The chester yawl has forward and aft bulkeheads on which the bow and aft seats rest. It has two ribs, forward and aft.

On my CY, I have three sets of oarlocks positioned as follow (risers on top of inwales):

The center of the fore oarlock is located 27" forward of the center of the aft rib.

The center of the mid oarlock is located 11" forward of the center of the aft rib.

The center of the aft oralock is located 16.5" aft of the center of the aft rib.

When rowing with two people, I use two seats and two foot braces. The adjustment is needed for different leg lengths, and it is not fun to have one rower constantly pushing on your seat back whith his/her feet. 

 Here is a picture (if I manage to post it) for a visual of the oarlocks:

https://drive.google.com/file/d/0B81mbFEcmsHodE90cl8tZUNzMmM/view?usp=sharing

Many thanks Eric. You boat is a real beauty! I can only hope mine turns out anywhere near as nice as that. I have the all-important paint and varnish finishes ahead of me...

Thank you very much for your measurements. I haven't tried marking them on my boat yet, but just doing the basic maths they are quite interesting. As I see it, the spacing between your fore and mid rowlocks is 27-11 = 16" and the spacing between your mid and aft rowlocks is 11+16.5 = 27". So your mid rowlock is a lot closer to the forward rowlock than the aft one. The plans I've seen (see my OP above) show them pretty much equally spaced, but without measurements. I'll be interested to see where your mid rowlock position compares to the distance shown on the official CLC plans I posted above.

I am encouraged that you seem to be quite happily rowing the boat with two adults. I look forward to doing that.

Many thanks again for your help, and congratulations on such a beautiful boat.

My aplogies, Giles!

I made a typo that I should have picked up on, before hitting send: the forward oarllock location is at 37" from the center of the aft rib (not 27). The rest is correct at 11 and 16 1/2, respectively.

Despite being CNC cut, all of our boats are ever so slightly different, and mine was an earlier kit, without alignment tabs for the ribs and bulkheads, so while the relative positions are likely accuate, the position of my aft rib, as referenced, may be slightly different than yours. I took a diagonal measurement from the bow to the port forward oarlock, and the distance is 83", exactly.

The CY rows easily with 1, 2, or 3 people (a stretch, but still easy to row). I have had two adults at fore and aft oarlock stations, plus a 10 year old on the bow seat, no problems. We were at 445 Ibs and the bottom of the top plank, amidship was 1" submerged (not much freeboard left, but the lake was warm, dead calm and we were only doing a straight cruise and back to the dock with life jackets on).

Sometimes I pop the Piantedosi row seat into the boat and go solo with the 9' oars and she glides like in a dream.

I will caution you, however that with more than one person, she becomes sensitive to trim and you want to make sure the heavier load is aft, in order to keep the skeg in the water.

I was taking passengers for a ride around the lake, switching people every so often, and I made the mistake to stay put and let one of the heavier passengers sit in the forward position. It was extremely challenging to track and as the wind picked up, it was impossible (skeg out of water). Otherwise, as long as you pay attention to that detail, she rows and tracks like she is on rails ... a true pleasure on a placid lake. I also took her into the ocean (along the shore, of course) and she performed beautifully with some waves and 12 kts of wind.

Thank you for the kind words, and post a photo as you finish yours. I am sure you are going to love it!

Hi Eric

Many thanks for double checking. Correction noted. I'll mark these positions and see how they look this weekend.

Warm water sounds like a useful criterion for rowing the CY with 3 aboard...!

I am also planning on having a sliding seat option (for when it is just me!) although I have bought the kit to construct the Angus Rowboats version https://angusrowboats.com/products/sliding-seat-rigger-hardware-kit-with-carbon-fibre-seat. I'm saving that, and building the sculling oars (also using Angus Rowboats design) until after I have the CY afloat...

I'll post photos once I have something photo-worthy.

Thanks again for your help. Greatly appreciated.

Hi Eric

I tried marking the locations you gave above on the boat. It seems that my aft rib is in a slightly different position than yours (maybe by a couple of inches) so the diagonal measurement from the bow was very helpful.

