Hey MD,thanks for the offer! Sorry can't make it. Maybe in the future eh? Would love to meet herb,as well as surf with him. He seems very knowledgeable with surfboards and fins as well. Please don't get bummed at my challenges. Just healthy debate.I like facts! If youse guys gots 'em...far out! I also repair boards and have for many years. Just because herb has only repaired one red-x box,doesn't mean they don't break. Joe roper fixes 'em all the time,and I have repaired many. Probably equals about a half of a percent of the ***'s i've fixed. I've seen all systems break. Bottom line is this: Red-x,lockbox,future are all vast improvements over what has been the norm in this industry for the last 8 years or so. IMHO,a system should not fail under normal surfing conditions ie: no impact. This industry has embraced a system which was DESIGNED to fail. Says so in their marketing. Fins are designed to break at the tab. HA HA! Sign me up. If I were to come on here and promote one particular system as hands down the best...it would be followed by detailed info including facts and photos,for the good people here to see how I came about my opinions. I visited mavericks last winter and saw tons of lockboxes all over the place. Malik had red-x in his board on that bomb at teahupoo. Slater rides FCS. So does OCCY. Just because parsons or whoever uses red-x, doesn't prove to me that it is the bar-none best. Just my opinion,and hope I haven't offended anyone!
Fin attachment methods are only as strong as the medium they are attached to. That said, there are configurations that distribute the load in greater and lessor efficient ways. Most surfboard fin boxes rely upon increasing the surface area of the encapsulation of the box to the single bottom laminate of each board they are mounted in. This is refered to as skin mounting in the composites industry. The wider and longer the encapsulation contacts the skin, the more load, the structure can take. That's why glass on fins rely upon the relatively large glass patch, compared to the base of the fin, to support the fin. There are two draw backs to this method. As you make the support stucture larger to distribute the load, it becomes more difficult to fit the structure into complex bottom contours at the desired angles. Second the structure is only as strong as the schedule of laminate on the bottom of the board. Since boards are typically glassed as light as possible. That laminate is typically only single 4 ounce with a 4 ounce patch possibly in the immediate area. Red X mounts through the board to incorperate the deck laminate into an I-beam structure. Now the bottom laminate acts as a pivot point and the deck laminate resists the tortional load. Deck laminates are typically a heavier schedule than bottom laminates. Consequently, the majority of the load is resisted by a stronger schedule of laminate. Take a look at how keels (or other appendages)on sailboats are mounted. There is always a box structure inside the boat to distribute the load vertically. Skin mounted appedages were abondoned years ago. The material we make the Red X boxes out of is 27,000 psi on tensile strength at yield. Glass filled polycarbonate does not even rate at 1,000 psi. What this means is that Red X boxes will resist twisting and breakage in excess of 27 times more force for the same wall thickness. You may break a Red X box out of too lightly a glassed board. But, you will not break the boxes. This means a more even distribution of load over the area of the structure. Which inturn means less likely hood of point loading on the structure. When the loads are evenly distrubuted there is less chance of failure. The roots of the Red X fins have a matching taper to the cavities of the boxes. Matching tapers allow structures to have more intimate wall contact. Consequently, the Red X fins rely upon the box wall structure for torsional support. Fin boxes with parallel walls depend upon fasteners to keep the fins in tensions. There again is a point loading issue. Red X is all about distrbuting the loads via superior materials and proven structural geometries more so than any other mounting system made. But, I will admit that if you are looking for the lightest way to mount a set of fins, the monocoque structure of glass on fins is hard to beat.
