Maximum simple trailerable power cruiser - looking for ideas

Discussion in 'Boat Design' started by Steve2ManyBoats, Sep 15, 2010.

  1. tom28571
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    tom28571 Senior Member


    I've just completed a 4' towing model. I made the hull down to the chine exactly like my earlier test model of the Bluejacket hullform and added the heel below that. I did this to have a close comparison between the two for tow testing. I don't like the term box keel because it sounds too much like Bolger's designs and it is nothing like that. My keel is pretty close to a catamaran ama of the same L/B dimensions. I found it difficult to fair the chine into the keel effectively. Sitting in the water the chine to keel area up forward is more hollow than I would like for appearance but, unless the forward chines are pulled in a lot while seriously decreasing interior room, that is inevitable.

    Bolger handled the problem by using a real box with 90 degree joints but I find that ugly, rough riding and noisy. How much the fairing that I have done helps is unknown. In order to increase the fairing up forward between chine and keel it is necessary to carry the fairing all the way aft. Either that or add to the length forward which may be the choice for your client.

    Edited to correct spelling/understanding.
  2. Willallison
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    Willallison Senior Member

    Tom - can't wait to see the results of some tow tests. And of course some pics of the model...
    I agree with you regarding Bolgers box keels - way too much compromise just for the sake of construction simplicity.

    Tad - if you do away with having clients, it does wonders for design freedom!:D

    Nothing to do with this thread, but it's such a great pic, I wanted to share it with you;)
    Graphite accelerating into a 20 knot northerly....

    Attached Files:

  3. Richard Woods
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    Richard Woods Woods Designs

    I find this an interesting thread as the boats under discussion are similar to one of the ideas I am working on right now.

    First though I'd like to define "trailerable" a bit more. To my mind a trailerable boat is one that you can keep at home and launch/recover every time you use it. A "transportable" boat is one that can legally be taken by road but may need boat yard facilities to launch it. Certainly it is not a boat that you would take by road more than once or twice a year.

    So it seems that this discussion is about the maximum "transportable" boat, rather than the maximum trailerable boat.

    I write this in the PNW, Saturna Island to be exact, (about 40 miles SE of Tad) which is where I spend my summers. However next week I fly to the east coast USA to sail south to the Bahamas and beyond. Something I have done for the last 6 years. It seems crazy to have two boats, one on each coast. In the same way it seems crazy to keep a boat in the Med, say, and another in N Europe. So finding a liveaboard boat that can be transported easily is a great concept (I don't think many people would chose to live on a trailerable boat)

    Thus so far I think we all agree.

    However this is when we start to diverge. I design multihulls, mainly sailing catamarans, but also a few trimarans and this year I launched my first power catamaran. You can see video of the prototype here.

    It has proven a successful design and that has given me confidence to develop my ideas further.

    A power catamaran has more room than a similar sized monohull. It is also much safer, as it has much higher stability and twin engines. It has a low drag hull shape so is more fuel efficient. And possibly more important still, it makes little wake, doesn't slam at speed and doesn't roll underway or at anchor.

    So why do people still cruise in trawler yachts? I certainly wouldn't want to go offshore in a European style canal boat. I wouldn't even cross the Strait of Georgia in a British narrow boat.

    Don't forget that boats are not only used at sea! One major disadvantage of the trimaran concept is that you have to be very skillful when coming alongside. You cannot just run to the bow to fend off. Manoeuvring in locks must also be tricky.

    OK, so here is my thinking. Imagine a 30ft RV (in the US), or a 30ft caravan/mobile home (in Europe) that sits on top of two 35ft pontoons/hulls. No accommodation in the hulls, just storage and tanks. Joining and unjoining the central cabin to the hulls is a trivial problem.

    The hulls would be about 4ft wide and 6ft high, so are road legal side by side. The central cabin is 9ft-ish wide and 7ft high. That is also road legal if turned on its side. Not only that, but it will fit in a high back container, the hulls going in a second container.

    Having two loads may not sound attractive (except that presumably a truck can also tow a trailer), but it does mean that a boat like that can be built in the Far East, for example, and shipped to anywhere for easy assembly. I have a contact in the Philippines whose yard rate is AUD/USD1.50 an hour (say GBP1/hr). Imagine only paying USD3000 for the labour to build your 35ft boat.

