Select to expand quoteIan K said..
Do engineers consider epoxy shrinkage? How long does it take for boards to fully cure? Have you noticed that the slightest bump on a new board leaves a ding, but once they've done a few seasons they are immune to minor bumps? They've always go a mm or two hollow between the footstraps. That's the thinnest section of the board but shape and layup are different top and bottom. Has anybody measured the flatness of a new board and measured it again having not sailed it? What about old stock? Is it a little hollow?
Theory is with an oven you can fully cure a board quickly, depend of resin but like you i often feel that surfboards i made became "harder" with time. Don't no way.
Select to expand quotegeoITA said..Ian K said..geoITA said..SchobiHH said...
Do you have something constructive to say? I don't think so.
I already told you something constructive. Go study some engineering or, better, quit explaining things you do not know. Sorry, but I am not going to explain things to a total illiterate. Grab a book or two instead, or even use Wikipedia. You do not even imagine how much far away from reality you are when you talk about "fatigue" in this case, for example.
There's always been a bit of chipping going on between engineers and physicists. You've taken it to the next level.
Which of the points made by SchobiHH do you disagree with?
Too many!!!
Just talking about "fatigue" clearly indicates he is totally unaware of what he is talking about. Also stating that "... There are 3 types of elastic stresses "shear, tensile and torsion stresses" is totally naive, and explains that our friend makes some good confusion between the kind of stress(es) an object may be subject to, and the way (more or less elastic) it reacts to those stresses.
And, by the way, who cares about "elastic deformation", as if deformation is elastic then it gets back to zero when the stress ceases ...
oh! now you are talking. Unaware of "what I am talking about beeing totally illatere". You are quite insulting and give no proper argument. I like that type of person. Blaming others to be stupid because the are questioning there profound argumentation....
I still can not image that you have a mechanical engineering degree.
There is one principal concept about "elasticy", you a apply a force to some body and the elastic deformation is of a "tensorial" kind. Which is nothing than stating, that the body reacts with shear and tensional stress. (forget my statement about torsional stress, that was wrong. Got abit rusty and have it looked up again. Because I want to sure I am stating the correct) Obvisously you are not aware of that fact.
Fatique is btw the special situation where the material encounters its limits of elasticity because of period loads...
Your statement "fatigue leader to sudden failure, not to a tiny yet important deformation that somewhat tende to "set in" is total nonsense.
Fatique is something what starts slowly and evenutally ends in total failure.
Your statement
"So from what I understand. Yes we see a lot of altered rockerlines, if we check. Most probable cause in my view (I will not explain this here, it would take too long, but I am sure that the eventual reader competent enough will understand with no need for explanations) is some crushing in the sandwich foam, that probably sets in and does not go on indefinitely. And best way to avoid it, is using extra heavy sandwich foam in the bottom in the area between straps positions, as this would cost a very marginal weight increase in order to obtain around 2x better strength."
is also wrong (because of the simple fact that the compression strength of a stronger PVC is nothing compared to the compression strength of the laminate. That is why there is sandwich construction. That is something every mechanical engingeer should have learnt is its undergraduate classes But you don't care because to you all others who not comply to your flawed ideas are stupid.
Can you please give me the calculation fo the 2x better strength? I really would love to see that. BTW the strength indeed can be calculated. It is not so complicated. You just need to know that is the correct formula to apply, i.e. the right theory that models that effect. You might share your indefinite wisdom with us.
Wish I was more experienced with the engineering side of the composites involved. But sounds like it's more of a creep issue (or fiber damage?). Creep simplified is tension over time (effected by temperature) resulting in permanent deformations. I haven't had anything to do with this subject but seems like it could contribute to what you are talking about? Unless there's something else going on like UV interaction, moisture, or something else like fiber breakage. I'm more familiar with it in metals where you are in a very hot environment and with a constant tension, it continues to stretch over time.
www.researchgate.net/publication/229915053_Tensile_creep_behavior_of_unidirectional_glass-fiber_polymer_composites
Select to expand quoteIan K said..
