Divinycell is commonly used for vibration and sound DAMPENING… so it would seem to be a relatively poor choice for building the most sensitive/responsive surfboard.
Wouldn’t it be much better to build with materials which do not inhibit sensation?
Has anyone ever catagorized surfboard core materials according to their resonance? In combination with other materials? Before and after construction?
you mean i finnally get an audience for the principals of amplification and stored energy ???
dale , really how many people do think would reply to that question??
is it time to dig some old data sheets out again??
it all comes down to the transfer of energy , the speed with which the medium allows energy to travel and the allignment or direction of energy transfer …
some mediums focus or allow force to pass through with no loss or even to amplify energy into a zone or focal point …
other mediums will dampen energy , or if not stiffle the energy and redirect it in uncontrolled directions . what this does is make a board feel lifeless and lack sensitivity …
you make the most valid point … you can have the best shape in the world , make it out of the wrong materials and youve got a dud … its that simple …
regards
BERT
http://www.duraflexinternational.com/diving%20boards.htm
It is tapered from the fulcrum area to the diving tip, and it is tapered from the fulcrum area to the anchor end. The double-taper allows the whole board to arc while flexing, giving it approximately 15% more lift than the 16’ Duraflex.
Hey Meecrafty,
With that kind of a diving board I’d have been able to make that 2 1/2 front of the the one meter board that I worked on for years as a kid.
Laird’s tow in boards are balsa. What does that tell you about resonance? Great show on “Ontold” on him last night on Spike-TV.
Sure wish I had the were-with-all build something like you’re building, Bert. If you were a little close you can bet I’d be surfing one when I wasn’t surfing one of my own.
Off to work, Rich
I’ve not categorized the various materials commonly used to build boards in a quantitative manner but instead, relied more on a gut feeling.
I do recall balsa having been described as having a solid “timbre” - I guess that roughly translates to resonance. By solid, I mean resistent to that chattering sound when hitting chop created by offshore winds as an example. Maybe the most sensitive/responsive materials are not the preferred materials in all conditions?
Conversations and “tests” with local shop guys have involved going around the shop and tapping boards with our fingernails. The comparatively hollow resonance of a Surftech compared to a polyurethane board was described as being disconcerting to some riders who apparently preferred a more solid feel (or sound) under their feet.
The hollow sound created by tapping a Surftech with the fingernail was quite different from the sound of a polyurethane board which was quite different from a balsa board. Hardly scientific, but telling nevertheless.
Bert,
This is a subject that has been nagging at me for a long time. I have brought it up before and it floats a discussion about as well as a lead balloon.
The quest for materials (and combinations of) which have the lightest, quickest and most consistent response, or the best acoustic, flexural and tactile qualities, i.e. intimate feedback to the user… that search is an ancient one. It encompasses the worlds of weaponry, music, sporting equipment, air and space craft, clothing, footwear, as well as many others.
So many things around us have an absolutely “dead” feel to them. Sometimes that’s what they’re made for… a perfect example being closed cell, flexible polyethylene foam: an excellent choice for shock absorbsion when used as a packaging material. But attach a sheet of it over a tuned flex tail and that tail’s response will be inhibited, if not ruined. Or make bodyboards out of it…?
Just because some materials are fairly cheap, readily available, fabricate easily and quickly, can paddle and ride waves… does not mean they offer anything other than the lowest common denominator in function and response.
Plus, if there is more than one material involved in creating a core shape, the means by which they are combined is just as important as the materials themselves… not only for a lighter weight and durability, but also for the highest quality sensory feedback to the rider.
Because of this, those who ride while standing (having the least contact with the board’s surface) should be vitally concerned about getting the best feedback/resonance out of their equipment. As you pointed out, someone can have the best board design in the world, but build it with the wrong materials, and it’ll feel like a dud…
Swaylocks, “Active Flex needs Passive Surfing”, July 19-26, 2002:
(DaleSolomonson): “One of the enigmatic characterisitics of high performance surf mats running over the textured and curved surfaces of a wave, is that they offer the rider a very pleasing, clear resonance, as well as a significant measure of shock absorbsion, yet without deadening sensation…”
(Håvard N. Jakobsen): “To me “shock absorbsion without deadening sensation” is one of the key elements to a fun ride on a snowboard. Wish I’d ever felt the same on a (standup) surfboard…”
For more fun reading, see the 32 archive results for “resonance”
This kind of stuff is intriguing to me, but how would I even go about trying to determine the resonance of a core material?
