Currently, glass-on fins are seen mostly on retro twin fin boards. They can look very nice if done right, especially if the fins have a wood grain.
Glass-on fins are laminated right to the board with fiberglass and are non-removable. There are several advantages and disadvantages to laminate fins.
Greater strength. Because they’re laminated right to the board, the entire base of the fin is sealed to the board, offering greater structural strength—-if the shaper knows what he’s doing.
Better performance. The way glass-ons are attached to the board is quite different from the removable variety, and so the flex and drive pattern will always be a little different. You’ll only feel the difference once you’re an advanced surfer, however. You may notice that most pro surfers use glass on fins.
Al Merrick uses both removable and glass-on fins for his boards, but considers the performance of glass-ons to be a notch above removables.
They just look good on some boards. If you have a retro fish, glass on fins just look better. This may not be an advantage if you could care less how your board looks.
If they break, it’s a pain to repair. If you snap off a glass on fin, it becomes a very difficult process to repair. You’ll have to take your board to your local shaper or surf shop and have them glass the fin back on, or put a new one on if it’s completely destroyed. You can’t experiment with new templates–they are there to stay.
They are expensive, and difficult to do right. Removable fin systems made life very easy for shapers, who often find that glassing the fins is one of the most difficult parts of shaping a board. If you want glass-ons, make sure your shaper knows how to do it right!
You can’t change them. This may or may not be a disadvantage, depending on whether or not you plan on getting several fin setups. Lots of surfers never change their fins anyway.
You can’t remove them for travel. Surfboards are not the easiest things to take on a trip, especially when they’re being stacked together in a bag. Glass-on fins become especially vulnerable in this situation. It is suggested that if you’re going to travel a lot with a particular board, use removable fin systems.