Decisions we need to make for the new design

Page 1 of 2 1, 2  Next

View previous topic View next topic Go down

Decisions we need to make for the new design

Post by topherdawson on Sat Dec 17, 2016 2:36 pm

1   We now have collected a lot of data on existing good oars. The spreadsheet is here: https://www.dropbox.com/s/s865ffbm16ok5pd/Oar%20comparisons%20November%202016.xls?dl=0
Note that at the top there is a row with the average values of all the measurements.

Looking at this we need to decide what targets to aim for and how best to achieve them. I have concentrated on the longest oars (in 2 and 3) because they are the hardest to get right. If we can settle on a design for these, the shorter ones will be easy.

2   The lowest gearing regularly used by a successful club is 2.6 which Crail use and like. Actually I see Anstruther use 2.5.

3   The highest gearing I currently know of is 3, which Ullapool use and like.

4   I suggest we provide 3 or 4 notches or holes defining gears between 2.6 and 3 so that rowers can use the gear which suits the conditions and the crew.

5   Robert Graham of Dundrum and I both suggest 2kg as a target UHF. It varies with the gearing but not much.

6   We need to decide a method of construction. Hollow outboards are strong, stiff and light, and lend themselves to using different species of timber. But solid shafts are easier to make, and could use cedar, spruce, or one of the light species available in New Zealand or North America. Australia seems to lack local light timbers.

7   We need to choose a blade shape.

8   The current long narrow flat blades are popular and well understood. They are easy to make and currently legal for the class. They look traditional and appropriate for sea use. On the other hand they can be heavy, their centre of area is a long way in from the tip so they are long for a given true gearing and thus increase the UHF. As different parts of the blade are operating at different gearing, they are probably less efficient than a shorter blade.

9   Shorter wider flat blades are probably more efficient but if rectangular may catch the waves during the recovery.

10   The next historical development was the "needle" shape which was curved but still long and narrow, tapering to a point at the inboard end. Curved blades are hard and thus expensive to make from the solid but have a more solid catch and better flow round the blade.

11   Then came the tulip, then the Macon, which are curved and narrower at the tip than the maximum width which occurs a third to half of the way up the blade. This narrower tip gives better clearance from the water during the recovery and concentrates the area around the centre of area.

12   Thin ply can be laminated into a curve which makes a light robust blade of an efficient shape, within the skills of a community boatbuilder. Such blade shapes have been around for over 100 years although not in sea boats from Northern Scotland.  Pilot Gigs use them and they look pretty good to me but that is only my opinion. To some extent it is a matter of length versus breadth. I suggest a curved blade about 600mm long and 200mm wide. What do others think?

13   Whatever blade we design we need to choose an area. Current blades average around 1000 cm^2 and I suggest we keep that.

14   Finally we need to choose an oarlock system. There are several systems we could choose from.

15   Pin and plate although common, and simple to make, suffers from wear and clonk due to geometrical clashes between the gunwale and pin as pitch references. In my opinion it is not a good system to go on making.

16   Pin and swivel works well but some think it looks out of place and it is certainly fiddly to make.

17   Modern stainless pin and nylon gate works well but looks very hi-tech and out of place.

18   A custom welded stainless oarlock would be tough, able to be locally made, and work well. Some think it would look out of place but it has to be said that metal oarlocks have been around for at least 150 years.

19   Don Currie's pin and keeper system and Crail's pin and hooked keeper both work better that pin and plate, are highly suitable for community boatbuilders and look traditional.

20   Kabe and humliband are not in favour with those who have tried them but they are very traditional.

21   Ball-ended pin and keeper is being investigated.

22   Almost forgot: Mounting the pins at 2 and 3 in blocks so that the pin centres move inboard by 70mm, would allow the inboards to be shorter and so the whole oar could be about 250mm shorter. Perhaps oars 1, 2 and 3 could all be the same length.


Last edited by topherdawson on Sun Dec 18, 2016 8:04 pm; edited 1 time in total

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by Rory Cowan on Sun Dec 18, 2016 6:37 pm

Skiff Oar Rating Scale (SORS)

It would be useful to determine objectively the merits of a particular oar.  It is simple to state that one oar is better than another or feels better than another - but it would be more helpful to be able to specify what it is that makes one oar prefereable to another.  

