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PostPosted: July 26th, 2021, 4:54 pm 
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Hey folks! Does anyone have any information about how many cubic centimeters of bog standard, grey, outfitting foam, aka Minicell, or cross-chain poly-something or other, are required to float 1 pound of weight at the surface of a quantity of water.

It's the stuff most people use for glued-in knee pads. How much of that is required to float 1 pound of weight.

I know that I'm mixing both units of measure and standard and metric, and that I didn't specify whether or not it is salt water of fresh water, or what temperature it is, yada, yada, etc. I'm just seeking a working rule of thumb based on something other than gut feel.

I'm curious about the concept of increasing flotation of pfd's, without permanent modifications to them, which is why I'm wondering about this foam flotation to volume ratio.

Thanks folks, cheers!

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PostPosted: August 8th, 2021, 12:20 pm 
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guyfawkes041 wrote:
Does anyone have any information about how many cubic centimeters of bog standard, grey, outfitting foam, aka Minicell, or cross-chain poly-something or other, are required to float 1 pound of weight at the surface of a quantity of water.

It's the stuff most people use for glued-in knee pads. How much of that is required to float 1 pound of weight.


Interesting question, perhaps more relevant to adding float tanks to a canoe (or, eh, outfitting with glued-in minicel pads and knee bumpers) than adding floatation to a PFD, but a question that deserves an easy experiment to satisfy my own curiosity.

In lieu of cutting up bog standard minicel foam I used an EVA foam yoga block; the weight/floatation difference between yoga block foam and minicel should be negligible. Yoga blocks are the least expensive, most ubiquitously available way to buy thick chunks of closed-cell foam.

First test, using what I had on hand, a 9” x 6” x 4” yoga block, with 2lb weight(s) taped on. To certify some degree of accuracy in my pseudo-science I put each of the little hand weights on a scale. Each were right on at 2lbs. Science!

ImageP8070006 by Mike McCrea, on Flickr

Starting with a single 2lb weight taped on, submerging the yoga block in a bucket of water. Uber buoyant, most of the yoga block was floating out of the water.

OK, let’s try two 2lb weights taped to the yoga block. Floated with half the yoga block still above water.

Moving on, three 2lb weights. Still floats, but with the yoga block is close to water level.

ImageP8070002 by Mike McCrea, on Flickr

Four 2lb weights, just barely buoyant, the top of the yoga block is right at water level. If I push it down it still rises to the surface without delay.

ImageP8070003 by Mike McCrea, on Flickr

In for a penny, in for, not a pound, but additional ounces, incrementally added until the yoga block sunk. It took an additional 7oz to “sink” the yoga block, but it sunk slowly, at near neutral buoyancy. An ounce less and it “floated”, mostly below the surface. An ounce more and the yoga block sunk more rapidly.

Have I blinded you with “science”?

https://www.youtube.com/watch?v=V83JR2IoI8k

Extrapolate centimeters to pounds to cubits as you like, but a 9” x 6” x 4” block of foam will float approximately 8lbs 6oz of weight. Albeit, for PFD considerations, in gentle, non frothy aerated waters while bouncing desperately off rocks. I have yet to end up submerged in a calm 5 gallon bucket of water, but there is a label that warns of drowning risk.

guyfawkes041 wrote:
I'm curious about the concept of increasing flotation of pfd's, without permanent modifications to them, which is why I'm wondering about this foam flotation to volume ratio.


Interesting idea. If you are thinking about some kind of strap-on extra flotation panel, to be attached when desired, you may face a design dilemma. If you add strapped-on flotation to the back of your PFD you will alter the floatation placement and possibly float face down. That is not a good thing.

If you add extra minicel to the front of a PFD you should float face up, but extra thickness of floatation on the front of the PFD poses another problem. I have an older kayak touring model Kokatat, with a mostly mesh back and a thin foam panel up near the shoulders; nearly ALL of the flotation is up front.

The chest area on that (admittedly XL) PFD is Dolly Parton-esque. Of course I have a large he-man chest. Or maybe those are man-tits. Fortunately I double blade 90% of the time.

Using a single blade the bulbous chest can be annoyingly in the way, more so because I have a rescue knife on the lash tab, and keep a few essentials in the front pockets (whistle & old expired driver’s license in one pocket, rescue beener and small pouch with a spare truck key and a 20 dollar bill in the other). Even with the pockets barely expanded the front of the PFD is mighty close for active single blade work.

