Author Topic: Adding weight to a SUP ...  (Read 16553 times)

pdxmike

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Re: Adding weight to a SUP ...
« Reply #45 on: October 23, 2014, 04:58:49 PM »
This is reminding me of going on ferry boats--outside lanes of cars get loaded last, and unloaded first.  Heavy trucks always go in middle.

Bean

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Re: Adding weight to a SUP ...
« Reply #46 on: October 23, 2014, 05:16:28 PM »
Wow, busy thread, I'm just catching up on this now.  Here's a thought that I don't think anyone has specifically stated.  If you like the WEIGHT of a heavy board then the mass distribution of the lead might not be too critical.  If you like the side to side stability of a heavier board then its the higher moment of inertia that you like.

On the heavy board that you like, there's probably more weight all over the board.  The extra weight in the middle does not add much to this. You can get a higher "roll" moment of inertia of the board (side to side tipping) by adding mass out near the rails.  The key here though is that if you get the right feel with 10lbs spread out all over the heavy board, if you weight out near the rails, all the extra wight out away from the center of rotation means that you won't need 10 lbs to get the same moment of inertia for side to side roll.  The moment of inertia is affected by the weight of the added mass multiplied by the distance from the center of rotation squared.  This makes a big difference.

This sounds like an interesting experiment, and if you can experiment with only about 5 lbs in various locations, (nose,tail, middle, rails, usual standing area etc) you might be able to figure out what property, other than just weight it is that you like the feel of, and you might achieve this without having to go to as heavy a board as you think.

Peter

Perimeter weighting to increase the sweet-spot...

linter

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Re: Adding weight to a SUP ...
« Reply #47 on: October 24, 2014, 05:43:55 AM »
Wow, busy thread, I'm just catching up on this now.  Here's a thought that I don't think anyone has specifically stated.  If you like the WEIGHT of a heavy board then the mass distribution of the lead might not be too critical.  If you like the side to side stability of a heavier board then its the higher moment of inertia that you like.

On the heavy board that you like, there's probably more weight all over the board.  The extra weight in the middle does not add much to this. You can get a higher "roll" moment of inertia of the board (side to side tipping) by adding mass out near the rails.  The key here though is that if you get the right feel with 10lbs spread out all over the heavy board, if you weight out near the rails, all the extra wight out away from the center of rotation means that you won't need 10 lbs to get the same moment of inertia for side to side roll.  The moment of inertia is affected by the weight of the added mass multiplied by the distance from the center of rotation squared.  This makes a big difference.

This sounds like an interesting experiment, and if you can experiment with only about 5 lbs in various locations, (nose,tail, middle, rails, usual standing area etc) you might be able to figure out what property, other than just weight it is that you like the feel of, and you might achieve this without having to go to as heavy a board as you think.

Peter

great stuff.  could you unpack the concept of "moment of inertia for side to side roll" a little for me?  i think i know what you're saying but not even to the degree that i could restate it in my own words.  do you have a sense of what more weight out to the rails would feel like?  thanks again!  and could you suggest an initial placement of weight, going with, say, 5 lbs?

peterwSUPr

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Re: Adding weight to a SUP ...
« Reply #48 on: October 24, 2014, 10:05:07 AM »
Moment of inertia is a property kind of like mass, but it is more like mass distribution and how it feels when you move it.  Take a long pole and add a weight to the middle of it and you can still pretty much spin it around like you could without the weight added to it.  Now, split the weight in half and add the pieces to each end of the pole.  The pole weighs the same as when the weight was in the middle, but it is WAY harder to spin it around and change direction of its rotation.  "Swing weight" has been used in this discussion, and that is pretty much the same thing. 

In terms of cars, planes, and boats -and boards, there is a moment of inertia for roll (tipping side to side), pitch (nose/tail up and down) and yaw (turning left and right) and they will be different (although pitch and yaw values will be similar).  Added weight at the nose and tail near the centerline would make the up and down of the nose and tail feel quite different, and the left/right feel quite different, but the side to side tipping would not change much.  If you add the weight on the rails on either side, halfway back from the front, the nose up/down, and the turning left/right would not change much, but the roll (side to side tipping) would feel different, and slower to rock to the left and right.  Actually, maybe for this example, near where you stand, and not at the handle, might make the least difference for everything but side to side roll.