To arrive at the Skiff Oar Rating (SORS) we need to go through the following filters:
(Sorry the table didn't translate too well) The original document is here:

https://www.dropbox.com/s/yp77mbdjetmol90/skiff%20oar%20rating%20scale.docx?dl=0

Principal questions to ask yourself
Improvement needed? Does it work? How easy for the oarsman to use        Rating - if you think this or something like this then this is how you assess the oar for the role you are asking it to do.


Can I use it? No It's terrible I simply can't use it without losing control       Rating    10
Does it work well enough for me to use easily?
                       No it has to be improved somehow
 I have to work extremely hard to get this thing to work                            Rating    9
I have to work very hard to make progress at all                                     Rating   8
I can only just make it work                                                                  Rating  7
It works, and does not need improvement
Yes but could be much better     It really should be a lot easier to use          Rating6
It should be easier to use                                                                      Rating   5
Preferably it should be easier to use                                                        Rating  4
It works and needs no improvement
                       Yes It's fine Fair - but I don't like some things about it        Rating  3
Pretty Good - nearly perfect                                                                 Rating  2
Excellent - just what I want                                                                 Rating   1
So what we have done is to note the conditions, put our own name / age / gender to the assessment, consider the operation of the oar and decide how it operates and whether it needs improvement.  We can then justify the number we put to the performance under the conditions by reference to the features we need to consider.  If there are any features that should be added to the table - then add them and describe what they are.

We can determine the specific features of an oar such as:

• Overall length
• Blade size and shape
• Overall weight
• Weight at the handle
• Springiness
• Gearing
• Heft - how it feels in the hand, the moment of inertia, the weight at the handle, the feel of the oar - is it solid or flighty

and so forth - there may be more, however we then need to relate those features to the conditions in which we need to row.  For example arguably the perfect rowing situation is a flat calm with the boat perfectly balanced.  The worst situation may be a borderline sea on the beam.  Equally a very difficult situation might be a quartering sea.

We normally row competitively by 'putting our back into it' and stretching forward for the catch, pulling crisply to the recover and then the recovery stroke made back to the starting position as economically as possible.

We need to make the oar entry into the water as positive as possible and the removal equally positive.  We do not need to catch the water inadvertently when we do not want to and we certainly do not want to catch crabs.

Clearly the individual rower's technique is of importance, however whilst some will forever blame the rigging of the boat and the juxtaposition of the thwarts, thole pins or crutches, type of blade etcetera, others will forever blame themselves for any mistakes and strive in silence to make the best of what they have.  Between these two extremes there is work to be done.

There is no perfect oar for all conditions.  An oar rigged / made for work in a seaway will never compete on still water with one rigged / made for still water and vice versa.   What we are seeking here is the compromise oar for all conditions  - unless we are flush with funds and have an oar for each condition.  

So we have established a SORS but we need to return to the need to put a number on the features of an oar that we use and from that determine a methodology of quantifying just what it is that makes one oar better than another.

With that in mind we need to consider the conditions in which we use our oars - are we good in calm conditions, rough conditions, with a beam sea, with a quartering sea, with the sea on the bow either side and so forth?

From this we can come up with an oar rating scale.  We can establish whether we are happy with a particular oar in specific conditions - we are not setting out to recommend improvements at this point (though that may be helpful) what we are in fact doing is setting out to put a number on the features of a particular oar in specific conditions.  So we have a table to consider which puts conditions on one axis against oar features on the other axis.  We can then put a number on the particular merits of a specific oar feature.

As an example if we have an oar that is 20 feet long we may find it difficult to handle because the stroke could be very long, the pull must sustained for an excessive time and high stroke rates are not an option.  Conversely an 8ft oar may be very difficult to use because you need to have a very high stroke rate in order to get the boat going, it is difficult to keep time and so forth - but it may be brilliant to use safely in a seaway.

Thus we have for oar length, to consider the conditions, the angle of the sea to the boat, the need to make good progress and the safety aspects.  So you can give a number to that feature - Oar length - in certain conditions, which will have a meaning and that meaning must be related to the conditions.

