Is there anyone that can tell me how much resin I will need to do a fin lay up for a center longboard fin in a box. My sheet of glass is about 12" X 24", I should get a few of fins out of that, 32 layers of 6oz cloth. Also if I were to put a tint in it for some color, what % of tint should I add. As I am in OZ metric would be helpful.
One other thing. I have read in earlier posts about putting a fabric inlay in the center of the layup for a floral design. It is mentioned about using cotton as in bed sheets. One thing I have noticed with bed sheets, and most other fabrics, is that the printed design is printed on only one side of the fabric. you can still see the design on the other side, but it is a lighter shade. My question is will the design be the same on both side after it has been wet out with resin and cured?
I will have to experiment at bit I guess, but if anyone has any answers, It would be very helpful
It will depend upon how wet you lay up and the type of cloth used. For fin panels we use 32 layers of the cheaper boat cloth. It turns out that this cloth is taller in profile than the more expensive surfboard cloth. This cloth soaks up much more resin as well.
Reasonably, I’d say between .5 and 1 liters of lam/gloss should do you right. (Use 2 parts lam and 1 part gloss; this should get your fin stiff enough for good spring-back). You will only apply enough of this mixture to do 5 or 6 layers at a time. DO NOT TRY TO DO THE PANEL ALL IN ONE BATCH; it always goes off too quickly.
One of those grooved aluminum rollers from your composites supplier is magic for getting no voids, use a squeegee just to spread and remove resin. Cottom fabric turns almost completely transparent when resin hits it so the dye should be visible just about equally from both sides.
Lay up your fin sheet on a thick piece of window glass. Car wax on the glass is a good idea for a parting agent.
Suggestion: do 5 or 6 layers of one color, let the batch gel, then do another color. Do this until you get to the middle 10 layers, then reverse the color sequence (this means you must divide your colored batches into two so colors are equal going into the core of the fin as they are coming out).
Color saturation is adjustable, pigments are of two types: tints and opaques. Good solid hiding using opaques occurs at about 15cc per liter of resin. Tints are about the same or less depending upon desired effect.
Howzit PlusOne, Do you do a clear coat between color changes. Just wondering since it was a trick I learned back in days of yore. Alos knew some fin making friends who would wet out all the layers ( 32 ) then place a sheet of wax paper on top and then a piece of sized ply wood and some heavy holow tiles. They did the whole sheet in one shot. Aloha,Kokua
yes that clear divider really gives the fin a high-quality 3-D look; just a slight shadow between the colors. Those guys shooting fin sheets in one batch are pros, man; I’ve watched them and they make it look easy, so I go back and try it on my own and some sort of time warp occurs where my clock spins twice as fast and I have half a bucket of smoking resin… Ha ha, I laugh now. I really have respect for those guys.
Howzit PlusOne, They would do a super cold batch and let it sit overnight. The clear coat between color coats also makes the color change a smooth transition so you don’t get a serrated look between colors.Aloha,Kokua
All the info in this thread on fin panel lay-ups is right on IMHO. I don’t wet out more than 3 layers of glass at a time cause I want perfect saturation and no, absolutely no air bubbles. I use sanding resin and catalyz about 6 oz. at a time with 20 drops of catalyst. I work with similar batches of epoxy This way I never have to worry about the resin kicking while I’m working it. A glass surface works the best for flat lay ups, but wax paper is a good call too. Cottom prints won’t look exactly the same on both sided of the lay up but they still look pretty nice. I find that panels aren’t ready to cut until the next day after things warm up for a while around here. Unless an epoxy lay-up of a dark color which can be put in the sun. It’ll go off in a big hurry cause it will get hot. Cutting panels that aren’t fairly well cured doesn’t work out well. I find that epoxy panels cut more easily than poly for some reason. There not a lot of difference but for some reason epoxy just takes a little less effort.
Hey Guys. After reading about fin lay ups in this and other posts, I noticed that different poeple use different resin mixtures. Some use just lam resin, some use just sanding resin and some use a combination of the two. What is the difference between using one or the other in application, and what benifit is gained in performance by using one or the other?
Hey Guys. After reading about fin lay ups in this and other posts, I noticed that different poeple use different resin mixtures. Some use just lam resin, some use just sanding resin and some use a combination of the two. What is the difference between using one or the other in application, and what benifit is gained in performance by using one or the other?
I’ve done it all ways, and as far as I can tell, there is no difference. Probably a small strength loss with the sanding resin, but nothing that is worth getting worked up about. Now, more important is finishing well with a good gloss and polishing…
the reason for mixing in gloss is to stiffen the fin a bit and increase its “k” value. Gloss is chemically different than lam and HC resin. Lam and HC resin are the same but for the addtion of more styrene and paraffin in the HC. This makes the HC resin a bit more brittle but not because it is stiffer or stronger, it just has less “mers” linked together (thus less “polymers”) and the increased number of broken chains is normally not a good thing.
Lam resin becomes sandable when contact with oxygen is prevented during cure. The glass pane will give a good sandable surface on that side, and a sheet of plastic will on the final layup even if all lam resin is used. A brushed-on hotcoat will suffice for the plastic sheeting as the floating wax cuts off the oxygen supply.
Really, the best spring action will come when the inter-laminate shear is reduced/eliminated and torsion is controlled. The shear causes the layers to “move” against one-another as one of the primary load paths. You can optimize a fin (if you have time) by glassing both sides after you have foiled it. Fiber orientation at 45 degrees to the lengthwise span is a good start.
If you use carbon graphite, then prepare to have your mind blown as this material loads up in compression as well as tension (glass has almost no compression resistance). Energy retention is excellent. Graphite is a great engineering material because of this reversing capability which allows designers to have even greater control of the part’s behavior.
This is why graphite is used in flex-critical devices such as tennis rackets, golf clubs, and fishing poles. IMHO, laminated glass sheets is the way our fore-finners made fins because that’s what was in the shop; and you know what? it works okay. Still, the above might not be a bunch of hogwash after all (at least as food for thought).
I do all mine the same orientation, and when I cut fins out of the plate the long axis of the fin is oriented with one of the sets of fibers and perpendicular to the other.
Howzit vern, by doing the clear layer between color changes it keeps the next color from filling in the weave texture which results in the serrated look. Aloha,Kokua