designing a fast rowboat

Well you know how it is. I'll spend the next six months critically eyeballing it from every possible distance and angle, then decide there are half a dozen places where if I just moved a line by 1/32" it would be so much better.

 

What nonsense, This boat is saying, "I want to go rowing, please finish me, summers almost here, hurry up"
I hope the next fotos show a smiling owner, and a happy rowboat.
looks real neat to me

 

I didn't mean it wouldn't get launched for six months, or that I won't enjoy it. It's getting launched this month and I bloody well am going to enjoy it. I know what I'm like though. I will be eyeballing it from every angle and thinking about how it could be improved. Clint calls it "sneaking up on perfection".

 

How long does it take to sand off a 1/32 of an inch, here and there?

 

Longer than I'm going to spend on it.

 

I'm a big fan of "near enough" perfect.
Diminishing returns and all that.

Actually, I'm contentedly enamored of "good enough for a Tuesday dinner date", about 6 on the ten scale.

 

I'm a big fan of absolutely perfect perfect, in that I'll take it if I can get it, but won't lose any sleep over it if it's not possible. This boat is good. It's certainly good enough to keep me and several other people happy.

If I ever build another one, by then I'd probably be able to think of a few ways to make it a bit better. Of course, being a inventive and capable lad, by then I would probably also be able to come up with new ways to stuff things up too.

 

Hi NoEyeDeer I have been threatening to build another rowboat for some time now, i am at that stage where I need the excersise, and walking is getting problematic. lots of excuses, but the Herreshoff Gardner 17 always seems to crop up, maybe use the type of construction that you have used, it would certainly be lighter and help solve land manouvering problems. Might decide to stretch the 17 to 18. to give about 17 on waterline
Do you have any comments , negative or positives with this construction method.
I would be using the boat on "protected" bays and lagoons, as well as exposed lakes,, any comments I would appreciate, whart type of glue did you use.
for me , I know that a boats use is inverse to its manouverability on land , and therefor its weight.
From what I can see its a fairly straight forward method, i see that you might have used 4 or 5 frames, did you have any in between?
all comments appreciated.
nice boat.
Mike

 

If you want more detail there is a build thread over at the Australian Woodwork Forums - Nice rowboat, nothing fancy - but I'm happy to answer your questions here too.

Regarding the H/G 17: whether or not it is worth stretching it depends on how hard you intend to row. If you don't intend to spend much (or any) time over 4 knots or so, the original length is fine. I deliberately took a penalty in the < 4 knot range to get a bonus in the > 4.5 knot range.

My boat is glued with one of the local epoxies (Bote-Cote). There are three permanent frames at 1 metre centres, with the middle one being approximately halfway along the boat. These are laminated from Surian cedar, sided 16 mm, and taper from about 50 mm depth in the middle to about 25 mm at the sheer.

The stringers are also Surian, out of 18 x 11 stock, with a 15 x 3 rebate to take the planking. Planking is 3mm quandong ply.

There were an additional two temporary frames, just to provide extra support for the stringers during construction. These are visible in the pictures earlier in this thread, but have now been removed.

The positives with the construction method are:

1/ Very little wasted timber and effort, since most of it stays in the boat.

2/ Looks nice, IMO, and hides the edge grain of the planking even with a clear finish (stringers are rebated to take the ply).

3/ The stringers give a good backing for the laps, even on the upper planks amidships where the bevel is quite sharp.

4/ Second stringer up also makes a handy place to sit the thwarts, since it's at just the right height anyway.

5/ I did a very basic calculation on longitudinal strength and stiffness, and it seems that this is better with the 3mm planking and stringers than it would be with 4mm planking and no stringers, which would be about the same weight. Would want to do a more sophisticated calculation to verify that.

6/ The stringers provide more support for the planking during building, which is good since it has almost no stiffness of its own until everything is glued up.

Negatives are:

1/ More cluttered interior.

2/ You have to make the stringers.

3/ Really, I should have used closer spacing on the temporary supports, due to the lightness of the scantlings. It works with what I used, but I wouldn't recommend it for a beginner since there is too much margin for error if you aren't careful. I ended up putting in extra props here and there with hot melt glue. These were just offcuts of whatever, temporarily propped from the strongback. This was me winging it out whatever worked, and someone with less experience might get themselves into trouble.*

It would be best to halve the spacing of supports to 0.5 metres. This means more temporary frames, which means more work and wastage.

If I was doing another one, and especially if I wanted to build two or more, I would probably build a jig to plank the boat over. This would be framed up at 0.5 metre centres, and use heavier stringers since their weight wouldn't be important. The permanent frames would probably be fitted to the boat once planking was finished. This is how the Savo's are built in production, and those guys seem to have things sorted well.

Regarding other details: I used a solid sheer clamp/inwale on this boat. The stiffness of the finished structure is quite adequate, so it's on the money generally, but a spaced inwale would be slightly lighter for the same stiffness. It may also be possible to use a thinner bottom panel and get away with it (I used 6mm ply).

Other dodges are possible too. The frames could be made mostly of paulownia, with the inner strip being a denser timber. Same for the sheer clamp/gunwale combination. Stringers would be fine in paulownia, at perhaps a slightly larger scantling.

Having given it some thought, I think it should be possible to bring the same boat in at 25 kg all up, including all paint, etc, with equal or better strength and stiffness, and no reduction in practicality, at the cost of a bit more work.


* The Norwegians do this sort of thing with their traditional boats, and I like the way the Norwegians do boats even though I was building something different. Incidentally, their faerings were the inspiration for using three comparatively hefty frames at 1 metre spacing, with only breasthook and stern knee to hold the ends together. It's all a bit of a fusion really. I just took good ideas from anywhere and added my own tweaks.

 

Hi NoEyeDeer, Thanks for your very detaild response. I have also registered with the Australian woodworkers forum and visited the site you have recomended, I have read about 1/2 the discussion and will finish reading the rest today, very interesting indeed.
You seem to have access to some very nice wood over there, here in South Africa, everything kool is imported, so it seems to cost a bit, Theres lots to contemplate.

 

From Paul Gartside's Facebook site:

This excerpt of the book (http://woodenboatstore.commercev3.net/downloads/Plans-Dreams-excerpt.pdf) contains the plans for the 17ft. Coastal Rowing Boat, design #179.

Fotos of the build of this lovely craft: http://www.mcnshipwrights.com/rowing-skiff.html

 

It's a nice looking boat (all of Gartside's boats look good) but IMO very heavy and complex construction. The Savo's come in a lot lighter (around 2/3 the weight) and they're 4 feet longer, with the same beam and equal or greater depth.

I never received a reply to my email, when I asked about the rough water performance of the boat in the photos.

 

Doing some calcs. Does anybody know the GPS distance, average, of people doing the Blackburn in rowboats? I can only find info that it is a 20+ mile race.

 

Found it. I knew it was in this thread somewhere.

If you want it in kilometres too, it'd be 31.6. So:

17.0 nautical miles
19.6 statute miles
31.6 kilometres

Take your pick.

 

nautical miles

fyi, my gps said 17.27 nm ( +/- ... as i veered off course a bit in the harbor )