designing a fast rowboat

Thanks for those links, Nick. Blue Skies is one cool boat. Petaluma sounds good. I will try to be there.

If I'm currently eyeing the St. Lawrence River Skiff Annie, especially if they offer her as a kit, but am worried about her windage, what do you think her limitations might be? If swells were not an issue, how windy would it have to be (in knots) before you think she wouldn't row into the wind, or with wind on her beam? Guessing would be fine as I tend to trust the instincts of those on those thread to correlate pretty well with real experience. Any other opinions welcome.

 

rowing unit

dcn blues, If you want to custom size a rowing outrigger , try looking at Glen-L kit boats site. They have plans and material to build your own rigger and probably size it to fit.

 

Good site, thanks. I also like their Sculling Skiff as an inexpensive and easy to build option (with the kit-made removable sliding-seat / outrigger setup inside). Good looking, clean little boat. The plans for an option to the Piantedosi rig are great to know about.



http://www.boatdesigns.com/17-Sculling-Skiff-recreational-rowing-shell/products/184/

 

Somethings funny about that picture of the Sculling Skiff - Those oar blades look huge !
I think I would still want the out riggers fastened to the gunnels some how to stiffen everything up. And I wand those deck to be sealed air chambers. I like the longer length of the Merry sea boats. But this might just be because I have spent most of my time in 24 ft and 27 foot sculls and 21 foot surfskis. Traditional boats just seem so short. Of course there is usually a lot more "boat" to them.
You didn't mention if you were going to trailer or car top?
I would not want to guess about wind speed and windage. people always think the wind is stronger than it really is and there are many days when I have looked a the Bay and thought it was flat only to be surprised when I was actually out on it. Wind on the beam is always the bigger issue due to the wind waves associated with it. Going straight out into the wind is fairly easy but slamming over waves can almost stop the boat dead . If the waves can be taken at a slight angle then the boat will come down more softly and maintain better speed. But it can be really nerve racking to turn around to come back in. I am thinking that it is the water conditions rather than the wind its self that will be limiting. Swells in open water are generally benin - they just look spooky. - N

 

Yup, I agree with everything you just said. I don't really have plans for car-topping, but it would probably be a plus. I do enjoy going out when it's too windy for sail. One oar in water that's 800 times denser than air means that short of a hurricane or an enormous amount of windage area, (or racing) I shouldn't worry too much about windage. You also have to schedule your row to the tide. There's little that's dumber than fighting the tide, and little more gratifying than rowing with it.

 

Although those outriggers look like they might not be stiff enough, having just made a similar set up (albeit using carbon fibre). I was surprised by how low the loads were on the outriggers when I did the calculations. I knew that the hull resistance was about 30N at 4kts, so could work back to get the average load on each outrigger (assuming that the power stroke was 1/3rd of the total). This gave a pull on each oar handle of around 45N average, say 135N peak. This is only about 30lbsf at the handle, so the load at the rowlock pivot isn't that high.

Jeremy

 

I've had a similar idea rattling around in my head except with a narrower hull and outriggers. Sort of a rowing trimaran. Thoughts?

 

That's funny. I don't know how I got there, but I saw this just last night:

http://www.wintechracing.com/index.php?target=/accessories/adaptive.php


Like the Rocat, it uses a sliding rigger which is great for reducing boat pitch, so the hull can be shorter. I'm not sure I want to be pushing the boat with my butt, lower back, even if that chair looks comfy. Of course I'd like to try it. As discussed earlier in the thread, sliding riggers won a few world championships in the early 80's, so the benefits seem sound, but were banned for competition.

 

Good information, thanks Jeremy. Any chance we could see your CF outriggers?

 

Hi,
That looks very much like the adaptive singles at my club. normally used for trunk and arms only, rowers

 

Here's a rough photo - they aren't finished yet. I still have to fit some Delrin blocks to take the rowlocks and finish off the clamping system that holds the outrigger securely to the rails



The plan is for the system to be fixed for the moment, with the position of the seat, outrigger and stretcher all adjustable on the alloy rails. This gives me the flexibility to experiment and to switch the whole assembly around to try a forward rowing arrangement I'm working on. I may try a sliding rigger system at some point, too, which is why I opted to fit rails the floors. The priority for me at the moment is getting the boat ready to row 50 odd miles down the river Thames in a few weeks time, though, so I'm going for the simplest arrangement to start with.

Jeremy

 

Wow, beautiful work. That boat is going to be a feather. Thanks for sharing.

 

Gorgeous work, Jeremy! I wish I had your skills.

 

Thanks folks, but I'm really just winging this as I go - I've never designed and built a boat before. BTW, there's no welding in this boat, the tubes are all just riveted together, using big stainless steel pop rivets. The tricky joint was the frame to gunwale one, so I had to come up with a way to get a strong joint, but keep it simple and easy.

The way I did it was to drill a 1/2" hole in the underside of the gunwales (the frames are 1/2" tube) and then make a sort of home made wall plug/split collet type fitting, from a bit of alloy bar. The frames have these split collets fitted inside their ends and a single 4mm stainless pop rivet inserted through the top of the gunwale goes into this and expands it to hold the frame very securely to the gunwale. Here are some photos of the test piece I made up to see if the idea would work:







The joints between the frames and stringers are just made with 20mm long 4mm diameter stainless pop rivets. The thick wall (16g) tube doesn't crush when these rivets are pulled and it makes for a simple and very quick way of building the frame. It took me less than three hours to put the frame together, much quicker than all the fitting out stuff!

Jeremy

 

great work

Jeremey, The boat is a real piece of work. I'm amazed at all the aircraft technology you are using as well as your own adaptations. Have you had it i the water yet, and if so, does the fabric press in to any degree?