But, humans are not lead weights; even skinny folk have some natural buoyancy. And fatty man-tits don’t add as much floatation as you might think, or so I’ve been told.

Child or sized small PFD’s usually have less buoyancy than adult versions. Serious WW PFD’s are designed with extra flotation. Recommended reading for calculating human weight-in-water and buoyancy needed (half way down the link)

https://goairkayaks.com/2016/02/06/unde ... life-vest/

If I wanted a “hi-float” PFD I’d save my pennies and buy one designed for the purpose. Pretty much every manufacturer makes a whitewater PFD. Lots of makes and models to choose from, most, depending on size, have 20 to 25lbs of floatation buoyancy.

The other thing I’d do with any new-to-me PFD is take few test swims in different waters. While I am confident a reputable PFD will float me, I always find some after swim strap re-adjustments are necessary, and sometimes, if I try to actively make for an eddy, using different swim strokes is more (or less) beneficial.


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PostPosted: August 9th, 2021, 4:11 am 
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nicely done Mike,

Mike McCrea wrote:
If you are thinking about some kind of strap-on extra flotation panel, to be attached when desired, you may face a design dilemma. If you add strapped-on flotation to the back of your PFD you will alter the floatation placement and possibly float face down. That is not a good thing.


problem solved with the blocks attached to under your feet,

:)


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PostPosted: August 9th, 2021, 12:33 pm 
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remogami wrote:
problem solved with the blocks attached to under your feet


That works best with the counterbalance of lead weights strapped to your ankles.

A word about yoga blocks, and my other favorite ubiquitously available foam, exercise floor mats. Both are commonly available in the exercise aisle of big box stores, with “exercise” mat sold as shop floor mat at some hardware stores.

My local-ish WalMart used to sell grey yoga blocks, which for canoe outfitting purposes are more aesthetically pleasing than purple (Oops, I thought they were blue). A friend further south recently bought grey yoga blocks at WallyWorld, YMMV.

Chunky yoga blocks are handy in some boat outfitting applications. FWIW the floral print on two sides of the purple blocks is micro thin; a pass over a 4’ sander removed that frou-frou pattern with ease. The purple ones smelled like Nehi grape soda when cut or sanded, which may not be a great thing for inquisitive critter nibbling.

The grey yoga blocks were unscented. Don’t ask what the brown ones smell like.

The puzzle-edged exercise mat at Wally’s, usually 2’ x 2’ squares, likewise used to be gray, now hereabouts two sided grey and blue, is also handy in some boat outfitting applications. Too thin and stiff to make comfortable kneeling pads, I use that stuff for non-slip heel pads adjacent to a foot brace.

Guyfawkes, if you decide to experiment with auxiliary PFD floatation - (additional foam flotation inside a fitted Cordura sleeve with webbing strap attachments or ???) - exercise flooring would easy to work with. The 2’ x 2” sheets are ½” thick and easy to cut to length/width/shape with a band saw or razor knife, and are easily laminated together for desired thickness with contact cement.

For boat outfitting purposes the embossed side of the exercise flooring is much more durable under boot heel abrasion than softer surfaced minicel. Yoga block knee bumpers and exercise flooring heel pads shown here as outfitting on the new fishing canoe.

ImageP1200027 by Mike McCrea, on Flickr

Thanks to the bucket of water and weights I can now calculate how much additional buoyancy I added to that canoe. Counting all of the permanently installed foam, some not shown, it is the equivalent of nearly seven yoga blocks.

7 x 8lb 6oz. That is 58lbs of additional buoyancy. In a Royalex boat!

Maybe not overkill in a composite hull. She should float higher now, and the under-inwale knee bumpers might more quickly right a capsized hull so that it escapes downstream gunwales up. It’s not the same as water-displacing float bags, but it can’t hurt in an un-bagged canoe.

That buoyancy number will be decreasing soon. After a few test paddles the aft set of knee bumpers are superfluous. I initially installed them in case some shortie borrowed the canoe, but they are not needed for any family member’s leg length and are somewhat in the way of adjusting the foot braces.

That pair and a half of yoga blocks is coming out, and the remaining knee bumpers are getting custom shaped depressions to better cup my knees and calves. I’ll have to recalculate.

I do enjoy the test paddle process of custom tweaking canoe outfitting for improved comfort and efficiency. Sometimes it is the little touches that make the biggest difference.


