induction? ( vented / ported / slotted ) boards : what's the principle at work?

while patent-pending designs of the newly-posted vented / slotted / ported boards are understandably kept under wraps, it would help to get some insight into how they work.

is this the principle behind the design ?

This is an interesting observation as it runs counter to my observations. About 25 years ago I made a flat-bottomed board to illustrate some of the characteristics of the hydrodynamics of a surfboard for a talk I gave to an oceanography class at UCSD. One of the features was a matrix of holes (straws) drilled through the board, terminating flush with the bottom and top of the board, and perpendicular to the bottom of the board. The objective was to provide a visual picture of the distribution of water pressure against the bottom of the board (this method is used to measure the static pressure for the altimeter in an aircraft). More specifically, the distribution of pressure pattern against the bottom of the board could be approximately measured by the height of the jet of water shooting upward from each hole (pictures by a photographer riding in a Zodiac running parallel to the path of the surfer documented these heights for subsequent analysis).  The observed distribution was in good agreement with the classical Stavinsky distribution for a planing hull.

So we have two conflicting observations. Surffoil reports a suction drawing air downward from the deck while my observations indicate a positive pressure everywhere aft of the spray line (where the water first contacts the hull). The only significant differences between the two boards would seem to be the size of the holes in the connecting tubes and the presence of a “step” in the bottom of Surffoil’s board just forward of the air holes. I suspect the the latter is the primary cause of a positive pressure at the air holes in the “no step” configuration versus a negative pressure in the presence of the step. A secondary factor may be related to the hole diameter (or to a hole diameter/step height ratio).

In any case, the net overall pressure on the bottom of the board must be positive when planing (otherwise the board would not support the weight of the surfer). The more area with a negative pressure; the greater the wetted area with a positive pressure required in order to compensate. At speed, the greater the wetted area, the greater the skin friction drag. The bigger the “step” in the bottom, the greater the form drag. On the other hand, if air is entrained board and flows downstream from the step, the drag from friction between the water/air and the board may be reduced. So it is not clear if the net effect of adding one or more steps (and air supply tubes) terminating just aft of a step would increase or decrease the overall drag, and how those differences depend on hole and bottom geometry. Obviously it is a tough problem to come up with the optimum configuration by calculation, or by trial and error. The fact that a number of people have experimented with such designs, but they haven’t become popular, suggests that these designs offered little, if anything, in the way of significant benefits.





Is this the principle behind the design ?




howdy bill,

no offense of course to those who’ve taken pains to develop forward-thinking boards like these, but-- in essence, what’s the principle at work ?

pablo’s ‘speedboat tub’ pic was merely featured above as an attempt to illustrate ‘induction’; online descriptions to date don’t suffice (yet) to help everyone understand how those (new?) board designs work. perhaps a simple explanation can be made without putting those pending patent apps at risk ?


I seriously hope nobody is trying to patent induction surfboards.  The principle is expandable beyond anybody’s design, so a patent won’t hold – it’ll just cost the guy seeking the patent money with no ultimate gain.  


Skip Kozminsky holds a patent on a hollow wood surfboard design that is close to everyone else’s – cost him more money than he ever made on the design.

ey J,

in any case that’ll be something the patent owner can learn from next hehe 

as patents go, they only cover what applies to the documented technical description that went into the original, approved patent application. any modification / mutation in others’ works whether minor or major brings 'em outside the scope of the patent in question. over time everybody’s design goes through incremental changes anyway so owning a raft of board design patents IMO aren’t that appealing from where i sit in the lineup " )

still looking forward to a basic understanding of why / how the design works…


I can’t wait to see video.


Oh, I just saw the thread where Herb says he is in fact going after a patent – that’d be great if he actually could patent it and keep it licensed, I just know there’s a million ways to vent and circumvent things like that. And I’m glad of it.  

It would seriously suck if the guy who invented this great thing that we all ended up using and loving spent his days embittered by money fights, partnerships that seemed like a great idea at the time, attorneys … 

“as patents go, they only cover what applies to the documented technical
description that went into the original, approved patent application.
any modification / mutation in others’ works whether minor or major
brings 'em outside the scope of the patent in question.”


