Online Since 1997.
Please also check out Kasten Yacht Design.

Kasten Marine Design, Inc. Logo - Copyright 2017 Michael Kasten 


Home  |  Intro  |  Our Design Process  |  Stock Design Info  |  Motor Yacht Designs  |  Sailing Yacht Designs   |  Prototype Designs
Plans List  |  Articles  |  Our CAD Design Stream  |  Maxsurf  |  News..!  |  SITE MAP..!  |  Site Search  | Design Team  |  Contact Us

Please see our AVAILABLE BOAT PLANS web page

Trailerable Trawlers...?

25' Boojum Tug Yacht on Trailer
The 25' Boojum, shown on her construction trailer at the builder's yard,
Q-West Boatbuilders, Wanganui, New Zealand

The Concept

Why trailerable? To save moorage costs; to avoid haul out fees; to quickly transit from one cruising spot to another; to check out large inland lakes; etc... The reasons are numerous.
 

The Trailer

With Charles Vollum's Boojum as the example, we looked around for good trailer makers. For Boojum, we found a good candidate that will custom build a variety of aluminum boat trailers. They offer trailers for boats up to 17,500 lb. and 41' LOA, and will build a custom trailer for Boojum rated for 18,000 lb., having 3 axles, hydraulic brakes rated for 20,000 lb., a custom bunk, and if desired an electric remote brake actuator.

Base price was quoted as of 1999 at around $5,000 plus about $1,500 for the brakes, and maybe another $500 for the electric brake override. Now, those prices are a few years old so will have very probably increased since then.

The trailer maker didn't seem to think that a boat weight of either 12k lb or 17k lb made all that much difference, except to the speed the truck could move the boat up hills. In any case, those guys say "no problem."

The trailer will of course be set up to allow being immersed when needed. The intent is to be able to launch and retrieve from a good boat launch ramp, for which these trailers are well suited. If the boat's underbody is kept to a shallow profile forward, the drag of the keel will match the slope of the beach or launch ramp best.

Unless the hauling truck is more or less a real Godzilla, a fifth wheel is the only way to go. Better weight distribution, better maneuvering, etc. With this set up, and proper brakes, a BIG dually pickup would probably do the trick up to around 16k lb or so. If the hauling truck is actually a tractor (as would be used for moving mobile homes and other big stuff) then the natural choice is a heavy duty pintle hitch.

Trailering "dry weight" of Wave Runner and Greatheart is around 15k lb, or around the same as Boojum. Due to the 8.5' beam restriction for Boojum, she carries over a ton of ballast which the other boats would not need.
 

The Highway

Per the State of Washington Dept. of Transportation, the Legal Height in Washington without a permit is 14 feet. This does not imply that all highway clearances actually ARE 14' or greater. Some older structures may be less, or there may have been an increase in road height due to new pavement, etc.

Washington DOT has a book in which they'll look up specific info on a per trip basis, but they won't release the book for sale due to liability concerns. They say that the 14' height threshold is also the case for the US Interstate Highway system. A special trip permit is available up to a height of 16 feet.
 

The Boat

The 25' Boojum for example has 11' 9" from keel bottom to top of stack and fwd end of PH top. Mast and tabernacle, etc. add around 6 inches, or around 12' 3" total, so for safety assume 12' 6" overall. That allows 1' 5" for the trailer bed height before you'd be at the 14' mark.

Trailer height to the top of the bed can be as low as around 15" if the axles are slung below the bed. The axles would then be torsion bar type, with a lever arm aft of the axle. The lever arms will have around a 22.5 degree up angle when the trailer is unloaded. With the trailer loaded, the angle would be a bit more and the bed would be lower than 15 inches.

With a 15" trailer and a 3" fudge factor, it leaves us 3" to spare, plus the squish of the trailer springs when loaded. The 15" trailer height is from a quick calc with the trailer maker, and seems quite achievable.

Another "tiny trawler" intended for long range cruising as well as for trailering is the prototype, Ferdinand, named after Magellan himself. Check out the Ferdinand page to discover why that name seemed apt.

The Wave Runner 36 prototype design has a height at present of 9.5 feet off the water, and just over 12 feet from keel to brow in "trailering trim" (bow down). Upright, the height is around 13 feet from brow to rudder heel. These are very similar to the dimensions of the Greatheart 36. If hauled "bow down" they would fit well within the 14' height "limit."

Draft for either design can be as little as 3' 6" without much fooling around. This is mainly a matter of deciding draft limitations versus the preferred propeller diameter for best propulsive efficiency. If it were necessary to limit the draft of Wave Runner 36 or the Greatheart 36, it would be most effectively achieved by the use of a "tunnel" stern. These are design issues, which given a specific requirement, can easily be accommodated.
 

Summary

The thoughts offered here are the result of some highly cursory investigation. Rather than attempt to offer a "done deal" solution, I have instead wanted only to introduce a few potentially interesting ideas, which given the resources to pursue them will most certainly result in a vessel ideally suited to the purpose envisioned by the owner.

In designing a functional rig / boat combination, it should go without saying that there will be quite a bit of careful planning required. It is further assumed that the funds will be made available for that planning to be done in a complete manner, including the requirements of the hauling vehicle.

These trailerable trawler conjurings are simply an attempt to acknowledge that, "Where there is a will, there is a way."
 

Wave Runner 36 - Fast Trawler Yacht
The 36' Wave Runner