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Ken_Potts

Slow power boat

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It's possible to have your cake and eat it comfortably too, if you can accept modest plane speeds. These would be in the mid to upper teens. You can have a very low power (probably quite narrow) boat that will sip fuel like a cheap date, while still having enough hull form to make a comfortable ride in a modest chop. Once you venture near 20 MPH, things change drastically and everything gets more costly (ride comfort, fuel use, power requirements, etc.).

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Are you saying that we can actually be more comfortable in the high teens than at our desired 8 knot (9mph) cruise speed?  Seems counter-intuitive, but I'd like to hear more.

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No I'm not saying you'll be more comfortable in the high teens so much as able to run there economically with a relatively small engine, if the right design is chosen. For example a full plane boat, will not be very economical at displacement speeds and likely will have tracking issues too, unless modified. On the other hand a Rescue Minor like design (for example) will run at displacement speeds all day, sipping fuel, yet capable of getting up and scooting along at a good clip (high teens) on the same engine when desired (she has to pee, a storm is coming, etc.).

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Not to take anything away from the previous recommendations but you might also want to check out Bluejacket boats.  I think they meet all of your specs with the exception of being designed for outboard power vs. inboard.  The designer, Tom Lathrop is an acquaintance of  Graham Byrnes.

 

Another one to check out is Cheseapeake Marine Designs Launch Cruiser 24.  Designed for a 9HP Yanmar 1GM10 diesel with a cruise speed of 6Kts.  A little slower than you stated but less power too.  A few minor modifications could probably get you up to speed.   Layout is almost precisely what you describe.  Modest cabin acoomodations forward and ample deck aft for deckchairs with shade.

 

The Redwing 26 is a little more boat with a 8-10kt cruise with a 20-30 HP inboard or outboard.  It is a Piltohouse style cruiser. A canopy aft would be an easy fit.

 

If I were to do a small diesel inboard I would consider Beta engines.  They are stock Kubota  block engines that are marinized to fairly high standards.  Parts are a lot easier to source and reportedly much cheaper than many of the other small marine diesels.

 

These are all available in stock plans. Of course having something designed specifically for you is the best way to go but will cost you a little extra for design work. Good luck and Godspeed.

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Not sure why I've not ever seen this thread.  Several good suggestions offered here.  For me, I would prefer modern construction for reasons of lighter weight which translates to lower cost of materials as well as stingier on fuel, not to mention building effort and possibly skill.  Bluejackets have a larger footprint than most boats and so are fairly tolerant of added weight.  That is not so much an issue at displacement speed but does use more fuel at high speed.  My BJ24 is pretty efficient at 7mph ( as long as the weight scantlings are followed) and easily handles most waters we are interested in, although I'd want to add some more depth to the keel for better tracking at this low speed in open water crosswind.

 

Yes, Bluejackets can handle a small inboard well but that does not take advantage of what it is best at.  That is running nicely at whatever speed you choose up to its maximum.  PAR's boats will be easier in big water mainly because of higher displacement and a shape that works best for that regime but does not match the Bluejackets where they shine.  The smaller B&B OB is good but it really needs about 40hp to do its best and an inboard might ruin it.  With 25hp it runs pretty well lightly loaded and at displacement speed.  I have tried a Rescue Minor and am not impressed except in the very shallow water regime it was designed for.  I would not consider taking one through our local inlets that are no problem with many others.  Carl's CMD boats are nice also, although I much prefer the V bottom to the flat ones.

 

All in all, these boats are good but they are not alike.  One or more will fit your needs best and its up to you to make that choice.  Making a non emotional choice works best in the long run but boats don't lend themselves to a dispassionate view.  For a story of one of my boats taking the Great Loop, look at: https://www.facebook.com/vesseldede

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   Hi Tom,

   Your Bluejackets are on my list if I decide to go with an outboard.  I'm not the type to make a fundamental change like putting an inboard engine into a hull that was designed for an outboard.  I agree that it's best to take a dispassionate view to selecting a boat design.  I think the best way to go about it is to define the mission before designing the boat.  There are emotional decisions to be made, of course, but they shouldn't take precedence over function.  I very nearly bought an old boat recently and if I was the type to follow my emotions at the cost of practicality I'd be the proud owner of a 108 year old ferry right now.  She'd have been gorgeous if we put her back on the water but she didn't fit our mission well enough.