Do engineers consider epoxy shrinkage? How long does it take for boards to fully cure? Have you noticed that the slightest bump on a new board leaves a ding, but once they've done a few seasons they are immune to minor bumps? They've always go a mm or two hollow between the footstraps. That's the thinnest section of the board but shape and layup are different top and bottom. Has anybody measured the flatness of a new board and measured it again having not sailed it? What about old stock? Is it alittle hollow?
shrinkage is a very good point! I think for epoxy it can go up to 4% Taking into account? Does somebody know where the spring back effect comes from? The situation can happen after the deck sandwich vacuum baging... Or when the board comes out of the mould.... BTW: Did you know that in the americas cup they do the foils from steel and not carbon composites. one of the reasons is that the are easier to control the quality of it.
But wrt you bumps. It is a well known fact that resins get harder over time....
From my experience racing in ancient times production boards tended to go slightly concave in the area between the mast track and footstraps. Some sailors re-faired this area to correct the problem, but most of us solved it by ordering custom boards from Mike's lab. Mike's boards were not only fast, but were stiff and stable enough to avoid this problem.
(I have degrees in both engineering and physics, but never persued the root cause of this problem because it was easily eliminated by proper construction.)
Select to expand quoteIan K said..
Do engineers consider epoxy shrinkage? How long does it take for boards to fully cure? Have you noticed that the slightest bump on a new board leaves a ding, but once they've done a few seasons they are immune to minor bumps? They've always go a mm or two hollow between the footstraps. That's the thinnest section of the board but shape and layup are different top and bottom. Has anybody measured the flatness of a new board and measured it again having not sailed it? What about old stock? Is it a little hollow?
I could imagine that the EPS core could get harder and more crumbly over time.Or is it that boards that are a few seasons old are built better than newer ones ?
Select to expand quoteChris 249 said..mathew said..Chris 249 said..
As I tried to make clear, I completely understand why people choose to have lots of sails and as you said it's up to the buyer, but the point is that the claim "modern sails have wider wind ranges" has been made for decades on end and yet there seems to be no evidence that it's really happening, or that modern windsurf sails have a wide range compared to other sails.
I think what you are observing is a reasonable assessment based on the evidence you presented. But I dont think it is accurate.
[ You noted "decades" which implies 80's to 90's era. In that era camber-inducers were only just invented by Gaastra. Full-length battens were still flimsy fibreglass or even wood. ]
A 6m slalom sail from that era could be used [ obviously depending on body weight ] from about 8kn to about 22kn. It didn't really matter what board you used because the sail didn't generate much top-speed. Due to their shape, they were typically quite powerful on the low-end, but sail deformation limited their top-end. The sail-deformation limited their use.
A 6m slalom sail from nowadays typically doesn't have good low-end ( its why formula-sails were invented because _area_ is key ), you use them from about 12kn. Those same sails - even a freeride sail - is quite capable of being used in 35kn of wind. The sail doesn't deform much at all - the limiting factor is typically the person's ability to sheet-in.
I agree that sail deformation limited the top end with the old sails and that the new ones have a vastly better top end. Manufacturers still seem to try to sell sailors just as many sails to cover the wind range. As your figures indicate, a lot of what it gained in top end handling with modern sails is lost due to their lower power at the bottom end.
I can't completely agree about your wind range figures since the wind range you quote for an ancient 6m slalom sail is way out of what I would have used at that time, and since I was top 20 at the slalom world titles at the time I wasn't particularly shyte. No one at the worlds or during the Aussie pro circuit at the time (which included Robby, Bjorn, Anders etc) would have used a 6m slalom sail in 8 knots because the lower wind limit was 15 knots and even in that a 7.8 or perhaps 7.3 was the standard sail.
Top end deformation and C of E shift were a problem, but that is to a significant extent a matter of technique, harness lines and back hand strength. Where those old sails did lose out, as we agree, was by having high aero drag that limited their top speed. I had an ex Pete Cabrinha Gaastra team 7.3 or 7.8 custom with foam/glass or carbon sandwich battens and something like 6 camber inducers and it, and similar sails, actually seemed to have amazing stability - at the cost of having a tight leach and deep upper camber that reduced the top-end speed. It would never make it as a production sail because it was also extremely unforgiving through gybes, although personally that suited my style very nicely.
I think essentially it's an issue about how we define range. We can have different (but equally valid) measures. Those of us who have done a lot of sailing on various OD longboards have spent a lot of time looking for power in light winds and practising holding onto a sail far over the top of its normal range, so our feeling for range is probably very different to that of other people.