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PostPosted: August 9th, 2021, 2:24 pm 
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Mike McCrea wrote:
I do enjoy the test paddle process of custom tweaking canoe outfitting for improved comfort and efficiency. Sometimes it is the little touches that make the biggest difference.


Yes I can tell you're all into it. Awesome stuff.

Mike McCrea wrote:
remogami wrote:
problem solved with the blocks attached to under your feet

That works best with the counterbalance of lead weights strapped to your ankles.


lol

Mike McCrea wrote:
A word about yoga blocks, and my other favorite ubiquitously available foam, exercise floor mats. Both are commonly available in the exercise aisle of big box stores, with “exercise” mat sold as shop floor mat at some hardware stores


Any thoughts on the puzzle foam at Toys R Us? Is that what you mean by the jigsaw you said was stiff? is it more stiff than standard canoe knee pads? or do you mean it's thin and so you feel the boat through them and so it feels stiff?


Mike McCrea wrote:
Thanks to the bucket of water and weights I can now calculate how much additional buoyancy I added to that canoe. Counting all of the permanently installed foam, some not shown, it is the equivalent of nearly seven yoga blocks. 7 x 8lb 6oz. That is 58lbs of additional buoyancy. In a Royalex boat!


nice, now you know exactly. 58 is a big deal. almost the boat weight.
should make portages a dream too.

Mike McCrea wrote:
Maybe not overkill in a composite hull. She should float higher now, and the under-inwale knee bumpers might more quickly right a capsized hull so that it escapes downstream gunwales up. It’s not the same as water-displacing float bags, but it can’t hurt in an un-bagged canoe.


i agree on the righting. great stuff here,
thanks for sharing


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PostPosted: August 9th, 2021, 3:36 pm 
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Am I missing anything?
Why to use such complicated procedure instead of a simple formula?
1 liter of foam provides floatation for 2 lb of heavy stuff


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PostPosted: August 9th, 2021, 3:46 pm 
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or even 2 lbs of Light stuff lol.
as to your question, probably because some are more hands-on and like to see it through in action.


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PostPosted: August 9th, 2021, 4:35 pm 
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Yury wrote:
Why to use such complicated procedure instead of a simple formula?
1 liter of foam provides floatation for 2 lb of heavy stuff


I had never heard of that formula, and since no one was answering the OP’s question thought a simple floatation experiment was easy enough.

Mixed math is not my strong suit. Comparing liters and pounds and square inches how well does 1 liter of foam providing floatation for 2 lbs jibe with one 9” x 6” x 4” foam block floating 8lbs 6oz of weight?

Something seems off.


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PostPosted: August 9th, 2021, 5:26 pm 
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Mike McCrea wrote:
how well does 1 liter of foam providing floatation for 2 lbs jibe with one 9” x 6” x 4” foam block floating 8lbs 6oz of weight?


quite well a jibing.
a ml of water = 1 cubic cm, so a liter is 1000 of those.

1 liter of foam means 1000 cubic centimetres of water will be displaced by that foam.
that much water weighs 2.2 lbs.
so, that 1 liter of foam needs to weigh more than 2.2 lbs, to sink.

1000 cubic centimeters in cubic inches is 61.
your block is 9x6x4 = 216 cubic inches.
so, your 216 / 61 gives how many 2.2 lbs will float = 3.5
that is, 3.5 x 2.2 = 7.8 lbs.


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PostPosted: August 9th, 2021, 6:26 pm 
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eg,
the question "How much of this do i need to float 1 lb?"
is the question:
"How big does 1 lb need to be to float?"

and the answer is: bigger than how big a lb of water is.
because all that's happening,

is the thing is trading the water in the space, for itself in the space.
which is to say, it is pushing that water out of its way. which is to say, it is lifting that water up

so, to lift that water up (eg, to sink), the thing must be smaller than that lb of water,
because then, the lifted water weighs less than the thing.

(this is a balance scale, essentially).

if the thing was bigger than that lb of water, then the lifted water weighs more than the thing,
causing that water to be the lifter (the thing floats).


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PostPosted: August 10th, 2021, 8:45 am 
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remogami wrote:
Any thoughts on the puzzle foam at Toys R Us? Is that what you mean by the jigsaw you said was stiff? is it more stiff than standard canoe knee pads? or do you mean it's thin and so you feel the boat through them and so it feels stiff?


