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oldguy

a question about The boston powered dory

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Hello all.This is my first post As the subject says I have a a question about the boston powered dory.More specifically the boston powered dory in Building classic small craft by John Gardner.If it has proper ballast Is it capable of offshore cruising? The version that has me curious is the 28` version on page 427. at this point I am simply exploring options in hull designs.While I do intend to coastal cruise the possibility of  offshore cruising would be nice.It seem to me that a tight decked swampscott dory properly fitted out might be just the ticket.

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This type of craft is a grotesque sort of powerboat. What was done in these dories was the age of propeller driven boating was upon them, but they had sailboat hulls and hugely heavy engines. 100 pounds per every couple of HP wasn't an uncommon thing. The hulls were not well suited, but they could manage the burden of the smelly monster lurking in the aft bilge. In fact they needed the dory, because it handled much better with some burden then without, unlike other craft which would prefer to have been kept light.

Given time, they did add some displacement to the sterns of these boats and engines did slowly get lighter, but for modern uses, there are much better shapes.

Is there a particular reason for this type of boat? It's a simple shape to build, but you may find that in the last 100 plus years, we've gotten a fair bit better handle on powerboat design, then the retro fitted sailing dories of the turn of the last century fisheries.

In fact, if you look at page 428 in the bottom picture, you'll note a few dories parked. The transom facing the camera is a classic example of a dory stern, modified for power. The dainty tombstone transom is gone and one of at least double it's girth is installed. This additional displacement accommodated the weight of the engine, which still took up the last third of the boat. Lastly, you do realize that your top speed will be limited to about 8 MPH in a 28' boat, right? On the other hand, you would use little fuel, make a very small wake and would only need a 10 HP engine to run at 8 MPH all day long.

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Thankyou Par for responding to  my post.

I agree 100% that there are hulls far better suited for motors however Is is not a motorboat that I am looking for.Perhaps I should say not strictly a motorboat.As a matter of fact my preferred mode of travel is sail. 28` is pushing it a bit when it comes down to available building space and should be considered the upper limit.I am not worried about getting "there" fast just alive and that means the most seaworthy hull design I can afford to build.The problem is I don't have the knowledge to make an informed choice.You must admit though that the swampscott dory has quite the reputation.28 feet tight decked?

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The dories in general, have developed this reputation while loaded with tons of fish and delivering their cargo and crew safely to shore. In this mode they're fairly safe, but within reason. For the most part these boats didn't have particularly impressive stability curves and wouldn't stand "muster" as a modern hull form without substantial changes, even if fully decked.

This brings us to the "modified dory" or the "dory skiff" hull types. These have similar shapes and look like a dory, though key elements have been altered to make them more suitable. The Boston power dories where the first of the modified dories, as these needed more hull volume aft to support the massive engines. The bottom plank and garboards where widened in the aft sections to address this. Of course the hull's nice lines went to hell, but it could hold up it's burden.

Modern versions of the modified dory show wider bottom planks, but with the volume midship, where it detracts less from efficiency, wider transoms, fatter beam/length ratios, flatter runs, less topside flare, decreased rocker and decreased sheer sweep are the most common changes made to most traditional dory shapes. Each change has a role to play and if you've ever owned a traditional dory and had it on a mooring or hook, when the wind changed direction, you'll know why they changed the sweep in the sheer. These changes bring the dory into the dramatically flared skiff arena as far as shape goes. I personally think if you're going to this much trouble, you might as well lose the flare too and give yourself some additional foot room.

There are several designers that specialize in "dory" shapes, though these are really modified dories. In fact, the term dory is difficult to recognize any more, except by us old farts that remember the differences and changes made to the original rowing and sailing versions, in an effort to make them more acceptable to a modern buyer.

I'd recommend you look at your needs make lists of your true desires and dislikes, with an attempt to find a design through requirements, rather then preconceived reputation of a vessel type, which can be a fairly big pitfall if you don't know the real history of the hull type. In this vain, isn't it funny how most of the "popular" antique hull forms were always called "good sailors", "weatherly" or good sea keepers". Compared to modern craft they're probably not especially close winded, their massive bulk helped tremendously in their comfort at sea and reputations are the only reason the type was continued to be employed, other wise they'd have abandoned it in favor of a faster, more close winded, safer hull form. This makes you question the reputations all together, especially if you've seen their stability curves.

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In all that you have written you have not answered the first question.I cannot see a yes or a no.All your points are valid but not what I asked.Or perhaps I phrased it  poorly. :smile:

I will try to find a better way to ask it.

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Paul,

You aught to get paid for all this reasoned advice and background.  Most likely though, it may not even be appreciated.  I'm sure you know by now that "dory" is one of the sacred terms in boat discussions even though there is almost always a better boat available for any specific need. 

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I must have pissed off "Oldguy" Tom. I appreciate your comments though.

I think you did well.  I personally would have thought it rude to just give him a NO! right off the bat.  But he insisted and you delivered your informed opinion.  Folks want thier own opinions to be confirmed not told in great detail why its a bad idea. 

I found your post very interesting on the level of boat design as a progression through time. 

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First post ever on this site, so please bear with me if I'm too enthusiastic.  I'm getting a "Gardiner" type dory built right now in Lunenburg, Nova Scotia.  It's a Bank Dory, kind of like a St. Pierre, but the sheer isn't nearly so pronounced, and the beam is more in line with the narrower, traditional design.  Better performance, but less deck space.  Not too many photos yet, as they're only just finishing side planking.  Can provide if there's interest.  She'll be 25'9" long, 7'1" at mid-ship.  4' across the floor at mid-ship.  Forward cabin with bunks, stand up wheel house with mini kitchen.  Main mast with boom and block and tackle.  In-board diesel with V-drive, so motor is covered over to produce a seat in the stern.  I'm up in the Northhumberland Straight, but I grew up along the North Atlantic and I'll be taking over to wild side once or twice each summer, when I go on my "camping" trip.  

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Paul has, sadly passed on but his words remain as clear as when written and will be forever so.  Dories evoke some wisp of reverence in many boating souls but those that bear the name are most always significantly modified to hide their worse tendencies that made them especially useful to Banks fishermen and their masters.  It's just a boat, crafted from common materials for a special purpose with some good boat design characteristics ignored in favor of those that were more important for the task.  That later dreamers imbue the banks dory with magical properties is not the fault of the highly practical designers, builders or users of the originals.

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