Foil: NACA 0012 (or as close as my skills will get me)
Keel type: Trapezoidal and Forward swept.
Cord: 3 3/4"
Tip lenghts: 2 1/4"
Fin depth: 6 1/2" (for now)
Ok, so I chose the NACA 0012 foil because of what I’ve read on “wavegrinder” website. Also according to this site http://www.worldofkrauss.com this foil has a good lift to drag ratio, and the stall angle (7.5 deg.) is a bit higher as compared to thinner or thicker foils.
Here is the NACA0012 foil:
I printed the foil to scale and made some test templates:
These were crap, so I printed these of again and glued them onto a cardboard backing (the cardboard used to be a photoframe backing)
I was only interested in half template, reasons for this will become apparent as we move on.
Here are both templatesglued to cardboard.
Using a pull saw I roughly cut out the templates:
And after some sanding with P150 this is what I got:
I cut the foam sections in half. The half sections dictated the fin depth.
I aligned the templates with respect to one another. I wanted to try a forward swept keel, so the leading edge of the tip template was placed a few mm infront of the leading edge of the cord template.
Secured these to the table, placed the foam between the temlates and used to hotwire to foil the fin panel. With this method the hotwire also gives the fin its plainshape.
So the result of the first attept were no good to say the least.
This time around I used CD cases to serve as templates for fin pannels, as opposed to using gravity.
I joined 2X two CD cases with masking tape. I also found that it was important to tape up the CD case edges to stop the hotwire from gouging chunks of acrylic. I mounted these onto the “Shapers Australia” measuring square.
Below you can see a stack of freshly cut fin pannels. These were much better than the previous lot. All pretty square.
When hotwiring the panels I placed an external disk drive onto the foam to keep it flush with the measuring square. To my surprise, masking tape was great at letting the hotwire slide over it
After the fin pannels were cut, I modified the templates by taping up all the CD case edges:
As you can see this one is set up for the forward sweep keel.
And here ya go, the first cut of attempt 2 went like this:
The trick to getting a good cut was yet again the masking tape.
I ran the sections of tape from tip to base in a straight line on both leading and trailing edges as seen in photo above. This tape served as a good guide and “cut stop” and I was able to judge better where was relative to each template.
It was also important to cut the panel in an arc motion because of the difference in template lenghts. The cord template has to be hotwired at a higher rate as compared to the tip template. Otherwise the middle of the trailing edge goes all funny shapes. (See the first attempt).
This one looks interesting, was thinking of doing something similar myself. Keep it coming, I'm keen to see how it turns out!
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Thanks Paul. I got the idea from RC airplane website. They hotwire their wings like this all the time. Although I think they hotwire both sides simultaniously. I wasn't comfortable with that because there was no way I could make a symetrical template.
Typed it up at 1 am, probably could have explained some things better.
The plan now is to tidy up each foil. Then I want to make glass pannels, cut out the fin plainshapes and use these to mount the foam foils onto. This should give the fins extra rigidity. 2x 6oz is the plan at the moment.
The next step was to make the fibreglass panel to be glued between the two halves of the fin. I used 2 x 6oz cloth for this:
I mixed up some RR KK, added black pigment. Placed the cloth on a piece of wax paper (baking paper). Saturated the cloth and added another layer of wax paperon to of wet cloth. I placed the wetted out cloth and the wax paper between two pieces of glass. (Glass can be salvaged from photo frames. Mine were two 10"x8"s).
To make sure that the pannels were as flat as possible, I placed some books on the entire assembly.
This was the result:
The pannels were nice and flat. Cool thing is that you can use regular scissors to cut out the shae you need. The pannels cut nice and clean.
the next step was to attach the two fin halfes to the pannels.
I roughed up the pannels with P100, and used RR KK to glue them on. The foam cores were straignt enough, mostly. There were a few touble spots were the foam would come away from the panel. I simply used a sponge and a book to weigh down the parts of foam that were bit warped. Also wax paper between the foam and the sponge was a must to avoid gluing the sponge to the foam.
Here is the trapezoidal set glued together. Note, at this stage the fibreglass pannel still need trimming to correspond with the foam core plainshape:
The next step was sealing the cores with light weight spackle (I used “Ronseal Smooth Finish Filler”) Its not AS light as red devil but that all that was available at the time:
The results were ok. the most important parts to do fo me was to smooth out the interfaces between the foam and the pannels at the leading and trailing edges.
I used the original cardboard plain shapes as a guide to cut out the pieces of cloth.
The glassing schedule is 1 x 4oz and 1 x 6oz with 4 oz on top:
One side glassed, (both layers simultaniously). I glassed it by wetting out the glass on wax paper first, then simply transfered the glass to the foam, and smothed it down with gloved hands:
Before glassing the other side I had to trim away all the sharp glass spikes. No need to sand em down, just used a set of small wire cutters:
Hereis the rough but fully glassed set:
After some carefull sanding:
But it aint over yet.
The next step is glassing the leading edge. this part still has exposed foam. The reason Im doing it now is because I knew if I tried to wrap the glass around it would have gone badly wrong.
if you check out the 'ryuzo' thread I posted , he has some really nice similar template glassons and fcs'd ones in some of his photos ....[yours may be a fair bit deeper , though , by the looks ? What height [ / depth] , and what length base are yours , please , mate ?]
At the moment the fins are 6 1/2" deep. The cord is 3 3/4" long, while the tip is 2 1/4" long.
They are intended as a quad set up. Zero cant, zero toe. But currently are WAY TOO big! Once I finished glassing, and hotcoating I will cut them down to more reasonable sizes.
These are intended as glass ons. No idea about the board yet. I have two boards on the go at the moment, but I think I will not use these keels for them.
I will try and make a board for these fins at some stage.
When i saw that these had reverse rake, i was worried it'd be so loose i t'd be mostly uncontrollable. Not so. Very loose, but still very controllable. I really love the board!
Very cool! I love that you’re using an actual NACA foil. Some of the handfoiled fins have cross-sections that are pretty sketchy at best.
A trick for doing the leading/trailing edges is to glass one side and let the cloth hang outside the fin. Once that side cures, then lay in wetted glass strand around the whole perimeter of the fin. Then you glass the other side and you’ve got a solid glass edge all the way around. Protects the foam core from nicks, rock chips, etc. and you don’t have to worry about sand-throughs when final sanding.
The whole DIYness of the project is rad. I could see these working well on a really wide-tailed board.
