Oar Length: All Blade No Shaft in the Water?

[Dinghy Pipedreams]

I'm looking into my lst pair of quality oars. I've borrowed 7.5'ers for my 48" beam which is what Shaw&Tenney and others show on their charts/formulas.
They worked very well but... I've always been under the impression that the "goal" is to have all blade and no or as minimal shaft immersed.

Is that something to aim for? Slightly longer oars-7'10"-8'ers might give me more blade/less shaft in the water but until I can find a pair to try, not sure if that'll screw up the other rowing geometry/aspects or not.

I've decided on spooned oars if that makes a difference. I've read the old pro and con threads but like the spoons after trying them in calm and a little chop.
So...is all blade/no shaft immersed a goal to be aiming for or is 3-4" of shaft immersion normal on any length oar?
Thanks for any advice.

[Ian McColgin]

Depends on the boat and the rower. People who like spoon oars to drive a shell sometimes have oddly asymmetrical blades to get all blade/no shaft in the water. Sounds like your boat's not a shell, no outriggers or sliding seat, but might be a light boat like a wherry that might like spoon blades. People like me who row open, often rough, water prefer symmetrical blades, no spoon but a good spine.

So practice and see what you like.

G'luck

[nedL]

when rowing shells & sculls, the locks have a flat side to keep the oar squared up properly during the stroke. When I have rowed a "normal" skiff with bronze row locks I found it fidgety to keep spooned oars squared up just right. I prefer symmetrical oars when rowing with standard bronze locks.

[cstevens]

Personally I think oar balance, hand position and technique are more important than minimizing the amount of shaft in the water. With asymmetrical hatchet blades there is much more blade in the water by design but with a symmetrical blade you are going to have some shaft in the water when the blade is at a good depth (top of the blade just at or below the surface) just based on geometry. For a single shell with outriggers the oar height can be adjusted for conditions using spacers. So in practice the angle of the oar is adjusted by the sculler based on conditions and oarlock height in order to get the right blade placement at the catch.

[Dinghy Pipedreams]

My hull is certainly no sculling boat. It's similar to an "Auk" but longer and has an underwater shape closer to but beamier than a Whitehall... Pennobscott-ish? F.G. faux lapstrake..

I'd be using symmetrical blades (traditional, anyway). I just haven't been able to find any info. online or in books so far that indicate whether or not immersing 3-4" of shaft (instead of blade only) is "OK" or if I'm losing much efficiency and should try to find some 8'ers to borrow (not too likely so far.)
So...basic pretty easily driven rowboat, no shell/scull, etc. Liking the wider (5.5") spooned blades so far.
Thanks guys. (CStevens, thanks. I just saw your response after posting). Do you think the longer oar 8'ers would give me more blade/less shaft immersion without screwing up the rowing geometry severely? I don't know if I'll find a pair to borrow before the season is out but the 7.5's worked fine.
Cheers, DP

[Dinghy Pipedreams]

Do you think the longer oar 8'ers would give me more blade/less shaft immersion without screwing up the rowing geometry severely? I don't know if I'll find a pair to borrow before the season is out but the 7.5's worked fine.
Cheers, DP[/QUOTE]

Did the final testing today with the loaned oars in one foot + chop which was pretty wild where I got cross chop/waves from breakwater "recoil" and then straight out into Padilla Bay.

I was concerned that I wouldn't like the spoons in chop and 15 kts. but they were fine, didn't catch wave tops or anything so
may have to start saving up for a Xmas present...

On the walk back up the dock, I saw 2 O.A.R.S. boats (Old Anacortes Rowing Society) leaving and they were using spoons so I got to see how much shaft went into the water above the blade and it seems 3-4" roughly is "natural" on average so got that question answered/demonstrated. Sometimes the fates line stuff up...

Thanks for the feedback. I'm now amazed how bad my old too short oars (6.5') were!

[johngsandusky]

Sounds like you're working it out. When buying oars I try to go a little long rather than short as I can cut them down a bit. I never looked to see how much blade or shaft was in the water. I judge any changes required by the feel while rowing.

[Thad]

A properly made spruce or ash oar shaft will become oval as it comes into the blade offering little drag, while supporting the blade along the central blade spine.

[Dinghy Pipedreams]

A properly made spruce or ash oar shaft will become oval as it comes into the blade offering little drag, while supporting the blade along the central blade spine.

Thanks, I hadn't thought of that. It did make a difference in the feel and it's nice to realize that will minimize the drag when immersed.
I redid the S&T formula after a friend checked it and it came out to 7.73333333333 so I guess 8'ers might be better. It's comforting to be reminded that they could be cut shorter later if need be.

[rgthom]

I am not sure that loom in the water is a significant loss. Steevers oar equations show shorter blades being more efficient. Thats because the blade is rotating during a pull. In the extreme of an oar consisting of a very long blade reaching all the way back to the boat, the inner part of the blade would be moving forward at boat speed and a very high loss. Any part of a blade that is inboard of the point of rotation in the water would be pushing in the wrong direction, and that point depends on boat speed and pull strength. Much better to have some narrow loom length immersed than a too long blade.

- Rick

[cstevens]

A note on the S&T formula: It's a good starting point but the basic formula doesn't account for hand overlap. If you like to set up your oars with overlap (as I do for flat water sculling) then you need to add 6" to the oar length from the S&T number. The S&T website actually notes this as well. Overlap is a little tricky to set up on a boat that doesn't have a way to adjust the oarlock height though. With adjustable riggers typically the left hand (starboard rigger) is rigged higher for left-over-right overlap.