(As an aside it is worth noting that in the distant past when rowing lifeboats were in use, that the oars were really quite long and the lifeboatmen did not 'put their back into it' - instead they went for safety and rowed with their arms when in very difficult conditions.  To be competitive in one of our skiffs, that is not an option - we have to move the body as well as the arms.)

It is possible to postulate a number of options and conditions for the features of an oar and from that we can establish what are good features and what are poor, and then move on to the relationship  between those features that go together to make a good oar.

From this consideration we can then formulate a table to concentrate on the relative features of the oar which then with a bit of tweaking go together to make an ideal one.  We could come up with a rough water solution, a still water solution and a combined solution.


Oar Number

Example
e.g. set 1 bow
Weather / sea conditions


flat calm
Overall oar length    assessed as   4
Inboard length         assessed as   5
Overall Weight        assessed as   4
UHF                       assessed as  8
Blade                    assessed as   6
Springiness            assessed as   8
Gearing                 assessed as   4
Heft / MI               assessed as   7
Handle size / finish assessed as   9
Stroke rate            assessed as   3 - liked it!
Comment on features above.
Oar felt long, low stroke rate, balanced - UHF light,  gearing too high, oar felt easily handled, too whippy
SOARS 5

GIve each feature a number from 1 to 10 to give an indication as to how well you think the oar's defineable features meet your preference.  Once you have done that you can give the oar a SORS from 1 to 10 (see above) to rate how the particular oar meets the task.

In the example above we have established that we have an overlong oar, that weighs OK but is too whippy,  (It may have felt good in the hand but was too whippy in the water), where the gearing does not permit a high stroke rate.  We are likely to find therefore that young fit crews may be able to get on with it better than older crews who aren't so strong and fit.  We have given it a SOARS score of 5 - which is quite useable but performance really could be improved.  What is important is that we should be able to specify what it is that we think needs to be done to improve the oar.

In Summary
What we have done is to break down the features of the oar so that we can give numbers to them and then an overall number to describe the performance of the oar in specific conditions.  To improve this oar we could reduce the gearing, stiffen it a little and / or reduce the size of the blade.  For example if the blade size is reduced then there will be more slip in the water (reduced efficiency) and a higher stroke rate will be possible.


We have measured a number of features of these oars and tabulated them - now we need to have a tool to assess what the oar does, how it does it and whether there is need for improvement.  This could be that tool which we can all use and would give useful feedback to those making oars or deciding what features of an oar need attention or should be promoted.

Rory Cowan

Posts : 20
Join date : 2016-12-04

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Sun Dec 18, 2016 7:42 pm

This seems to me to be the basis of a good way to assess how much a rower likes any new design we come up with.

I'd suggest cutting the criteria down to six:
Balance (is the UHF what you like?)
Stiffness (is it too floppy or too stiff?)
Ease of rowing (is the oar too hard, too easy or just right to pull?)
Catch/finish (is it easy and positive to put into and take out of the water?)
Oarlock (smooth, precise, no friction or slop)
Any other comment.

Also I'd prefer the scale to go from 1 terrible to 10 perfect.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by Don Currie on Mon Dec 19, 2016 8:44 am

Just a note of caution here - we don't want to start giving the impression that clubs will be able to build sets of oars that all feel the same. When I measured our #2 and #3 oars from one set there was a difference of 8% in the weight, a difference of 13% in the stiffness, and 12% in the UHF. Wood is a naturally variable product, so none of the differences I measured will come as a surprise. Even with oars made to a "standard" design there is going to be a huge variation in the feel of each oar. We ought not over sell the idea that a disparate group of clubs can make highly standard wooden oars.

How the oar feels at the catch is also going to be influenced by the pitch of the pin (and by the rowlock system selected). I wonder whether a simple and effective way forward from here might be to build a couple of "average" oars from the data supplied. The numbers are already there. If you use a simple rectangular loom and light ply blades, you should end up with a UHF of something like 3kg. Fit the oars with a rowlock system that references to the pin and then see what rowers think of them.

Don Currie

Posts : 39
Join date : 2016-12-03

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Mon Dec 19, 2016 10:46 am

Agreed that even if we all use the same species of wood there will be variation, and as we have discussed before, different continents have different local species.

In any case we will not be measuring UHF or stiffness to decide whether an oar is legal, I'd think just length, width, maybe not depth to allow for species variation, but definitely blade shape and size.

