24 February 2011

SHOP: retractable grab handle

The latest addition to my fleet of kayaks needed a toggle handle to be repositioned since I deemed it to be attached in a dangerous location.
The kayak’s deck is designed to accommodate an optional rudder and the designer could not attach the grab handle at the stern of the kayak since it would interfere with the rudder.
I have previously detailed the reasons why I regard some grab handles and its position on some kayaks dangerous. After a few pinched fingers and a bruised knuckles I now like to have all of my handles attached at the ends of my boats.
I believe that the best handle on a kayak is the single cord (not a loop) one from SKUK (Nigel Dennis).
SKUK grabhandle (c)
handle on SKUK Exporer
While some argue that it is not as easy to use in an emergency towing situation (no loop for a carabiner to be attached to) I prefer that type of set up to prevent injuring my fingers.
One thing that I don't like is the banging that the handles produces when the kayak is paddled in textured waters. Some other set ups (like Valley kayaks) have a bungee cord tensioning the handle back onto the deck which stops the annoying banging.
Then it dawned on me: why not combine the two? Why not tension the single line?
retractable handle_3
the handle was originally attached on top of the deck
While simple in concept the details of the execution and the quality of materials for this handle set up must be first rate.
I used a sheeted Dyneema core 4 mm line for the cord and quality bungee cord for the retracting/tension section.
retractable handle_4
Dyneema line through a sleeve in the hull
A knot joins the two and a bit of heat shrink covers the ends to make it look neater. The knot stops the cord from being pulled through the sleeve in the hull. The bungee is attached to the toggle's original anchor point on deck.
retractable handle_2
Dyneema/bungee junction
The handle has a short stand-off from the hull so it can be grabbed easily when in a hurry (like in the surf).
retractable handle_1
handle with stand-off
The idea of having a retractable handle came to me after I had drilled and sleeved the end of the hull of my kayak.
If I had to do it again I would position the sleeve on a slant to alleviate the (right) angle of the hole and have it more in line with the toggle cord. That would achieve less friction when the handle is pulled out and possibly reduce the wear on the line.

PS You have seen this set up here first

15 February 2011

Kayak length, speed and stability: observations

Don't get too hung up on length and speed. Because, as you say, all other things aren't equal here. Longer hull at the same beam and hull shape also means increased wetted surface and more drag. It also requires more materials to build, so its heavier and that takes more energy to accelerate. 
Even ignoring that, the relationship between hull speed and length is proportional to the square root of the waterline length not the actual waterline length. Note: Waterline length not overall length. A long boat with less than it's design load sits up out of the water and has a shorter waterline length than the same boat loaded. The difference in hull speed between a 580 and a 530 would be less than a quarter of a knot or 0.5 km/h. For both boats it would be between 9 and 10 km/hr and thats a very fast pace to maintain cruising any distance. Unless you're racing you probably won't notice the difference.
(10FEB11, John Anderson_SeaKayakForum.com )
John's comments are similar to my findings.
In paddling groups I have observed that paddlers left behind occasionally blame their shorter kayak for the lack of speed and them not being able to keep up. However the pace is usually around 6-7 Km/h at best.
Some paddlers are convinced that if they had a longer kayak they would be able move faster.
It would be interesting to see what would really happen if they tried the longer kayak. Chances are they would be actually slower, if they could not improve their paddling technique.
Obviously things are different if a paddler can bring his/her kayak to hull speed (maximum speed that their particular kayak can achieve). Most sea kayaks hit "the wall" at much higher speeds than at recreational paddling pace.
Club paddle_1_c
One must really push hard to eventually feel the kayak being unable to go any faster.
At slower speeds (Club outing pace) a shorter kayak will create less resistance and therefore be easier to paddle.
Here are some resistance stats for known sea kayaks hulls.
(Posted by: wilsoj2 on Nov-24-09 2:44 AM (EST) www.paddling.net )

Here are some drag figures for 7 boats from Sea Kayaker from 2 to 4.5 knots (2.3 to 5 mph) listed from most drag to least at each speed:
at 2 knots:
 Valley Rapier 20 = .97
Epic Edundrance 18 = .97
NDK Explorer = .94
Chatham 16 =.93
Foster Legend = .9
Avocet = .9
Nordkapp LV = .9

at 3 knots:
Valley Rapier 20 = 2.04
Epic Edundrance 18 = 2.03
Foster Legend = 2
NDK Explorer = 1.96
Chatham 16 = 1.93
Avocet = 1.92
Nordkapp LV = 1.88

 at 4 knots:
Chatham 16 = 3.89
Avocet = 3.74
Foster Legend = 3.7
NDK Explorer = 3.63
Epic Edundrance 18 = 3.55
Nordkapp LV = 3.52
Valley Rapier 20 = 3.45

 at 4.5 knots:
Chatham 16 = 5.58
Avocet = 5.4
NDK Explorer = 5.25
Nordkapp LV = 5.24
Foster Legend = 4.9
Epic Edundrance 18 = 4.73
Valley Rapier 20 = 4.45

The drag figures given are calculated assuming flat water.