Not really true at all -

Matt (a patent attorney)

my design is unique…the photos show that.


of course i knew the second i posted info and pics here,there was going to be emails/pms/phone calls…,“i did the 10 years ago”…or," how can you claim that design,(i,we,they,him) invented it 40 years ago"…with lots of nasty threats and words too boot!

fyi…to those who are trying to intimidate me …fo.






care to explain why this is “not really true at all”, matt ?

countless patent infringement lawsuits originate from patent owners’ insistence that mutant designs infringe upon their patented work, while modifiers counterclaim that their development/innovation/modification brings them outside the scope.

obviously it can be argued either way but in the end, successfully arguing the case all the way (to the supreme court if it goes that far) that their modifications exempt them from the patent indeed wins in the end.

although in the end you know that it’s patent lawyers like you who actually make money every step of the way  " )


“care to explain why this is “not really true at all”, matt ?”


An illustrative (hypothetical) example:


If someone invents and patents the basic automobile and a competitor modifies existing, patented automobiles to make them specifically fuel injected when previous automobiles only had carburetion, then - if the patent was drafted properly - the person who created the fuel injected automobile will still infringe the patent despite the modification.


Everything depends on the scope of the patent. If Herb were to get a patent broadly covering induction-type surfboards, then it wouldn’t matter if someone changed port sizes or locations - their efforts would still infringe his patent.


In short, everything depends on the scope of the patent. Breakthrough inventions/innovations typically result in broader patents which are more difficult to design around. Other patents may have narrow scopes which are easy to design around. What is not true, however, is that any modification of what is specifically described in a patent will get you out of infringement. Many other issues aside, there is something called the Doctrine of Equivalents (in patent law) which is intended to prevent just that. If the opposite were true, patents would be almost valueless.

howdy herb,

sorry to hear you’re getting razzed for patenting your own design hehe telling 'em to go f.o. instead of “oh yeah? well, see ya in court!” is much more eloquent IMO but maybe you can give us a basic understanding of the principle behind the design ? it could also serve to bring such infidels closer to the light too hehe


love your explanation matt except i wonder hmmm how is it that to this day, chinese businessmen can still get away with their copycat creations off patented designs ? hehe enforcement after all is what gives value (a.k.a ‘cold hard cash’) to patent ownership


It is pretty simple to go to the USPTO site, where you can search see the track record of what patents were granted to a particular pat attny.   If the patent produced any money for the inventor it is sometimes revealed by the notation that it had been “assigned” to some other entity.  The other way is to enquire to the inventor.  The huge majority of patents went nowhere, except to the attns. bank account.  But they can’t be absolutly honest because they got to pay bills.


Yes, enforcement can be very expensive (more costly than almost any other type of litigation), but - if the invention is valuable enough - you can often find law firms that will represent a case on a contingent fee basis.


I’ll be the first to admit, patents certainly won’t be valuable to everyone (most are never even commercialized), but they can be critical to success for others. Just as well, some defendants/infringers successfully design around patents, others get hit with injunctions and multi-million (sometimes multi-hundred million) dollar damage awards. Everything just depends on the facts and the merits…


Man.  How sad that a creative breakthough gets mired in this.  Herb - wish you the best with this, your board looks awesome.  If Thrailkill is on board, I know its a winner!

“If the patent produced any money for the inventor it is sometimes
revealed by the notation that it had been “assigned” to some other


This can be helpful, but not all assignments are listed on the face of a patent. If the assignment takes place after issuance, then it will never actually be printed on the patent. You can separately check the assignment records, however (which is similar to checking property records for real property deed information, like for land titles). Moreover, licenses may never be recorded at all (and therefore never public) and they are just as common as assignments.

glad to have a working patent attorney onboard explaining the risks & rewards of patent ownership hehe hopefully the designers can weigh in on the principle behind the vented / ported / slotted board design too.

otherwise we may be compelled to let pablo’s innovation (first revealed by disney animators in 1943!) have the final word here  x D


Happy to provide information here and there…it’s certainly more accurate than any surfboard design advice I might offer (though I surf plenty)!