   While I'm leaning toward an inboard design for our slow boat I'm happy to consider outboards as well.  One really good thing about an outboard is that the noise is way back there. ;)

   I've got no desire to cruise any faster than 8 knots and one of our favorite designers has mentioned putting a Beta 30 into a displacement power boat but he's otherwise occupied at the moment.  I've been reading Dave Gerr's "Propeller Handbook" over and over lately and I've just in the last few minutes I ordered his "Elements Of Boat Strength"* and "Boat Mechanical Systems Handbook" to entertain myself until I find the right design.  At this point I might end up designing it myself.

 

* I ran across this book today when visiting a local boat builder who is building a Herreshoff Mobjack Ketch in aluminum.  He used it as one reference to design the scantlings for the conversion.  I wish I'd gotten photos of the frames set up on the keel.  Quite impressive.

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Hello, 

I just came across this very interesting discussion and would like to add my suggestion.  I don't know if my comments will still be helpful since the last post was over 6 month ago.   Anyway....  I see that no one has mentioned Glen-L marine that provide plans for many different type of boats of different sizes.  Most of their plans are for plywood construction and sometimes they even have full sized patterns for the ribs, transom, and stem. They have a nice trailerable 25' cabin cruiser that might meet your needs http://www.boatdesigns.com/25-Coastal-Cruiser-trailerable-motoryacht/products/802/But, in any case it is always fun to look at their inventory of over 300 plans.  

 

I myself have built their 26' St. Pierre Dory and cruised it extensively in Puget Sound.  It is one of the safest boats in which I have ever been but its hull speed is only a little over 5 knots (it has a 20' water line).  That said however I can get to hull speed with only the equivalent of a 6hp gas engine.    The nice thing about this design is that Glen-L provides plans for an inboard with a shaft that can be lifted into the hull for trailering or beaching. I use a regular bimini top over the cockpit to keep out the sun and the rain (we are in the Pacific Northwest)

 

Tom 

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Here's a good book on the subject. It concerns larger cruising boats, but is a good read for anyone interested in displacement power boats. http://www.amazon.com/Voyaging-Under-Power-Robert-Beebe/dp/0071767339/ref=sr_1_1?ie=UTF8&qid=1429794790&sr=8-1&keywords=cruising+under+power+by+beebe

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I haven't started yet. Life (and sailing) keep getting in the way.  That's just a fancy way to say I'm lazy.

I'm still interested in the project Graham told me about, a fuel-efficient boat designed with the Beta 30 in mind, but I'm wondering if new tech is starting to make electric power a competitive option.  The biggest challenge to electric propulsion in my case is that the boat might well live on a mooring so I'd have to have enough battery capacity to sustain me for a trip and enough generating capacity (solar and wind) to refuel in-between.

On the other hand, my wife has mentioned an interest in maybe sailing around Australia at some point so I might stick with sailboats for a while.

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Well then, I'll mention Tad Roberts Wedge Point 27, if you haven't already looked at it. It has the classic styling, efficient hull form, low power, and large cockpit with full roof, all fitting your SOR with the exception of the outboard. For that, there may also be propane and electric options to consider. A bonus feature of the Wedge Point is the emergency/auxiliary sail which could be used when the course is favorable and you want some peace and quiet.

 

http://tadroberts.ca/services/small-boats/tender-launch/wedgepoint27

 

wedgepoint27-classic-launch-02-S.jpg.699708e8ae17034a6bf3327280c9a1c9.jpg

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