Oar dimensions, double-banked pulling boat

[Dick Wynne]

I have a heavy pulling boat (Montagu Whaler) and plan to double-bank the oars. In view of the weight of boat (3/4 ton) + 11 crew (3/4 ton!) and the expense of oars (I'll be buying them) I'll use Ash for strength and knock resistance & durability. Q: what length? Transverse distance between crutches is 5'6" down to 5' or so according to station, so fulcrum will be max 2'6" or so from inboard end. Boat may be pulled by ladies or men, not all immensely strong. However I don't want to find that, say 10' oars prove too short to keep up with the boat's speed when the crew gets used to it. 10' would leave about 25% inboard, 12' must be about the limit, and Ash is heavy (50% more than spruce). Freeboard is about 18-20". Is it normal to load the inboard end of looms to achieve balance? Should I do this? Etc etc...any ideas out there?

[Bob Smalser]

Here's the drill for the Shaw and Tenney formula for a 7:18 leverage ratio:

Inboard length of the loom is 1/2 the distance between the oarlocks plus 2 inches.

Total length of the oar is 1/7 of the inboard length multiplied by 25.

Distance from the center of the leather to the end of the grip equals 7/25 of the total length of the oar.

[Donn]

I use 10' fiberglass Sawyer "Polecat" oars to row a very heavy 16' fiberglass 'Amesbury Dory' and the weights on the inboard looms make a huge difference in handling the big oars. It takes a little placement tweaking, but, IMO, well worth it.

[Bruce Hooke]

Wouldn't the Shaw & Tenney formula need some adjustment for a double-banked boat because presumably on such a boat you would not have any overlap on the oars...in fact it seems like there would be some space between the inboard ends (grips) of the oars?

[Ian McColgin]

Bob's formula is a start.

To apply it we'd need some clarification as it's unlikely that you'll have a singe person handle an oar on each side.

Sometimes oars are double banked by having two people to the thwart, but this results in oars that are really too short.

Generally you'll have a person sitting on the starboard side with the oar out to port and visa versa.

Depending on the boat's shape, you may need to lable each oar - or at least the fore- and aft-most oars - as you can't use one size with differing lever arms.

If you can, check with the nearest Atlantic Challenge group as they have lots of experience. I think they even have well worked out how you increase a crew's skill to row together so you can get away from the dock and come back without creating too many splinters.

G'luck

[Dick Wynne]

Thanks Bob, seen the S&T formula but that's for one oar in each hand. Don't think the intereference of the handles would go down well in a double-banked boat! Incidentally some of my friends thinks that overlapping handles is a big problem, never known it to be one myself, it's easy enough to miss colliding, and the extra leverage is worth it. Can't see any double-bank formulas on the web anywhere...

(I posted this before the previous 2 posts appeared!)

[ 03-09-2005, 10:17 AM: Message edited by: Dick Wynne ]

[Bob Smalser]

Just ordered an out-of-print book on it I'll have in a week or so if you can wait. Dunno if it'll discuss your question specifically, but 7:18 is spose to be the optimum ratio mechanically....and if that's so it'd fit one oar or two and 4 hands versus two.

Personally, I think the 7:18 ratio makes for a shorter oar than I can handle....but my pulling expertise is very limited, and a 6-mile pull with a heavy oar on a 3/4T boat might change my mind.

http://webpages.charter.net/janesaugstad/oars1.jpg

http://webpages.charter.net/janesaugstad/oars2.jpg

[ 03-09-2005, 10:33 AM: Message edited by: Bob Smalser ]

[RonW]

I would suggest using a 2x2 - 8ft. long and sitting in the boat at each rowing station using the 2x2 to determine the proper inboard length.
Then use the 2/7th. rule, divide the inboard length by 2 and multiply that answer by 7 to get the total oar length. 2/7th. rule works out to being 7/24 & 1/2, the 7/18 is way too short, particularly on a deeper sided boat.

[ 03-09-2005, 10:39 AM: Message edited by: RonW ]

[muscongus]

That book is still in print, at least it's still listed as available from Mystic Seaport at:
Oars for Pleasure Rowing (http://www.mysticseaport.org/shop/item.cfm?mc=88C&mid=19557)

[Dick Wynne]

Thanks Bob! This book looks the business, have ordered a copy, whether or not it answers my specific questions, every home should probably have one...

[htom]

The oars in the ends of the boat are going to have crutches higher from the water than those in the middle, too, and that may need to be taken into account.

Initial cheap trial oars of 2"x2" with adjustable length shafts and plywood blades might be worth while.

[dcobbett]

Dick Wynne,

Last Saturday was the 25th Snow Race which is held in Hull, MA. Most of the competition was in large, multi oared gigs and similar craft.
One of the highlights of the event is the so-called Le Mans start required for the larger boats; effectively, each boat grounds out with its bow on the beach and crews line up further up the beach. On the start signal, the crews run to the boats, get in, back off, turn 180^, and start the 4+/- mile race.
The event is sponsosed (I believe) by the Hull, MA Life Saving Museuma and, at least one crew was rumored to be from your side of the Atlantic. As a group, I bet they have answers to your questions, and I suggest you try to contact them through the following link:
[URL=http://www.lifesavingmuseum.org/]

http://img.photobucket.com/albums/v247/dcobbett/e1cdf20e.jpg http://img.photobucket.com/albums/v247/dcobbett/DSCF0023Large.jpg

[boatlover]

Richard:

Have you tried the RN historian ? I seem to recall reading that there was competition between ships in the Montagu whalers. There must have been "standard issue" oars for the whalers.

If nothing there, there has to be some RN retiree boatswain somewhere in the UK who could give you some useful info. (And a few good stories, as well.)

Regards,

Ed R

[Tonyr]

The 1938 and 1952 Admiralty Manuals of Seamanship both give the numbers and lengths of 27' Whaler oars as four at 17 feet, and one at 16 feet. They were heavy suckers, and took the full strength of a fit man to handle them in any sort of a sea. Probably ash, but I was not interested in their material at the time (!), so I could easily be wrong. Double banking makes good sense, in that it would let smaller/younger people pull smaller/lighter oars without too many heroics.
Tony.

[ 03-10-2005, 02:16 PM: Message edited by: Tonyr ]

[Dick Wynne]

Thanks all for your comments etc. I have gone for 10ft Ash. This gives a 1:4 ratio of inboard to outboard length and should balance reasonably. Should also allow ladies & less strong gents to have a fair go at it. Greater length might be theoretically better for the sort of boat speed we could achieve, but the beam isn't enough to get the balance without weighting the grips, and the extra overall weight might put novices off. Ash is 50% heavier than Spruce, but a lot stronger and knock-resistant, and since the materials cost about the same it makes sense in what I plan to be a well-used boat. Incidentally she'll be based in a central London marina from April and I'm raising a local pulling crew -- see my post in People & Places if interested in signing on.

[ 03-11-2005, 09:00 AM: Message edited by: Dick Wynne ]

[Bruce Hooke]

Remember that while heavy oars are harder for less muscular people to ship and move around, better balanced oars will be easier for such people to actually row with because they will not have to push down as much to lift the end of the oar out of the water. You may well already know the following: the traditional solution to this issue, at least on small boats, is to leave the portion of the loom that is inboard of the oarlocks square or hexagonal.

[RonW]

I will add a word of caution. I believe your decision on 1/4 beam to length ratio out of ash will produce a set of oars that are unbalanced and way to heavy.The 1/4 will be 25% inboard and 75% outboard, the 2/7 I quoted above which is a old standard, produces a inboard length of 28% and a outboard length of 72% a little better balanced oar, also bruce already mentioned leaving the inboard length from the leathers up in square loom as was a very common practice to also help balance the oar.Another old time trick was to drill the handle out length wise with about a 1/2inch bit and fill it with lead to balance the oar.You can predetermine the lead in your shop by putting the oar on a edge at the oarlock position and laying the lead on the oar to determine the amount needed to balance, leaving the inboard loom square will help a lot.
Ash was generally reserved for oars that where used in rivers, open water oars usually where spruce, the spruce oars where a little bulkier then where the ash, but they tried to get as much weight as possible off of the ash oars because they where so heavy.
I have a set of 10 foot oars, they are balanced by the addition of lead, you do not want to try and row 10 foot oars that are not balanced, think you will find that out.
Good luck, I will add the shaw and tenney site for info.
http://www.shawandtenney.com/wooden-rowing-oars.htm

It is very pleasurable as well as relaxing and fun to row a nice rowboat that is set up properly. On the other hand it is nothing but miserable to try and row a poor quality rowboat with improper oars, I mean miserable. There are way too many poor rowboats that are set up poorly and that is the main reason that no one wants to row anymore.In america I believe the boats you posted are referred to as gigs.

[ 03-11-2005, 11:23 AM: Message edited by: RonW ]

[StevenBauer]

Just so I have this right, you are talking about the second definition?

DOUBLE-BANKED:
DOUBLE-BANKED, the situation of the oars of a boat when two opposite ones are managed by rowers seated on the same bench, or thwart. The oars are also said to be double-banked when two men row upon every single one.

Steven

[Tonyr]

By double-banked I mean two rowers on one thwart, each rowing one oar. The R.N Montagu Whalers we are discussing were designed to be rowed single banked, with one rower on one bench, sitting on the opposite side from his oar blade. Three rowers rowed on one side (starboard, usually?), two on the other. This gives a reasonable length of oar inboard, which helps with the balance problem discussed in several of the earlier posts.

A gig, by the way, used to refer mostly to a longer, lighter carvel built boat with less beam than the whaler, although it is hardly a defined technical term! Today it seems to be reserved for boats more or less patterned on the Cornish gigs of the Scilly Isles. Lovely boats.

Tony.

[ 03-11-2005, 06:25 PM: Message edited by: Tonyr ]

[Dick Wynne]

Thanks again to all for these comments on balance and terminology, which I will attempt to address.

Balance: Yes I am aware that 25/75 is not quite ideal, actually this leaves 12" between the grips of a pair of oars, and this gap could be closed a bit by the adjacent crew members to reach the ideal ratio. The oars have long sleeves and no buttons, so people can think for themselves gearing-wise.

The MW was not I think originally designed to be pulled with 10 oars in this way (although I have an old drawing showing 10 oar crutches in place). It would be beamier if it were so designed. To have less than 7.5ft of oar outboard would I think be a mistake because the boat has quite high freeboard (20" or so to the crutch), resulting in perhaps an uncomfortably high grip angle and too high a stroke rate for comfort once we get to 5kts or more we could achieve on flat water. I have a time and money constraint preventing the square shaft solution, so must base my approach on a standard product. Decision on 10ft was finally made from study of this picture:

http://www.jetphotographic.com/showphoto.php?id=66162

I know this identical boat as I pulled in her, with those oars, for a few months. You can see the entire length of the stroke oar, and the inboard/outboard ratio is exactly 1:3. In fact they may be 11ft oars, since there may not be 12" between the fists of the pair, and the outboard-mounted crutches are no more than 6ft apart. I recall the oars were heavy (look like Ash I think, bit pale for Doug Fir) but we had crew down to ladies of 5ft nothing, and no hint of mutiny from them. And I retain the option to weight the grips of course.

As for terminology, call it what you like, I always took single- and double-banked to mean one or two oars per station, with always one person on each oar, and have never come across a different definition, but then no-one knows what a bireme and a trireme were either. But please respond to that quip somewhere else!

[ 03-12-2005, 06:13 AM: Message edited by: Dick Wynne ]

[Dick Wynne]

Well, after some earnest last minute advice from another former Montagu Whaler skipper I went for 12ft Spruce after all, and glad I did. Anything shorter would definitely be too short on the whaler. They arrived on Friday and on Saturday we pulled her 11 miles around London's Isle of Dogs. No complaints from the crew regarding weight or balance. Worth reiterating that everything written in the way of formulas etc referred to in this thread seems to relate to craft with two oars per person, so is not relevant to whaler-type craft. These were not intended for double-banked use so there appears to be a dearth of published knowledge on the subject. Erring (on the short side especially!) would have been expensive.