Powered O'Day Javelin

I have a 14 ft Javelin planing sailboat hull that I converted to an electric cruiser (3/4 HP) years ago. Now I want to put a flash steam plant into the hull and go fast (I know, that is a relative term), with 10 to 15 horsepower.

The total weight will be 1000 pounds, maybe a little less. I have a 1 inch diameter shaft installed, with the motor mount just forward of the original centerboard well location. Of course, the centerboard well has been cut out, and a stern tube/propeller shaft glassed into the hull. The electric drive setup swings a 14 x 17 three blade prop, and makes about 5 MPH.

Any comments welcome, especially any indication of what speed might be expected. I have no knowledge of planing hulls, we steamboaters usually cruise along at displacement hull speeds.

 

I think the first time you put the boat in the water it is going to sink. The Javelin was designed for a crew weight of around 500lbs. Your 1,000lb rig plus a 200lb person plus gear means you are going to be somewhere around three times designed weight. If you don't sink, I would be absolutely shocked if you can get up on a plane with the boat that much overloaded.

 

The Javelin Electric routinely carries 4 Adults (750 pounds) plus outing supplies (say 50 pounds), plus 2 marine batteries (128 pounds) plus motor/drive system (say 50 pounds), so that is almost 1000 pounds without the weight of the hull/shaft/prop etc.

The 1000 pounds I mentioned in the initial post is total displacement, with boat, steam plant, and one person. This boat has a potential good advantage compared to typical outboards, in that it swings a 14 inch prop, which can give much better propulsion efficiency.

So the question still remains, what power/speed relationship might be expected with the proposed setup?

 

With a 15 HP outboard you'll max out the hull form around 14 - 15 MPH, but she'll have a nasty bow up trim at that point. This assumes you have enough "punch" to get her over the hump. You see, sailboats plane quite differently than power boats, so she'll start to squat badly, once you're over say about 7 - 8 MPH. If you try to push her much faster then this, she'll be come progressively more unstable, sticking her nose higher in the air, the faster you go. She'll start rolling around and eventually get so unstable that it'll flip, swap ends or do some other undesirable thing underway. Powering along at twice the speed most of your other friends are traveling will be nice, just don't get greedy.

 

Javelin Conversion

During the original conversion I was concerned about steering stability since there would be no more centerboard.

Cut the centerboard well out of the boat and added two bilge keels for stability, (picture attached) as well as providing a good anchor for the new machinery stringers mounted inside the hull. These are 2 x 2 Aluminum angles, each 8 feet long. I would think this would prevent rolling around, "swaping ends" or similar events.

The steam plant would be mounted just aft of the forward deck, where the motor and batteries are located now, that is more forward than is typical with other more conventional arrangements, and should check excessive bow rise.

I will have a 16 horsepower engine out of my tractor (Case 746) this spring, I guess I will just put that into the boat and try things out to see if the boat behaves reasonably.

 

When she's standing on her tail with 3/4's of the boat flying out of the water, how much do you think those runners are going to be engaged? They also may cause ventilation/cavitation at your prop in high speed turns. The rolling I mentioned is a dynamic instability based on hull shape and S/L it's driven to. This is one reason, why you see a huge predominance, of hard chine powerboats.

If you have a reasonably sized rudder, your steering will be fine, though if sized to work well at full plane speeds, it'll be undersized at displacement and of course the reverse.

 

Fred; Par is telling like it is. The Javelin is a nifty little SAIL boat. It will plane, sort of, under sail. Power...? Not in any way that you'd want to endure. Best advice is to abandon this idea and build a boat more suitable for what you seek.

I can see it all now. A Bolger Sneakeasy with steam power. That thing would haul ***. (relatively speaking) That design has the looks of a sexy old timer and it will go fast with small power. It will also accommodate the thousand pounds that you estimate, and give you fairly decent ride quality. Ditch the Javelin project for a more appropriate design.

 

Maybe two Javelin's glued at the transom?

 

not to jack this thread, PAR, but how about two aluminum runabouts attached at

transom to make a cheap and easy 'long boat'?

Since some aluminum runabouts lines run straight back 90 degrees from transom it would look and function "right" in that regard.

Plus easier to transport as most of those boats nest.

I'm thinking of a cheap, durable, safe(already USCG approved...sort of) rowboat or super-canoe for tourists etc.

Kind of scary for a resort operator to commission a real one of a kind proper wooden longboat at great expense and time lag, with storage and maintenance issues looming.

But just attaching two common tinnies, and maybe one piece of belt sheet metal to streamline the gap at transoms, wouldn't be risky because you would still have two usable/resell-able boats.

 

That would be sort of like Bolgers folding schooner.

C.O.
http://whatsintheshop.blogspot.com/