Thread: Nice rowboat, nothing fancy.

Right. Progress, of sorts. Spent the afternoon going through a pile of old hardwood I had lying around. Scrounged some good bits for the strongback. It wont be pretty, but it'll do the job and it's free. Gratuitous pic included. Will do some more cutting and some assembly tomorrow.

Now the other problem is that I had to go and look at the lines again, and decided the lap lines and sheer and a few other details needed a tiny bit of tweaking here and there. The sort of thing that if I don't do, I just know I'll be kicking myself every time I look at the finished boat. So, that means redrafting the patterns of course. I'll do some of that tonight.

Getting the strongback started is good motivation to do the redrafting (which wasn't really an appealing prospect). I wont bother posting a new lines plan, because the changes are very minor and would be hard to pick in the lines. They're more noticeable when spinning 3D perspective views around and scrutinising the thing closely.

Anyway, it's started, which is something.

Originally Posted by Sumbloak

Anyway, it's started, which is something.

That is the hardest part.

This looks like a very efficient boat to build. What is the spread, pin-to-pin, of the oarlocks?

I too like a narrow flat bottom.

I like how the aft end of the hull acts as a skeg. That should also help beat a H/G rowboat...it was amazing how unstable the boat became at higher speeds.

Cool stuff,

Clint

Spread is 1280 mm (a shade over 50").

The Sea-Bright-skiffish garboard aft is partly for directional stability, but it also happens to give the best distribution of volume for minimising wave drag in the target speed range. So it ends up being a win/win.

I gave the chine for'd quite a bit of rocker in an attempt to equalise (more or less) the pressures on topsides and bottom panels at the bow. This should cut drag and improve directional stability, due to the lessening of vortices off the chines. I know that traditionally sharpies and the like minimised curvature for'd, but with the bottom in this boat being so narrow I think it'll work.

Also, after thinking a bit more, I reckon I can get away with three permanent frames at the obvious locations, and just use temporary moulds for the bow and stern stations. With three frames and the stringers behind the laps, I think it'll be strong enough. If it wobbles too much, I make some extra frames.

Of course if I was building several of the things, I'd probably just make a mould that had stringers set in it and build the boat in 4mm ply without permanent stringers (same as Tom Hill's boats). At this stage I'm just building one, so am going for a method that suits. The whole thing will come out of 4 sheets with very little wastage. That includes two layers for the 6mm bottom. I'll just laminate that up on the concrete slab in the carport. I have a pile of old bricks to weight the layers down, so it'll be easy.

And LOA? I did not see that...BWL?

Drake has 3 frames and the rest of the stations are moulds.

With 3mm...I might keep all those frames in....????

LOA is 5505 mm (18 feet 3/4")

BWL is 708 mm (slightly under 28") at 247 lbs displacement in fresh water.

I'm not nearly as hefty as you are (5'8") so that displacement will be about right. I suppose I really should put all five frames in, and then decide if some could be left out of the next boat. The weight penalty would be very little. That would be the safer bet, but the Tom Hill boats are 4mm with no stringers and no frames, and from what I hear they do just fine. Also, the ply I'm using is quandong, which is a bit denser and stronger than the gaboon Hill uses.

Originally Posted by Sumbloak

Spread is 1280 mm (a shade over 50").

8 1/2 foot oars or even like 8'9" would work if you use crossed hands on the drive. That is nice.

Originally Posted by Sumbloak

I gave the chine for'd quite a bit of rocker in an attempt to equalise (more or less) the pressures on topsides and bottom panels at the bow. This should cut drag and improve directional stability, due to the lessening of vortices off the chines. I know that traditionally sharpies and the like minimised curvature for'd, but with the bottom in this boat being so narrow I think it'll work.

I was wondering about that cut away forefoot. What do you mean by "equalise" pressures on topsides and bottom? Do you mean the forefoot won't grab as much?

I hate crossed hands on the pull. I find that a real nuisance in rough water. I was thinking of using 8 foot max. Bear in mind that because of the height difference, I don't have as long a reach as you do.

If you have a bottom with no rocker for'd, there's not really any pressure exerted due to forward movement (angle of incidence = 0) but the entrance angle means there is such pressure on the topsides panel. Result is that the flow will want to wrap around the chine, which will cause turbulence. That's the theory (Bolger was into this too).

