Maximum simple trailerable power cruiser - looking for ideas

Has anyone set forth reasonable cg heights for trailer boats with 8'6" beam. It would appear to be a three variable problem. Displacement, length, and intended use. As far as I can see, a lightish trailer boat would need to keep the deck very low- sharpie low- in order to retain stability. If you want to have floorspace above the waterline you will almost certainly have to add ballast. To me, any standing headroom implies more displacement than required by the boat's structure. This, to me, is the primary motivation in extending the beam past the 8'6" limit. I suspect standing headroom is expected in a 35' cruiser. If you make it sufficiently heavy, it is a PITA. Lighter, and it lacks sufficient stability and has too much tophamper for it's underbody. Once a cg is established, it should be quite easy to assign an "implied" displacement for each feature. A standing headroom head=1000# or whatever. How much lighter can a 35' boat be made if the beam is increased by 6"? Would the wider boat have better fuel economy due to less weight, or worse due to more surface area?

 

Good points...

Phil:

I was planning to make the hull, stringers, frames and decks/floors out of ply, epoxy and cloth/roving on the outside, epoxy saturation on the inside. Figured that the decks and floors would be as low as I could get them consistent with tankage amidships (both laterally and longitudinally) and a self bailing cockpit aft. Since I will need standing headroom in the main cabin (salon) but there will be no bridge, I figured I could build the superstructure light. Might even go to honeycomb if I need to. Figured I'd concentrate the weight low and centrally. Most weight will come from hull panels, stringers, frames and physical plant. Very little weight will be atrributable to superstructure. Also, I plan on minimal internal furniture, which also could be built with foam core or faced honeycomb if necessary.

Bolger's Wyoming, which is an extreme example at 51' by 8'6", seems like it would work - minimal but decent accommodations for two and standing headroom, though I'm not sure any were actually built. It has a completely flat bottom , though I'd prefer a warped bottom - flat or nearly so aft transitioning to a modest vee forward. Too much vee and the bow will plunge in head seas and root and broach in following seas.

Ruell Parker's 36' Commuter is along these lines too - long, skinny, shallow draft, slight arc sections aft and moderate vee forward - and the original seems to have stood up pretty well until it was overdriven into a chop and suffered some damage. I think RP actually altered the design with more vee forward to handle more open waters.

I still think (hope) the 8'6" beam can be made to work and usable boat can be made light enough and long enough to be both functional for extended trips and not too much of a pain in the a$$ to actually trailer.

Thanks...Steve2ManyBoats.

 

My 2 cents worth

Great Thread. I am working on a model of Atkins River Belle, as the size just fits my needs. What are thoughts on the tunnel drive concept? I live at the confluence of the Illinois and Mississippi rivers, so shallow is desirable if one wants to venture into the side sloughs and rivers.

 

Dave Gerr designed a similar boat using a a tunnel...

The boat was called "Summer Kyle" I believe. It was a significantly wider than trailerable but was a relatively long, narrow design. I believe it was a sampan style hull with a flat center panel bottom to take the bottom upright at low tide and had a pretty radically tucked tunnel - that I believe left the upper tips of the prop blades exposed to air at rest. Claimed that the boat went well and backed fine regardless. I believe they even had a short production run in fiberglass.

I've actually been rethinking the propulsion and a small diesel with a straight drive with a tunnel would provide better reliability, better fuel economy, a source for hot water, power for an A/C compressor and water maker and a neater external appearance. Costs would be hull complexity, an engine box to deal with and added weight. If I can keep the weights down to afford the weight penalty of a lightweight 200 hp diesel, that might be an attractive option.

Steve2ManyBoats.

 

Steve, I posted a sketch in the Option One Area, The Most thread. It could be adjusted for higher power.

 

The sea keeping , ride and ability to take the ground has been in favor of the Atkins. At SL-3 or under.

I'm not sure the reverse deadrise concept , is really a "tunnel drive" as it is the entire stern of the vessel.

The box keel would present an ideal engine location , as well as battery , and chain location.

The hassle seems to be the boat will have more wetted surface at speed than say a V bottom , which would also be a smooth rough water ride.

Our concept was to take River Belle style bottom to 7 ft 6 so it could simply fit into a cargo box. World cruising with an inshore boat.

Regardless of the chosen beam the ability to take the ground is very useful on a cruiser.An additional concept is a simple well over the prop (above the WL at rest) to clear debris , or perhaps change between speed or power prop.

The following plan was done by Rick W , THANKS!!!

FF

 

was torture remembering were I saw this one but its 32' with a 7.5' beam 1925 Alden design
not sure this pict will come up but

 

A modified Wyoming, built in Australia

A couple of photos of a modified Wyoming.
Graftonian

 

More pix of modified Wyoming

Another set of pix of Wyoming

 

That profile looks errily like Dashew's FPB.

And I like the look of that vessel compared to the modified version above it

 

Have you looked at Terra Wind for ideas?

http://www.terrawind.com/terrawind.htm

They built an RV to act like a boat on lakes.
You want to build a boat that acts like an RV: 40 ft long by 8.5 feet wide, drive to a nice location and stay for a week or two. So borrow two tricks from Terra Wind and the RV world: RIB and pop out rooms.

A pop-out room probably isn't sea worthy, but use that room for when you're anchored at that nice beach.

You could use the inflatables to support the pop out rooms when at anchor and/or increase the sea keeping ability.

 

I haven't read everything in this thread, maybe this has been posted.
He has motored this all the way down the Mississippi and up the East Coast I believe. Here's two of them in Florida...




http://markvdesigns.tripod.com/boatbuilding/id12.html

He's got plans for 20, 28, 36 and 39' with an interesting photo journal of the construction...

http://markvdesigns.tripod.com/construction/

 

Interesting, but...

Regarding the amphibious RV, I'd rather have a simple boat, on a simple trailer pulled by a simple truck. Trying to build an amphibious anything geometrically complicates everything. Since I already have the diesel truck, I've got the land powered problem solved. Also, it looks like a water borne motor home can't do much more than a couple of miles per hour. In the original design brief, the intent was to use a 200 hp. four stroke outboard to get a long, narrow 20 mph boat. Since I already have the truck and since triple axle aluminum trailers for 40 ft. offshore powerboats are readily available for a decent price on the used market, that still seems the best way to go.

Regarding the Mark V, that boat really is a river and ICW cruiser since it's a flat bottom design. In the same theme, Bolger's 51 ft. Wyoming is closer to what I was looking for, but still is a flat bottom boat with significant use restrictions. I was thinking of a hull with minimal deadrise aft and more significant deadrise forward to reduce pounding at anchor and when motoring into a head sea (but not so much deadrise that it will root and broach in a following sea.)

Thanks...Steve2ManyBoats.

 

I'm the crazy one...

You want trailerable which imples size restrictions while on land.

Once you get your boat in water, inflate the sponsons and pop the top up for an enclosed second story, or push out the wall in the galley to double the area.

Pop out rooms are probably tricky, unless you salvage one from a motorhome, but poptop canopies/tents go back decades.





I'm the crazy one that wants an amphibious passagemaker/RV.

 

"Pop out rooms are probably tricky, unless you salvage one from a motorhome,"

In trailers and motor homes the slide out concept is 30 years old with thousands installed.

And they are the most common broken item on the camper , sealing against wind at 70 mph is harder than it seems, even for the $2,000,000 custom bus conversions.

An origami boat is a fun concept , but a dry inside might be a few sq ft area , hopefully the bed.

FF