By New Year I hope we can agree on design criteria for the new oar and I will be making a prototype and encouraging others to do the same. If we can make prototypes which are better (in UHF, stiffness and/or overall weight) then why bother making what we already have?

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by colinmuirhead on Mon Dec 19, 2016 11:35 am

Hi Topher,

Not sure why you are opting for Macon blade that is 190mm at its widest when looking at the data from the 15 clubs that have supplied you with measurements, the majority of clubs are using parallel blades ranging from 98mm to 203mm wide with an average blade width of 140mm and the majority being between 120mm and 160mm?

Other that yourself, do you have any feedback from any other clubs that are using Macon shape blades in the varying sea conditions or who have tried both types and may have a preference?


colinmuirhead

Posts : 8
Join date : 2016-12-03

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Mon Dec 19, 2016 12:30 pm

Hi Colin,

I have rowed with such blades and I do think they are more efficient for two reasons. One is that shorter wider blades have all their area around the same gearing, or looking at it another way they have less area near the root which is backwatering. The other reason is that the curve aligns the blade with the flow so there is less turbulence and a better more positive grip of the water.

The reason that these oars are not common in working boat situations is that when made in solid timber they are more delicate and more expensive to make. However thin plywood allows us to make them easily and cheaply, and they don't split like solid timber so are suitable for club use.

Gigs have been using them for many years which I think means they work well in races and they do race at sea.

From our point of view they would allow a light blade with its centre of effort fairly close to the end of the oar. With a shorter blade the oar can be shorter for the same true gearing, thus lighter overall and less UHF. Curving the blade makes it stronger so it can be made from a single skin of 4mm ply.

The macon or tulip shape are slightly narrower at the tip than at the fullest part which help concentrate the area near the middle and reduce the chances of the lower tip catching in the waves.

We can make it narrower and longer if that is what people want, but I think we should at least try the curve because it does appear to be more efficient and I personally think it feels nicer to row with. This is such a personal viewpoint we really need to try it with rowers to see what they think.

Royal West as you know have a stock of old solid wood spoons and much prefer them to flat blades.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by Finlay Robertson on Wed Dec 21, 2016 12:41 pm

I’d just like to add to Topher’s point here by talking a bit about slippage – the amount that the oar blade moves through the water during a stroke. Oar efficiency and slippage are one and the same. Slip means that the rower is expending energy accelerating the water rather than the boat; a 100% efficient oar will not move through the water at all but grip it perfectly. Turbulence in the water is an indicator of slippage, rather than vice versa.

Pressure drag is the principal property we are concerned with – the higher it is, the less the oar blade will slip. It is characterized by the equation 0.5*C*ρ*S*V^2 where C is shape coefficient, ρ is density, S is projected area and V is velocity. The shape coefficient is lower for low aspect ratio shapes than for high aspect ratio ones (the exact values vary slightly depending on Reynolds number); this is why the latter are more efficient.

Ventilation (sometimes incorrectly referred to as cavitation) is another effect worth mentioning as this also reduces efficiency (by increasing slip); it occurs when the pressure differential is sufficient to draw air down from the surface of the water to the region of the blade. (This is one of the main reasons that the blade becomes more efficient as it gets deeper in the water … albeit while the rower him/herself becomes less efficient!) I’m of the view that this can be eliminated through technique alone, allowing us to disregard it from our design discussion, though I’m happy to be challenged if anyone disagrees.

It is worth noting that an inefficient oar can have the ‘feeling’ of a lower gearing due to the increased slip, but in doing so the rower is still wasting energy by putting it into turbulence in the water rather than into driving the boat. Much better to have an efficient blade and reduce the gearing the normal way.


Last edited by Finlay Robertson on Mon Jan 16, 2017 9:22 pm; edited 2 times in total

Finlay Robertson

Posts : 27
Join date : 2016-11-29
Age : 28
Location : Edinburgh/North Berwick

Back to top Go down

Re: Decisions we need to make for the new design

Post by John Irvine on Wed Dec 21, 2016 5:43 pm

I had the pleasure of racing for several clubs last summer. I recognise that most rowers will like the set-up that they're used to. I like North Berwick's Macon shaped blade (610x198), which seems to give good grip at the catch and, assuming good technique is applied, doesn't slip during the stroke. My impression is that narrower blades tend to tear through the water or bounce out and in during the stroke.
The Macon shape also allows the whole blade to be covered during the stroke without going too deep. It seems to me that a longer, narrower blade will either be rowed partially out of the water, or fully covered but deep.
I suspect seat height is another factor in choosing oar length and blade shape. Too low and the hands at the finish will be too high; too high and there is no room to get the hands away over the thighs.