    Tad will know Tony Bigras has already done something similar. (Although I didn't know that until recently)


    The problem to solve is how to make it not look like an RV on two floats. My thinking is to go for a centre cockpit design with the main "bedroom" aft and galley and seating area forward, where headroom is lowest

    I have tried sketching a 30ft trailerable folding catamaran, like my Skoota 20 and 24, but as I said at the start, I doubt if many people would chose to live in such a small space. So a 35ft boat makes more sense to me, even if transporting it costs more.

    I'll keep reading this thread, and keep sketching away

    Richard Woods of Woods Designs
  4. Willallison
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    Willallison Senior Member

    You said that just to get a reaction, didn't you...;)
  5. srimes
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    srimes Senior Member

    Isn't that the one that started out with wave-piercing hulls and jet drives, and the engine where the bathroom is now?
  6. tom28571
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    tom28571 Senior Member

    I'll let someone else bite. I took a cruise across Pamlico Sound in a 36' powercat last year in relatively mild weather. First 40 mile day was very calm and the trip was uneventful. The return had a bit of chop but not bad at all and the ride was ok but chop slamming into the bridgedeck became very tiring and annoying. Much less satisfying than on a 36' sailboat. I never took it out into any rougher water and don't want to. The bridge deck on Skooter looks pretty low to me and the water in the videos is flatter than we usually see around here.

    Cruising catamarans have a lot of features that are attractive to many people and some of my friends own them, both power and sail. Just not my cup of tea other than fast sailing multihulls where I generally prefer trimarans. Horses for courses and to each his own.
  7. Steve2ManyBoats
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    Steve2ManyBoats Junior Member

    Richard, thanks for the input

    I agree with your ideas about the relative differences of transportability and trailerability. At the start of this thread, I suggested a design brief that would most assuredly fall into the catagory of a transportable minimalist power cruiser, not a trailerable one. I'm thinking that trailerability presumes that most people could trailer it frequently for day use.

    The boat I envision would, complete with trailer, possibly top 8,000 to 10,000 pounds so all but the most powerful pickup trucks are out as tow vehicles. Also, the person trailering would need to know what they're doing, particularly regarding launching and retreival. I've dumped and retreived more than my share of 42' offshore raceboats from trailers so I know how to do it and can avoid the need to get a marina and a travel lift involved with launching/retreiving.

    My thought was to develop a power cruiser that was relatively easy to transport, launch and retreive - meaning you provision it in your driveway, fuel it at a gas station on the interstate (that can accommodate commercial trucks), then find a large ramp to dunk it and go potter around for a few weeks. Although I love multihulls - I have a 26 ft trimaran daysailer/racer - I didn't see any way clear of having a big assembly job at a launch site if more than one hull is involved for a trailerable power cruiser. For me, that would increase the hassle factor to the point that the boat wouldn't get used much.

    I keep coming back to a traditional design - like a Chesapeake bay workboat with a charterboat style cabin and a hard canopy over the back desk that can be canvas/eisenglass enclosed. Or something like a stretched out variant on the Blue Jacket theme. Traditional boats used to be very long and skinny and can look "right" in those dimensions. Hard chine boats are easier to build inexpensively, tend to plane easily if well designed (especially if they're long and skinny) and are reasonably stable. Since this is an experiment, I'm trying not to burn up my retirement nest egg in the process. A simple ply/epoxy/glass single chine hull would be the order of the day. Relatively inxpensive and very quick to build.

    With judicious use of some of the light foam core and honeycomb panels available, I'm thinking that a nice, airy and very lightweight interior can be made as long as one resists the impulse to have a curvy French charterboat style interior.

    Sounds like this kind of boat might have some interest for others than just me. I still haven't found anyone working on a design like this, or at least a hull like this.

    Thanks for the interesting ideas all.

  8. tom28571
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    tom28571 Senior Member


    I hear you in all but one point. I am not too interested in the "transportable boat" based on experience. My largest Bluejacket is the BJ28 which is the full 8' 6" beam and built a bit heavier than the smaller ones. The first client for the BJ28 was a couple who wanted to get away from their transportable boat and its logistical problems. Since our BJ24 is plenty big enough for us for several weeks coastal and inland cruising, I had considered the BJ28 as a practical large trailerable cruiser that can still be hauled with a family type vehicle, be stored at home inexpensively and operate on plane with modest fuel requirements.

    If a larger boat is wanted, that is fine with me but I guess it doesn't fit as well in my profile.