For all I know I have been riding “dead” boards my whole life. It’s kinda depressing actually!
I wanna live board!!
Has anyone tried Cork? or peetmoss? What about a board that is hollow but has a water filled skin?
The stradavarius quality of the diff balsa hollows immediately comes to mind…the resonance has always been a facination whiling away the moments between sets finding the deeper tones submerging the tail deeper and shalower as waves pass…’ the jensen frames’ picture arrived next in the photo brain review…yet the lam bend ply rails are short of a fine grained single piece rail certainly…the shape of the interior frames they allow the sound waves access to the entire sounding cavity … come into consideration,the spacing as with the spacing on the holes in the wood flute or the spacing of the frets on that ol guitar ,critical,the intelect to accomodate this high resonance board are truely facinating… ambrose… I’ll be ruminating…with the sander on
if I may add to this discussion,it seems to me that the live feel of something like surfboards and things like them has a lot to do with the lightness and stiffness of the core material and the quality of the coating and the finish.maybe it’s the just right amount of stiffness,lightness,and spring and the care that was taken in applying the coating.my dad is a lifetime model builder and showed me a long time ago that balsa wood is not even close to being all the same.there is a,b,c grain and the c grain is lightest,stiffest and strongest in all directions,but it does not bend,it just snaps.
Shawn
could it be that an object that resonates is acting as an entire unit as it is built so that the entire surfboard for example becomes one whole thing and not an assembly of different materials?more than the sum of it’s parts?
as usual the cost is less than half the value the espeertise and quality control rae still only a fraction of the value ,true appreciation will deteermine the real valueI.E. the stradavarius instruments are documented numbeered dated and most of all cared for.
appreciation increases value on a continium leave it on the ground in the yard it 's compost cheap,in a velvet lined case with polished brass and mother o’pearl closures sounds appropriate for this fine instrument,and others of its kind…last for lifetimes/ not on the roof of a vw van…
…inspiring job ,hard to do out in the yard…ambroseplanet earth corespondent to olympus,my best to zeus
Are we talking apples to apples?
In physics, resonance is an increase in the oscillatory energy absorbed by a system (spring/mass) when the frequency of the oscillations matches the system’s natural frequency of vibration (its Resonant frequency ). Examples are the acoustic resonances of musical instruments, the tidal resonance of the Bay of Fundy, orbital resonance as exemplified by some of the Jovian moons, the resonance of the basilar membrane in the biological transduction of auditory input, and resonance in electronic circuits.
A Resonant object, whether mechanical, acoustic, or electromagnetic, will probably have more than one Resonant frequency(especially harmonics of the strongest resonance). It will be easy to vibrate at those frequencies, and more difficult to vibrate other frequencies. It will “pick out” its Resonant frequency from a complex excitation, such as an impulse or a wideband noise excitation. In effect, it is filtering out all frequencies other than its resonance.
Dampening is not exactly a bad thing…take the shock absorbers (dampers) off your car and ride it…at speed it may bounce slowly up and down and give you an interesting sensation but the car would be much more difficult to control in a performance situation. Similarly, the controlled ride characteristics of dirt bikes and mountain bikes would be compromised without dampers…the bumps on the dirt track are somewhat synonymous with surface chop or bumps on the water.
I has been stated here that flex and flex return characteristics, dampened or undampened, is the critical characteristic…too bad no one has scientifically tested, measured and analyzed such things…it would be interesting to quantify scientifically.
I think the reason resonance is relevant to the discussion, even though we are not studying an oscillating system but springback characteristics, is that it would seem that finding the best frequency of the surfer/surfboard system, were it to theoretically oscillate, would be close to the optimum point of energy return-ability.
The way I am visualizing it, though largely uninformed and untested, is…
Damping is good for control’s sake, because it absorbs shocks the human body doesn’t like, but it is also neutralizing of energy-return, ie less potential for positive energy return.
IMHO, surfing is in little need of shock absorbing. the water already does a pretty good job. So increasing spring-back, when dialed in, would increase the performance potential of the board, allowing the surfer to throw more weight into turns, bend the board, and redirect as the board snaps back, using the snap to rebound faster.
However, spring has potential to be worse than a neutral damping board also. on one end, the snap could be too tight. in moderate turns, the impulse would be too quick to use, and in extreme turns, the release would buckle knees. On the other end, if the board is too flexy, it would bog before releasing. Take the surftech type for ex.: they are very stiff, so damping helps alleviate the response problems. Loosen up the flex, though, and the damping would hold the design back.