I didn’t know there still were Toys R Us, no idea if their “puzzle foam” is the same stuff. The jigsaw edged exercise or shop flooring I was referring to is this (some of the shop flooring stuff is ¾” thick)

https://www.homedepot.com/p/PROSOURCEFI ... lsrc=aw.ds

Another FWIW with that stuff. I cut the sides square to start with, but trim the puzzle edge off the 2 x 2 sheets the same width as the side puzzle strip. The two pieces, puzzled together, are then straight edged 2’ long x 2” wide, and work nicely to pad canoe trailer crossbars and the like. Waste not, want not.

I don’t know how to describe the “stiffness”; it is still pliable enough to wrap around the chines of a canoe when contact cemented, but isn’t as cushiony compressible as the same thickness of minicel. Beyond boat outfitting it makes a good sound deadener on the walls/floor of clangybangy cargo vans.

Image20181030_082724 by Mike McCrea, on Flickr

Image20181101_134514 by Mike McCrea, on Flickr

remogami wrote:
nice, now you know exactly. 58 is a big deal. almost the boat weight.
should make portages a dream too.


Out of curiosity I weighed yoga blocks to determine how much weight I added with that glued in foam. The yoga blocks weigh 4.5oz each, so just under 2lbs for all seven.

In comparison, using what I have in the shop, a 2” x 11” x 17” chunk of minicel foam weighs 6oz. The minicel foam may be a bit lighter than the yoga block EVA foam, but, again, ugh, math.

In narrower canoes or the bow of tandems, where my comfortable knee braced leg spread is less, the bumpers do not need to be as thick.

ImageP6100006 by Mike McCrea, on Flickr

ImageP7140006 by Mike McCrea, on Flickr

remogami wrote:
a ml of water = 1 cubic cm, so a liter is 1000 of those.
1 liter of foam means 1000 cubic centimetres of water will be displaced by that foam.
that much water weighs 2.2 lbs.
so, that 1 liter of foam needs to weigh more than 2.2 lbs, to sink.
1000 cubic centimeters in cubic inches is 61.
your block is 9x6x4 = 216 cubic inches.
so, your 216 / 61 gives how many 2.2 lbs will float = 3.5
that is, 3.5 x 2.2 = 7.8 lbs.


Even if I had known the “formula” or been able to do that math, I would still have turned to the bucket of water and weights. Trust, but verify.


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PostPosted: August 10th, 2021, 10:04 am 
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Wow, there were well over 100 views of my original post before anyone responded to my question about how many cubic centimeters of grey outfitting foam are required to float one pound of weight on the surface of fresh water, but it was no surprise to me that it was you Mike, who responded first, with the results of your own experiments. Thanks.

While waiting for any responses, I got a bit busy with an experiment too. Using a Ziploc baggie holding coins, which I could add or subtract from weight-wise, I secured the baggie to a piece of grey foam and kept adding coins until the foam sank just below the surface. I took the weight required to sink the foam and the dimensions of the block of foam, and mathematically deduced how much foam would float one pound of coins.

I then cut the foam to those dimensions, and floated exactly one pound of coins on it, and it resulted in learning that it takes 341.25 cubic centimeters (or 20.8 cubic inches) of grey outfitting foam to float one pound of weight on the surface of the water.

Put another way, by my calcs, to float a pound of weight at the surface of the water, it takes a piece of grey foam measuring 1" x 4 1/8" x 5 1/8", or really any combination of dimensions which total 20.8 cubic inches.

I was interested in this because I recently added a mesh pouch containing a pin kit to the back of my whitewater PFD (Kokatat Maximus Centurion), and I wanted to compensate for that weight by adding foam into both the zippered belly pouch and the cowtail sleeve, on the front.

So, I now know that have added just shy of two more pounds of flotation to the pfd, which already provided 22 pounds of lift.

The foam pieces are securely contained and will not float free, they do not appreciably change the angle of flotation for the wearer, and they do add any bulk to the thing, as they fit into pre-existing spaces in the pfd. and thus do not make paddling more difficult.

I just wanted to know what the new total flotation for the pfd is after addition of the foam.

At any rate folks, thanks to all for your thoughts. Cheers!