I'm now quite clear on the location for the forward oarlocks and the mid oarlock position you gave was about 3 inches aft of the location given on the CLC plans (above), so I don't have too far to go wrong there.

However the aft oarlock location still has me puzzled. In the photo below I have positioned the oarlock risers in the location of the measurement you gave above. I have also put the foot brace in the aft-most slots in the floor. To me the relative position of the oarlock and foot brace doesn't make any sense, as they are more or less in the same line.

It seems to me that either I need to modify the design of the aft foot brace so it can be positioned further aft (or do away with it altogether and the aft rower will need to brace their feet against the aft seat) or the aft oarlock position will need to be about a foot further forward.

I note that you said that you use two foot braces when rowing tandem. Is there any chance you could send a photo showing the aft rowing position with oarlocks and foot brace both in position?

Sorry for the ongoing questions, but this does seem fairly critical and once the oarlock risers are glued in position I don't want to have to move them...

Thanks again for your help.

I pulled out those two different sketches, got 'em to the same scale accorging to the length of the boat, and it appears that the oarlock positions differ between the two, particular with the aftmost ones.

The topmost sketch above shows the aft ones located just aft of that bulkhead, the lower one shows them farther aft, much as in the mock up photo.  If I had to vote, say the location in the topmost sketch seems more likely to produce the desired results, but I'm guessing.

Sounds like a good question to raise with the folks at CLC.  You're right, you don't want get this wrong.

.....Michael

   Thanks for your thoughts Michael

I have contacted the CLC people and have mentioned this thread. Hopefully they may reply here. It seems like a fairly straightforward problem which should be addressed in the plans...

   For anyone following this thread, or interested in it in the future, the answer to the problem has been provided by CLC in the form of these two diagrams:

and

The rowlock position more or less matches the location given by Eric above. However the key point is that the foot brace used by the aft rower is different from the one used by the front / centre rower.

My kit was sent with 2x footbraces like the front one. Hence my confusion.

Many thanks for your input. I think this mystery is now solved.

Shezam!  I'm saving those drawings.  Thanks for sharing that, Giles.  I have long lusted after a chester yawl as a rowing-only expedition boat with sleep aboard potential, given some clever canvas work...and I might actually do it one of these days.

.....Michael

Thanks for posting these, Giles! I find it interesting that the aft braces are different. Mines were identical, and seem to work fine.

I must say, also that my kit was a 2007, so the Mark  II, or whatever version is slightly different and improved, I would assume.

   Interesting thread but the upper drawing above is pretty weird, is it just me or is the aft rower's oar not on the aft oarlock position like the forward rower's is?

Yes, indeed. That same sketch threw me as I have been working on setting up my second rowing station in my CY. Frustrating. 

   Yes, indeed. Frustrating.

I sent this image back to CLC more than a week ago and have received no response.

I'm afraid I've decided that I will just have to figure it out for myself.

I've tried mocking up a rowing position using a low stool and some books as a foot rest and I estimate that I need a distance of about 25" from aft edge of seat to heel of footrest. That is approximately in line with my scaling off the above CLC diagram with the rowers shown.

There is also very helpful information here https://angusrowboats.com/blogs/news/fixed-seat-rowing-geometry which states

"The oarlocks should be placed approximately 13” back from the aft edge of the rowing seat. This is a suitable distance for most rowers. If you are customizing the distance specifically for yourself, add an inch if you are taller than average or subtract an inch if you are shorter."

This would put the oarlocks in about the centre of my 25" space from seat to footrest - which seems about right.

I think the location of the aft rower's seat in the above diagram is about right, so I'm intending to locate my aft rowlocks about 12" aft of the aft frame. Like this
I am still awaiting the replacement aft foot brace kit, but I think it'll end up about where I've placed the one in the above image.

Hopefully that works out right. Frustrating that we need to work it out from first principles. Oh well, I feel I understand more about rowing geometry now.

