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Lightwind kiteboard build, planing ahead

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phuqit
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Re: Lightwind kiteboard build, planing ahead

Postby phuqit » Sat Jul 07, 2018 12:30 am

Alright, first test results are in. I am not at all convinced infusion is the way to go now. While the 250g unidirectional carbon + 200g biax works just fine when laminated upon red cedar, and ~60cm x 20cm piece holds my weight just fine, I need to figure out how to laminate it consistently... Vacuum wasn't perfect though, first lesson learned...

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Re: Lightwind kiteboard build, planing ahead

Postby phuqit » Fri Jul 13, 2018 12:09 pm

Alright, finally started with the real thing. Made a shape from the PVC board, then cut out the core ~1cm less than the final shape, will be sanding the edges and tips from 10mm to 3mm, then will pour the epoxy + carbon powder rails and inserts/fin reinforcements. Can't get proper PU or ABS rails within reasonable timeframe, so epoxy will have to do for now.
IMG_20180713_134839.jpg

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Re: Lightwind kiteboard build, planing ahead

Postby fluidity » Sat Jul 14, 2018 3:50 am

phuqit wrote:
Fri Jul 13, 2018 12:09 pm
Alright, finally started with the real thing. Made a shape from the PVC board, then cut out the core ~1cm less than the final shape, will be sanding the edges and tips from 10mm to 3mm, then will pour the epoxy + carbon powder rails and inserts/fin reinforcements. Can't get proper PU or ABS rails within reasonable timeframe, so epoxy will have to do for now.
I see your belt sander on the table. I've stayed well away from those things for years now! Fast but terrible for getting a flat surface!
Got my own vacuum pump now as I'm also gearing up for some infusion moulding 8)

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downunder
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Re: Lightwind kiteboard build, planing ahead

Postby downunder » Sat Jul 14, 2018 12:42 pm

No need for perfect flat on top, providing the wood IS dressed well.

phuqit
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Re: Lightwind kiteboard build, planing ahead

Postby phuqit » Mon Jul 16, 2018 12:36 pm

I've finished the core - it was 3-4mm at the tips, and ~9mm at the center. Gradual thinning was done starting around 5cm from the pads area - hopefully that doesn't compromise the strength of the core too much.

Then, I've done the rails. It was messy as f***, infusion epoxy gets into every tiny little hole there is. I've used a PVC blank as base, and a cutout of a real board in same PVC sheet. Laid it down, pressed it down with bricks, then poured epoxy + 10% of carbon fiber powder mix into the rails. It started coming out from every possible hole there was, had to move it onto a plexi sheet to avoid damaging my living room floor :)

Putting the inserts failed miserably as well - I should have secured the bottom with a tape first, now half of the epoxy just bled out onto the bottom. Separating the outline PVC board from the bottom wasn't trivial either - cut my fingers couple of times - epoxy+carbon is sharp! Destroyed the bottom PVC board when doing that, too - it broke in a couple of places. Other than that, the rail is pretty tough - made a few samples, tried to break them with a hammer - no luck. Will use the same compound to pour fin holders and fins themselves, just for fun.

Now, I need to sand off the extra epoxy and trim the rail (outline moved during the rescue-the-floor phase) to something like 5-6mm. Gotta get myself a respirator for that, carbon dust is bad for your lungs I hear.

Other than that, I'm quite happy with the result. Sanding and pouring the inserts (again) tomorrow, and laminating (hopefully) in a couple of days. With luck, I should be able to test drive it over the weekend!

not final, I thinned it quite a bit more
IMG_20180713_181417.jpg
playing Queen - Under pressure ft David Bowie in the background
IMG_20180713_194419.jpg
top view
IMG_20180715_174240.jpg
bottom - dat bleed radius :(
IMG_20180715_174311.jpg
insert, barely stuck with all the epoxy that bled out
IMG_20180715_174337.jpg

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downunder
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Re: Lightwind kiteboard build, planing ahead

Postby downunder » Mon Jul 16, 2018 1:02 pm

Good effort man!

