20' Motorsailer

I designed and built this boat based on a 18' daysailer I had designed. The design was inspired by the Fisher motorsailers in the UK and featured a center cockpit and helm station and 6' headroom in the wheelhouse with its own inside helm station. You could sail w/o having to see the pilothouse and when it got cold or wet you could go inside. The engine was in its own isolated and fully enclosed module to keep sound and vibration down. The keel ballast was an "endplate" which dramatically reduced the motion of the boat. The boat had a 700 mile range under power and is now living in Jacksonville ,FL..
The pictures are pictures of a picture-so quality is not great:

[newinertia]

Hey- Thats great Doug! good ingenuity winning over the almighty dollar!
I started a few days ago converting a Coronado C-15 day sailer into an inboard harbor launch type long distance cruiser. Power is one of the new V-Twin Four stroke 25 hp lawnmower engines- mated to a lower unit via belt drive

Looks interesting! Keep us informed and good luck.

[newinertia]

well- heres what I did yesterday- foam supported flooring, built the aluminum
microstructure, fitted windows with 1/8" Lexan, cut pattern for the roof, out of waferboard, stood on it! I cant believe how strong it is- could carry light cargo or sunbathe- or make my dog a 'crows nest'? in the pic is the motor Im using- 25hp 4- stroke Tecumseh- belt drive so I can change pulley sizes for optimum slow cruise performance at 850-950 rpms- this is a sweet spot for this engine for vibration balancing.

[newinertia]

here are the ones from this morning.

[newinertia]

By the way, is GE silicone compatible with lexan?

[marshmat]

Check the data sheet for your specific sealant and specific type of Lexan sheet, and do a pull-tab adhesion test on a scrap piece to be sure it'll actually stick. In the data sheet for Lexan 9030 (standard grade, no UV protection or surface treatments), General Electric does recommend the use of silicone sealant as a glazing compound for bedding Lexan windows. The GE SEA210 or Silpruf SCS2000 type is specified, with a warning that amino- or benzamid-containing silicones will cause stress corrosion to the Lexan.

[newinertia]

Thanks Matt- waiting for the silicone to cure now for the test, I tried to get some info from GE about the Lexan recomendations on sealers, but the site redirects you to a new company! it seems as though GE has sold their lexan branch of business. the new website is impossible to navigate!

Well, it doesnt look like I got much done today, but the devil is in the details... Installed a one piece (firewall) cab back, used 1/8 5052 and made some nice little saddle strips for the screw and glue mounting to the hull.
also beefed up the windshield framing by welding in a strongback to the original frame- see pic- will look better when painted, but damn its strong!

[newinertia]

well this is what I did yesterday- motor is in and lower unit is hung.
Underside of boat reinforced with a 24x12 sheet of .125 alum. will be finishing and starting in the next few days, water test when the silicone dries....

[newinertia]

Ok- this has turned into Frankenstein- had the exhaust bent this morning, Im working on the wiring right now. You can count on Missouri winters to be a serious detriment to your work schedule! Finally today we are warm enough for silicone to cure....

[newinertia]

sorry- new security software....

[PAR]

How have you handled the shift dog issue? I'll assume the original powerhead had a ignition kill lever or roller switch on the shift arm, though it could be handled other ways too. Have you incorporated the switch or are you using another method to present a "no load" engagement to the gear set. If not, you'll eat up the clutch dog or gear set pretty quickly.

[newinertia]

OK, got it in the water this weekend, it was a little rushed as I did not Have the shifting linkage hooked up yet. I first did some tests while in the water resting on the trailer at the ramp, started the engine in neutral to get her warmed up, then braced myself as I was standing on the gunnels straddling the engine- slid the shift rod up and couldnt believe the boat tried to push the truck, trailer, and boat all back up the ramp! (unloaded the suspension)
So, figuring that test went well, I decided to let her off the trailer to get her sea legs on. I quickly drifted sideways and down along the bank about a hundred yards, the wind was pretty stiff out of the north. I put it in gear and at an idle, went full port with the rudder and she simply spun on her center 180 degrees and as I straightened her out, she felt like a tugboat as you shift into gear- there was no drop in rpm's but an effortless immediate acceleration to probably 4 mph. and thats at a 600 rpm idle! I think I got the gearing a bit high, but am leaving it for now, the sound of that V-Twin Idling thru the tall smokestack rumbles nicely!
So- I know a bunch of you guys already think this is a little crazy, so i know it wont surprise you as I begin the next phase, adding a set of hobie cat 16 outriggers to it. I have been contemplating this idea from the beginning, stability and an increase in load carrying ability are a high priority, and possibly by using the cat hulls to take some of the existing load, she will ride the main hull a bit higher and therefore reduce the bow wave. not to mention the increased tracking accuracy. So, I have been studying the asymetrical cross section of the Hobie cat hulls, as the outside surface is flat vertically, not concave, and the inside of the hulls are curvy and perform well when the 16 is heeled way over flying and trapeezing. I think the most prudent setup would be to swap sides so the flat side is to the inside, I wont be heeling it over anymore!

There it is, stability is the first priority, buyancy and redundancy, and real estate increase are a welcome side benefit.
I am thinking they should also have a wide range of adjustability, and be suspended with a compression spring in the middle of the boat so I dont break welds when that big wave hits, it just takes it- like a car hits a speed bump.

Ok- the question really is, should the new hulls be mounted as the original configuration, or swapped port for starbord to keep the wake going to the outside?

[newinertia]

this is close to scale....

[newinertia]

PAR- You'll have to excuse my ignorance, I did rebuild the lower unit but I have not noticed anything like what you are proposing, do you mean that i need to kill the engine before changing gears? The lower unit is from a 1960 Johnson Sea Horse, with a 1.75:1 reduction, can you tell me more about what I need to do to prevent this? When the boat is Idling in the driveway, and foreward is engaged, there is a bit of 'chugging in the gears, but when in the water, it goes away due to the forces on the gearset. It does'nt grind or anything when I shift....