I'll also say that I'm unsure how many people these days use a 6 in a true 35 knots. That is hitting well over 50 knots in the gusts. In such winds, people find it difficult walking, the water is covered in spume (not just white caps), things ashore are breaking, etc etc. I sail Sydney-Hobarts where we have sophisticated wind instruments so spend a lot of time getting real windspeed info and with respect, what many people call 35 knots is a wind that may hit 35 knots for very short times at the peak of the gust. That is actually a true 20 knots, by meteorological definition. Some people may be capable of using a 6 in a real 35 knots, but not the average sailor in what I would call normal conditions, with normal chop and gusts.
I often pull out my pocket wind meter at the lake to check and chuckle at the true wind speed (8-14 knots as often as not with gusts 12-18 at best) whilst people around declare "must be blowing 25 out there..." white caps and shaking casurena trees are trick indicators of true wind speed. The other factor ignored that you would be aware of as an ocean racer is wind density, cold wet dense heavy air v's hot dry summer sea breeze. 35 knots in Hawaii is windy but pleasant. 35 knots in Northern Europe or winter UK/Ireland is horrible and destructive!
WE that love windsurfing want to find ways to make it grow, I think thats what we have in common, some of these arguments here even if resolved wont contribute greatly to the growth of windsurfing. Let me digress only slightly. In human psychology, there are what is known as the big five personality factors. One is openness. Openness is a positive attitude toward new ideas, experiences, and solutions. People who are high in openness are often curious, imaginative, and creative. Those high in openness want to continually try new things. So when kiting, SUP and Winging emerge windsurfers high in Openness will move to the new sport. Those low in Openness will windsurf till we die, coz we know how good it is. Now for non-windsurfers, it is how to get those high in Openness try windsurfing and get hooked. One disadvantage is that windsurfing has been around 40 to 50 years so those that havent windsurfed before have had many years to try it but never found it appealing, so we cant win them over. Its only the odd straggler of a certain older age we might get, or its the young to give them an experience. The difficulty with the young is that windsurfing is no longer cool, kiting and Winging are cool. I dont think any great innovation in windsurfing equipment is going to attract the young. Its young sailors in Yatching Clubs who are taking it up for Olympic selection, but thats a Foiling discipline. Wish I could be more optimistic, but these are the barriers, its more psychological barriers than equipment barriers that prevent large growth in windsurfing anymore. Decisions to participate and invest in sport are made inside our brain and filtered through our personality lens. My 4 cents or is it 2 cents?
Select to expand quoteImax1 said..Ian K said..
Do engineers consider epoxy shrinkage? How long does it take for boards to fully cure? Have you noticed that the slightest bump on a new board leaves a ding, but once they've done a few seasons they are immune to minor bumps? They've always go a mm or two hollow between the footstraps. That's the thinnest section of the board but shape and layup are different top and bottom. Has anybody measured the flatness of a new board and measured it again having not sailed it? What about old stock? Is it a little hollow?
I could imagine that the EPS core could get harder and more crumbly over time.Or is it that boards that are a few seasons old are built better than newer ones ?
When i open old eps (surf)boards and recently old (1995/1998) f2 windsurf store outside i find eps core in perfect condition, like you imagine core retracted and crumbly like eps you find on the beach. Skin around protected it. I don't know if old boards built better but it really seems that epoxy continues to harden over time although resin manufacturers say not.
Select to expand quotelemat said..Imax1 said..Ian K said..
Do engineers consider epoxy shrinkage? How long does it take for boards to fully cure? Have you noticed that the slightest bump on a new board leaves a ding, but once they've done a few seasons they are immune to minor bumps? They've always go a mm or two hollow between the footstraps. That's the thinnest section of the board but shape and layup are different top and bottom. Has anybody measured the flatness of a new board and measured it again having not sailed it? What about old stock? Is it a little hollow?
I could imagine that the EPS core could get harder and more crumbly over time.Or is it that boards that are a few seasons old are built better than newer ones ?
When i open old eps (surf)boards and recently old (1995/1998) f2 windsurf store outside i find eps core in perfect condition, like you imagine core retracted and crumbly like eps you find on the beach. Skin around protected it. I don't know if old boards built better but it really seems that epoxy continues to harden over time although resin manufacturers say not.
I was thinking harden with time was correlated with further shrinkage with time. Maybe,maybe not.
Hardie is probably right, as we die off so will windsurfing.
Select to expand quotehardie said..
