I’m thinking about getting an epoxy for my all round board but unsure what size to get.On the surftech website it states that the epoxy board floats 10% more than a board with the same dimensions.If it floats 10% more, do you go shorter than your regular board to accommadate the extra floatation?If I ride a 6’2’,18.5 wide,and 2.25 thick, will a 6’1" ,18.25, and 2.2 epoxy board be right for me?
no dont take away area …you will take away valueable planeing area …leave it the same dimensions and lose 10% of the thickness only…
even tho i think 10% maybe an over estimate of the extra float …
from my experience 5% is closer which usually translates to 1/8 of an inch…if you were gonna split hairs…maybe 6 or 7 % would be about right…
plus you need to take away proportionatly more rail volume…
which also needs to be dialed into your body weight…
but considering the surftechs are moulded your gonna have to take what you can get…
regards
BERT
I find on longboards, 2-1/2" floats as well as 3" poly with EPS
actually, no.
While a board may float a little higher because it weighs less…floating all by itself, that is… overall, it’s irrelevant. Where your floatation comes from is the volume of the board and the overall weight of the board and you. The water displaced by you-and-the-board weighs the same as the combination of you-and-the-board.
Let’s say your board now weighs ( picking figures out of thin air just as an example to do the numbers with ) eight pounds and the other one ( assuming the exact same dimensions ) is 10% lighter ( call it 7.2 lbs, playing fast and loose with the math). Lets say you weigh 150 lbs.
Okay, the conventional board has to float 158 lbs, overall, to let you sit there comfortably the way you’re used to. The other board is gonna float 157.2 lbs with the same volume. I kinda doubt you’d ever notice any difference.
So, I guess I should get an epoxy with the same dimensions as my board now but go thinner…thanks guys.
What factors more when it comes to choosing your board size…your weight or height?I know it all depends on your ability and what you’re comfortably with.I had a 6’1" two years ago but gained 10 pounds since then, so I bumped up to a 6’2".Sometimes I feel like its 2 much board for me.I’m 5’7" and 165 pounds.Should I have just stayed with a 6’1" but gone wider and thicker?
don’t bother with a thinner board if you want the same floatation.
Again, when you’re thinking about how much floatation you’re going to lose or gain, you have to think of how much the board and you weigh, combined. It’s not, repeat not about the weight of the board alone. No matter what the surftech ads say.
Now, as you mentioned you weigh 165, let’s do the numbers. Let’s assume heavy for a 6’2" board, conventional polyester resin and polyurethane foam, call it 12 lbs. Lets go absolutely nuts, lets assume that the epoxy board weighs in at 4 lbs for the same size, 66% lighter. Crazy, exaggerated, but lets go with it.
Okay, add 'em up.
Polyester: 165 + 12 = 177
Epoxy: 165 + 4 = 169
Eight pounds difference in board weight ( 66% ) is still less than 5% difference overall, and again that was exaggerated way beyond reality.
The surftech hype about floating 10% better, well, if you’re talking about the board alone I’ll believe it. It may weigh 10% less than a conventional board. But to try to translate that into that board being able to float itself and you 10% better because it’s 10% lighter than a conventional board, well, that’s not the way things work. It’s an ad, it’s not science or engineering. To put it another way, they have worded their ad to give you an impression that is simply not true. That’s what advertising is all about.
In order to do that, to float you better, it’s have to be a few percent bigger too, displacing more water to carry the weight of you plus board. That’s how boat and ship design has been done for a few hundred years. It works. If you have something with a volume of one cubic foot, it will float a combined weight of ( the thing and whatever payload it has) of 64 lbs, give or take some for salinity, temperature, etc. Two cubic feet, 128 lbs, three cubic feet, 192 lbs. It’s all about the volume or, in ship design terms, the displacement. Ships are designed to carry weight, that’s how they make money, and the calculations involved are something that’s been very important in ship design for a long time.
Now, if you want to go with a smaller board, that’s another thing entirely.
hope that’s of use
doc…
makes alot of sense…thanks Doc.
I just dropped two 1" square 1/4" laminates of the same layup, both were made via infusion so the resin content was identical. One was polyester and the other epoxy. Both sunk to the bottom of my test tank at the same rate. Where do I get this epoxy that floats?
Love the depth of your analysis testing.
Possibly talking in context of finished surfboards, one epoxy styro, other poly glass…
Finished weight is the main diff, as epoxstyro can be up to 2 lbs. lighter in a shortboard, as much as 5 lbs. lighter in a longboard.
Quote:
The water displaced by you-and-the-board weighs the same as the combination of you-and-the-board.
that’s funny…when I paddle and surf my body is only partially submerged. Doc, youre argument may be flawed because youre assuming that the surfer’s entire body is displacing water and this is not the case. When I paddle my shortBs I would estimate that less than 40% of my body is under the waterline. Surfer water displacement is even less with a longboard. I made the transition to EPS/Epoxy within the last year the the difference is quite amazing. Im riding shortBs that are 1/4" thinner than with PU (from 2.7 down to 2.4). Board weight makes a big difference…what’s gonna float better a EPS foam board or one made of concrete? The percent weight difference between a 6lb board and a 8lb board can be as high as 33%…in this case would the 6lb board float faster if both a sunk down and released? One simply has to try an EPS/Epoxy to see for themselves. The most accepted opinion seems to be 1/8" thinner and that may be your best starting point.
If 40% of your body is in the water when you sit, that means the board has the volume of 60% of you bodymass minus the weight of the board. It’s that simple. Now a board weighting 2 lbs less is gonna do as much a change for this as surfing on an empty stomach or taking a good, long piss before you go out. The volume of a 6’6" at 2 1/2" thick by 18" board displaces about 60 pounds of water. Now the change of 2lbs weight means that instead of supporting 60 pounds of your weight it will now support 62 pounds of your weight, which is a change of about 3 percent.
How much of your body is in the water when you paddle is a much more complicated because the water hitting the board at speed generates lift, also you can generate upwards force with you paddling, etc.
I think the reason people think you can go much thinner or smaller with an EPS is because most (if not all?) of those EPS blanks are hotwired. If the shapers doesn’t spend more time than normal foiling it, it will have more volume than a PU surfboard. I guess people have noticed that EPS board with the same general dimensions floated better through the years and figured: “wow, this EPS floats much better than PU” when in reality they had a board that had more volume. Atleast that’s my theory.
On the other hand, if you do have a board that is 2lbs lighter for the same dimensions, then you can remove a cubic desimeter of volume and have it float the same. That equals 1/8" of thickness for your average 6’6" generic shortboard. Or, if your like me you can glass the board heavy, make it float the same and last you a lifetime.
I don’t understand why on earth you would want to remove volume from a board that is in general the same dimensions, but is lighter and float better.
regards,
Håvard
Maybe I could have worded that better - the part of your body displacing water ( in the water) plus the part of the board that is displacing water are displacing a certain amount of water between them. That amount ( providing you’re floating and not sinking to the bottom ) has a weight that is exactly the same as the total weight of your board plus you. This bit, by the way, is what caused a Greek chap by the name of Archimedes to make the Greek word for I have found it kinda well known. He realised that it’s all about the volume displaced.
The weight of the body doesn’t go away when it’s surrounded by the water, nor does the weight of the board. Otherwise, guys in submarines would be in zero gee down there, floating around. And obviously it’s still there above the water for both board and body. Both are acted opon by gravity at all times. If you think about it, the board weight would matter even less if there was more body out of the water.
Board weight…look, unless board weight changes enough to make a significant change in the weight of the board-and-body unit, it really doesn’t matter. If the boards were identically shaped ( yeah, right, like that happens in real life) , one at 6 lbs , one 8 lbs, the lighter board is going to be sitting shallower in the water than the heavier one… just by themselves, no other weight on them. Put enough weights on them to get 'em completely submerged, though, seeing what they will float, and you’ll find that weight you need to submerge the lighter board is exactly the weight difference between the two boards, not 10% or 33% or whatever percent difference. If one board is two pounds lighter, it’ll float two pounds more. Only two pounds more, not 33% more or whatever the percentage weight difference is between the boards. That difference in board weight rapidly becomes insignificant.
I have used epoxy boards. I don’t especially like or dislike them floatation wise, though I do like the strength improvement. But the ‘most accepted opinions’ are what you might call scientifically incorrect.
doc…
From a scientific standpoint you need to find out what the 2lbs came from that you shave off.
Lets face it Air floats surfboards, nothing else. Either air trapped in the foam or in the case of hollow core boards glassed into pockets. Now you have to consider this, while you say 2lbs lighter will only make it 2lbs more bouyant. I think you actually have to know something a bit more complicated. You need to know if you got those two lbs of reduction by removing volume of foam, or the equivilent of less dense foam. If you kept the same deminsions yet shaved off 2lbs of foam on the core you would have to know how much that volume of air can displace in weight. Take for instance a milk jug if you filled it with foam it would weigh what 2lbs maybe, now are you telling me that it would only take 2lbs to submerge that milk jug. Sorry but that’s not the way it works. If you keep the volume of the board it will float more. What we really care about more then anything else when taking floatation into account would be density of the board, and surface area. Since the surface area directly effects the amount of the material in the water acting as bouyancy.
does this make any sense or am I way off here?
I don’t know what size milkjugs you’re having, but I know this: One liter of water weights 1000 grams, one liter of EPS foam weights something like 20-30 grams. That’s closer to air than to water. It’s so close that if you shave of 2 lbs of foam or a decimeter of foam it’s pretty much the same. It’s in the magnitude of the amount of wax you’ve got on your board. One liter of foam would take a 1000 grams to submerge, minus the weight of the foam.
Air does not float surfboards. It’s the mass of the water the board displace that floats it. You know you can get steel to float without encapsuling the air fully, but it has to displace as much mass of water as it weights.
regards,
Håvard
I’m afraid you’re way off there, my friend.
The example you’re using - lets take the empty milk jug and weigh it. Call it one ounce. Okay, hang a weight from it or pour in sand, the same weight as a gallon of water. Put the whole shebang in water, it floats just at the water’s surface. Use a strong milk jug or else water pressure is gonna squash it down, actually a two liter plastic coke or soda bottle with the screw-on cap will work better.
Now, fill it with foam or put in some sand or whatever so that it weighs two pounds. Hang the same weight you used the first time and it’ll sink. Hang a weight on it that’s two pounds lighter and it’ll float just like it did empty. It’s the overall weight versus the volume ( the density, to use the scientific term ) that makes it float or not float.
Air doesn’t make things float. Consider that oil floats on water, but there’s no air in it. So does Ivory soap, wood, apples, lots of things. For Monty Python fans, Ducks float real well too. They just have to be less dense than water. Air or no air. Here’s another one - things partially float. Huh? Yeah, take a brick, hang it from a scale. Weigh it. Then, dip it into the water…and somehow the weight the scale is showing is less. Take the brick, put it in a bucket of water that is full right to the top and catch the water that the brick pushes out, that it displaces. Funny thing, that water weighs the same as the difference between your scale readings. Exactly the same. That’s what ol’ Archimedes discovered when he was in his bathtub and shouted Eureka!!
hope that’s of use
doc…
doc,s got it. It’s pretty simple. If an object has a density of less than 1.0g/l, the density of water, it will float in water. Greater than 1.0 it sinks. How does an aircaraft carrier float on water(Huge mass)? It has an huge volume and overall density less than one. Submarines float and sink by changing the mass(ballast)thereby changing their density relative to water.While were splittin hairs, mass is not a measure of weight although we tend to use it that way. Mass is a measure of the matter in an object, weight is a measure of gravitational attraction between the objects. Measure the mass of your board and it’s weight, take it to the moon, the mass remains the same, it will weigh less, however. Quiz on Friday.
yay …we finally got there…now we just have to take into consideration the difference in speeds of rising to the top of the water by submerged objects of different densitys ,and shape the board to those characteristics ,because were constantly weighting and unweighting ourselves as we move on a wave…
ahhh lights on…
regards
BERT