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PostPosted: August 10th, 2021, 11:03 am 
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@ Mike
yes, absolutely. I'm all for how you did things.

by the way, part reason you floated more than 7.8 is because the weights themselves displaced water, not just the foam displaced water. More water up allows more weight to float.

thanks for your ideas on foam etc, and i like how you mod things up, it does add a nice touch.

@guyfawk, "just wanted to know the flotation"
flotation = the weight of the water that is displaced by your foam.


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PostPosted: August 10th, 2021, 12:19 pm 
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remogami wrote:
Yes I can tell you're all into it.


After 30 years of rebuilding & outfitting canoes I know exactly what I want, where I want it and how installed in each boat. Or mostly so, I still find myself tweaking and changing some things after a few test paddles.

But, mostly the same stuff in any solo canoe. Strap yoke, foam knee bumpers, pad eyes for a back band, utility/sail thwart for convenience, D-rings and webbing loops off the shank ends of any machine screws for tie downs. Thwart bungees, through hull painter flanges, partial DIY spray covers with snap rivets, adjustable foot brace.

Even the foot brace sometimes gets tweaked a bit. The foot brace in the photo above was installed in a tandem, most often used as a loaner boat. I know how high I want the foot brace set so that it hits the balls of my size 12 clodhoppers with legs angled, but shorter paddlers often have smaller feet and, of course, shorter legs.

So that foot brace bar is slightly angled, the further back towards the seat it is adjusted the smaller feet it fits. In that photo it was adjusted well back to fit a shortie borrower’s smaller feet. Half way up the slider bar fit my footsies, near fully extender fit a 6’6” friend with flipper feet.

One more small piece of minicel. The barrel in any of our tripping canoes is habitually positioned sideways in the same near mid-hull location, “trapped” against a thwart. Part of that “trap” is yet a minicel wedge contact cemented to the floor, that locks that the barrel in place against the thwart and keeps it from rolling fore or aft.

ImageP2170546 by Mike McCrea, on Flickr

Unintended benefit, the food barrel is shaded below the partial bow spray cover, so my Snicker’s bars don’t melt. Sometimes, not always, the barrel gets a strap over it as well.

The little touches add up, both comfort/efficiency wise, and, admittedly, in hull weight. Next total canoe gut and rebuild I plan to be judicious about weighing and re-weight the hull and any permanently install outfitting. And, if I find the right derelict, challenge myself to keep the finished weight down.

guyfawkes041 wrote:
So, I now know that have added just shy of two more pounds of flotation to the pfd, which already provided 22 pounds of lift.

The foam pieces are securely contained and will not float free, they do not appreciably change the angle of flotation for the wearer, and they do add any bulk to the thing, as they fit into pre-existing spaces in the pfd. and thus do not make paddling more difficult.


Thanks for the added PFD floatation explanation. And for the thread in general; I got to do another quick and easy shop experiment, and learned some new to me stuff. And will make a note of the various foam floatation calculations for future reference.

This thread illustrates why I enjoy canoe forums; for the exchange of thoughts and ideas, information learned and shared, different approaches, concepts proven or disproven. It is the discussion, the virtual campfire camaraderie complete with tale telling and off-topic wanderings that makes for an interesting and lively place.

Serious paddling forums and discussions are going the way of the dodo, diminished by geezer paddlers aging out, or simply tiring of responding to the same old, same old and decimated by Facebook and other social media outlets. Even lengthier, more thoughtful posts have become increasingly scarce.

A geezer paddler and poster friend offered an explanation for that phenomenon, one that I, as a non cell phone-ian much less smart-phone-ian, had not considered.

“Most of today’s humans are unwilling to type text into a forum. For one thing, they mostly interact using their phones, and only the most fleet-thumbed type more than ten-word replies on a phone. So forums are dying. Sad for the few of us geezers that enjoy it so well”

Obviously I did not thumb-type this, or anything else, on an I-phone. Apologies to anyone offended by my verbosity or off topic meanderings. (Or, ya know, just don’t read it)

I write a bit every day, scrawled in the tripping journal or pecked away on the shop computer. My social media presence consists entirely of two paddling forums. Or, one canoe forum and one dwindled to a sad Monty Python reference.

ImageP8030025 by Mike McCrea, on Flickr

Apologies also to my friends on Canoe Tripping; haven’t seen y’all since June, miss that virtual campfire.


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PostPosted: August 10th, 2021, 2:28 pm 
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:thumbup: Two thumbs up for verbose geezer paddlers! And for newbies too!

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