WE that love windsurfing want to find ways to make it grow, I think thats what we have in common, some of these arguments here even if resolved wont contribute greatly to the growth of windsurfing. Let me digress only slightly. In human psychology, there are what is known as the big five personality factors. One is openness. Openness is a positive attitude toward new ideas, experiences, and solutions. People who are high in openness are often curious, imaginative, and creative. Those high in openness want to continually try new things. So when kiting, SUP and Winging emerge windsurfers high in Openness will move to the new sport. Those low in Openness will windsurf till we die, coz we know how good it is. Now for non-windsurfers, it is how to get those high in Openness try windsurfing and get hooked. One disadvantage is that windsurfing has been around 40 to 50 years so those that havent windsurfed before have had many years to try it but never found it appealing, so we cant win them over. Its only the odd straggler of a certain older age we might get, or its the young to give them an experience. The difficulty with the young is that windsurfing is no longer cool, kiting and Winging are cool. I dont think any great innovation in windsurfing equipment is going to attract the young. Its young sailors in Yatching Clubs who are taking it up for Olympic selection, but thats a Foiling discipline. Wish I could be more optimistic, but these are the barriers, its more psychological barriers than equipment barriers that prevent large growth in windsurfing anymore. Decisions to participate and invest in sport are made inside our brain and filtered through our personality lens. My 4 cents or is it 2 cents?
I don't think young kids think much of kiting and winging either. But as far as bringing young blood to the sport is concerned, winging has 2 big advantages: 1) it requires far less physical strength than windsurfing, so can be started earlier, and 2) it's much safer than kiting.
I don't see any way that e-windsurfing can ever be a thing.
Generally, to appeal to most young people nowadays, you must add an "e-" to everything; wind-power is too unreliable and unpredictable (And hard work)! 
Windsurfing will never be as popular as it was in its heydays, the late 1980s and early to mid 1990s. There are too many new sports that have come along and many are much easier to learn and become decent at. If anything that's a good thing, it's thinned out the herd and there's more room on the water.
Windsurfing is still very popular in places that have strong wind that enables planing, there's other watersports for the lighter winds. Go to Gruissan in the South of France and you'll see over a thousand windsurfers together at once for the Defi wind, there's nothing like it in the rest of the world. Windsurfers flock to it from around the globe. I'm heading over for 2 weeks with a couple of mates to sip from the windsurfing Kool-Aid! I'm even leaving a quiver of 4 race sails and 3 boards there so I can fly over anytime to get a fix.
Windsurfing has evolved, it's still popular in the Gorge and South of France and I wont give it up until they nail the lid onto the pine box and put me out with the rubbish! If the wind is blowing I'll keep going.
Besides it's capacity to emerge as an online discussion forum persona; Creep is a time-dependent deformation of a material while under an applied load that is below its yield strength.
Anyways, regarding new water sports developments: nothing like the spectre of a bunch of hydrofoil rollerbladers on your homespot 
just to revive the idea 
you know you crave something new and expensive under your wing :))
To the original question...absolutely. Take snow skiing. They have been doing this for hundreds of years. Last time I did this, I was going down black runs on short peanut shaped skies trying to keep up with my kids. All good , I was doing great
Have to point out , I'm a spastic, skied half a dozen times in my life. So i would say , windsurfing could be made better and easier, so much more to go. Sadly little interest.
Video above looks like a quick way to break some bones.
I think there has been a lot done to make windsurfing easier if you compare it to the narrow and heavy gear that was used back in the days, the difference is day and night.
Especially beginner gear is now so user friendly, we're able to teach adults and kids how to windsurf in basically no time. 20 minutes of practice on the beach and in the right conditions, most people with zero experience are able to uphaul, sail back and forth while holding the boom, tack, and gybe from the get go. It's absolutely amazing and wouldn't have been possible without the modern gear.
After that, progressing to planing also gets easier but takes a little longer (we've had folks planing on their 5th session). Don't forget that windsurfing is a super technical sport and that makes it so appealing/frustrating (choose you're version) to many as you're never done learning. That can't be changed with any evolution if you're still staying true to windsurfing.
Some consider wingfoiling an evolution of windsurfing and I don't disagree although it's still quite different so it should be more seen as a variant of windsurfing maybe.
Select to expand quoteIan K said..
Do engineers consider epoxy shrinkage? How long does it take for boards to fully cure? Have you noticed that the slightest bump on a new board leaves a ding, but once they've done a few seasons they are immune to minor bumps? They've always go a mm or two hollow between the footstraps. That's the thinnest section of the board but shape and layup are different top and bottom. Has anybody measured the flatness of a new board and measured it again having not sailed it? What about old stock? Is it a little hollow?
Yes epoxy does shrink, but it's not the epoxy the part that provides resistance. The resin is the matrix that bonds together the fibers, these are what provides resistance. Epoxy shrinkage typically will not cause deformation in the laminate, but rather will cause tiny "holes" in it. One of the reasons why you have to apply some "coat" on it.
Apart from that.
Actually in a sense everyone here is right, because everything actually happens, and materials behave in a way that is a mix of every possible way: materials will be somewhat elastic, somewhat plastic, will shrink or bulge, will be affected by creep, and fatigue is always there lurking in the dark. BUT. Each material will behave MOSTLY in a certain way, and others will be mostly negligible. In example: materials will show plastic deformation when the elastic limit is exceeded, but in the case of carbon this is negligible ("brittle").As far as I know, "curing" epoxy laminates is greatly accellerated by oven treatment, but polimerization is an ongoing process and time has a big part in it. So, fresh uncured laminates will show some "softness", cured ones will be "harder", and old ones will be somewhat stiffer and brittle.
Select to expand quoteSchobiHH said..geoITA said..Ian K said..geoITA said..SchobiHH said...
Do you have something constructive to say? I don't think so.
I already told you something constructive. Go study some engineering or, better, quit explaining things you do not know. Sorry, but I am not going to explain things to a total illiterate. Grab a book or two instead, or even use Wikipedia. You do not even imagine how much far away from reality you are when you talk about "fatigue" in this case, for example.
There's always been a bit of chipping going on between engineers and physicists. You've taken it to the next level.
Which of the points made by SchobiHH do you disagree with?
Too many!!!
Just talking about "fatigue" clearly indicates he is totally unaware of what he is talking about. Also stating that "... There are 3 types of elastic stresses "shear, tensile and torsion stresses" is totally naive, and explains that our friend makes some good confusion between the kind of stress(es) an object may be subject to, and the way (more or less elastic) it reacts to those stresses.
And, by the way, who cares about "elastic deformation", as if deformation is elastic then it gets back to zero when the stress ceases ...
oh! now you are talking. Unaware of "what I am talking about beeing totally illatere". You are quite insulting and give no proper argument. I like that type of person. Blaming others to be stupid because the are questioning there profound argumentation....
I still can not image that you have a mechanical engineering degree.
There is one principal concept about "elasticy", you a apply a force to some body and the elastic deformation is of a "tensorial" kind. Which is nothing than stating, that the body reacts with shear and tensional stress. (forget my statement about torsional stress, that was wrong. Got abit rusty and have it looked up again. Because I want to sure I am stating the correct) Obvisously you are not aware of that fact.
Fatique is btw the special situation where the material encounters its limits of elasticity because of period loads...
Your statement "fatigue leader to sudden failure, not to a tiny yet important deformation that somewhat tende to "set in" is total nonsense.
Fatique is something what starts slowly and evenutally ends in total failure.
Your statement
"So from what I understand. Yes we see a lot of altered rockerlines, if we check. Most probable cause in my view (I will not explain this here, it would take too long, but I am sure that the eventual reader competent enough will understand with no need for explanations) is some crushing in the sandwich foam, that probably sets in and does not go on indefinitely. And best way to avoid it, is using extra heavy sandwich foam in the bottom in the area between straps positions, as this would cost a very marginal weight increase in order to obtain around 2x better strength."
is also wrong (because of the simple fact that the compression strength of a stronger PVC is nothing compared to the compression strength of the laminate. That is why there is sandwich construction. That is something every mechanical engingeer should have learnt is its undergraduate classes But you don't care because to you all others who not comply to your flawed ideas are stupid.
Can you please give me the calculation fo the 2x better strength? I really would love to see that. BTW the strength indeed can be calculated. It is not so complicated. You just need to know that is the correct formula to apply, i.e. the right theory that models that effect. You might share your indefinite wisdom with us.
My best suggestion to you is the following.
Take 20' of your precious scientific time and do the test:
test.mensa.no/home/test/en
Obviously the result will not be certified, so it's nothing one can brag around; but it can be extremely useful for you. Once you will know exactly where you sit among the general population, you will also know how you do appear to others every time you speak your mind.