The main effect of 8' oars over 7'6" oars will be a higher "gear" given the same inboard length rather than any issues with blade/loom angle or other geometry concerns. The oars will take a little more effort to pull through the water and the boat will move a bit farther per stroke. But so much of this conversation depends on now you have the hand position set up now and whether it's where you really want it. And that's a fairly personal choice. Normal sculling practice is left-over-right overlap. If I am rowing without overlap then I like to have around 1"-2" between the handles at the closest point. Since you are using borrowed oars you may not have the hand position where you really want it now so that's the first thing to sort out.

[cstevens]

A follow up to the hand position issue as it relates to oar angle. There are a bunch of factors involved in setting up a puling boat that are all interrelated. Oarlock height and hand height also affect the angle of the oar and are somewhat up to the preference of the rower/sculler rather than some ideal geometry. With the same boat and the same oars I would adjust the oarlocks higher for open water and wave conditions than for flat water (assuming that adjustment is available). That change raises the hands and provides more room to adjust the placement of the oar blade for given conditions at the catch. I think most traditional pulling boats have the oarlocks set somewhat higher than an open water shell which make that adjustment moot, but the point is that hand position is more important than loom angle within a certain range. If the oar is too short (as with your 6'6" oars) then the geometry just doesn't work at all, but otherwise there is plenty of room for adjustment.

It's also worth noting that for a given oarlock height and inboard length, a longer oar will result in a lower hand position or a deeper blade depth. Again with a pulling boat there is probably plenty of room to compensate for the angle change but since we don't know where your hand position is with the oars you have it's something to consider.

To in order of importance, I would say get the inboard length set so that you have your hands where you want them. From there, assuming that the height of the oar handles is ok, then the choice of oar length is just about perceived effort (assuming you are not racing so absolute boat speed is not really an issue).

[cstevens]

And....while I'm thinking about it, I'll throw in one more area of adjustment that may be up to the rower. On a rowing shell the outriggers and sculls are set up to have a fixed inboard loom length. The oarlocks are designed so that the button is always supposed to be in contact with the oarlock. But for a traditional pulling boat some people prefer to set up the oars with leathers but no buttons, or at least with longer leathers, so that they can change hand position and inboard oar length while rowing. I've never managed to get comfortable doing that myself but it's a thing that people do.

[Dinghy Pipedreams]

Great details thanks again. The borrowed 7.5'ers gave me a hand spread of roughly 4". I've always had about 2" between handle ends which has been comfortable for 40 yrs. So I'd likely try for that. The oarlock height isn't adjustable but I experimented with pulling into belly and very low chest height by switching out two boat cushions under me. Either position seemed to work fine and when I got into rough water and wind I used no cushion to keep my center of gravity lower. It all worked but when seated on cushion I had to be a tad bit more conscious specially to be sure I'd clear my knees.

I wondered if 8'ers would change the knee clearance making it untenable without raising oarlocks (which I'd rather avoid) or if the extra six inches overall in oar length wouldn't affect that aspect. I could also learn to live with overlap if I find 8' to be too long it would just take some drill & practice but would rather not. So, the bottom line adjustments would be either overlap or shorten the oars later. I just want to get it as right as possible because one pair of expensive oars are the limit for the foreseeable future. (age and $).

I debated whether or not to do stops/buttons as I've never had leathers before with their "gearing" aspect, but have also concluded that I'd rather have them. This boat is currently a yacht's tender 90% of the time so the stops/buttons are helpful in coming alongside, dropping things quickly while fending off,etc. as I also prefer round/enclosed oarlocks. I've tried horned over the years and they just don't "like me" ;-)


The blade length vs. shaft physics was something I hadn't seen before (except perhaps on river rafting sites). I did notice that Vern Fancy's blade length is longer by quite a bit than the Barkley Sound Oars. (I think I measured a nearly 10" difference!) I'll have to see how long S&Ts are. Different patterns/different histories used.

I'm also thinking that 8'ers would allow me to go up in boat size later (maybe to 15' or so) and still have this pair be workable, perhaps in 2nd rowing position.

I greatly appreciate your educating newer members and everyone's generosity with input and experiences.
Cheers, DP

[cstevens]

Yes, for a tender I would absolutely want buttons and captured round oarlocks. But your knee clearance issue with the cushion does bring up another point worth mentioning - which is whether you are feathering the oars and using a flat stroke. If you are not feathering then you will have to drop your hands at the release, which reduces your hand clearance. With a sculling stroke the oar is feathered and (ideally) the hands are perfectly flat and at a consistent height through the entire stroke. (My first coach told me I should think about keeping a glass of wine steady on the back of my hand through the entire stroke.) The oar is held in the curve of the fingers, and the feathering action is just a finger roll, with no wrist bend. That's easier to do with sculling oarlocks and sleeves because they are designed to hold the oar at the correct angle when in the water and when feathered, so it takes less effort to feather the oar. But even with round sleeves and oarlocks you can minimize your wrist action and keep the stroke as flat as possible.

[SalsDad]

I get a kick out of S&T and all those other formulas. A complex equation, and then round up or down to the nearest half-foot. It almost always works out to double the beam, until you get to a very wide boat. Don't worry too much about the exact length and geometry of the oars, until you have rowed a good many miles. And by then, you will be more expert than the experts.

How much shaft in the water? I prefer little or none in flat water, but that's me. Of course every boat is different, and a bit of chop changes everything.