luck.

    Right now it all seem to point to a little bit of a lot of things, Loa, RM, hull form, scantlings, etc. Even the skipper has a huge part to play. With all the miles I've put under the keel, I have come to one significant observation that will eliminate 90% of offshore risks to skipper and crew if practiced religiously. Firstly, watch the weather and don't leave until it is favorable. Finally, if the other 10% sneaks up on you, slow it the hell down, take measures to stay seaworthy, maintain way and don't fight the lements. Even that 10% may be anticipated and be readied by hanking on your storm suit and preparing you drag deployment so that you "wait at the ready" for the storm instead of being caught off guard.

    I reworked the hull again and I'm attaching the updated information for her at light displacement and full heavy displacement. So far it looks good since I reduced the sail area and did some other trimming. I hope I get feedback from anybody.

    Thanks
    J:cool:
     

    Attached Files:

  7. Meanz Beanz
    Joined: Jun 2007
    Posts: 2,280
    Likes: 33, Points: 0, Legacy Rep: 585
    Location: Lower East ?

    Meanz Beanz Boom Doom Gloom Boom

    J,

    No not my boat, I am hacking around in an old Seawind 24 learning what I like and dislike about larger multis before getting a much bigger multihull. It will be 40' plus if plans work out and we do the big cruise. A few factors might delay the big trip so if I resort to a small boat for the bay the Sango looks like it covers a few things I don't like about the SW24. I also like to build things, so it would be a bit of fun.

    Some shots to give an idea of the accommodation that this format can offer. The hulls have sitting headroom.

    I can't comment on seaworthiness from a technical stand point, others here are much more qualified in that area. I am gaining an idea of what I'd like to see in a design but as you point out there's a lot of latitude in ideas about that subject.
     

    Attached Files:

  8. JCD
    Joined: Jul 2006
    Posts: 359
    Likes: 3, Points: 0, Legacy Rep: 36
    Location: Coney

    JCD Follow the Bubbles!

    Good Morning Meanz Beanz,

    Getting a lot of action in this thread now...albeit from limited members. But, I like it.

    Hacking around with something yours is a lot better than having to wait for a friend to feel well enough to go out with you, so feel proud that you got what you got and can use it anytime you want. I've only been able to log about 1000 in my friends 23 footer and it feels like I could have already logged much more. He offered for me to take her out on my own after about 400 but I don't like to impose like that and hesitate to do so. As far as getting the 40 footer for the big cruise...I hope it happens as you plan it and wish you the best of luck.

    Now...I have been reviewing the scantling rule for DuraKore from the author N.A. Mr. Gerr and have decided that the trailerable catamaran will be made from Durakore. I already wrote a spreadsheet that performs all the calculations for both mono and multi and feel very confident with the results from the rule. The only part that was not addressed for the multihulls were the main structural members like cross beams and their connective points etc., but it is very thorough and actually covers everything from glass and core to ring frames, keel shoe and rub strip and even commercial service. The monohull side provides the same for fishing, pilot, patrol and workboats and covers just about everything from 18 feet to 80 feet and up to 45 knots. Unbelievable.

    It is an amazing document. He mentions that the multihull calculations for the rule would not have been possible without collaboration and generous support from several respected N.A., which include Dick Newick, Ian Farrier, Kurt Hughes and Tillotson Pearson Inc., sooo, you know that this is a document that can without a doubt be considered authoratitive within the described limits. I honestly and truly respect them and that type of camaraderie.

    Anybody care to share their believed cons or experiences with this material?

    Thanks
    J:cool:
     
  9. JCD
    Joined: Jul 2006
    Posts: 359
    Likes: 3, Points: 0, Legacy Rep: 36
    Location: Coney

    JCD Follow the Bubbles!

    Hello one and all,

    Well…been trying some different folding forms. I couldn’t shake off the nervousness with the centerline folding beams and pinned articulating ends so I decided to give the noggin a little break. I haven’t given up on it yet, but I figured I would just look at something else. Enter telescoping beams and leggo blocks.

    I had to get really imaginative with the accommodations in order to make this folding form work. Right now the hulls are 6’ high and there is standing headroom only in the aft cabin with a pop top hatch providing the same at the galley. I have not incorporated soles and may not do so in the aft cabin. I hope I can explain it clearly, if not please ask for clarity and I will do my best to explain further. Any cold hard opinions would be appreciated at this point and suggestions are always welcome.