The thing about moment of inertia of added mass is that it is calculated by mass x D^2.  So if you take a weight and add it all to near the rails, the distance from the centerline, maybe 12", when you square it is quite large.  If you added the same weight in the form of a layer of glass all over the board, a lot of that weight would be much closer to the middle of the board, and only a small amount would be out at the ends where it really makes a big difference and benefits from the distance squared. 

So the point I was making is that with the heavy board you like, IF it is something about the side to side tipping, or the slower left right turning that you like the feel of, then you might not need a full 10 pounds to achieve this.  I'm not sure what it is you are feeling, but I bet for the pitch and yaw (up down, left right) if you need 10 pounds distributed all over the board, you might get the same feel with only half that (or even much less) if all the weight is added out near the ends.  Same idea with the roll (ride to side).  The feel of 10 pounds spread out all over might be the same as a 2 or 3 pounds near each rail.

OR, maybe you like the feel of "heavy", no matter where it is.  Or maybe heavy near the middle, so it does not affect the turning as much (like the pole with the weight in the middle at the start of my description).  I think the key here is to be able to move it around and experiment.  You may not like the feel of your first setup at all, but moving the weights to different places might just change the feel a lot.

HTH,
Peter

PonoBill

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Re: Adding weight to a SUP ...
« Reply #49 on: October 24, 2014, 10:19:37 AM »
I like your idea for initial placement--two pieces on the rails close to the front, one at the back--sort of a Y configuration. I might do that myself just for the heck of it. It will slow the pitching quite a bit, and slow yaw pretty dramatically at the front. You'll have a somewhat strange effect at the back that might be helpful, you should be able to carve the tail a little faster than you can carve the nose. I need to model this to see, how it works, the board isn't all that flexible but motion on a yielding surface is complicated.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

linter

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Re: Adding weight to a SUP ...
« Reply #50 on: October 24, 2014, 11:40:31 AM »
i think i got it, peter, maybe, sorta.  in any event, i think i'll start w/ similar to what bill is thinking -- weight out on the rails -- but where he's going to put his forward some, i'm going to try mine in the middle, and then i'll do the same as him and put a bit of weight in front or in back of the fin, somewhere around there.  if i did 2 lbs at each position, that'd be 6 lbs total, good enough for a start.  thanks for the explanation!

blueplanetsurf

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Re: Adding weight to a SUP ...
« Reply #51 on: October 25, 2014, 11:44:16 AM »
I did a weight/ speed test a few years back, where I added 30 lbs of weight to the board to test the difference in speed, posted here: http://www.standupzone.com/forum/index.php/topic,9446.0.html

Robon suggested spreading the weight out instead of putting it in the center and I was surprised by the results:

Here are some related observations from the experiment:

"Like PonoBill and pdxmike I did not think the weight distribution would matter for the speed test for the same reasons they mentioned and I don't think it did but I tried it anyways.
To my surprise, the board seemed to handle a little better.  I tried to figure out why and then it made sense- with the weight spread out over the length of the board it yaws less especially from a standstill. 
I know you could turn this into a science project as well but here is the simple explanation I came up with: When you are doing a flip off a diving board, you can speed up the rotation by pulling in your arms and legs closer to the center of rotation, while spreading out arms and legs- weight away from center of rotation- slows down the rotation.  Same thing on the SUP.  If all the weights are at the center, the board will yaw more easily (center of rotation is center of board), while spreading the weight away from the center of rotation makes it yaw less- makes sense, right? "

and

"You could argue that putting weights on the nose and tail of a board would make the board more directional (and slower/harder to turn- like straightening out your body to slow down the rotation of a flip).  I don't think this would make the board faster but it's an interesting thought.

Thinking along those lines:
When you are SUP surfing (as opposed to racing) you want the board to turn as easily as possible, so if you are turning the board off the tail, having less weight, especially in the front of the board and/or a shorter length, will make it easier to pivot the board. "

So, if you want the board to turn easier, put the weight on the pivot point (under your center of gravity where you stand when turning), to yaw less, spread the weight out, to make the board more stable, put the weights on the bottom and close to the rails.
« Last Edit: October 25, 2014, 11:49:05 AM by blueplanetsurf »
Robert Stehlik
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http://www.blueplanetsurf.com

PonoBill

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Re: Adding weight to a SUP ...
« Reply #52 on: October 25, 2014, 12:14:22 PM »
I"m not surprised at all that changing the weight distribution in your interesting test changed the handling, but I would be surprised if it dramatically changed speed. Life is full of surprises though.

