Perfect Length Oars? Measurements Needed! - Mountain Buzz
 



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Old 04-26-2012   #1
 
Boulder, Colorado
Paddling Since: 1986
Join Date: Apr 2007
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Perfect Length Oars? Measurements Needed!

Do you think the length of your oars is perfect? I am working on an oar sizing formula. Please provide the following three measurements to help out:

1) Span of your boat from Oarlock to Oarlock
2) Distance apart (or overlap) of your oar handles if they are pointed straight at each other
3) Total length of your oars including handle and blade.

The old rafters formula is one part inboard and two parts outboard, but I think this is a bit off for narrower boats. Van Claussen's formula was developed for fixed-seat rowing skiffs and dictates an ideal 7:18 leverage ratio for maximum efficiency, but this too seems a little off.

The more data points I can get, the better. I will post the results when I'm finished. I am aware of the secondary concerns related to ideal handle height, not reaching too far into eddy water, and 25ish degree similar triangles.

Any other info you can provide on other lengths you have tried that didn't work, secondary considerations, etc... is appreciated.

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Old 04-26-2012   #2
 
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Kalispell, Montana
Paddling Since: 1997
Join Date: Apr 2012
Posts: 2,388
On a 7'-10" wide, 16' raft:
1) ~75"
2) 1" apart (37" from tip of handle to oarlock side of Oar Right
3) 10'


Quote:
The old rafters formula is one part inboard and two parts outboard, but I think this is a bit off for narrower boats.
In which direction?

Quote:
Van Claussen's formula was developed for fixed-seat rowing skiffs and dictates an ideal 7:18 leverage ratio for maximum efficiency, but this too seems a little off.
That seems like you'd need really, really long arms to get the blades to move at all--and you wouldn't have much blade depth/bite. No doubt the formula was developed for skiffs with a lot less freeboard than rafts.
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Old 04-28-2012   #3
 
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NorCal, California
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Here's my formula that gets you in the ball park. Measure the distance between oar towers, multiply that number by 3, divide by 2 and then of course convert to feet.
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Old 04-29-2012   #4
 
Redstone, CO
Paddling Since: 2000
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I think the height of the oarlock above the water makes a difference too. If the oarlock is higher because of bigger tubes or a taller oar-tower, you need a little longer oar.

1. 72"
2. 0"
3. 10.5'

I have 25" tubes w/ about 6" tall oar-towers... counter-balanced Sawyers.
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Old 04-29-2012   #5
 
Golden, Colorado
Paddling Since: 1975
Join Date: Oct 2007
Posts: 536
hey pearen,

here is some math for you....

1 rafter + 4 MFS permits reserved within a few days of each other + Zero intention of using 3 of them = 1 throbbing dickhead

"Quite a few permits have been popping up for late May Middle Fork Salmon (MFS) launches. These trips typically involve launching on Marsh Creek, navigating Dagger Falls and dealing with high flows, but for the right party they are wonderful opportunities to explore an amazing section of river. Other advantages to a high water MFS trip are the reduction in other groups and the feasibility of running the river in a long weekend rather than a full week commitment. In just the past couple of days, I have picked up launches for May 18th, 20th, 22nd and 24th to provide my group a bit of flexibility in hitting water levels and weather at their ideal."
- Keith Pearen
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Old 04-29-2012   #6
 
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portland, Oregon
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1) 78" (72" frame)
2) width of hand to keep pinch hazard down or knuckle crashing
3) 10' but would prefer 10.5 or 11. On flat water i add 1' extensions

Have leopard tubes 26.5? And 8" nrs towers. The 6" towers were too short
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