Thread: Sea going rowboat design considerations

Speculation on design considerations can never go too far. How would you get "outside the box" if you didn't?

I think the option of deck types, bags, chambers, etc can be left to the builder. I'm not a chamber person, nor do I think bags are particularly useful. If this boat was completely filled to the rails, it'll still be floating. It could be rolled, partly emptied and boarded, maybe pushed to shore, whatever, but I think planning for extremely rare events on protected waters or near shore craft is "burdening" a design, which doesn't make a lot of sense to me on a weight sensitive boat. A canvas deck will keep the boat fairly dry. Something more substantial will make the boat heavier, decreasing it's car topping potential. If the car topping desire came of the list, then more substantial decks would be reasonable.


I don't see why you couldn't install a bilge drain. It would be pretty foolish to store the boat right side up without one I'd think.

Your heels will probably be below the LWL, unless you're a paraplegic strapped into her. Her thwart would have to be well above the LWL, she's no shell.


These conflicts are the very reason I leave these sort of things to the builder, as they are the one who will best know how the boat will be used. My plans usually include options for several elements of the design. Sheathing schedules, material deviations, scantlings changes or adjustments, different configurations, etc. I usual cover most of the obvious possibilities. I do this to keep the phone calls down.

I got a call from Tom this morning. He's building a gaff sloop of mine (RYD-14.11) and wanted to know more about the plywood keel option I described in the scantling list. The regular strip plank build has a built up deadwood assembly of 1x6's, but a plywood option is mentioned. It's about the same amount of work, but uses more epoxy and has some complicated cutting. The advantage is it's lighter, the disadvantage (there's always a trade off) is it has a higher "goo factor". So, he called and wanted a better understanding, so he can make a informed decision.

Without this option on the plans, I'd get calls like"Hay man, how you doing, can I substitute the deadwood assembly for a plywood box sort of thing and how thick should the plywood be, etc." I've found if you give them options, it keeps them happy and they also learn the design isn't as stiff as my ex-wife's heart, but has some flexibility.

I had a very unfortunate experience a couple of days ago , that brought me "back to earth" , with a thump.
I finally got my swing mooring in Portland Harbour for HS , but its a fair way out.
I took my little tender down , to go and check out the mooring , and found a fairly typical strong offshore wind.
Getting out was easy , but I thought I'd better check on my ability to row against that wind fairly early , and lucky I did , because although I had the strength , no problems , my arthritic wrists were screaming in protest , and my hands started to lock up.
I made it back , just , but I'd only got a 1/3 of the way out !.
Damn !.
I guess I'm looking for a motor of some sort now !.
Rob J.

Brian, I think open v tanked comes down to intended use. Is it likely to end up in breaking surf? If yes go tanked, if not go open with perhaps small tanks each end. Also do you need to carry passengers or cargo?

"Tanked" has a quite different meaning in some jurisdictions...

I can think off no good reason -not- to have in-built buoyancy in a boat.
Even the best prepared & experienced people have bad things happen to them, even if
they themselves are not the cause.
Rather like wearing seatbelts really. You can be just as readily cleaned up by a drunk
"popping around to the shops" as on the Big Trip.

As MIKs designs shown, they can add much rigidity without adding weight if designed
into the structure. monocoque vs cab/chassis.

that's my 2.2c worth anyway.
cheers
AJ

Originally Posted by b.o.a.t.

As MIKs designs shown, they can add much rigidity without adding weight if designed into the structure. monocoque vs cab/chassis.

Mik's style of boat need something like a tank to give them the rigidity, hence the extra knees needed in that non-tanked rowing skiff built at Duck Flats. A glued lapstrake boat gains that rigidity by the overlocking planks being glued together ... a non-glued lapstrake (the old clinker boats) is very flexible because the boards can slide over each other.

Richard

Just been out in the Skerrieskiff.





Tried sailing her in 10 to 14 knots, somewhat gusty and variable, built to 20 knots after I came in I am glad to say.

Found her very much a rowing boat with a rig. Rather wobbly and not enjoyable as a sailing boat. Pretty quick and better when properly on the wind so I could sit against the side of the hull. Any lull and immediate movement inboard needed. I have found this before with rowing hulls with rigs.

On a broad reach, kneeling inboard seemed the only position. Really uncomfortable. I have found similar "no allowance" for the sailor with Iain O's boats before. Almost as if he designs for beauty but bugger the sailor.

Wind so gusty and boat so unstable went back in. It may have been my simple sail, centre of effort much more stable in the battened version.

Took rig out and went rowing. Much nicer. 100% more comfortable. She's a very nice row boat. Lots of compliments how nice she looks. Rowed about half way out to Hurst Castle and back, very pleasant. Not confident yet in my back after a recent re-injury. Want to row to strengthen it, but don't want to damage it either. Last weeks regatta rowing did seem to straighten things up a bit.