It's a journey which counts, not the destination:)

To help you with the destination, a lot can be 'premade', and the rails are #1 to solve before going further :)

I'll post again how I'm doing it and how fast this can be once you crack it!





Trust me, well worth of investing in a mold etc...

D.

phuqit
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Re: Lightwind kiteboard build, planing ahead

Postby phuqit » Mon Jul 16, 2018 1:21 pm

Hey mate, I've read all your posts, and I appreciate the amount of know-how you bring into the discussion. I'm just trying to get something going as soon as possible, and waiting for shipment from USA is a bloody showstopper. Can't get proper PU here in EU :(

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Re: Lightwind kiteboard build, planing ahead

Postby thewindego » Mon Jul 16, 2018 9:54 pm

Next time you might want to try no abs or epoxy rails just let the top skins meet and add another 1in 20oz glass or so around the perimeter instead. If you look at a new boards like to ozone torque as an example.

I have been doing this for some years in a pneumatic press with great results. The thickness is easily adjustable and no headache with pouring rails as you have experienced.

I go for 2-3mm rail that is 80oz eglass thick. Solid as heck and if you ever do really mess it up totally repairable. The tips and fin area is only glass and makes an area to adjust flex. I have done various rails fills with abs/pvc/pu /epoxy /hdpe and have now find this the best...your mileasge may vary.

Cheers
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Re: Lightwind kiteboard build, planing ahead

Postby phuqit » Sat Jul 21, 2018 3:27 pm

Alright, a status update. We've built the board using vacuum resin infusion. The top came out perfectly, the bottom, not so much. Had to manually resin out the patches of dry carbon, not sure how much structural integrity I lost by doing this. The bottom is not exactly even, I covered it with another layer of UV resistant resin using a paintbrush. The epoxy rail has a few tiny cracks from coming in contact with the rough tile floor, but nothing major. I've laminated it by using the following:
300gr biax
250gr uni
wood core (3mm at tips, 9mm at the center)
250gr uni
300gr biax

I just folded both layers of carbon in half over the wood core. This worked out just fine. On top, I added a peel-ply, and infusion mesh, which was approx 10cm shorter than the peel-ply, to act as a resin stop. That last bit took a lot longer to infuse, but worked out just fine.

Used approx 1kg of resin, and used the leftovers to cast the fin holders, which turned out great.

24 hrs later, I opened it up, noticed some dry patches at the bottom of the board, and gave very few fucks. Wetted them with some faster curing epoxy resin, squeezed out the extra by pressing it down with my palm, and let it cure for a couple of hours. Then, added another layer of epoxy, to both top (which had a rough finish from the peel-ply) and bottom. Cut the rough shape out using the jigsaw, then sanded the edges using a belt sander - until it reached the epoxy rail. Formed it to not be completely square, but at slight angle (bottom plane being ~1mm shorter).

Then, attached the rail inserts, found the pad inserts using a ball neodymium magnet, drilled the holes (which were filled with candle wax), and made sure the M6 scews are going in properly. I somehow managed to fsck up the hole distances though, will have to redo this - these ones work just fine for my 9y/o son though :)

Tried it out using my 21m kite in 4-6m/s wind, and it worked wonders - reasonably stiff, cuts water like a knife going through butter, zero splash, I even managed a few jumps, but they were compromised by the uncomfortable pad positions. In general, I would call it mostly a success - I got what I wanted, and I learned quite a few things in the process.

Few things to do differently for the next board:
-Use a thinner core. 9mm at the center actually bent worse than the thinner tips, so the rocker profile is somewhat weird. Works just fine though.
-Bottom concave (used a simple 1cm height wood plank under the plexiglass rocker table) - worked out great, but the resulting concave was like 5mm.
-Paulownia instead of western red cedar - cheaper, lighter, probably easier to machine.
-Extra layer of epoxy is probably redundant. Vinyl film is probably a better idea: https://www.aliexpress.com/item/8-15-20 ... 07219.html
-To make sure infusion works on the bottom, make 1.5mm holes at 5cm intervals, and tiny grooves diagonally to them. Pretty sure that would solve that dry patch issue.
-ABS rails. Found a 3mm x 1m x 2m sheet @ 40€ here locally, will try to cut out something like 1cm wide strips, and place them on the edges, and bend it with a heat gun. After I sand and flame it, of course.
-Inserts are probably fine to do with epoxy+carbon powder mix, just make sure I tape the bottom of the hole, or don't route it completely through, so it doesn't run out. I'll give it some more thought, perhaps pressing the flanged nuts into polyamide or nylon holders would be better? Not sure if epoxy binds to PA or PE11 though...
-Anything less than 3mm thickness is very hard to machine using a belt sander. I'll probably just cash out for the CNC job.
-300 biax +250 uni each side is bloody strong and flexible. If I can CNC the edges of the wood core to 2mm, it would probably be perfectly strong and flexy enough for kiteboarding. I could probably use the same amount with a foam core.

Some photos of the process and result:
IMG_20180717_204429.jpg
IMG_20180718_000845.jpg
IMG_20180718_000859.jpg
IMG_20180718_102344.jpg
IMG_20180718_105025.jpg
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IMG_20180719_081303.jpg
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IMG_20180719_084953.jpg
IMG_20180719_090713.jpg
IMG_20180719_223615.jpg
IMG_20180721_162043.jpg
Infusion video:
https://photos.app.goo.gl/CfyaMrMNfMBbU4Qw5
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IMG_20180719_082308.jpg

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Re: Lightwind kiteboard build, planing ahead

Postby rynhardt » Sat Jul 21, 2018 8:16 pm

First of all.. congrats on finishing the board! :thumb:
phuqit wrote:
Sat Jul 21, 2018 3:27 pm
Few things to do differently for the next board:
-Use a thinner core. 9mm at the center actually bent worse than the thinner tips, so the rocker profile is somewhat weird. Works just fine though.
-To make sure infusion works on the bottom, make 1.5mm holes at 5cm intervals, and tiny grooves diagonally to them. Pretty sure that would solve that dry patch issue.
-ABS rails. Found a 3mm x 1m x 2m sheet @ 40€ here locally, will try to cut out something like 1cm wide strips, and place them on the edges, and bend it with a heat gun. After I sand and flame it, of course.
-Inserts are probably fine to do with epoxy+carbon powder mix, just make sure I tape the bottom of the hole, or don't route it completely through, so it doesn't run out. I'll give it some more thought, perhaps pressing the flanged nuts into polyamide or nylon holders would be better? Not sure if epoxy binds to PA or PE11 though...
-Anything less than 3mm thickness is very hard to machine using a belt sander. I'll probably just cash out for the CNC job.
-300 biax +250 uni each side is bloody strong and flexible. If I can CNC the edges of the wood core to 2mm, it would probably be perfectly strong and flexy enough for kiteboarding. I could probably use the same amount with a foam core.
1. Do you mean the rocker flattened out and bent the other way between the foot pads? 9mm thickness in the centre with 250gr carbon (0 deg, I assume) both sides should be plenty stiff, especially with some concave.
2. Yeah for infusion you want to have plenty of tiny holes from top to bottom, with the grooves crossing the holes at the bottom - this will prevent the dry spots. Have a look at the core at the end in the video below, prepped pretty much as you described above.
3. Depending on how expensive your ABS is, you can either cut strips and bend them, or cut the entire outline (see pic below). I've had good success with just an alcohol wipe,abrade, alcohol wipe regime for bonding the ABS. I haven't flamed it and my boards have held up fine so far.
4. My inserts are mounted inside an ABS rail (pic below). This was for my split board, so there's extra inserts in the middle which you can ignore.
5. Machining with a belt sander takes enormous finesse.. lots of guys use a router instead. In the video below I use a router table with a profile.
6. Yeah, your carbon layup would be fine with a foam core and is probably over specced for a wood core.

Anyhoo, my 2c.

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