    Imagine 4 beams of which 2 beams will support the cuddy. The top views show how the cuddy and hulls would look deployed and folded. The cuddy is 6’ loa , 6.5’ boa with a height of 3.6’ and there would be approximately 1’ clearance between the sides of the cuddy and the inboard sides of the hulls which may need some type of catboard to keep the cockpit dry. At full cruise displacement (6025#) with a draft of 1.416’ the lowest bridge deck clearance is 2’. Everything forward and aft of the cuddy will be netting between the remaining beams.

    I show the cockpit in the hulls open on top but they would also be open on the inboard sides. I didn’t get to that yet. In essence, it would be a rectangle with the top and the inboard sides open so that the cuddy can “telescope” or fold into the cockpits when the hulls are folded up for trailering. The beams would sit above the cockpit sole and the cuddy would fit inside the cockpit when folded into place. The cockpit would have modular seating and they will be extremely comfortable at 6’ x 5’ each. The steering and navigation would be from the cuddy with seating and table to the sides and convertible to a full. This arrangement is still murky.

    The front of the cockpit has a companionway and pop up hatch for headroom in the galley which will lead into the galley. Buried beneath the cockpit approximately 2 feet aft of the companionway is the galley with plenty of clearance. The salon is forward of the galley. From the companionway to the forward watertight bulkhead it is 6 feet and the full length will be a settee and hinged table which may convert to a single. When the hulls are folded, the cuddy would effect full access to that companionway so access would be from a hatch on the deck approximately 4 feet forward of the companionway although the companionway hatch would give contorted access.

    The back of the cockpit has a companionway with sliding hatch which will lead into the master cabin and the head further aft. The 6.5’ berth will be buried beneath the cockpit approximately 4 feet forward of the companionway and the remaining 2.5 feet will protrude aft of the companionway serving as comfortable seating in the cabin for 1 and cozy for 2. From the companionway to the rear watertight bulkhead it is 6 feet, and the remaining 3 feet from the bunk to the rear bulkhead will be used for head/shower with some legroom to spare. All tanks will be beneath the berth under the cockpit except fuel tanks which will be aft of the watertight bulkhead with the outboard motors. When folded the cuddy would also restrict access to the aft companionway unless a contortion act is executed to climb down the sliding hatch, but I believe I can overcome this if I place 2 outboard companionways in the cuddy which would line up with the aft cockpit companionway when the hulls are folded. If done, it would not create a trap because the cuddy also will have a centerline pop top and hatch to provide standup headroom while at anchor. The cuddy can definitely use some shaping up and streamlining but not yet.

    I would imagine that folding the cuddy would be difficult because there would be a hell of a lot of friction. I’m not sure how it would all play out, but I imagine it will either take a lot of grease or some type of ball bearing or casters. Not sure yet.

    I am not even thinking about the mast yet. I would like to try to get to the point where the folding form is clear first. By the way, if this form works out, there is no longer any question that the trailer height will meet parkway height restrictions of 9.5’. In fact, if the hull is 1’ above ground level, it will still clear the restriction by 1.5’ since the mast can be set low on the trailer between the waterlines.

    Okay...there it is. Has anybody seen this type of folding form? It is starting to feel like I'm exploring all kinds of first precedents. Is that thinking too far outside the box?:confused:

    Thanks
    J:cool:
     

    Attached Files:

  10. Fanie
    Joined: Oct 2007
    Posts: 4,603
    Likes: 170, Points: 63, Legacy Rep: 2484
    Location: Colonial "Sick Africa"

    Fanie Fanie

    Hi J,

    I've a battle with the same issue. I'm scared of the way some of these beams work, getting the impression they may not be the strongest.

    I've had this idea of the full length beams swinging back over the hulls... a pole through the nose could keep them upright during the launch.

    I have loose beams that gets assembled one to each hull and so they protrude over the next hull, this keeps the hulls upright, it works quite well. Drift apart when launched and tie them down.
     
  11. farjoe
    Joined: Oct 2003
    Posts: 161
    Likes: 1, Points: 18, Legacy Rep: 26
    Location: med

    farjoe Senior Member

    Could you please explain which document by Mr Gerr talks about multihull scantlings? I have his book " The Elements of Boat Strength" and I have seen little reference to multihulls.

    regards
     
  12. Richard Woods
    Joined: Jun 2006
    Posts: 2,207
    Likes: 163, Points: 63, Legacy Rep: 1244
    Location: Back full time in the UK

    Richard Woods Woods Designs

    I haven't been following the discussions on this forum much recently. Mainly because some threads seem to be more about trading insults rather than opinions on multihulls. Fortunately it seems this thread isn't like that.