John Irvine

Posts : 6
Join date : 2016-12-02

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Wed Dec 21, 2016 6:04 pm

It might appear that a long narrow blade takes less vertical movement to get in and out of the water but this would only be true if the blade was parallel to the water, i.e. a cleaver. The oar and blade actually angle down to the water from the gunwale and so getting all the length immersed takes a fair bit of vertical movement.

Paradoxically the wider shorter blades may take less vertical movement especially if they are wide in the middle and taper towards the tip and neck.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by colinmuirhead on Thu Dec 22, 2016 10:07 am

I know where you are coming from but looking at the survey results, clubs would prefer a long narrow blade over a Macon blade and there are also several comments saying they don’t want a spooned blade. What the end user wants is important as they are the people using the oars in their local conditions.

Macon Blade – 58 total replies
Essential / Desirable – 9 in total
Not Bothered – 15
Undesirable / Terrible – 34 in total

So even taking the total of essential, desirable and not bothered at 24 it is still not close to the undesirable / terrible total.

Long and narrow flat – 57 total replies
Essential / Desirable – 32 in total
Not Bothered – 18
Undesirable / Terrible – 7 in total

So this time taking the total of undesirable, terrible and not bothered at 25 is not close to the essential / desirable total.


As for the height, you must raise the oar for the blade to come out of the water, it doesn’t matter what shape the blade is if it is wider at the tip you will need to raise it higher to get it out of the water.

If using a Macon curved blade with the tip width is the same as a long narrow blade, arced back along the blade to the widest point and with the distance back from the tip to the widest point set so that the section of blade between the widest point and the tip is parallel to the water.

This would only be the case in flat water, when being used in swell with the water coming higher up the skiff, sometimes close to the gunwale you will have to bring the oar higher than a narrow blade  to get it out of the water as you will need to clear the widest part of the blade, not just the tip, this may not be possible due to the rowers legs the oar will catch the water and may increase the possibility of knocking the rower from their seat.

colinmuirhead

Posts : 8
Join date : 2016-12-03

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Thu Dec 22, 2016 10:26 am

Hi Colin,

The picture of the Macon blade I used in the survey is shorter and fatter than the blade I'm experimenting with, which is about 600mm long and 190mm at the widest. The picture also looked unfortunately like fibreglass, which I think probably put people off.

I agree with you that it did not get a good response in the survey, although not as bad as the cleaver.

The issue of how much vertical movement is needed is not only about clearance from waves when the oar is out of the water. It is also about how far down the blade has to be moved to be completely submerged. If a long blade is to be completely submerged right up to the hilt, the handle may be so high that it's level with the rower's face, which is higher than comfortable.

So the issue is, what is the range of vertical movement between completely in and completely out of the water? Then the seat height of the rower can be adjusted with spacers or cushions until the arms are horizontal during the stroke but the rower still has good clearance from waves while the oar is out of the water.

I still think the Macon shape in the dimensions I'm suggesting, similar to gig oars, has a smaller vertical range of movement than a long narrow blade. This applies whether the water is flat or wavy.

The rowing qualities of a spooned blade are still unproven in the St Ayles because only Royal West have tried them with their old spoon oars, but Royal West say they are great. I have rowed with spoons in other boats and like them. I think they will show an advantage over flat blades in racing. They are lighter to make in ply than flat blades, being made stiffer and stronger by the curve, and this is important on making the UHF smaller. So I intend to go on to make and test them, and then others can decide whether they like them or not.

To some extent people vote for what they know, and they should at least get the chance to try something before rejecting it out of hand.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by John Irvine on Tue Dec 27, 2016 2:54 pm

Please could I add buttons (stops) to the debate. NB uses a rotating gate, made of layers of plywood. We have small blocks of plywood under the sleeves to stop the oar sliding out through the gate, while allowing the oar to be pulled inboard. These are simple and effective, but it does mean our gearing is fixed. How would people feel about the plastic collars used in other forms of rowing, which allow gearing to be adjusted? Given that we allow PVC sleeves, these wouldn't be much of a departure from the traditional materials principle.