Imagine, as your basic hypothetical resonant system, a board suspended tip and tail between two supports with a man standing in the middle. The man gives an impulse with his knees, then just stands there. Assuming a board with no dampening, the man would bob up and down at, I’m assuming, the resonant frequency of the man/board system.
Thus, could finding a resonant frequency at which the man standing there could start boosting like a trampoline, be a way to get in the ballpark with a flexy board?
By the way, if a board is to have flex-ability, it would pretty much have to be strong enough to put between two padded sawhorses or blocks, and gently bounced-on. I’m gonna try it with a homebuilt stiff foam board…Yep. that and an old poly board…OK, the stiff epoxy over dow blue-board was the “quickest”, with the poly board harder to find the right pace, but slower. (it’s buckled in a few places already, so it’s pretty dead…) Interesting… I think it would be neat to try a flexy board that you were able to bounce a bit into the air on…
Disclaimer: sunday daydreaming content, not responsible for accuracy…
wells
Of the six hollows I have made, two were framed plywood “kookboxes”, two were glass made in female moulds, and two were cedar and glass on male moulds. The boxes were stiff and both fit the surfer description of a “log”. The hollow glass boards while incorporating foam sheeting were very heavy - similar to an old style poly boat. Initially the two cedar,carbon, and epoxy boards could be described politely as “lively”. A more accurate description was “squirrelly”.
The problem was how to control the vibrations so I could comfortably ride them - granted I am an old, slow, poor surfer. Towards this goal I incorporated ethafoam bulkheads. The result was a kin to adding new shocks to an old beater - as meecrafty has pointed out above. The bottom line is the boards work, but they certainly do not have the neutral feel pro-surfers speak of as desirable.
Moreover, the irony of having to add foam to make the boards work kind of defeats the purpose of removing it to increase the interaction with the wave - perhaps as roadrunner pointed out I have not found the equilibrium. Whatever the case, the result made mats more interesting - thin flexlble membrane with easily adjusted shocks. Towards this end I recently and primitively attached a piece of plywood to an old air mattress. Didn’t result in any insights but it was cheap fun - two qualities that seem to be disappearing from many activities. Take care. Patrick
Bert-
Please… will you explain more on this subject??
Your personal experiences?
thanks
hey parker , im hell busy at the moment …
theres some almost relevant stuff on the thread "flex materials " started by swifty i think …
energy travels in waves , different mediums carry waves at different wavelengths and frequencies …even tho we cant see it with the naked eye like ocean waves , all materials pass on energy in wave form , even tho microscopically small …
as a wave travels from one medium to another it can either speed up or slow down , in that process it can also bend and be redirected …
things can get in the way of waves and break them up and scatter there power …
things can also make waves form a focal point …
laying down different mediums in the core of a board , being selective about what to put where , knowing that different materials can either absorb , transfer,scatter, redirect or converge energy …
dales ponderings are right on the money …
i just dont have time to explain the ins and outs right now …
regards
BERT
I’ve run some recent experiments on flex (lab stuff, not actual in the field… I always have to question lab stuff but it does give a starting point) and have an interesting conclusion I’d like some feedback on from you guys. What I’ve believed for some time and what these tests seem to say is that the compression side, while riding, offers most of the stiffness (overall) while the tension side gives most of the return. Of course each contributes to each but overall this seems to be the case. And this is just concerning the glassing. The foam also contributes which wasn’t part of the test. But if this is true then we can begin to look at engineering towards maximizing those areas to their best advantage… any thoughts?
Really interesting ideas here. The surfer definitely complicates the equation. How much do resonant frequency, amplitude of flex, dampening, etc. depend upon factors such as where along the board the rider is standing, the positioning and separation of the feet? Walk the board, change the characteristic responses. Way too complex for my simple mind. Got to feel it.
Resonance is very complicated stuff, I suspect though that very few surfers will every experience true resonance. Probably more relevent is beam theory, below are some links for the basics behind beam bending, this would be the starting point for surfboard structures. Work and energy are really at least another level above this, so it’s probably best to start at the bottom.
https://olt.qut.edu.au/bee/civil/gen/static/content/theory/context.htm
Most examples are for a beam supported by say a two walls with a distributed load acting down, so when you look for something analogous to a surfboard you need to turn everthing upside down (this doesn’t affect the maths). The distributed load is the water pressure acting upwards, the supports are the surfers feet acting downwards. The examples are idealised, so pressure distributions, non consant EI etc will all be approximations, add to this that classical beam theory is usually thought to work where L/W > 8.
It’s a start though.