Summary - lovely rowboat not a sailing boat. Would be super for a couple rowing with kids in each end. The only design that I have experience of which seems to manage both is the Oughtred Tammie Norrie, a really sweet boat my son owns.

I have sailed Iain O's Elf in light winds and liked her a lot, so perhaps a softer steadier wind might have been better. The Scows were having their usual great time.

For me personally for rowing, I think I would prefer a lighter boat, less effort. Less strain on my back whilst I strengthen it. Yes, the Guideboat / 14.9 style.

Brian

Originally Posted by Daddles

A glued lapstrake boat gains that rigidity by the overlocking planks being glued together ...
Richard

I had an Oughtred MacGregor sailing canoe for a while, another long lean machine. Open decked, no bulkheads.

Watching the hull rack as load came on the sail was interesting indeed. Surprising amount of twist induced. Rowboat does not have that racking force but certainly is stiffer with decks and bulkheads.

I was hoping perhaps the 14.9 might have two versions. Open with 6mm and 9mm bottom, and decked with thinner ply but same weight overall.

For use as described in first post for launching through waves, decked with bulkheads would seem to me to be the choice. An open boat full of water in the shore break would be very heavy indeed, I would have thought.

Brian

G'day Brian
Your description of Skerrie Skiff's character rather accurately matches my Teal.
In fact, the only significant difference is that Teal (as I built her) is really only good for
odd numbers of occupants. The one time I've had a single passenger aboard rowing, it
worked out easiest & tidiest to turn around & row the boat stern first.

The other significant difference is looks, although I think Teal is about the nicest
possible out of two sheets of ply.

cheers
AJ

Originally Posted by Daddles

Mik's style of boat need something like a tank to give them the rigidity, hence the extra knees needed in that non-tanked rowing skiff built at Duck Flats. A glued lapstrake boat gains that rigidity by the overlocking planks being glued together ... a non-glued lapstrake (the old clinker boats) is very flexible because the boards can slide over each other.

Richard

G'day Daddles
My point was more that buoyancy tanks need not be a significant weight penalty,
even on the simplest & lightest structures. Therefore there is little or no reason not
to incorporate them into a build, except perhaps on ultra-light competition craft.

Even so, I'd wager that light tanks would stiffen even an open glued lapstrake boat
appreciably, unless it were already carrying extra weight as bracing. Frames &
chunky spaced gunn'ls aren't just there for decoration!

cheers
AJ

Howdy Brian,

Boxed in seats particularly in the ends (or corners of a non double ender) are a general panacea against twisting. Make a huge difference. Some like the traditional looking seats though.

We have one tram line here that goes out to Glenelg by the sea. The old wooden trams have been mostly phased out (a year or two ago) but still do some runs on weekends and holidays.

One of the joys is to sit up one end. Adelaide is very flat but when they come down the one hill at high speed you can see the front of the car laying over at about 5 degrees compared to where you are sitting. All the windows become visibly trapezoidal too. They don't break because they are a very loose sliding fit - so the rattling is tremendous.

Gives one as sense of the perils of land transport as earlier bods must have felt them. All at about 60kph!

Best ride in Adelaide!!!

The modern trams with glued in glass and monocoque construction are boringly rigid.

I think this goes a long way toward explaining the continued interest in sailing craft.

MIK

It seems that PAR has rightly stated his design will be 6mm and 9mm bottom and open, and he's the designer. Also that we can make it thinner if we wish to risk racking and add tanks if we wish. So I guess subject covered!

I am wondering about beach "storage" for a 6mm, 9mm version.

I am lucky in living on a cliff top, with a broad shingle beach at it's base. Some of the best fishing in the UK is off the Needles (western corner of the Isle of Wight) which I look over. So how great would it be to store the boat actually on the shingle, slide her into the water and go fishing! I feel sure that some local council law will prevent it somehow, but it might be fun finding out. Surely for thousands of years men have done just the same. There is even a Bronze age settlement just a few miles down the coast at Hengistbury Head.

The fishermen of British Columbia used a similar boat for longlining and hand trolling. This modern version is quite similar to 14.9. It also has a reputation for being pretty quick.

http://westlakeboats.ca/ and click on Brightsides.



Brian

Hi PAR, is the .56 Cp for the 14.9 with one person on board or fully laden?

Kelvin

No, the numbers were generated at the drawn displacement, which is 3" of draft and somewhere in the 200 pounds range. Naturally, her Cp will rise the deeper she sinks to a certain point. Except for racing craft, the prismatic coefficient being much higher then a rower's abilities (S/L of 1.5 or less) is meaningless and in fact is more wetted surface to haul around, for no particularly good reason. In this format, the Cp is more a gauge of how fine the ends of the boat are.

Great picture of one of the handliners with small sail set in rough conditions on the 2009 Shipyard School Race.



and a bit calmer here



Brian