John Irvine

Posts : 6
Join date : 2016-12-02

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Tue Dec 27, 2016 5:58 pm

My feeling (opinion alert) is that what we need is not one fixed gear even if adjustable, but multiple fixed gears which rowers can change between before and even during a row, though not while actually rowing.

Plate and pin with more than one hole allows this, as do Ullapool's swivel/multiple groove system and Crail's pin/keeper/clam system. So in one form or another I'd say most of us are already using a multiple fixed gear system.

The plastic collars you refer to also assume a mostly circular oar which we don't have. So I don't think we would be likely to go down this road although if everyone else speaks up for it maybe we will.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by John Irvine on Wed Dec 28, 2016 12:26 pm

Could the rules be loosened to allow use of plastic collars? Also the use of plastic washers under the gates? Neither of these would provide any unfair advantage at regattas.

John Irvine

Posts : 6
Join date : 2016-12-02

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Fri Dec 30, 2016 3:17 pm

I think John that the whole idea here is to make one design and then stick to it rather than adding to the plethora of ideas already out there. But if you want the existing rules which apply to the existing oars to be loosened in the way you describe, your route is to apply to the SCRA committee directly rather than here.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by Ian Mills on Thu Jan 05, 2017 9:57 am

I agree with Colin that any 'standard design' should have a needle type blade.

Regardless of the science of why Macons are more efficient than needles (whilst buried in the water), in practical use for the St Ayles skiff, with a non feathering oar, the needle is the preferred shape of the vast majority of the fleet.
Most people agree that needles are easier to handle in the rough and windy conditions which are often encountered in the skiff.
Tapering the tip in a slightly 'tulip' manner would be an improvement to this shape. So it becomes a 'stretched Macon'.

Our own experience is that we used a Macon shape (when I mistakenly thought I could manufacture a simple feathering system) but found them awkward on the extraction and recovery in rough conditions. More windage in a headwind. So we switched to a needle shape (about 800 mm x 150 mm) and everyone in the club prefers the new blades.
I should add that the forward faces of our blades are rounded which helps them shed water easier, is slightly more aerodynamic on the recovery and looks nice! Also it presumably helps hydrodynamically with a bit more 'grip' in the water.

Macons would be fine to recommend to all if the oars feathered but are not so good (for the majority) on non feathering oars in our experience.
I realise that North Berwick use the Macon shape successfully, but the majority of clubs use and have asked for (in the survey) longer thinner blades.

Obviously we like our design 820 x 150 mm (I would say that wouldn't I … but it is very similar to that used by many clubs).
However, I think Eastern's design is perhaps an even better compromise between the Macon and the Needle.
750 mm x 160 mm. Area about 975 cm sq.
Tapered towards the tip. Looks nice and behaves well in the water – helped by a strip along the centre of the power face of the blade.

Ian Mills

Posts : 22
Join date : 2016-12-03

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Thu Jan 05, 2017 10:26 am

Hi Ian,

There is a bit of overlap historically between needles, tulips and macons. The blade I made is probably a stretched macon or a tulip, since it is 700 mm long as I now measure it, and 190mm wide:












Not much different to Eastern's but the proportions are negotiable. What I'm suggesting is that we treat ourselves to a lighter more efficient blade of whatever aspect ratio we eventually decide.

I certainly agree it's helpful to taper the tip slightly to reduce the crabbing potential and concentrate the area a bit more in the middle.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by Ian Mills on Thu Jan 05, 2017 10:35 am

Hiya,
Looks amazing!
This is skiffology at the highest level!

Ian Mills

Posts : 22
Join date : 2016-12-03

Back to top Go down

Re: Decisions we need to make for the new design

Post by Rory Cowan on Thu Jan 05, 2017 12:10 pm

Hi All,
The possible weakness in our survey to date is that we have asked for feedback on what we already have and know in house and not on what we could have.  For that reason there are arguments based on a small number of options relating to what is in service as made/built under the present interpretation of the rules  (possibly slightly stretched as in using materials other than timber to weight the looms).  That said, what we could usefully do now is to have a period where we swap experience of each others' oars and add a few innovations to get a wider view and assessment of what could be available.  Presumably this is where we now are.  Referring back solely to who currently has what blade shape and whether that is preferred, could lead us in the wrong direction purely because arguably we like what we are used to so that's what you get.  

