Thursday 20 October 2011

Oar length

I've been discussing oar length with Gavin Atkin of intheboatshed. He has received the exciting news that the first Oarmouse has been built to his plans for a fast, stable, easily-built sculling boat that can be made from just two sheets of ply.
The builder, Fred Rodger in the US, says it fulfils all his expectations but needs a skeg to stop it turning too fast. A skeg is under construction. He is also rethinking the outrigger and thole pin arrangement.
Thole pins are very ancient and still used in many parts of the world, mainly in traditional fishing communities. The rope holding the loom of the oar against the thole is called a humlibaund in Scotland and an estrop in Catalonia. 
Fred doesn't say how long his oars are but Gavin thinks they may be too short.
There are lots of formulae for calculating the 'correct' length of oars of varying complexity ranging from a simple 'half the span, times three, plus six inches' (span is the distance between the thole pins) to the widely-quoted Shaw and Tenney equation that you need a computer to calculate.
I personally use trial and error. Start with oars that are too long and take them out for a thrash. Then cut them down by half an inch. Repeat the process until you feel really comfortable. Then go rowing.
With modern oars, you will need to adjust the button that holds the oar in place against the rowlock to maintain balance, but with Fred Rodger's thole pins it will mean simply repositioning the strop.
It is also worth looking at the height of the rowlock. Even a small change in the height will make a big difference to the height of the handles above your knees - raising the rowlocks just a little can transform an uncomfortable and cramped stroke into a lovely casual swing.


Mike said...

Do any of these ‘formulas’ make provision for the age (increasing weight) of the old git rowing?

And what about compensating for weight distribution if the wife (large) or girlfriend (petite [who are you trying to kid?]) is sat in the stern-sheets twiddling her parasol?

Chris Partridge said...

However old or lardy the rower, the ideal length for the oars remains the same (don't ask why I know this).
The same is true about the weight distribution in the boat - you may need to relocate the oars, but they will be the same length.

momist said...

I agree about the height adjustment at the rowlocks. I've never used thole pins, but would assume the same sensitivity to this. For a long time I've been thinking that my rowlocks should be about 1/4" higher than they are, and it would have been so easy to do in the construction stage, but hard to adapt now.

doryman said...

Chris, I like to start with twice the beam (or outrigger, if applicable) and go longer, if possible. Longer is better. Same goes for waterline.
A man can never have too many oars.


Jake Millar said...

I've been using 7 1/2' S&T spoons with my "Needlefish" - the same oars I use with my Barnegat Bay Skiff and the Graham wherry. Culler and Michalak call for 8'8" oars for the "Otter/Batto" design but since I use a drop in rowrig (fixed seat) the oar length can be fitted to the outrigger length. I may plunk down the $$$ for a nice pair of 8' spoons soon though.

Antonio Majer said...

hi all, I have been following this blog for a while now. Just to say that in my experience the oar stiffness is also very important; I built two pairs of oars out of ash, and the oars with loom are my favourite because very rigid.