MI12 Launch, and a rowing geometry question

Boats up to 15' for oars, power or sail. Please include the boat type in your question.
User avatar
glossieblack
* Bateau Builder *
* Bateau Builder *
Posts: 2985
Joined: Wed Jan 02, 2013 1:28 pm
Location: Australia

Re: MI12 Launch, and a rowing geometry question

Post by glossieblack » Mon Nov 11, 2019 6:33 pm

The top of the seat needs to be about 7" lower than the oars when horizontal, perhaps a tad more for 6'+ rall rowers.


Completed R13 two part nesting rowboat. ST 21 under construction .... where seeking perfection is recognized as the enemy of the good.

User avatar
jacquesmm
Site Admin
Site Admin
Posts: 27152
Joined: Wed Aug 14, 2002 1:00 am
Location: Florida USA
Contact:

Re: MI12 Launch, and a rowing geometry question

Post by jacquesmm » Mon Nov 11, 2019 10:09 pm

The seat ergonomics are based on the well known Mc Innis design as described in the Gardner book but I located the seat height to fit me, I am 5-10.
I use that height in several other row boats of that size.
I row with legs extended and the oars get close to my knees but don't hit them. I often use longer oars than most people and in a boat that size and beam, I use 7.5 oars and row cross handed.

However, I see a problem in the pictures.

To solve the problem:
use oarlock extenders or extended oarlocks like those:
https://www.hydeoutdoors.com/product/oar-lock/
and/or spacers:
https://www.hydeoutdoors.com/product/oar-lock-spacer/
or raise the oarlock this way:
Image

I had long oarlocks from Shaw and Tenney but can't find them in their catalog.
Image
The wooden riser is very common and probably more durable. I don't think you need more than 2". Look at this pic:
https://en.wikipedia.org/wiki/Whitehall_rowboat
the seat is not much lower.

You can always lower the seat but that is a big job plus, you will not sit comfortably if you too low.
Jacques Mertens - Designer
http://bateau.com

User avatar
jacquesmm
Site Admin
Site Admin
Posts: 27152
Joined: Wed Aug 14, 2002 1:00 am
Location: Florida USA
Contact:

Re: MI12 Launch, and a rowing geometry question

Post by jacquesmm » Mon Nov 11, 2019 10:32 pm

I wonder if these extenders would help:
https://www.shawandtenney.com/productdi ... r-brackets

They move the pin outboard and that raises the oar above your knees. many years ago, I have used similar folding oarlocks and they worked very well.
Jacques Mertens - Designer
http://bateau.com

Nick Werner
Frequent Poster
Frequent Poster
Posts: 21
Joined: Tue Feb 20, 2018 7:43 pm
Location: Indiana

Re: MI12 Launch, and a rowing geometry question

Post by Nick Werner » Tue Nov 12, 2019 7:52 am

Jacques,
Thanks. It's a big relief to hear you say that I will likely only need to raise the oars 2 inches to get them into the comfort zone.
That should be a pretty easy fix.
I'll try new hardware first, and if that doesn't work will make some risers out of leftover ash.

Thanks!!

User avatar
jacquesmm
Site Admin
Site Admin
Posts: 27152
Joined: Wed Aug 14, 2002 1:00 am
Location: Florida USA
Contact:

Re: MI12 Launch, and a rowing geometry question

Post by jacquesmm » Tue Nov 12, 2019 9:46 am

Test the new height before doing anything. With the oars raised just above the water, you should barely touch your legs.

I checked it all and here is how I got that high seat.
The original McInnis has the rubrail 6.5" above the seat top.
My design has it at 2.5", 4" difference. Why?
In my design, when you sit in the middle, your feet hit the forward bulkhead and you can't get your legs straight. It is the height of your legs that set the limit. I tested what would fit me and arrived at 2.5" but you are not only taller but more muscular. I had in mind that builders could always raise the oarlock sockets by a couple of inches if needed.
Glossieblack and others are correct that the ideal height would be 6 or 7" but this boat is too shallow for that. With the seat lowered to 6" below the rail, you hit your knees and sit crooked. BTW, that 7" is at the oar, about 1" above the rail. let's say ideal = 6".
I just checked a boat that I row often, it sits in my backyard, the FS12. The rail is 5" above the seat and there is some room left for a larger guy.
In your case, you can get to 5.5" by installing a raised block under the oarlock sockets. You can go higher with a long stem oarlock, let's say up to 7".
Do not neglect the idea of folding oarlock sockets. Those will spread the width between the oarlocks and raise the height above your legs by about 2".
That gives you a choice of options. I would start with the wooden block. They look good and are easy to make.
Jacques Mertens - Designer
http://bateau.com

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest