All about oars

It is wonderful to see all these new skiffs that were in build over the last few months making their way onto the water. Some fantastic looking boats, beautifully finished, all they need is hardy crews to make them really go.
Since the first skiff was launched a number of things have been tried with oars, kabes, rudders, seats etc and I feel that after a lot of initial helpful guidance, assistance and sharing of ideas this aspect has dried up a bit. Clubs are happy to share ideas at regattas but the very useful online guides mostly furnished by the Ullapool clubs have remained fairly static.
New boats are still being built with kabes whereas most racing clubs use pins, and the online guides still recommend quite short oars as the Ulla uses and what I would call medium oars as used by Anstruther.
There is a lot of emphasis placed on the community aspect of skiffing, as its should be, and perhaps many clubs feel that small oars are more user friendly and less intimidating and thus better for the younger and older, or say less robust members of the community, but small oars for recreational use can be purchased easily and rowlocks even fitted on the non racing side of the boat to fulfill this role.
There is a strong case to be made for using the wide beam of the St Ayles to accommodate long oars and offsetting the rowers to get maximum mechanical advantage and length or stroke, flatten the plane of the stroke and get better drive through the strongest phase of the stroke. Long oars also encourage a slow stroke rate with proper breathing and better technique suitable to a sea boat.
We have rowers from 14 to mid 60 ages and all can manage these long oars, we have made slightly smaller ones for the women's team and they have bee rejected. Our U 17 team, made up of one 13, two 14 and one 16 yr old were pipped at the post for third in the men's open at our Regatta this year against some of the best clubs in skiffing, so long heavy oars are really no drawback if properly balanced
I would urge new clubs firstly to try using pins instead of kabes, square section oars ( at the pin area to keep the blade at the optimal angle ) using as much inboard as is comfortable when sitting as far away from the pin as possible and an outboard three times that to give a 3:1 gearing.
We started off too big and slowly cut down the blades and handle till we got a good balance between drive and sustainability.
We scarf 2.4 m lengths of selected 63 x 38 mm pine studwork ( CLS ) to 16 ft length, bond two of these together and square off to 60 x 60 mm, bond on the blades and then shape for balance, good stiffness and get the weight down to 5-6kg. There is no particular skill in making these and our club members who make the oars are not woodworkers. They cost about £20 each in material and take a day each to make or less if you are handy.
I will post more detail with some photos if anyone is interested, or email our club and we will offer any advice we can, or feel free to come up and try one of our boats before you finalise your build.

Here is a more detailed description of Coigach's oars including a CAD drawing thanks to John McIntyre of Ullapool :
coigach oars.pdf (7.82 KB)


[ IMG width=500 height=300 ]https://www.dropbox.com/s/rmro6jn06fs4l4v/coigach%20lass.jpg[ /IMG ]

The oars we make at Coigach are between 4690 mm for the two middle oars and 4190 mm for the stroke oar. These weigh between 5.5 and 7.5 kg depending on whether they are made from douglas fir or pine, and that may seem quite heavy but weight is not the issue some would make it out to be, a small badly balanced oar can be much harder to row with than a good heavy oar. We still use one of our old oars in training though it cracked and has been repaired with a long fillet of oak and now weights nearer to 9 kg, it is still a favourite oar though we cannot take a chance on it cracking again in a race.
Coigach have been very successful with these long oars from U17 to 60+ teams, in sprints , very long races and everything in between, we reckon they are a large part of our success, and an oar that you can win with is basically one that is easy to row.
The oars are made to the above dimensions and most of the work is done at the blade first to get the outboard as light as possible, leaving the inboard as heavy as possible to begin with and gradually fairing the outboard shaft to give a little flex when leaned on hard, try to keep it as stiff as possible as under the pressure of rowing the oar will bend a lot and you just need it stiff enough that it unbends while still in the water giving up all the energy you have put into it, also a good reason for rowing long and slow. The bend on the oar should not be very apparent to you while rowing but will show up quite dramatically in photos. We now make the oars more rectangular in section as this saves a lot of shaping and is arguably stronger. To start with the oar can be left quite heavy and tested for stiffness and balance in the boat before final fairing. The oar should be balanced on the gunwale with just a light downward pressure from your arms. The blades can be made very fine. You can continue to get the weight down if the oar proves very stiff but keep the 60 x 50 section for a good length around the area of the pin. Once you have made one good oar it becomes a reference for all the others.
If we make them from pine we use 38 x 63 x 2.4 m lengths of Wickes studwork hand picked for weight, straightness and small knots. These are scarfed into two 4.7 m lengths and then are glued together with the scarfs reversed to make super strong and light 76 x 63 x 4.7 m oar blanks with enough scrap left over for blades.
Simple scarf jig We use this size of timber as larger sizes have too many large knots, shakes and other defects.

Then they are sawn down to 60 x 50 ready for shaping. The cost is about £20 including epoxy glue but does require a lot more work. However you do not mind making any mistakes like you do when you mess up £100 worth of straight, knot free timber you have had to have shipped from Bristol and we have never broken any made in this way, only ones made from one piece of timber.

Blades can be made quite thin to get weight down and achieve good balance.

Here is another take on oar making. These are quite short but it may be possible to scale them up and it offers some opinions on what forces are at work and also points the way for those wanting to feather.
dl.dropboxusercontent.com/u/91326340/a-superior-oar-shaft.pdf

Hi Andres, still at 120 mm but we are thinking of making the blades just a bit bigger on one or two of the oars which might be a bit ambitious, we will never forget you beating us all through one summer until we made them slightly smaller each race and finally got a win. It is easy to make alterations but very difficult to assess how much difference they make unless they are a disaster. We will spend the winter trying to make small improvements like balancing the oars out a bit better and I will try a new oar design with hopefully a bit more stiffness. If successful we will unveil them at our Regatta. I am of the opinion that wooden rollocks are an interesting project for those with little else to do, a round pin in a round hole for me. Good to have you on board.

You have probably considered it already but would it be worth getting the pin positions on these scooped oars sorted and using them for practice/social rowing without having to butcher them completely, I would imagine it is difficult to splice a flat blade onto a spooned profile depending on where the hollow section ends.

As usual you have thought of everything Andres. I remember you talking about buying a new skiff, here is a link to one that was for sale, probably gone by now but you could put your name down if they do another one  scottishcoastalrowing.org/2013/07/23/st-ayles-skiff-for-sale/. Just finished gluing our prototype semi-isoscocles-trapezoid hollow oar together, I have high hopes for it, but the crew will probably just laugh at it and stick with the old ones.

Are there some serious misconceptions about oar length? I think so.
The crux of the matter is the gearing. That is the ratio of the length, inboard of the pivot to the length outboard. The ideal situation is to match the hand speed to the boat speed. So lets throw some numbers about.( please excuse the mixed units!)
The maximum rowing speed of the skiff based on its waterline length is 5.9knots which converts into 119.5inches per second.So, that is roughly the speed that the blade will be travelling at full speed if there is no slippage.
At a stroke rate of 32per minute the time taken for a complete stroke is 1.88 seconds and of that, 40% is spent on the drive and 60% on the recovery .ie the drive takes 0.75 seconds.
The average length of the hand stroke is 39inches so the hand velocity in the drive is 39/0.75 is 52inches per second.
So at a first attempt to match the hand speed to the blade speed, the gearing should be hand speed/boat speed ie 52/119.5= 1:2.3
However the oar blade has considerable slippage in the water so that it is about 70% efficient. this means that the blade speed will be about 30% higher at 155inches per sec. This makes the gearing 52/155 = 1:2.9 so lets round off at 1:3.
This gearing is appropriate regardless of the length of the oar and seating position so the notion that long oars give a mechanical advantage is not correct.
If you sit on the skiff centre line then the distances to the oar pivot in a typical skiff are Bow,34inches, No2 40inches,No3 39inches and Stroke 35inches. If you apply a gearing of 1:3 to these inboard lengths the appropriate oar lengths come out to be, Bow 11.3ft, No2 13.3ft, No3 13ft and Stroke 11.6ft.There are details regarding the grip length and the centre of effort of the blade but a rough guide would be Bow and Stroke 12ft oars Nos 2and3 13.5ftoars.
If you choose to sit off-centre the same gearing argument applies but the oars will be correspondingly longer.
If a particular rower has a shorter stroke than 39inches then for a fixed stroke rate the hand velocity will be lower and a higher gearing will be needed to match the boat speed . On the other hand if the rower has a longer hand stroke than 39 inches the hand velocity will be higher and a lower gearing is need. This means paradoxically that big guys need smaller oars and vice versa!
That's my penny-worth for today.

A point I should have mentioned in regard to long oars. We have fitted 40 mm oak plates ( are they called sclates ? ) where the pin is fixed to the gunwale as we were have problems clearing our legs when rowing with a sea on the beam. This will depend on your seat height. We also have a 20mm oak plate fixed beneath the oar to receive the pin so there is quite a lift from the standard position.  The extra height solved this problem but you may have to experiment with spacers to find the optimal height for your boat and it is not so critical on bow and stroke.