A 3/4 inch thick fin with a ten inch base is proportionally the same in foil section (all else being equal) as a 1/4 inch thick fin with a 3.3 inch base … . . . not abnormally thick at all in proportion to the base.
Quote:
Chip,
From your picture it looks like you’ve got a light layer of say 4 ounce cloth capping a coarse layer of woven roving. They will flex at different rates and have a tendency to “delam”.
hi Tom !
it DOES look like that in the photo , for some reason , yes. But no , it’s actually just made up of :
five layers of 5oz , 1 layer carbon fibre , 5 more layers 5oz , 1 layer carbon fibre , then 5 more layers of 5oz cloth . [I don’t use rovings in my fins , even my wood keels] . I think it must look a bit like that as a result of the different colour / texture of the delammed bit , perhaps ? not sure, really .
Anyway , thanks for the tip …that’s good advice for others who also may be contemplating making a few carbon fibre fins , and may have been thinking of putting a rovings ‘halo’ around the edges .
cheers !
ben
And your point is…?
Just that foil thickness is not very meaningful unless expressed as a percentage of the chord length. . . and that the fins you were talking about are not unusually thick in proportion to their chord length.
I use a fin with a base or chord length of ten inches (in places) and a thickness of 7/8 ths of an inch on my 17 footer and like it very much.
Foil thickness, as described, was very meaningful in the context of the time I began using thick, foiled fins. (1960) The “normal” fins of the period were 3/8" glass, or 1/2" multi-piece wood, unfoiled flat sided slabs. I posted the base length for those fins so that people interested in the ratio relationship could make that calculation. A fin base of 5 1/2", with a depth of 7 1/2", is much more to my liking on smaller more “modern” boards, with of course the same 3/4" thickness. I felt no need to overstate the obvious. You apparently do.
So would I be correct in saying that your ten inch based 3/4 inch thick fins of the 1960s were unusually thick (proportionally) for their time, but are not unusually thick by modern standards, whereas your current 5 and a 1/2 inch based fins of 3/4 inch thickness are thicker than is standard today ?
In other words you were using thicker foils than the norm in the sixties,and are now using even thicker fins, which are again thicker than the current norm.
Sorry if I am ‘overstating the obvious’. . . . just interested in understanding what you have to say.
Roy,
Thank you for the courteous response. Certainly in the 60’s a 3/4’ thick fin was not the accepted norm. I was influenced by Phil Edwards, who was using thick foiled reverse fins at that time. Every claim he made about their superiority at that time, I found to be true. Some time in the mid 70’s Bahne’s F.U. came out with a series of thick foiled Lexan fins. (3/4") The 7" fin was the superior fin of that group. I put one on a board I had been riding for over a year, and with only that change a very good surfboard was transformed into a truely MAGIC board. That and other similar experiences have made me a strong advocate of thick foiled fins. I am out of touch with what may be considered thicker than “standard” today, so can’t really comment. But I would think 3/4" might qualify.