'Hi Steve, I wanted to ask your advise on paddle length & Shape if possible? The paddle I have is just over 7ft and quite rounded. I've read online that the paddle should be 6 to 8 inches taller than your height and rounded for surfing and square for flat water. Is this right? Does arm-span have any effect? I'm 189cm tall but my arm-span is 198cm. Should that have any effect on length? Also, do you include the handle with the overall length? I'm a keen surfer and I try and get in the water at least every other week. Although I've never surfed an SUP as of yet. Should I get more of a square paddle for flat water and use the rounded one I have for surfing?' Bobby Thatcher.
The current popular measurement promotes 6-8" above head height rule, which is of course fundamentally 'unscientific' as it fails to account for a range of issues relating to individual physiology, board type and circumstance. In particular this simple formula fails to account in simple terms for;
1. Your arm length (relative to your height)
2. The free board (thickness) of your board
Paddle Length
This is measured from, blade tip to the top of the grip (handle), so in answer to the inclusion of the handle (grip) as part of overall paddle length, yes it's inclusive.
A Tried and Tested Principal
'Your top hand (on the grip) when mid way through the forward stroke, should be level with the bridge of your nose (or at eye level), which approximates the point at which the shaft is vertical.'
If your top hand is working above head height at this point, you will be unable to exert sufficient rotational torque (through the spine) or compression via the abdominal muscles in order to be most efficient and exert even sub maximal power. More of a concern, rotator cuff injury is not only likely but almost certain over time as a consequence. This means we need to use the paddle firstly (or a variety of paddle lengths) to determine what suits us.
While we can say that more length could equate to more leverage (potential) the problem comes in being able to maintain control over the blade face itself via the lower hand. In addition we only need bury the blade, not the blade and shaft which is essentially unwanted drag which contributes nothing to forward propulsion.
A Possible Formula
If you could apply a formula, it would be along the lines of; measure the distance from floor to eye level + the freeboard (deck to waterline) of your board, then add the height of the blade measured from the tip to where the neck of the blade joins the shoulder (shaft) to give you an overall length. This approach is used by some professional canoeists for example, I can't say I have used it in the context of SUP but for regular paddling and racing it would be close. (A canoe paddler would take measurement to eye level when seated in canoe...)
Surfing Paddle over Cruising/Racing
The maxim here, is that a surf paddle should be shorter and have a smaller blade surface area in order to achieve;
1. Higher potential stroke rates
2. Speed of being able to switch sides
3. Ease and speed of handling
4. Accommodates the paddler better when crouching in surfing stance
5. Less likely to pull the paddler off the board when using draw strokes etc
Square Paddle Vs Rounded
A square blade will tend to have its centre of effort lower down the blade towards the tip, whilst a more rounded blade will have its centre of effort more balanced in its mid section, but that's a generalisation without seeing the blades. A rounded blade is likely to be more 'agile' and less likely to pull you over, whereas a squarer blade will tend to be less easy to throw around and more principally dedicated to working unilaterally (ie in one plane of direction as in the forward stroke). Additionally they can sometimes provide more 'lift' at the beginning of the stroke on account of added width towards the blade tip,.
In short, yes, the rounded blade for surf would be preferable...in Hawaii, surf blade areas are getting smaller...though racing blades also seem to be getting smaller...like the T-Shirt says, 'It's not the size of the dog in the fight, it's the size of the fight in the dog...' and so it has evolved with paddles, it's not the size of the blade area which really counts, its how you use it...the smaller the blade you can be most efficient with, the better, as there's less drag and less to carry around and to some degree, this also holds true for paddle lengths...SUP paddlers originally had overly long paddles (as did outrigger canoe paddlers), but with experience and time, these paddlers are now moving towards shorter length paddles for all disciplines.