I have been wanting to do a “how to” thread on making halo’s for your old school style fins. There is a ton of info here on Sway but it is in a few different post by Austin Saunders and Jim.
This is a bit of both methods wrapped up into one and I will keep it short and to the point.
The most important thing in making a nice wooden fin is having nice and expensive wood. The wood in this fin is Koa.
1: Thickness the piece of wood. I start by using a thickness planer then move to an overhead drum sander to get the final thickness.
2: Cut the outline to the template. I have a couple different bandsaw in the shop with different size blades that do different jobs.
Get the edge of the cut fin to be perfect. Very important that it is smooth cause you can’t fix this later.
Use the slot router bit to cut a slot in the edge of the fin at the half way point between the L and R side of the fin. Picture is attached of the bit I use. I believe it is a 1/16’’ slot. I have a homemade router table but using a handheld router works also.
Cheater coat the edge of the fin where the resin is going to go.
Build your resin dam and place wax paper underneith the dam and use mold release on the edge of the dam.
I used Casting resin for this fin but regular resin work. If you use lam resin then you will need to brush it with sanding resin after you pull it from the mold so you can sand it. Casting resin costs more but I like how it sands.
Place the fin in your mold and weight it down.
Pour your resin. Some people do this in 3 steps…I did it in 1. Your choice. It is very important to add MEKP your resin vs. UV only. The UV rays don’t get inside the slot and if you kick the resin slow it will give the bubbles time to raise to the surface and not get stuck in the halo.
Remove the fin from the mold and clean it up. I run it through the drum sander to get it back to an even thickness. Also, I made my mold about 1/4’’ bigger then the final halo size to provide room for error. The resin does funny things sometimes when it is up against the wall of the mold.
Make the guide marks for the edge of the fin and the fattest part of the fin. I place my fattest part at 25% of the entire length of the fin back from the leading edge. Example: 10’’ base x 25% = 2.5’’ back from the leading edge of the fin.
Before you foil you want to cut a tang to hold the fin in the vice. This will allow you to see the slot at the bottom and make sure you are keeping an even foil.
With Koa I sand all the way down to 220 grit. This gets the scratches out.
Cut the tab off. I place the fin on a piece of wood that I then slide through the bandsaw. This keeps my fin from being scratched by the table on the saw.
Since the base on these fins is pretty long they tend to rock when glassed on to the board. I take a bending stick and clamp in down to use as a guide. This makes an arch which I trace on to the fin creating a two points for the fin to sit on the board.
Glass how ever you see fit. This fin is glassed with 2x 6oz E glass on both sides.
That is it. Honestly, I believe this is the easiest method to making a good halo. There are a bunch of different way and I have tried them all with varied success. Lastly cause I didn’t mention it earlier…the reason for the slot is to provide a strong foundation for the resin. When sanding the trailing edge thin I have previously heated up the resin and it has moved off of the edge of the fin ruining all my previous work. This doesn’t happen anymore. Also, when doing a colored halo this method works well in keeping the colored resin off of the foiled wood.
Woods with high tanin (oil) don’t work great with Poly resin. They sometimes fog up your glass job.
I have used everything from organic homemade release to commercial release. Both work but both are not great. When you find something that you like please post up so I can use it.
Good writeup Dave! Can you see the slot when finished? I use new finish car wax for my release agent. It is what I had laying around and worked like a champ the first time I used it. I looked for my old build thread and couldn’t find it.
Hi Dave-
Thanks again for the templates earlier this month. I have already cut out one of each. I forgot to account for the inner edge of the halo. I went back and made three templates for the first one: intended fin, inner halo, outer halo. I cut that blank down to the inner halo template. I found the Whiteside 1/16" slot cutter and arbor at Woodcraft. I did the first slot holding the router but did not have a good way to secure the blank while leaving enough clearance for the arbor of the slot cutter. I am thinking a table like yours would make it easier. I made a mold/dam out of scrap 3/4" pine and 1/8" Masonite and hope to cast the first one soon.
I have a couple questions related to this process:
After casting the halo, do you ‘re-template’ the fin back to the intended outline before foiling?
What do you like to use (machine type, grit, rpm) for the initial foiling?
Thanks, Jim
I have done the Halo both ways. User preference I guess.
For foiling…I use the Harbor Freight Variable Speed Sander. Basically a total piece of garbage. Click the trigger 45 times until it starts. RPM is based on how soft the wood is and how fast you move the sander. Softer the wood the slower the RPM and faster I move the sander. Helps prevent divots. As far as grit goes…you can start anywhere. Just sand until the scratches can’t be seen when you do an Acetone wipe.
Dave
Thanks Dave.
I have two HF sanders. the older one has a good speed control (no trouble over 4 years) and the other failed on use #2. I took it apart, metered out the trigger as being OK, and traced the issue to a broken speed control output wire and found another wire missing insulation. Fixed those and it ran fine a couple times after that. Last time I used it I had to monkey with the speed dial while pulling the trigger before it will turn on.
Hey Dave what kind of Pad do you use for foiling? I have used a medium flexpad on variable speed sander for foiling with success but are there better options? Thanks again!
I got a pour in the other day. Overall I am happy with it. The wooden dams and Masonite worked with the PVA and #2 paste wax treatment and epoxy. My double-sided tape and hot glue sealing job (blank to mold) was not so good and I did not use any wax paper (like Dave mentions) or shelf paper (from my own experience) so the epoxy leaked and I tore up the bottom Masonite removing the fin. I will probably discard this dam and build something with taller removable sides (to account for the 1/8" [3.2mm]resin-to-mold meniscus) and a non-stick base. Also, the big tab should be full-thickness and full-length for sealing into the dam and the dam should not have corners, nooks, etc. to hinder de-molding.
Thanks Surfer O. I am thinking of trying it on some bigger boards, a 11’ long board and a flat water stand-up. These reverse D templates are all new to me.