    Oh, and a Bluejacket is sailor in the American Navy while a blue jacket is a jacket that is blue.

    Good luck in you quest.
  9. u4ea32
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    u4ea32 Senior Member

    I must admit I am waffling on the transportable-trailerable thing. However, the live-ability of the UK canal boats that must be very narrow (6'6" beam) and low, strongly suggests the distinction may not be necessary.

    The widest things in the layout need only 7'6" beam, with 8'6" being overkill. Therefore, I can't find an interior layout requirement that forces beam to be impractical for trailering.

    And the height limit of 12 feet simply drives a low CG configuration that is a good thing, not a bad thing.

    I have not completed trade studies on the total interior layout, but the trade space seems flat enough that there really does not seem to be a significantly optimal layout.

    So the current concept is something like this, from bow to stern, length only:
    4' foclse
    8' hanging lockers/storage
    8.5' stateroom (6.5 berth, 2' space around foot of berth, walk around double)
    3' head/shower separate P/S with stairs to pilothouse between
    6' pilothouse floor, 360 degree visibility, floor is 5' higher than below, systems under.
    8' saloon, full beam, includes the stairs down from the pilothouse
    8' galley, full beam
    8' dinette around the transom.
    53.5 feet LOA

    Lots of slack in those fore-n-aft measurements, so it all works anywhere from 45 to 65 feet by compressing or stretching the "compartments."

    This layout puts everything but the pilothouse on the same low level, and allows the pilothouse to have that essential (to me) 360 degree view of the gunwale of the boat. The deck can then be mostly flat (appropriate spring and camber).

    Propulsion could be outboards, or that wacky 4-electric thing I've mentioned before.

    And styling remains totally flexible, everything from early 1900's cruiser and commuter (or Turbina), up to mini super-yacht. Nothing seems to be constraining the styling.
  10. wardd
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    wardd Senior Member

    My approach is figure out what you want inside and let the outside appearance wrap around that

    so in order of importance for me is


    sea keeping ( if I'm using the word correctly)





    outward appearance
  11. Tad
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    Tad Boat Designer

    Another of Tony's ideas....the Skeeter Mk. III wave-piercer......not super-successful.

    His big aluminum cat Osram VII has been tied in front of my office for the past 9 years...........
  12. tom28571
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    tom28571 Senior Member


    Trailerability is also at the top of my list based on 10 years of using my 24 footer. The others follow in about the same order as you have. Other than the trailering requirement, no one goal is overwhelmingly more important than the others. I might move up to the BJ25.5 for what it offers over the 24. Other basic arrangement plans can change things a lot.

    I don't see how anything over 28 to 30 feet fits in with the easy trailing and home storage goals though. If it takes too much time and effort to plan and execute a cruise several hundred or a thousand miles away from home port, it just won't happen very often. Marinas and back yards are crowded with boats bought on the volume or complexity of features and not enough on the reality of cost or effort.

    If the boat is not actually used very often, it makes more sense to charter.
  13. Willallison
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    Willallison Senior Member

    Eeww.... now that is ugly!:eek:

    The trailerboat / trailerable boat / transportable boat discussion has been covered a number of times here over the years. There is generally loose concensus, but in the end it all comes down to ones 'comfort level' and area of operations. And these two parameters ought to dictate the order of importance of the various design elements.
    As you move up the size scale, there is no doubt that you begin to limit the number of places where a boat can be towed to, launched and retrieved. For some, that will be a compromise that they are willing to accept, for others it won't.
    Here, for instance, there are plenty of good launching ramps, it's rarely very busy and I have 5 acres of "boat parking" space at my house (inexplicably, my wife seems to think that it's there for her horses to graze on...women!:rolleyes:). I generally keep my boat in the water, because there are excellent cruising grounds at my doorstep. But every now and again I want the ability to cruise further afield without the hassle of having to coast hop to get there. So, for me, the decision to go for a trailerable boat (as opposed to a trailer boat) was a no-brainer.
    I often spend up to a week on board with said wife and two VERY active kids (no horses... but occaisionally a dalmation or two...). The idea of doing it in anything smaller than Graphite, would lead me to despair... and possibly divorce!!;)
    I rather like Steve's concept... I would caution that bigger is definitley not always better... but in general terms it has merit and is IMHO worth exploring further.....
    The first step in that process, as I've said before, is the SOR......
  14. Steve2ManyBoats
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    Steve2ManyBoats Junior Member

    Understand your tradeoff analysis...


