designing a fast rowboat

Wherrys

I'll come late to this party, if it's still about fast rowboat designs. I'll confess I haven't read all 40+ pages of this thread, but, as for what makes a fast rowboat, the racing shells - obviously - have it right: Round hull sections, low wetted surface, long waterlines, little rocker, double ended, sliding seats, light weight, stiff hulls.
Incorporating these facets into a more seaworthy craft would go a long way towards a race winning pulling boat . . . .

There are ocean going shells, but, to me, what the scullers consider a "wherry" is a more useful compromise - more seaworthy and capacious than a shell, by far, but faster and more performance oriented than a typical "rowboat" (dory, peapod, etc).

Ken Basset's Firefly and Liz designs are good examples, as is CLC's Annapolis Wherry and the Appledore Pod.

I liked those designs, but I wanted a much lighter, much easier to build version, with some personal ideas incorporated into hull shape and her character. From other forums, some of you may know me as a fairly prolific builder of SOF kayaks, and, true to form, I designed and built my pulling boat for (non-traditional) SOF construction.

Here's a pic of RUTH, set up for fixed seat rowing:

I built her last year. She's 18' long by 33" wide, built of WRC and 1/2" marine ply, skinned with 8oz polyester. She weighs about 45lbs, can take a passenger and uses either a sliding seat or a fixed thwart for rowing.
And, she's great - goes very fast with very little effort, and takes wind and waves with aplomb. Easy to cartop by myself, too, and certainly no need for a trailer or dolly.

Anyway, she's my contribution as a fast rowboat design. The wherry concept is clearly not new, but I like to think this version is - and she does move right along.

Dave Gentry

 

Dave ; that boat is gorgeous ! More pic's please - Nick

 

"Ruth"

A very nice boat, and one that must be a joy to row. My only negative is that in my racing rules, the outriggers put me in the same class with sliding seat boats such as an Alden ocean shell. The 8 0z Polyester you covered her with, Is that some thing special or can you buy it anywhere. Also,what did you use to waterproof it? I covered my boat with canvas and painted it with acrylic housr paint. it works just fine but is very heavy, probably adding 20 or more pounds to the weight of the boat ( 90 lbs - overbuilt for the ocean, maybe too much ) I'd appreciate some more construction details.

 

Thanks, guys
I like your skinboat, too!

I get my boat skinning fabrics from the famous George Dyson, who carries many varieties - email him and he'll send you the data sheet. GDyson@gmail.com

I coated the skin of this boat with ZAR exterior oil-based polyurethane varnish, which is relatively inexpensive and works well.

Construction is cedar stringers on ply frames, with substantial inwales, breasthook and transom knees. For more info on non-traditional SOF construction, visit Tom Yost's wooden framed kayak builder's guide: www.yostwerks.com

A couple of pics

 

Nice wherry there. Looks very slick.

Good to see this thread still going as I used to follow it for a while. Unfortunately I lost my password and the other account (melong) was on a now-defunct email so I've only just got around to re-registering.

I've been pigging around in DelftShip recently and, apart from fairing being a bit of a nuisance in the free version, I'm liking it quite a lot. Attached are a couple of shots of my current nefarious plot. This is not for ocean racing with two hefty blokes on board. You'd swamp in no time.

The idea is for recreational rowing on the rivers and dams around here, which means hardly anything in the way of waves. LOA is 6 metres, LWL is 5.74 m, BMax is 0.73 m, BWL is 0.52 m at a designed displacement of 120 kg in fresh water. Freeboard at lowest point is cut to 0.15 m (yes, it'll still work) with an illogical but nice sheer because I like it like that. The plumb bow is logical and the trailing stern is there for the same reason as the sheer. It wont slow me down much. I'm a lazy old sod and wont be going flat out very often so the prismatic is 0.55, which is about right for 5 knots cruising speed. Waterline is long enough not to pitch much with a sliding seat and the boat is narrow enough to use a double paddle in tight quarters.

Stability? If you have to ask you need something different. Suffice to say that the metacentric height is still positive, but barely. Construction will probably be 6 mm ply because I like wood and you can kick 6mm ply without worrying about it.