.......THANKS Mike,now I know why it looked like Disneyland in the summer @ 21 yesterday!!!!!!!!!!!!!WHOWA!!!!!!!! ............As far as my past statements,I stand behind them,and if you took a precentage of fin/box repairs,FCS IS PROBABLY the worst or the most frequently repaired,and I would bet Red-X is the least.........everything else falls in the middle. ...........I still try out other fin systems out there as they are made available to me,like the Edge systems,and I'm willing to tryout others,but I always seem to come back to Red-X for my favorite choice..........but that's what this country is all about isn't it??? ..........Freedom to choose and to express your choices. .........STL your Q&As are welcome here,keep firing away!Herb
Material and design are complex issues, and tensile strength is but one number. Ultimately most design engineers will test failures of their boxes. If a Fins Unlimited box doesn't break before the board does, it is strong enough, and there is little point in changing the material or challenging its choice in use. If it ain't broke... I agree 100% about fin taper - that is quite clever. I solved the problem a different way, but it also involved load distribution over a more continuous area. As little as half a square inch on each side seems to be more than adequate. The Fins Unlimited box uses a long, linear load (a 0.350 wide fin in a 0.375 inch box) which can lead to unnecessary concentrations of stress where the leading edge of the fin meets the box. http://www.blakestah.com/surf/
Keith, There is a thing called "end plate effect" which is advantageous in reducing vortex drag in foil sections. It is used commonly in aircraft. Simply put the streamlining (filet) that you claim reduces drag in fins actually interrupts endplate effect thereby increasing base vortex (drag). This isn't something I invented, this is something written about extensively in aero and hydrodynamics.
I'd almost agree with you regarding material except that I said "tensile strength at yield". Tensile strength at yield is the point at which the material begins to flex. It just so happens that this material has the same number for tensile strength at break. The importance of tensile strength at yield is that the side wall of the box don't flex or twist. This is key when you want uniform distribution of the torsional loads the fins generate. It may be true that not every application needs the most rigidity available. But, at what point do you say, I don't need Michelin XGTs I'll get by with my bias plies.
Greg, Excellent point. Can a lump of resin around the fin make it perform better. I think not. The trailing edge of a fin where it meets the board is probably the point of greatest turbulance on a surfboard. IMHO the more simple the exit the better. Raising the area with a tapered bead off the trailing edge of the fin has always seemed to be a counter productive practice even though it has and continues to be standard practice with glass on fins. A bead may be necessary but it seems to me that the smaller it is the better. Epoxy would allow one to minumize its size I would think. Another option is routing the board out for the fin and making the fin with a root on it the way we do with modern fin box systems only without the fin box. and thus boxing the fin into the board permanantly. If this is done it will result a more streamlined configuration. It would require setting the fin into the board much in the same way as a standard center fin box is installed. Has anyone ever done it this way? Frankly I think the fin box is a huge improvement aquadynamically and structurally over glass ons but what do I know? Mahalo, Rich
You make a semi-reasonable choice, try to break it with a standard load. If it works, put it in a board. If it still doesn't break, don't mess with it. In the case of fin boxen, I'd be prejudiced that the substrate upon which it is mounted is a P O S compared to the box. And I'd work out how to maximize that. I mean, if you are gluing something to foam and 4 oz glass, how strong does it really need to be to be intact when the board mount breaks? Does it need 75000 PSI yield strength, or will the board yield at 500 PSI anyway? If so, who cares how much higher you design it than that required to do the job? You guys did a nice job on improving the strength of the board mount, and I am impressed at your IP protection on through board mounting (BTW, did you really make that misspelling in your patent app or does the USPTO listing have it wrong?) 5,997,376 Cheers, off to the CAD shop. http://www.blakestah.com/surf/
You're missing a very important point. It's not breakage that we were concerned with. It was flex. If something is going to flex we want it to be graduating from base to tip and throughout the tail of the board. Not some stack tolerance or psuedo breakaway tab or point loading fastener or the box itself. That's the reason I used performance radials as an example. The stiff sidewalls are all part of a performance suspension that minimizes roll and maximizes control. Yeah the ultimate breaking strength is far above what it need to be. But, we are more concerned with how firm the entire circuit is. That's where the tensile at yield comes into play.
Sorry, that was a patent office error. Our application does have Surf spelled with an "f".