looking for a designs

[DLC]

I have a line on a 30 hp diesel and am wondering what designs there are out there.
Here are the parameters that I have in mind.

Flat bottom (jon boat)
Ease of construction
Tough
Cheap to build
About 18 foot
As fast as possible


This is to be a work boat (hauling freight, beach combing logs)

Thanks

[Paul Pless]

You want a tunnel for that prop?

[P-man]

http://atkinboatplans.com/Utilities/Huskie.html

[Paul Pless]

That Huskie design is studly!

[P-man]

That Huskie design is studly!

the man did say "work boat".

[TerryLL]

Another Atkin design, the Barnegat. This one is 23', but otherwise meets the specifications.



http://www.atkinboatplans.com/Utilities/Barnegat.html

[TerryLL]

John Gardner has plans for an inboard flat-bottom garvey in More Building Classic Small Craft. It's about 22' and construction details are for solid wood construction, but going plywood would be an easy change. Your local library might have a copy of the book.

[johnw]

Well, the bow is veed, but in most ways, this plan from Our Sponsor fits the bill:

http://www.woodenboatstore.com/19-Be...tinfo/400-127/

[DLC]

The husky is close to what I was thinking but I think Iwant some flare in the sides and no tunnel.

[johnw]

Like this?



17'9", by 5' 7". I've shown her at a displacement of half a ton, but she'll carry a lot more. Here's the resistance curve:



Figure about 25 lb of thrust for every horsepower, so at half a ton of displacement, she'll plane with less than 10 horse. Put 20 on it, and she should plane with quite a load. Deftship doesn't go very high on the speed range, but you can see where the resistance is headed when she gets above hull speed. You'll want something designed by a pro, but for purposes of discussion, is that what we're talking about?

[DLC]

Like this?



17'9", by 5' 7". I've shown her at a displacement of half a ton, but she'll carry a lot more. Here's the resistance curve:



Figure about 25 lb of thrust for every horsepower, so at half a ton of displacement, she'll plane with less than 10 horse. Put 20 on it, and she should plane with quite a load. Deftship doesn't go very high on the speed range, but you can see where the resistance is headed when she gets above hull speed. You'll want something designed by a pro, but for purposes of discussion, is that what we're talking about?

I like that.
The basic idea i had was 4 foot bottom with a 5 to 6 foot top and bring it back to 4 foot at the bow with 2 foot sides.
T
hanks

[johnw]

So more like this?



I'm showing it with a slightly bow down posture, because if you put a great honkin' diesel in it, that how it will sit unless you're using a v-drive to keep the weight aft. I'm also showing it at 1800 lb., which is probably closer to the load you're talking about.

With the narrower beam and heavier load, here's what the resistance cure that Delftship gives me looks like:



Even at that weight, it would take only a little more than 10 hp. to get it planing (with the right prop) so I'd say your plan is practical.

[DLC]

That is so cool.
I just need to stick a deadwood on it and I am off to the races.
thank you for this.

[johnw]

Hey, if you want to try and build from that, we might conspire with Lewisboater to provide offsets and panel developments. If you're fool enough to build it, I'm fool enough to let you.

[TR]

Can I just mention that those resistance curves apply to a hull form series completely different from the one envisaged......thus they are misleading at best.

[johnw]

Can I just mention that those resistance curves apply to a hull form series completely different from the one envisaged......thus they are misleading at best.

Thank you for checking in! My tools are limited, as is my knowledge. The cartoon above was to get at what DLC wants, although I'm thinking a johnboat is not all that complicated. Do you know of an existing design that fits the parameters?

[TR]

It's effort vs outcome......more effort equals a more capable, efficient, and better handling boat. A Garvey (vee bottom) will be better than a straight scow. Bob Stephens and Sam Devlin have big Garvey designs, though neither for inboard power. Fit a full length keel so she's not always chasing her tail. In any sea a scow will take the bow wave right over the stem, unless you go very slow or trim her stern way down. She's not going to plane unless built very light with just the right gearing and prop, and no skeg. So there may as well be some rise to the bottom aft, again making her a better boat.

[DLC]

I'm not really after a nice planing hull so much as more of a shallow draft (without a tunel drive) stable, work boat.

I'm thinking 1 1/8 inch plywood bottom, and 3/4 inch plywood sides.
Twelve knots more or less would be fairly optimal.
Not too worried about the handling of a flat bottom scow, as I've run these for several years.
This boat isn't to be entirely permanent in that I won't be treating it with the utmost care. I would be surprised if I got three years out of it, hence the cheap build and ease of construction.
Any ideas?
Thanks

[johnw]

What's the use you'll put it to?

12 knots is planing speed, so maybe Bill Garden's 20' garvey in More Building Classic Small Craft would be the ticket.

[DLC]

I will be landing on to the beach with it to get logs, firewood, loading and unloading a couple of small motorbikes.

[Ben Fuller]

What you want is the simplest of what around here is a commercial boat from the Carolina Skiff. Comes in a variety of sizes and styles but the simple one is the DLX. Basically a lat box with a curved up bow. They are designed for OB. Swipe dimensions from one. You would be in the larger size because of the weight of your engine.

[DLC]

http://www.youtube.com/watch?v=pCpl-...feature=relmfu

In this video at 2:44 the boat is scooting along and from what I can gather it only has 8 hp the smaller ones have 4 hp and seem to do similer speed.
From what I can find they have a 3 foot wide bottom and are 20 to 30 foot long.
So what I am thinking is a bit shorter and wider but has 3.75 x the hp?
What am I missing?
Thanks

[johnw]

I've seen similar boats in Thailand that seemed to scoot right along. I was puzzled by what Tad said, so I looked up garveys in Henry Sucher's Simplified Boatbuilding: The Flat-Bottomed Boat. He says that flat-bottomed power garveys with straight runs can be fast, but tend to pitch in a seaway, and most garveys were therefore built with some rocker to improve their seakeeping abilities, and as a consequence ran at 9-11 knots. He includes the lines of an 18'6" "high speed" outboard garvey that looks a lot like the picture I drew, but with more beam. You should try to get a copy of that book.

I suspect that what Tad is talking about is the limits to how fast you can push the type in a seaway, so it matters a lot how protected the waters you have in mind are. The vid you posted is in a slow-moving river. Go out in a bit of chop and the boats might not do as well.

[johnw]

Evidence that a flat-bottomed boat can be quick, though perhaps not in a seaway:

[peabody]

LOL!!!! I just cracked up! !!

[johnw]

.

[DLC]

Thanks for all the help I am still waiting to find out about the motor.
When i find out i will let you know what it is.
DLC