Just 20'. And leave the tensors alone.
P. s.: as for the 2x better strength in heavier PVC, no need for calculations, it's in the charts already (www.3accorematerials.com/uploads/pdf/TDS-AIREX-C70-E-08.2022-ex-Europe.pdf).
P. p. s.: as for "the compression strength of the laminate", apart from the fact that you don't seem to understand how the sandwich structure works, do you really think that the thin outer laminate will resist compression by itself?
P. p. p. s.: maybe you didn't notice, but fatigue is out of question here, as we are not talking about "total failure" of hulls, but just about possible deformation of the rockerline.
P. p. p. p. s.: you can study deformation by means of tensors, but there is no such a thing as a "tensorial kind" of deformation.
Select to expand quotegeoITA said..SchobiHH said..geoITA said..Ian K said..geoITA said..SchobiHH said...
Do you have something constructive to say? I don't think so.
I already told you something constructive. Go study some engineering or, better, quit explaining things you do not know. Sorry, but I am not going to explain things to a total illiterate. Grab a book or two instead, or even use Wikipedia. You do not even imagine how much far away from reality you are when you talk about "fatigue" in this case, for example.
There's always been a bit of chipping going on between engineers and physicists. You've taken it to the next level.
Which of the points made by SchobiHH do you disagree with?
Too many!!!
Just talking about "fatigue" clearly indicates he is totally unaware of what he is talking about. Also stating that "... There are 3 types of elastic stresses "shear, tensile and torsion stresses" is totally naive, and explains that our friend makes some good confusion between the kind of stress(es) an object may be subject to, and the way (more or less elastic) it reacts to those stresses.
And, by the way, who cares about "elastic deformation", as if deformation is elastic then it gets back to zero when the stress ceases ...
oh! now you are talking. Unaware of "what I am talking about beeing totally illatere". You are quite insulting and give no proper argument. I like that type of person. Blaming others to be stupid because the are questioning there profound argumentation....
I still can not image that you have a mechanical engineering degree.
There is one principal concept about "elasticy", you a apply a force to some body and the elastic deformation is of a "tensorial" kind. Which is nothing than stating, that the body reacts with shear and tensional stress. (forget my statement about torsional stress, that was wrong. Got abit rusty and have it looked up again. Because I want to sure I am stating the correct) Obvisously you are not aware of that fact.
Fatique is btw the special situation where the material encounters its limits of elasticity because of period loads...
Your statement "fatigue leader to sudden failure, not to a tiny yet important deformation that somewhat tende to "set in" is total nonsense.
Fatique is something what starts slowly and evenutally ends in total failure.
Your statement
"So from what I understand. Yes we see a lot of altered rockerlines, if we check. Most probable cause in my view (I will not explain this here, it would take too long, but I am sure that the eventual reader competent enough will understand with no need for explanations) is some crushing in the sandwich foam, that probably sets in and does not go on indefinitely. And best way to avoid it, is using extra heavy sandwich foam in the bottom in the area between straps positions, as this would cost a very marginal weight increase in order to obtain around 2x better strength."
is also wrong (because of the simple fact that the compression strength of a stronger PVC is nothing compared to the compression strength of the laminate. That is why there is sandwich construction. That is something every mechanical engingeer should have learnt is its undergraduate classes But you don't care because to you all others who not comply to your flawed ideas are stupid.
Can you please give me the calculation fo the 2x better strength? I really would love to see that. BTW the strength indeed can be calculated. It is not so complicated. You just need to know that is the correct formula to apply, i.e. the right theory that models that effect. You might share your indefinite wisdom with us.
My best suggestion to you is the following.
Take 20' of your precious scientific time and do the test:
test.mensa.no/home/test/en
Obviously the result will not be certified, so it's nothing one can brag around; but it can be extremely useful for you. Once you will know exactly where you sit among the general population, you will also know how you do appear to others every time you speak your mind.
Just 20'. And leave the tensors alone.
P. s.: as for the 2x better strength in heavier PVC, no need for calculations, it's in the charts already (www.3accorematerials.com/uploads/pdf/TDS-AIREX-C70-E-08.2022-ex-Europe.pdf).
P. p. s.: as for "the compression strength of the laminate", apart from the fact that you don't seem to understand how the sandwich structure works, do you really think that the thin outer laminate will resist compression by itself?