Which raises another point, and perhaps I should start another topic for this: The rowlocks on a CY seem quite narrow (close together) if they are mounted on the inside of the gunwales. I'm therefore tempted to mount them on the outside of the gunwales instead. Initially I thought this would be a terrible idea, but the more I've looked at it, the more sensible it seems to me. Yes there is the obvious hazard of the rowlock holder bumping against a boat/wall etc if the CY was moored up against it, but I think I can live with that. This boat is made for rowing!

   Yes, indeed. Frustrating.

I sent this image back to CLC more than a week ago and have received no response.

I'm afraid I've decided that I will just have to figure it out for myself.

I've tried mocking up a rowing position using a low stool and some books as a foot rest and I estimate that I need a distance of about 25" from aft edge of seat to heel of footrest. That is approximately in line with my scaling off the above CLC diagram with the rowers shown.

There is also very helpful information here https://angusrowboats.com/blogs/news/fixed-seat-rowing-geometry which states

"The oarlocks should be placed approximately 13” back from the aft edge of the rowing seat. This is a suitable distance for most rowers. If you are customizing the distance specifically for yourself, add an inch if you are taller than average or subtract an inch if you are shorter."

This would put the oarlocks in about the centre of my 25" space from seat to footrest - which seems about right.

I think the location of the aft rower's seat in the above diagram is about right, so I'm intending to locate my aft rowlocks about 12" aft of the aft frame. Like this
I am still awaiting the replacement aft foot brace kit, but I think it'll end up about where I've placed the one in the above image.

Hopefully that works out right. Frustrating that we need to work it out from first principles. Oh well, I feel I understand more about rowing geometry now.

Which raises another point, and perhaps I should start another topic for this: The rowlocks on a CY seem quite narrow (close together) if they are mounted on the inside of the gunwales. I'm therefore tempted to mount them on the outside of the gunwales instead. Initially I thought this would be a terrible idea, but the more I've looked at it, the more sensible it seems to me. Yes there is the obvious hazard of the rowlock holder bumping against a boat/wall etc if the CY was moored up against it, but I think I can live with that. This boat is made for rowing!
Mounting them on the outside of the gunwales adds almost 4" to the distance between rowlocks, and brings this up to about 44" - the lower limit of the range suggested by Angus Rowboats.

Looks sensible to me. Any thoughts?

I think I'd resist the temptation.  Mounted on the outside, they'll be forever wanting to catch on things.  The fittings themselves probably aren't likely to be damaged much, but transmitting a hard shock back to the boat might break something, e.g., the riser, rub rail, sheer plank, etc.  Seems best to let the rub rails do the rubbing without anything sticking out to catch someting or form an armor tipped point of contact against another boat.  Not sure the extra spread would be worth the risk.

Just my .00003108 cents...

.....Michael

Apologies for the two "goof" posts, first cup of coffee. 

So, after much noodling over the various diagrams and posts, my building partner and I have come to agreement that what really matters is the distances between each footbrace and stool (a bit more than two feet) as well as the distances between the oarlock and stool (a bit more than a foot).

The forward-most oarlock is already in place on my boat and the stern-most slot dictates how far back the rear footbrace can be. Of course, positions of the stools and forward footbrace can be adjusted a great deal. From there it is a matter of measuring off of those fixed variables as to where the third oarlock is placed.

I am also accounting for an earlier observation that there is a benefit in terms of tracking to putting the larger of the two rowers in the stern. 

It took me a while to get past the diagrams showing evenly spaced oarlocks and one showing the oarlock as a fixed distance from a rib. Then there was the diagram with the two rowers with the rearar oarsman not using the rear oarlock. What cinched it for me was putting the rear footbrace in the boat and measuring 17" back from the rib for the rear oarlock. That left about 8" between footbrace and oarlock. I couldn't picture squeezing myself into that space!

Initially I will screw the stern oarlock down, to be epoxied once I am comfortable with its location.

DaveJ

Sounds like a good plan.  When we built our PMD take apart, we mocked up both rowing stations by clamping them up and trying it out on the garage floor, which yielded some minor adjustments before screwing down and gluing up, being careful not to screw up.

Hope you get a good photo of her underway with tandem rowers soon!

.....Michael