It seems that the shorter kayaks have less resistance than the long ones, at recreational/Club speed.
I also find intriguing the emphasis put on  maneuverability and stability observations from paddlers' reports on a given kayak.
They vary incredibly.
I hear/read comments like: "the kayak is very tippy" or "the kayak is very stable" for the same very kayak.
So what gives? how can a person really find out what are the characteristics of a kayak?
I believe that stability is difficult to quantify.
Sure there are scientific measurements taken and published for most kayaks out there (Sea Kayaker Magazine being a great source) but those numbers are much harder to interpret and to come to a conclusion than the simple measurements of speed.
What one person finds stable other might find tender.
Las Chicas de Rio Mistico Kayaks
Photo: Rio Mistico Kayaks_used with permission
The biggest factor in objectively assessing a kayak's stability is the paddler's skill level.
A novice might find a narrow round hulled kayak very unstable while a proficient kayaker will pronounce it "rock solid". Needless to say that quality seat time in any kayak will increase one's skill level. It certainly did for me: here
Being able to roll also adds an incredible sense of security and a kayak that used to be regarded as tippy suddenly becomes OK. Before I could roll proficiently I would be very wary of narrow kayaks.
A paddler's weight is probably the other most deciding factor on a perceived kayak stability. I however find that more weight doesn't equate to more stable. Gear or ballast in a kayak will increase stability but a paddler's weight might not. There is a marked difference between the weight distribution between men and women; the latter being advantaged by a lower centre of gravity that in terms equates to a more stable kayak.
I notice girls having an easier time balance bracing a kayak than guys.
Balanced brace training (c)
Being top heavy and having broad muscly shoulders does actually make it more difficult.
Last but not least: the paddling conditions.
Some crafts are excellent in calm waters but become a bit of a handful in following seas.
Regular readers of this blog will also know that I find ruddered kayak less stable in following seas where the rudder no longer can function to aid directional stability. A kayak that can be controlled by the paddler's body and paddle stroke is usually a more stable kayak, in conditions.
While listening to reviews is often beneficial in the quest of selecting a new kayak, some reviews/observations are so terribly subjective that give the researcher little help. What most reviewers forget is to state their weight and height.  What really can not be quantified however is the skill level of the reviewer, to then be able to draw any conclusions from the review.

08 February 2011

GEAR: carabiners for sea kayaking.

On my sea kayak I often use carabiners (snap shackles) to attach items to the deck.
The convenience of being able to release the item without tools or too much fumbling is the main reason that a biner is used. Other items, like stays for a sail, that don't require quick release are usually secured by D shackles with a screw on gate.
I use this type of biner for the items that might need occasional use (hand bilge pump secured below deck).
This biner is compact, light and cheap.
But I don't like using this type of gate on a towrope.
There was an incident where the sharp hook ripped somebody's hand open when grabbed by its end.
A larger snap shackle is desirable when trying to attach a towed kayak since some kayak handles will have a hard time accepting a small opening gate.
A larger stainless steel snap shackle from marine chandleries seem to do the job.
What I don't like on this option is the little hook that the biner has when the gate is open and often snags on ropes when least needed.
I thought that a high quality anodized aluminum climbing biner with a key-lock style gate would be the perfect tool.
It was, for a while. The biner has a spring gate and the spring is housed inside the gate itself.
With time the spring corroded and failed leaving the gate wide open. While the rest of the biner still looked in great shape it was no longer usable/safe.
I then tried a carabiner that uses a wire gate as spring. The anodized climbing crab was perfect. The gate was free of hooks that could snag on a rope and would shut securely.
Less then a year later the carabiner started to show signs of corrosion and eventually just exploded!

Finally I sourced a biner that meets my needs.
Stainless steel with a key-hole gate designed for salt water.
The carabiner is made by Kong in Italy (holders of the key-hole gate patent).
There are no signs of corrosion after a year and the action of the gate is very positive.
I don't snag on ropes when releasing from a towline and there are no sharp edges to cut myself on.
The biners come in different sizes but they are not easily sourced. Only high end marine chandleries seem to carry them.

01 February 2011

Sailing instead of paddling

The paddling conditions this season have been rather windy.
Week-end forecasts have regularly been 15 knots or more which most seem to consider an unpleasant environment to paddle in.
Slogging into a wind of 20 knots for hours on end is not exactly great fun.
Not wanting to spend precious days of my free time off the water I plan my paddles around the direction of the wind instead.
I try to pick a launching location that, with the wind blowing on the beam of my kayak, would give an island destination in Moreton Bay. And then I pack a sail.
What could be a slog suddenly becomes great fun. Sailing my sea kayak is not strictly paddling but I don't mind mixing it up a bit.
FEKS sailing_2_c
sailing with Flat Earth Kayak Sails
The best part of windy day on the water is that it's usually deserted.
No stinkboats to destroy the mood. Just a few yachts that usually are friendly enough to give me a wave seeing that we share the same medium.