P. p. p. s.: maybe you didn't notice, but fatigue is out of question here, as we are not talking about "total failure" of hulls, but just about possible deformation of the rockerline.
P. p. p. p. s.: you can study deformation by means of tensors, but there is no such a thing as a "tensorial kind" of deformation.
ohhh, know you say that I lack intelligence. What of an insulting person are you. Obviously it is only argumentation can can deliver. Mankind has to feel sorry, that all your wisdom never came to use.
Select to expand quoteSchobiHH said..
ohhh, know you say that I lack intelligence. What of an insulting person are you. Obviously it is only argumentation can can deliver. Mankind has to feel sorry, that all your wisdom never came to use.
Insulting? Me? Why? Did I state anything wrong about you?
To say that is the "only argumentation" is a false statement, as I answered to a few of your points, those that could be answered to briefly. And one should be grateful to be explained, for instance, that the mechanical properties of most commonly used (in sandwich boards) PVC foam are readily available in the data sheets so that he needs to make no calculations, or that fatigue is not involved in the alteration of a rockerline.
Select to expand quotegeoITA said..
Insulting? Me? Why? Did I state anything wrong about you?
To say that is the "only argumentation" is a false statement, as I answered to a few of your points, those that could be answered to briefly. And one should be grateful to be explained, for instance, that the mechanical properties of most commonly used (in sandwich boards) PVC foam are readily available in the data sheets so that he needs to make no calculations, or that fatigue is not involved in the alteration of a rockerline.
As i already said, you suggestion of just looking up the technical properties of one component (i.e. the PVC) of the whole construction is a much to simplistic view. And you are not able to give any explanation for why this should be the main factor. As a physistist I learn that before you come up with a statement you need to understand the underlying cause and effect. This is unfortunately not a skill which is very well established with Ingenieurs as can learn from your statements. Frankling I don't believe that you understand the physical phenomena which is happening and therefore which equations to apply.. In my understanding There are 2 physical phenomena "local" vs "global" buckling which are reasonable candidates for this. If you do not know the difference, this can be simply looked up in the internet. The formulas behind them are not difficult but the combination of different materials to take into account make it challenging. Therefore I have asked chatGPT to come up with a calculation. thickness of sandwich / Weight of PVC / and weight of overall glassMatrix.
I checked the calculation of ChatGPT and found it reasonable.
It was kind of fun when it started........
So......
Should we be loosen vent plugs after each ride ?
Select to expand quoteDoggerland said..
only a split-toe booties duel can restore honors here 
Yeah , with wet tipped tea towels.
Funny story.... not so funny... at a school swimming event at my school, a boy copped a ripper wet tipped towl to the ball sack. A couple years later , died from testicular cancer 
. So.... a wet tipped tea towel split toe booties duel is still a manly way to settle these kind of moments. More modern than musket fire.
Select to expand quote
Take 20' of your precious scientific time and do the test:
test.mensa.no/home/test/en ... Once you will know exactly where you sit among the general population, you will also know how you do appear to others every time you speak your mind.
hum ... I just scored 149 in that silly (and long) "test", but what has that to do with how I do appear to others? I am confused ...
Well ... on other news ... i am coming to be annoyed by everything electrical (the Tesla effect) but has everybody tried a jet e-foil with a windsurf?
New developments are certainly possible (imo)
One aspect that seems to gets little attention is how to reduce the friction of the hull (board). The only manufacturer (that I have seen) giving this some attention is FMX boards using paint developed in America's Cup.
Imagine a hull with absolutely no friction - earlier/easier planing, higher/more accessible, top speeds etc etc.
In Norway there is an on-going project working to develop the world's fastest cross-country ski.
A ski moving across the snow creates friction, that melts snow resulting a small amounts of water on the ski surface. This creates drag.
This project just might produce some results that are relevant for windsurfing.
Link to article (in English)
www-forskning-no.translate.goog/bygningsmaterialer-laser-materialteknologi/na-skal-forskere-lage-verdens-raskeste-ski/2470932?_x_tr_sl=no&_x_tr_tl=en&_x_tr_hl=no&_x_tr_pto=wapp
mclube have a couple of products worth looking at that have been around for many years. Sailcote probably the most known
Cross-country skiing has been the subject of research for quite a long time, now AI is also invoked in Sweden:
www.ltu.se/en/latest-news/news/news/2024-04-29-new-method-improves-glide-for-cross-country-skis