I have been in the process of making the first of a fresh set of oars for our boats here on Arran and I suspect that there is merit in making a number of different blade shapes and loom designs - (so I suppose it won't be a fresh SET after all!) and then inviting as many people as possible from here - and from neighbouring clubs - to come and tell us what they think. Can we all take the opportunity actively to invite others to experience our own oars and oarlock systems so that we can get a wider opinion of where we are and where we could be going. A variation on ''I'll show you mine if you show me yours!!" (By the way if you find yourself on Arran and want a row - then make yourself known to us and come and do it.)

I am about to put a simple oar rating scale on the Dropbox site so that we can have an easy way to asses an oar and give some feedback as to what we like or dislike about the oars we have used under various conditions.

Rory Cowan

Posts : 20
Join date : 2016-12-04

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Thu Jan 05, 2017 1:09 pm

Hi Rory,

Yes people tend to like and want what they have got used to. In the survey I used a Macon blade picture off the internet which was fairly broad and short, and looked like fibreglass. I think rowers used to long sea blades reacted against this but I still want to try a longish needle/tulip/stretched macon as pictured elsewhere.

Good idea to collate reactions to new oars and blades and oarlocks using your new form.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Thu Jan 05, 2017 1:15 pm

Thanks Ian for that stirring accolade!

It is stiffer than it looks because the vee gives it depth, so it is a lot stiffer than flat 4mm ply.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by Don Currie on Sat Jan 07, 2017 4:25 am

Good comments by Rory about taking an effort to try out as many different options as possible, and also about leaving enough time to do same. The comments about blade shape reinforce what I've learnt - wider blades are more efficient, but they can be a handful if you don't have the ability to feather. We've been having a windy old summer down here this year, and I've spent most of the time with an experimental feathering oar. Today I was using a non feathering oar in 15 knot wind with maybe the odd gust to 20, and it was a stark reminder of just how much harder it is to row in a breeze with non feathering oars. I know it will add time to the project, but I strongly feel that most of the bits we need to produce a nicely balanced and easy to use feathering oar are known, albeit in somewhat undeveloped form. I think the process of agreeing on a good oar will take a year or more - I hope everyone is prepared to give it that long.

Don Currie

Posts : 39
Join date : 2016-12-03

Back to top Go down

Re: Decisions we need to make for the new design

Post by topherdawson on Sat Jan 07, 2017 8:20 pm

Hi Don,

We are trying to have a design ready in time to get a lot of rowers to try it by the end of the 2017 season, but that may not be realistic. But I do feel we are making progress.

topherdawson
Admin

Posts : 211
Join date : 2016-11-24

http://sasoo.forumotion.co.uk

Back to top Go down

Re: Decisions we need to make for the new design

Post by Rory Cowan on Sat Jan 07, 2017 11:45 pm

Hi All,
For what it's worth, on Arran we frequently have significantly differing weather and sea states ranging from flat calm to force 7 (or more if you want to go out) over relatively sheltered sea loch conditions, but if the wind switches to easterly we can get conditions when bow has a bit of difficulty even getting a blade into the water.
Of late in calmer conditions our rowers declared themselves strongly in favour of the longer more slender (Anstruther pattern) blades, however when the conditions changed significantly recently and we had quite a bit of wind and a sea, people voluntarily declared that they preferred the older heavier oars with the macon shaped blade.  It seemed a bit counter intuitive to me because the macon needs to be lifted further out of the water to clear the blade and there is arguably more wind resistance.
So that seems to be a strong unsolicited vote for the macon shape - despite the fact that our macon blades (Iolair) were comfortably the heaviest in the survey.

Rory Cowan

Posts : 20
Join date : 2016-12-04

Back to top Go down

Re: Decisions we need to make for the new design

Post by Sponsored content


Sponsored content


Back to top Go down

Page 1 of 2 1, 2  Next

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum