Author Topic: fairing my gofoil GL210  (Read 2071 times)

jondrums

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fairing my gofoil GL210
« on: September 18, 2019, 11:46:39 PM »
I am seriously considering using some kind non-permanent filler to "fair in" and streamline my GL210 in a quest to eradicate drag and maximize glide.  Going too far you say?  Maybe, but I won't know until I try it - maybe I won't be able to tell the difference, or maybe it'll be revolutionary.  If drag is reduced 5% it would be worth it, and I wouldn't be surprised if it did.  On occasion I feel like I can't get the board moving, and I flip the board over to find a tiny strand of grass stuck on it.  I am continually surprised at how much that little bit of drag is noticeable.

Think I'm crazy? Fine, move along and comment elsewhere.  The rest of you - who has advise on exactly what filler product or mix of products I can use for this?

I'd fill in and sand to smooth the following spots:
The main wing screw and countersink gap
The gap between the fuse and the main wing
The gap between the fuse and the tail pedestal
The two phillip heads screws holding on the tail
run a small fillet radius around the connection between the tail and the pedestal

Together I think these improvements will be noticeable.  But I don't want to forever lock the parts together, so it would have to be removable somehow.  Don't care too much how it looks, it'll be underwater most of the time that matters.
« Last Edit: September 18, 2019, 11:48:22 PM by jondrums »

PonoBill

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Re: fairing my gofoil GL210
« Reply #1 on: September 19, 2019, 07:32:20 AM »
Good idea. The easiest thing to use is wax. I've done this to raceboards before a race, closing gaps in the fin box and smoothing transitions. You might not feel the difference, but if you come up with some ways to measure your drag you can likey detect it. People can't feel 5% changes, the threshold is around 10%. At least that's what car and motorcycle engineers claim. As the late great two-stroke specialist Gordon Jennings "Seat of the pants measures only changes greater than ten percent. Your cherished appurtenance won't replace a dyno or a stopwatch."
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Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Beasho

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Re: fairing my gofoil GL210
« Reply #2 on: September 19, 2019, 08:59:32 AM »
Nice word.  As an engineer my vocabulary was terrible.  Someone used the word 'serendipity' on me and I nodded not really knowing what it meant.  But it stung and I started a database to write down every word I didn't know.  I was 22.  1 or 2 words a day from the NY Times . . .

500 words later and people now consider my vocabulary intimidating, erudite.   That's all it was 500 fragging words.

Beasho

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Re: fairing my gofoil GL210
« Reply #3 on: September 19, 2019, 09:06:40 AM »
Good idea. The easiest thing to use is wax.

I am a fan of clear packaging tape.  I have used this to cover the fin boxes on boards, the right type is nearly waterproof and will last for years.   It's cheap and thin.  Although it does have a tiny edge  ::)

Another pet peeve of mine is weight.  I noticed there are 2 screws in the tail.  They are ~ 1" long with 3/4" of an inch of purchase.  Between the two of them I can therefore eliminate the weight of 1.  On my latest board I didn't use a deck pad.  Those things have to get heavier when wet.  And what is the benefit of covering the whole deck?   I've even been weighing the footstraps (dry) and trying to opt for the lightest least absorbent style. 


clay

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Re: fairing my gofoil GL210
« Reply #4 on: September 19, 2019, 09:47:12 AM »
I heard guys put a Kai foil in a test tunnell/tank and found all the seems joints and such that were causing unnecessary drag and then designed a foil addressing those drag points.

A word of caution on bolts, the purchase keeps the threads from breaking or pulling out.  Neccessary if the bolts are holding stuff together, probably not so much if just set screws.
Aloha, I welcome and appreciate all responses of positivity and good feeling.

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Beasho

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Re: fairing my gofoil GL210
« Reply #5 on: September 19, 2019, 10:00:16 AM »
A word of caution on bolts, the purchase keeps the threads from breaking or pulling out.  Neccessary if the bolts are holding stuff together, probably not so much if just set screws.

Roger that - Go and unthread one of the pedestal tails.  You will be unscrewing a stainless nut for a while.  My gosh this has 3/4" of threading X 2.   The tail wing manages ~ 15% of the lift of the whole rig.  Aka if Wing is carrying 200 lbs.  Tail has to manage 30 lbs.  Should take many threads to handle that maximum threashold.  Add a little for unthreading.   Forward set screw I'm better with overkill.   Cantilevered tail has to bounce up and down.  All about swing weight and sprung vs. unsprung weight. 

JEG

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Re: fairing my gofoil GL210
« Reply #6 on: September 19, 2019, 02:29:34 PM »
I don't wanna go back to weight and drag again, those days are gone and will give me nightmares. I'm good at everything and that's including English language and master of none.

jondrums

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Re: fairing my gofoil GL210
« Reply #7 on: September 19, 2019, 03:12:09 PM »
I assumed in this case that appurtenance = "butt"
which makes some sense - it is an accessory that I use for certain activities.

PonoBill

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Re: fairing my gofoil GL210
« Reply #8 on: September 19, 2019, 07:38:16 PM »
The late Mr. Jennings was indeed using it to refer to "butt" in terms of it being an accessory that doesn't work as well as a stopwatch and a dragstrip.

There are some zooty calculations involving shear area of the female threaded material and tensile area of the bolt, but in most cases, a screw is considered fully engaged when five threads deep and if the bolt is over torqued the bolt should break before the threads pull out.

None of that applies in our case though, since the bolts are generally stainless steel and the female threads are either a bronze/brass barrel nut or threaded holes in aluminum or something equally wanky. I created problems for myself by measuring the number of turns of engagement of every bolt and shortening them to something more appropriate for the part. There isn't much sense in screwing a 6mm tuttle screw in for twenty turns when the barrel nut is seven threads deep. One and a half turns past the end of the nut gives as much strength as the assembly is going to have. So that's how long my screws are. Now I need to keep track of which screw goes where. Bit of a PIA.

Add to that, most aluminum mast and fuselage foils use 8mm screws. I've been sorely tempted to standardize my gofoils to 8mm torx heads instead of the wimpy #3 phillips. Laziness has prevailed so far, but when I start getting ready for Maui there might be a sudden flurry of drilling, tapping, thread counting and cutting. Or not.
Ponohouse is for sale: http://www.ponohouse.com
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

clay

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Re: fairing my gofoil GL210
« Reply #9 on: September 19, 2019, 11:15:08 PM »
Appreciate the math and science and such knowledge.

2 years ago we were foil practicing behind a ski, guy riding started porpoising like crazy, stabilizer bolts had wiggled loose and fell off.  Luckily we found the stab.

Last year on the dog boarder swell at cowells Denton and all the foil crew were out scoring.   I tried an extreme stab shim and didn't like it so I paddled in to change it.  In bolting everything together while the swell was pumping I stripped or broke out the stab threads.  My choices were now:  miss out on a great swell, spend all day looking for a 6mm tap and retapping, or drill and tap with the 8mm tap I had in my tool box.  I choose to Franken drill to 8mm and 90 minutes later I finally made it back out, missing most of the smooth lower tide goods.
Aloha, I welcome and appreciate all responses of positivity and good feeling.

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jondrums

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Re: fairing my gofoil GL210
« Reply #10 on: September 20, 2019, 12:43:01 PM »
I went with packing tape for the first try at this.  it won't be nearly as good as fairing in with wax as Pono suggested, but should be some improvement.
This morning conditions were so terrible that I have to say "the jury is out". 
Benefit of using packing tape is that if I get a consistent day, I can pull off the tape in the water and see if I can tell the difference on back to back waves on the same day.  So I'm excited to try that over the weekend.

Pono, out of curiosity, what kind of wax did you use?  regular surfboard wax or something harder/less sticky?  I'm thinking about that hard wax that is used for investment casting patterns for jewelry.  I think I'd have to melt it into place and then shape it.  Maybe I'm overthinking this, but since you've done it, I'd love to hear what you did before.

jondrums

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Re: fairing my gofoil GL210
« Reply #11 on: September 26, 2019, 11:23:35 PM »
Well I figured out something that DOESN'T work for fairing the gaps.

Freeman Blue flakes - casting wax.  I got blue so it matched the wing color, but I didn't realize that blue is optimized for flexibility.  It didn't stick at all.  Goes on like crap and peels right back off when I tried to "carve" it smooth with a sharp razor.

I used my ski wax iron to melt it and applied with plastic spudger


« Last Edit: September 26, 2019, 11:29:04 PM by jondrums »

jondrums

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Re: fairing my gofoil GL210
« Reply #12 on: September 26, 2019, 11:30:40 PM »
packing tape works infinitely better than crappy wax, but I haven't given up and will keep trying because I know I can do better than the packing tape

PonoBill

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Re: fairing my gofoil GL210
« Reply #13 on: September 27, 2019, 06:57:50 AM »
I use warm water surf wax. Readily available, sticks well, easy to make smooth and well faired with just your fingers, a credit card, or a spudger if you're a complete geek.

Yes, I have a good-sized collection of spudgers.
Ponohouse is for sale: http://www.ponohouse.com
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

jondrums

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Re: fairing my gofoil GL210
« Reply #14 on: September 27, 2019, 11:00:11 AM »
I might just go directly to bondo.  A little wax for "mold-release" in case I ever want to change the wing.
In this morning's session I got a legitimate 2for1 which has been elusive for me in the past.  Maybe I'm getting better at riding the GL210, or maybe its the packing tape fairing...