In practice, with my old boat years ago (double ended, three panel job) I found that it had to be trimmed so the heel of the stem was about at the waterline. That meant the heel of the sternpost was slightly below the bottom at midships. If the bow dug in much, the thing got squirrelly under some conditions. I've heard that skiffs and sharpies tend to have the same problem, and I think it's to do with the turbulence off the chine dragging the nose around a bit.

Anyway, lunch is now done. I'm going to go make some more noise and mess. BBL.

Had to do some other stuff as well today, but the basics of the strongback are together now. That's about 200 pounds of old hardwood and batten screws, and is already very solid even without any bracing. Solid is good.

Originally Posted by Sumbloak

I hate crossed hands on the pull. I find that a real nuisance in rough water. I was thinking of using 8 foot max. Bear in mind that because of the height difference, I don't have as long a reach as you do.

If you have a bottom with no rocker for'd, there's not really any pressure exerted due to forward movement (angle of incidence = 0) but the entrance angle means there is such pressure on the topsides panel. Result is that the flow will want to wrap around the chine, which will cause turbulence. That's the theory (Bolger was into this too).

In practice, with my old boat years ago (double ended, three panel job) I found that it had to be trimmed so the heel of the stem was about at the waterline. That meant the heel of the sternpost was slightly below the bottom at midships. If the bow dug in much, the thing got squirrelly under some conditions. I've heard that skiffs and sharpies tend to have the same problem, and I think it's to do with the turbulence off the chine dragging the nose around a bit.

RE: crossed hands...Drake has none because it is designed for open water rowing. So I know what you mean. But in sheltered, calmer waters, I know I'd be more efficient in m y stroke with cross hands....the St. Law. R Skiff uses this style, higher stroke rating. Quite different from how I row in Drake. My new boat will likely have pinned oars and similar rowing style to the SLRS.

Originally Posted by Sumbloak

Had to do some other stuff as well today, but the basics of the strongback are together now. That's about 200 pounds of old hardwood and batten screws, and is already very solid even without any bracing. Solid is good.

Now we are talking my expertise...building stuff. When I teach strongbacks, I have the students let me know they are done. Then I take my 205 lbs walk up to the work, grab hold of it and play king kong. If it moves I make them add more wood! Usually I rip it off the floor. So their first task is regluing it with construction adhesive to our cement floor!

Sounds about right. Don't worry, I'll be adding more wood. I do not like things wobbling around when I'm trying to work on them. Yesterday I was busy helping a bloke drop some trees, which among other things involved loading, and then unloading and stacking, around six tons of firewood. Knackered I officially was. Boatbuilding last night I was not.

About the stroke: yes I agree it would probably be better to have slightly crossed hands in smooth water. I can always make two sets of oars if I think it necessary.

Originally Posted by Sumbloak

Sounds about right. Don't worry, I'll be adding more wood. I do not like things wobbling around when I'm trying to work on them. Yesterday I was busy helping a bloke drop some trees, which among other things involved loading, and then unloading and stacking, around six tons of firewood. Knackered I officially was. Boatbuilding last night I was not.

About the stroke: yes I agree it would probably be better to have slightly crossed hands in smooth water. I can always make two sets of oars if I think it necessary.

One of the things I think about with crossed hands is that the seat height and gunwale/oarlock height relationship is key. In Drake, where I sit low and the locks are pretty high for knee clearance when in rough waters, if I were to row cross handed, I'd need to have one hand over the other vs one hand in front of the other. In a set up where my hands were lower on the drive, much like a scull, I'd prefer having one hand lead in front of the other on the drive.

Feather vs no feathering is another big factor. In Drake, I row without crossed hands and no feathering, but I am considering for the next Drake having Douglass oarlocks and D-sleeves so I can feather.

In my race boat I'll likely have pinned oars.

Happy strongback building.

Here ya go. One strongback, now with extra wood. The thing is as solid as a hip hop girl's thighs.

It has enough bracing to be bulletproof, but still enough space for easy access to the inside of the hull. The crosspieces at the bottom of each set of legs are stuck to the slab with standard construction goop, just because I had a tube lying around and didn't want to mess around with dyna bolts. I'm not worried about it moving before I want it to, but getting the thing apart when I'm done with it might be fun. I'll deal with that when I have to. No worries for the moment.