ha!
Yep, I believe you about that too Bill
optimal lift/drag ratio
Lets break it down.
There is decreased surface area with a roving.
The fin is smoothly formed to the surface as a keel is formed by way of a fillet to the hull of a yacht and a jet plane wing to a fuselage , well the same. The filling of the hard edge is for coefficiency to reduce drag as well as add strength .
Hans is talking about dynamic Co efficiency
Sailboat designers figured out by modeling that the filet between keel and the hull was unnecessary and added drag.
Over the last year or two I’ve gone back to glass-on fins. I still have a few boards that I travel with that have FCS but pretty much everything else I’ve made recently has had glass-ons.
I don’t notice any difference in the performance of the board with glass-ons. I guess Kelly Slater can but not me. The main reason I’m using them is because they’re a heap harder to knock out. It’s rather rocky round here and I hit rocks all the time. Removable fins get knocked out or damaged so easily. This can get very expensive very quickly, notwithstanding the hassle of having a session ruined from hitting a rock while paddling out! I’m with Bill on the cloth vs rovings thing. Plenty of cloth and the fins are almost impossible to break off. I’ve actually had fins snap off half way up rather than break off at the base.
Another advantage is that glass-on fins are much easier to make. No tabs etc to worry about. Also you can make them as thin or thick as you like. I reckon I can make a thruster set for about $6 of materials. No plugs or boxes required so that’s a saving of something like $80 for a board: not to be sneezed at. Of course I’m just making boards for myself and a few friends so I suppose if I was in full production I’d be using removables just for the convenience.
Over-all I reckon glass-ons add about an hour to the production of a surfboard. They look pretty nice as well.
Considering the amount of appendage drag created by the fin itself protruding down into the water ( which is there to give you directional stability and control) , my opinion is that the rovings around the base becomes insignificant…unless it’s excessive , to the point where there’s far too much rovings than is need to give adequate strength and durability .
Its a case of splinting hairs
Ive tried to find the interview with Kelly Slater , where he talks about his fins…it’s a good one . He claimed that the main difference between removeables and glass-ons was the reaction time…when switching to a board with removables , there was a noticeable “delay” in reaction in turns , and that he had to take a few waves to re-adjust to the slower reacting removeable fins…I think this is because glass-ons have a better “attachment” to the board , and so give more feeling directly to the rider…this is all pro-level stuff , and probably not so relevant for your average punter.
Absolutely true Greg…but if you take a high performance skiff , with a retractable dagger-board type keel , and pull the dagger-board up , while the skiff is planing along , the skiff become almost totally disfunctional.
Sorry should have mentioned but I was referencing fixed keel yachts not swing keel or dagger board yachts you wouldn’t be able to have any type of filleting around the base of one of those.
Fin systems allow options. Fin location, shape and size will make a big difference on a board’s performance. It can turn a decent board into a one board quiver, for small to overhead waves. If you start looking at the other possibilities like proboxes, you can change the way a board rides quite a bit.
That’s why I prefer probox for the sides and a long center box for the middle. I have an assortment of fins for the sides and even have double foiled versions. I’ll try double foiled sidebites with a 2 + 1 setup, or go with a single foiled set and a small rear fin to make a thruster setup. I try both double and single foiled fins as the rears in my quads.
I suppose that you could get to a point where the fin style and location work the best, and then you can switch to glass ons for a copy of that board, but I think the options that box fins add is a big bonus. It also makes travelling easier or stacking a lot of boards up way easier.
So fin system are not “better” just more convenient and marketable than fixies? I love it. Now if only there was a hydrofoil fin system I can buy into.