 

Hi , Welcome back, yes this thread has been something else. Nice looking plot you have there,
I've also been messing around with freeship and have come to the same conclusions as you,
Wanted a old type wherry for basically flat water , and a bit , to enlarge the normal scull conditions envelope,a tad, but didnt know where to start,, eventually bought some plans , and as nice as they were , they were not quite what I was after , may even go back to them one day.
so I came up with , Length 6.4 m 650mm beam max 530mm waterline free board is running at 160mm . and cill at pin having a height above water of 267/270mm, and prismatic of .61
Plan to build 4mm ply clinker, and a bit nervous.
Mike

 

SOF construction

Dave, you are a bold person, or I am very cautious. The rib spacing in your boat is quite wide, while I spaced my bent and laminated ribs on 10" centers. You also used fewer but heavier stringers than I did. €my stringers are 3/4" wide X 3/8" thick and, I have 5 per side. My gunnel is very much heavier than yours although you have built in a lot of strength with a lot less weight than in my boat. Does the fabric have any " give" as you row? My canvas moves just a little with no discernable bulging in even in a fairly rough chop. I am finding that my seating position isn't great. I need to raise the oarlocks about 2" to get the oars to clear my thighs in rough weather. If I do another, it will be more on the idea of your boat: longer narrower and lighter. Have you rowed with a GPS to check your speed, and if so, what are your cruise and race speeds? Thanks for the great pictures, they gave me some great ideas

 

Nordvindcrew, are you racing a skin on frame boat now or is this just for solo recreational use? Got any pictures?

Mike1, sounds like your idea is a bit more serous as regards speed than mine. I find that in practice I end up pottering around looking at the ducks and just enjoying the glide a lot of the time.

 

I like both your wherry ideas, guys. In practice, I find that the stability in my boat is enough - even in confused chop - that I could have gone with much less width for the type of rowing I am usually doing. I had visions of the Blackburn Challenge in the back of my head when I designed Ruth, but the reality is that, now that I'm back in Colorado, there is little need for rougher water capability. Maybe it's time for another boat . . . .
Of course, Ruth is actually perfect for the casual use I put her through - looking at ducks is nice, too (though I miss the seals and otters, etc, of Puget Sound). I'm not sure an even more performance oriented boat would make me happier.

I'm pretty familiar with non-traditional SOF construction, and the scantlings on Ruth are just strong enough, without being overbuilt. Lightweight was one of my goals. The polyester skin has a little give, but I've never noticed it in use - only when I push on it.
I have never brought my GPS along for a row. Seems fast, though! There's basically zero human powered boat racing going on around here - other than the sculls and shells - so all my rowing here is just for exercise or fun.

Nordvindcrew, perhaps you could lower your seat, rather than raise the oarlocks?

A couple more pics of fixed thwart rowing, from last weekend:

 

Here's an idea. If you're mostly happy with the boat for now how about making yourself some spiffy spoon bladed oars?

I made a set once that had redwood for the shafts with an Oregon strip down the tension face and a tallowwood strip down the compression face. Tallow is a eucalypt that is very strong and stable and about 62 lbs per cu.ft.

Wood is usually about twice as string in tension as it is in compression, and strength scales roughly with density for high quality timbers. The strips tapered from 5mm at the looms down to about 2mm at the blade tips. Blades themselves were stacked up out of some WRC offcuts with an Oregon strip across the end grain to stop splitting.

They ended up very light, stiff and well balanced. Lovely to row with and not that hard to make.

 

This is a very long thread and I've read at least most of it and don't remember any input on front rowers. I have one and am about to get another. The one I have is by Ron Rontilla on the east coast. It's a rowing machine that most often is put into a canoe. See: Frontrower.com
It's not a sliding seat but works better than a sliding seat. One dosn't make a large CG change during the end of each stroke, Only about half the energy that reaches the oars goes through ones shoulders, arms and wrists, and your'e facing the direction the boat is moving. The oars do not, however, help w stability but they automatically rise and fall the correct amount and automatically feather at the perfect time. Non stretch lines (hooked to foot pedals) pull the oars back when legs are extended. One can row entirely w legs, arms or feet. Take a picture, eat a sandwich or rest "one end". While rowing a 3' X 16' canoe one can go as fast as a kayak and into the wind too. Is this of interest?

Easy Rider

 

front rower

I've seen Ron Rantilla in several races and the front rower really works. It is clased as experimental and competes with sliders and multis and does very well. The product seems complicated but looks to be of high quality and well built.

 

skin on frame racer

Yes, I'm racing my skin on frame boat and doing OK for an old, out of shape guy. It is very simlar to Dave Gentrys' boat but deeper and wider and a lot heavier. I purposly over built it knowing that it would be rowed hard in nasty conditions with 2-3' chop on top of whatever swell is running at the time. I've got some hollow shaft oars under way and just need to find the time to laminate the blades and finish them off. In regards to lowering my seat; it is a good idea, but my legs cramp up terribly if they are too straight and flat. I need to be able to flex my legs and get some knee bend in to get the power to the oars. If you google Essex River Racefor 2009/2010 there are photo galleries and each has one shot of me in the Nordlys. It is the only blue single in the race

 

Umm, in the 2010 gallery there are half a dozen different blue singles. How about a direct link to the relevant pic? Dis is de internet innit.

 

hmmmm

sorry about the lack of precise info on the pictures. I'm an internet incompetant with little in the way of skills. Way back in the thread there are some pictures of the boat on its' trial launch. To identify me, look for an old guy with a pony tail. Look on page 27 for launch