# Correct seat placement

-- Last Updated: Sep-24-08 2:12 PM EST --

All right, I got inspired by the recent scientific threads, here is good question for the inquiring minds.

Assume you suspect that the seat in your kayak is not placed correctly. How would you fix the placement?

So far, I came up with two approaches:
1. Pry it loose and start sliding it around until satisfied. Too practical, not worthy of this p.net reader
And, satisfaction is so subjective.

2. It is probably safe to state that COG of paddler should be right over COB of boat. So, how to find both?

Edit:
Just thought of this one:
3. Let's assume that kayak sits in the water naturally balanced. Then, addition of paddler, if the seat is placed correctly, should sink both bow and stern equally. Then one approach would be to remove the seat - we can assume weight negligible, and ask the paddler move back and forth within the cockpit while measuring/judging how much bow and stern sink.

Oh yea, if someone knows "correct" placement for 2005 VCP Avocet RM, don't be afraid to post. 2005 Avocet was one year before 3-layer poly, still had plastic pad for foam seat. Pad has long extension up front with 3 bungees and much shorter back extension. Measurements defining pad placement would be welcome

As a pretty good indicator
you might try using the force x distance balance method. Moving say 180 lbs of your weight 1" should produce about the the same effect as moving 10lb 180".

Try putting various weights of water forward of your feet or in the rear hatch. When you find the weight and distance of water that makes the kayak handle like you want it to then use the formula

inches to move seat = water weight*inches from seat/your weight.

This will be closer to reality if you are not putting the water all the way forward or rearward. Of course you want all the gear you normally carry to be in its normal location (as much as possible with the added water).

Mark

Yes, that would work
However, I am trying to take “till you like it” out of equation.

Actually, I have nothing against this approach - some fine kayaks, Mariners for example, have movable seats for the purpose of adjusting trim and tracking.

Variables
I would think one of the prime variables would be your foot size seeing it would be the farthest point forward a variable might be of the boats CG. This might be compensated by loosening your back band. Don’t forget your paddle weight as that should be mostly forward of the boats CG also.

There should only be

Use a spotter
If someone can watch you from the side in flat water as you move the seat forward and back a bit, they can tell when it is most balanced. If you error, try to error to having the boat back heavy not bow heavy.

Even a manufactured boat with a molded in seat is an average. If a person is big and round with small legs it will sit quite different than a person with big fat legs and a small torso.

Email Valley or take a measurement off another same model.

To further confuse things
http://clydewinter.wordpress.com/2006/08/06/ithe-peripatetic-pivot-point/

Since you have to remove the seat to relocate it, while it is out why not make a temporary foam seat from scraps and run some sea trials?

Jim

yes
Spotter - that is pretty much the 3rd line that I came up with.

I have friends who own 2004 Avocets - that’s how I noticed the difference; I have asked them for numbers.

Of course, who knows if their seats are placed correctly

Now, my quest for the scientific method is probably more obvious - otherwise, the way boat handles depends on how fast it is going.

It is possible that Valley seat slides around as there are two screws holding something to the sides of coaming.

I hesitate to rip the whole thing open without having a B plan or a good understanding how the seat is put together.

good points NM

easy?
Hmm, this sounds deceptively easy, I must be missing something.

On dry, level land (parking lot), find a 1-2-inch-diameter straight stick and lay on ground. Remove seat from kayak, place kayak on stick, move kayak forward and backward until it approximately balances, mark this point as COG.

Remove kayak from stick, place seat on stick, place paddler bum on seat and paddle in hand, with both body and paddle held in approximate neutral position, move seat forward and backward until it approximately balances, mark this point as COG.

Line up COG mark on seat with COG mark on kayak and affix seat.

What did I miss?

CG vs CB
Well the center of gravity of the boat is one thing, but it doesn’t necessarily coincide with the center of buoyancy. To trim a boat properly, it has to be floating in the water; to trim a boat at speed, it has to be moving at speed, etc. An external observer is generally needed to judge or photograph what is going on.

As you said - academic -
I’ve so far found that I like my seat somewhat forward when I’m going downwind and trying to catch waves to surf. That position may not be optimal for going upwind or flat water.

So, from that prospective, you need to figure out how you use the boat most of the time and trim for that purpose.

As for me, I have very little choice in terms of moving the seat in one of my boats: it has to be almost all the way back and the foot pegs - all the way forward or I don’t fit in -;).

good point
Oh yeah, good point, CB is what you want. I have to admit that I couldn’t figure out what the OP meant when he used the term “COB”, but now that it’s explained I have to agree. I just note in passing, that I would expect the two to be so close together in this class of boat that I expect both methods would produce very similar results.

Still, I agree COB is what you really want, and the OP has already described a method to do this - put the boat in the water, and the paddler in boat sans seat (or with the detached seat in his lap, and let’s say also holding paddle in his hand, in a neutral position), and have him move about until the observer detects the boat is floating level (with level defined as how it floats without a paddler).

It’s still pretty easy. However, I only say that because of the condition the OP put on the question - that no part of the test be subjective. As to where you REALLY want the seat, that’s going to be undeniable subjective, and much harder to determine. But I think the neutral method will give you a good starting point, especially since the boat itself is so light in comparison to the paddler. I’ve been careful to describe the paddler as being “in a neutral position” for the purpose of the tests because, in real life, shifting your weight around will determine the operational center of gravity.

COB & COW
COW = center of wind [resistance] -

To fine-tune things like weathercocking for instance. COB may not correspond to COW…

Another take … DON’T Look …
Use gps and your butt …

Not sure what you are going for so will only speak for if you were going for boat speed with good handling still.

Synapsized version.

Mark inside boat as you move the seat around 1/2" @ a time is good to start.

Try to do this all in one shot / day with same same conditions.

Gradually move seat forward and do a series of sprints and timed/gps-ed ‘race pace’ runs over same course … You will probably notice your boatspeed will increase as you move forwards. Mark down speeds and SOP remember handling wise everything as you go. The will be a point where your sprint speed will max out along with a tapering off of a balanced feel of the boat’s handling … back the seat up to where your ‘race pace’ speed is the best for the handling you like in the boat … Fine tune from there for varying conditions and rudder / no rudder. After doing all ths you will have a good understanding what your boat can do and how to vary it with no guess work.

Call me if you want a good way to make the seat fore / aft adjustable.

probably true
Probably true that the CB and CG are very close together if the boat is symmetrical +/-, so the balance test would be a very good starting point and might not require any further adjustment. There is also the fact that when you’re paddling, you’re exerting a moment that makes the boat want to squat in the stern, which it will do more or less depending on how much volume is back there. The trim while paddling is more important that sitting still. Sprint boats are trimmed an inch or two low in the bow to counter the squat - a regular boat paddled by a mere mortal should need less compensation, I imagine.

Thanks
Patrick,

Thanks for the detailed description. I might take you up on that adjustable seat offer.

Thanks!

I think I, and possibly many others, might be interested in your ideas for an adjustable seat. Any chance you could make this information available, such as photos or something? Ken

Basic idea is …

– Last Updated: Sep-26-08 3:10 PM EST –

Lay up glass on inside or outside using your hull as the mold to make a thin plate, bond seat to plate. use 2" velcro for 'rails' between the plate and the hull. Seat does not move unless you want to adjust it's positon.

Side benefit, pulled from old website: pic too,