    I was pleased to see you (JCD) are using my 1992 vintage Wizard and Sango designs as a basis for your minimum trailerable offshore cruiser design. The hull shape appears identical, while the cuddy looks similar to the Sango that was modified in Australia. Not sure if you will have good forward vision from the cuddy though. Remember it is always nice to see all around when at anchor and also when underway.

    If I was developing the design I would definitely have started thinking about the rig and mastbeam by now. I assume you will be having one mast somewhere on the boat centreline, rather than a mast in each hull (please don't go that route). So you need to decide how/where to sheet the genoa, but more important you need to decide how to make the mastbeam. You will probably have 1.5T (3500lbs) downward compression on the mast; loads which you will need to transfer into the hulls. Typically you will be looking at a 6in deep mastbeam even if its made in carbon. You have to design the cuddy and hull interior round it. Of course, if you are using them, then the interior layout is also determined by the daggerboard positions.

    In 1998 I did two singlehanded ICW trips from Savannah to Annapolis and back in a Savannah 26 fitted with an Aerorig, which removed the mastbeam problem, but created many more (so don't go that route either). The year before we had trailed the same boat to Annapolis.

    That trip we spent the nights in motels, but in 1993 we trailed our Wizard 400miles from SW England to Holland. We spent the nights by the side of the freeway, sleeping in the cuddy. A bit noisy and the truck wake rocked the trailer all night, but it can be done.

    I chose the folding system and beam configuration on the Wizard/Sango/Savannah 26 for two reasons. One, it was really simple, each beam is held in place by a 1in pivot bolt and a nut. Two, the really clever bit; as you launch the boat down the slipway into the water the buoyancy of the hulls forces them up so that the boat opens up automatically. No lifting or straining. Conversely as you take the boat out of the water gravity makes it all fold up gently.

    Another minor advantage of my system compared to say the Farrier folding system is that it is easy to get the boat onto and off the trailer when on land.

    I write this in BC, Canada where we own a 25ft trailable Merlin. I thought it would be fun to trail it first to the Great Lakes and then south to Annapolis and from there sail to the Bahamas and later back to Canada via New Orleans and the Baja California. However my partner Jetti is more practical than me and has convinced me that we are too old to live on a boat for 3 months or so without a proper shower or even standing headroom. Maybe we grew too soft on our Eclipse. So however much fun I might find it, I don't want to sail without her, so instead we have decided to have two boats, one on each American coast.

    So I can see where you are coming from (or rather, where you hope to go to), but I still think you want a bigger boat. A "transportable" boat rather than a "trailable" one. If you haven't done it yet I suggest you spend a week on a small catamaran (under 26ft) and don't go ashore during that time. Just to see if you both (I assume) enjoy it.

    As I said before, it isn't possible to get a Category A trailable boat under 35ft. No discussion, no argument. Even a category B boat is pushing it. So you are aiming at a category C and you should plan your cruising grounds round that fact.

    I'll keep reading about your design and hope this helps you design the boat of your dreams.

    As always, you can see all about the boats I have mentioned here on my website www.sailingcatamarans.com

    Best wishes

    Richard Woods of Woods Designs
     
  13. Pericles
    Joined: Sep 2006
    Posts: 2,006
    Likes: 133, Points: 63, Legacy Rep: 1307
    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

  14. JCD
    Joined: Jul 2006
    Posts: 359
    Likes: 3, Points: 0, Legacy Rep: 36
    Location: Coney

    JCD Follow the Bubbles!

    Hello Fanie...

    Glad to see you pop in. Can you elaborate on the bove a bit? I can't picture the swing. A picture or doodle?

    Thanks,
    J:cool:
     

  15. JCD
    Joined: Jul 2006
    Posts: 359
    Likes: 3, Points: 0, Legacy Rep: 36
    Location: Coney

    JCD Follow the Bubbles!

    Hello Farjoe...

    Welcome to the thread. The document that I received from Mr. Gerr is the Baltek Durakore Scantling Handbook that he apparantly was commissioned to publish for the Baltek Corporation in 1995. It is a scantling rule book specifically for Durakore although you could modify the calculations for other materials, which I will not do.

    It is pretty intensive and thorough. It even has specialized charts and calculations for everything right up to the keel bolts and backing plates for mono's. There is a whole section for multihulls which as I mentioned before, was a collaboration with accomplished and highly respected NA's.

    The spreadsheet I created from the calculations produce very realistic and close results for everything required to call out every part of a mono or multi, except that it does not calculate the multihull structural members such as cross beams because they require significant expertise and engineering.

    Thanks and feel welcome to peruse and contribute your thoughts.

    Thanks
    J
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.