Our friend Linter is a special case. He's looking to slow the response of his board to make it more controllable with his neurological condition. For him it's a fine idea. I will probably try something similar in Maui this year to help with my own neurological condition--being a geezer.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

linter

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Re: Adding weight to a SUP ...
« Reply #53 on: October 26, 2014, 01:11:38 AM »
Such interesting stuff. 

One thing that hasn't been talked about is glide on the wave.  Once my 30 lb is on trim, all i have to do is stand there and do nothing at all and it's the fastest down-the-line board i've ever ridden.  i would assume that this is a purely a function of weight and has nothing to do with weight distribution.  right or wrong?

linter

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Re: Adding weight to a SUP ...
« Reply #54 on: October 26, 2014, 09:02:37 AM »
six lbs total, 2 lbs per ugly black square.  no waves until wednesday.  we shall see!

surfcowboy

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Re: Adding weight to a SUP ...
« Reply #55 on: October 26, 2014, 09:48:21 AM »
I'm watching this one closely. But anyone who disputes this need only ride a couple of longboards. Logs are way more fun, IMHO, when they have increased weight. The reason has been said here, we don't want low swing weight. We want to draw out our turns and slow everything down.

Volan is far from the most high tech material but guys love that heavy old glass for more than just leash less landings on the rocks at low tide, they feel better to ride for most folks.

My longboard will match or outweigh every one of my SUP boards from now on as I like having a high performance SUP but love the slow, drawn out movements of a big log... like Linter.

Now, eric, where are you landing this Winter? Are we going to get to work on some nose riding together?

linter

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Re: Adding weight to a SUP ...
« Reply #56 on: October 26, 2014, 11:54:37 AM »
  can't wait to see what the added weight does for the board, SC.  and i'm glad that at least a few people on this forum understand why i like heavy.  to me, the feeling is the greatest.

  i'm trying to go to san diego this winter for 3-4 months, somewhere b/ ocean beach and encinitas.  so far no luck on finding a room but i'm not going until sometime in dec or the beginning of jan.  worse comes to worse, i'll do an airbnb for a few weeks and use that time to track down better month-to-month lodgings.

  once i do, yes, indeed, let's get together for some toes on the nose.  well, mine'll be toes on the 18" line but, hey, if i squint, looks like the beak to me!

supthecreek

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Re: Adding weight to a SUP ...
« Reply #57 on: October 27, 2014, 07:09:12 AM »
I totally agree with "weight works" on a proper longboard.
The lightweight longboards surf more radically, in a high performance way, but lack the grace of a true longboard.
There is a certain metered finesse required to access the "On button" of a heavier, classic.
When done well.... it's the most amazing thing to watch.
 
My problem with this theory in SUP, is this: Heavy SUPs hurt me. I fell in love with SUP on an 11'2 x 36 - 230 liters @ 35 lbs.
It tried to kill me. Over and over. Too big... too heavy. I couldn't get away from it.
In a fit of self preservation, I was motivated to loose a LOT of weight, so I could ride a SUP that wasn't laying siege to my body parts.

After I went "short" I missed the longboard challenge, so my search was on. I went with the "lighter is better" theory for a few boards... my 10'6 Hobie RAW weighed a scant 19 lbs..... but I sold them all. High performance wasn't as good as the shorter boards, and they never satisfied my "longboard" ideal. I gave up.... stayed short.

Till I found the 26 lb, 10'6 Alana... not a true classic LB, but a happy medium between too light and killer heavy. Keeps me long... keeps me alive.

Linter, your threads always spark interesting conv's.... good luck with the testing!

Here's one for you mr Erik.... don't turn the music down... it works.

http://www.youtube.com/watch?v=66-sCRx4QRI

Tom

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Re: Adding weight to a SUP ...
« Reply #58 on: October 27, 2014, 07:51:59 AM »
Weight placement will definitely change the speed and handling. Placing the weight towards the front or back will change the swing weight. An example is if you hold a coke bottle at the base you can swing it back and forth easier than if you held it by its neck.

Where the weight is concentrated for and aft will change the trim of the board due to rocker line. Most long boards have a flat section just in front of center and having weight there speeds up the board. With increased rocker on the nose, the board slows down for nose riding.

SlatchJim

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Re: Adding weight to a SUP ...
« Reply #59 on: October 27, 2014, 05:10:22 PM »
This is reminding me of going on ferry boats--outside lanes of cars get loaded last, and unloaded first.  Heavy trucks always go in middle.
You told me they wouldn't let you on those anymore...

 


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