    I understand and appreciate your analysis of the tradeoffs size/length force. For myself, I've been living with a 24' pilothouse fishing boat (one of 11 boats I have) for quite a few years. I built the cap, deck, interior and superstructure to my own design on a gutted shallow draft commercial fiberglass hull that started out as a side console workboat. That boat - 24' by 8' - is great for day work and the occasional overnight trip, but I definitely need more elbow room than that if I'm going to be on-board for a month. In living with this boat for about 5 years, I've learned that weight is far more important a factor in transportability/trailerability than length. I've taken a beam of 8'6" as an axiom - it's a given. I've found that my 24' pilothouse is more easily trailerable than my 20' center console with a T-top simply because the 20'er is a battleship - very heavy. The lighter the boat, the easier it is to deal with, including getting it on and off the trailer and moving the trailer around. I absolutely agree with you that a boat on a trailer that is a chore to move around and get on/off the trailer will seldom get used. Might as well leave it in the water at that point, and, if so, you just lost all reasons to optimize it for trailerability.

    Based on this experience, I'm more concerned with weight than length.

    In looking for a boat to do my retirement voyaging/cruising, my first thought was a roomeran like a PDQ 36 or a Tomcat 9.7. Actually, the folks who build the Tomcat have a really nice boat optimized for a couple...and no guests. The entire floorplan is open and gives the impression of spaciousness more than the physical dimensions would suggest. However, in looking at how the boat would be used - a one month cruise every summer and a two month cruise every winter - getting to a distant destination in the continental US at 55 mph began to make sense. I've also learned over the years that spaciousness can only be overcome by clever design to a degree, in the end you just plain need space. When I add up the linear space I think I need, it still comes out to about 40 ft. - a little more if I want a forward and aft cockpit, a little less if I get clever with overlapping/multitasked spaces.

    If I can't find a hull design close to what I'm looking for, I'm tempted to take a crack at sketching something up this winter. There are enough public domain designs/plans for older long, skinny workboats available (like from the Mariner's Museum in VA) that I ought to be able to have a decent starting point for a sketch.

    Once the water gets solid, messing about with boats becomes a reasonable substitute for messing around on boats.

    Again, I appreciate all the contributions to this thread.


  15. u4ea32
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    u4ea32 Senior Member

    Piquant (or Pecant)

    Here is an interesting example I've found.

    Piquant (pr Pecant), for the design concept. Designed by Strawbridge with naval architecture by L. Francis Herreshoff. Long, skinny, easily driven. And I prefer the double ender for the clean wake. Designed for 10 to 20 mph cruise. Based on beam/length ratios from 1880's steam launches. 47' LOA, 6'6" beam, 2' draft, 6700 lbs displacement. 15 statute mph cruising speed burns 3 gph, so gets 5 mpg on the twin gasoline engines. Each engine turning a 20x24 prop through 2:1 reduction. Slow turning gasoline Lathrop LH-4 31HP engines, about 1700 RPM at cruise.

    While I have not seen an accommodation plan, Herreshoff describes the accommodations as "two separate sleeping compartments which had double beds, a galley, and other space to move about" and "The accommodations of Pecant are most convenient for cruising because her two cabins are separated by about 14 feet of cockpit and her berths are perhaps the most unusual feature of her whole design. The consist of canvas berth bottom stretched from side to side near the ends of the craft so that the sides of the boat make the berth frame. The two berths are about 4' wide by 6'3" long and will each sleep two persons comfortably. The forward cabin has a quite well fitted galley with a two burner alcohol stove, dish rakes, etc., while the after cabin has space for a toilet. On Pecant a cedar bucket is used with much savings in space, weight, cost, and smell, as well as getting rid of the disgusting chore of cleaning up around the usual toilet."

    The engines were amidship, under engine boxes in the cockpit that provided comfortable places to sit.

    And he did not feel this was as narrow as one could go, but wrote "Undoubtably the economy of Pecant could be increased with an even longer and narrower hull, ... apparently the optimum length of non-planing craft is much more than is generally realized"

    He felt the design could be improved by using a diesel engine, even slower turning propellor (perhaps 3:1 reduction gear), and quite a bit lighter displacement.

    Here is the reference from the L. Francis Herreshoff Collection at Mystic Seaport

    Attached Files:

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