Saturday, October 17, 2020

Spencer's Board Repair

 My friend Spencer had a little problem with his board:

Thanks to Kalmus chop, it had developed a crack, as if ready to break into two pieces. Spencer has several newer boards, both larger and smaller, but he really likes this one. So I said I'd have a look. I thought there was hope because the crack did not go all the way to the other side:

But there was a soft spot on the end of the crack:
First thing to do was to have a look inside:

Sanding off the top revealed a layer of carbon-kevlar fabric - nice! That stuff it really expensive, and the kevlar is almost indestructible. It was covered by a thin layer of fiber glass. The kevlar is probably why the board did not break all the way. On the other hand, the construction meant that just a partial layer of carbon provide all the structural strength. Carbon is quite brittle, so it just broke. Below the carbon was standard sandwich construction: high density foam (in a somewhat unusual bright red color), a thin layer of glass, and then the EPS core.

I cut out some of the sandwich layer, and removed a bit of foam underneath that was damaged:
Overall, the EPS foam was still in good shape, so I did not have to remove much. I then used polyurethane pour foam to rebuild what I had cut out:
Next, I had two options on how to proceed: rebuild the sandwich, or just glass over the foam. In nose repairs, I usually just glass over. That's good enough for typical use, and it the mast hits in a bad catapult, even a sandwich will break. But in standing areas, I discovered the hard way that rebuilding the sandwich is a better choice. The affected area was a bit a grey zone: it's in front of the foot pads, so it won't be exposed to the full stress of planing though chop, but it will get some load when not planing. 

One issue here was that the kevlar does not sand well - it just gets all fuzzy. That would have made a smooth connection of the new sandwich harder. Other factors were the age of the board, and that the short days severely limit how much time I can spend doing repairs. Finally, it is possible that the internal damages is worse than it seems, and that the board will soon break completely, anyway. So I decided to just glass directly onto the foam. The cut out area got an extra layer of 6 oz carbon, and the entire crack got a layer of 6 oz carbon and a top layer of 4 oz S-glass. Here's what it looked like afterwards:
Now it just needs some sanding, a top coat, and some anti-skid. I'll skip the painting for now so that any damage that might indicated a pending break will be easier to spot. Spencer can always paint it later :-).

Sunday, October 11, 2020

Egg Island Videos

Gonzalo jibing at Egg Island

Yesterday brought some warm south westerlies around 30 mph, which drew a crowd of windsurfers to Kalmus. I escaped to Egg Island, with Jon and Gonzalo keeping me company. The trip to Egg Island near low tide was easy, with only moderate chop:

It was nice and flat at the outer sandbar for speed runs:

Jibing in the flats is always fun - here's Gonzalo and Jon up close:

We took turns standing in the warm water and holding the camera, which gave me motivation to plane through a few jibes:

Here's one filmed with the Clew View mount:

Jon and Gonzalo played around with duck jibes - here's one from Jon:

The wind at Egg Island was a bit lighter than in front of the launch at Kalmus, especially a bit further into the bay where the wind came across Great Island. A larger board and/or a larger sail than my 3S 96 and 4.7 wave sail would have avoided a bit of slogging every now and then. But on the way back, I was glad to be on the small board and sail, since the chop had gotten bigger, and I was quite nicely powered. Rocktober rocks!

Here are yesterday's GPS tracks:

Thursday, October 8, 2020

It Floats

After a surprising number of delays, Nina's new wing board finally hit the water today at Barnstable Harbor. Despite multiple rounds of epoxy coating, the board floated! I think it really helps that epoxy is lighter than salt water. On the other hand, Nina was able to carry the board to the water without being utterly exhausted, so perhaps it's not quite that heavy. Well, I did spent many hours sanding it, so maybe I removed a lot of that epoxy again, after all!

Fortunately, Nina had not problem wing foiling on the board, either, and actually like it. I think she did have problems seeing the board in the original foam blocks when we bought them at the local Home Depot, and ended up a bit surprised they ended up as a functional board. Here are a couple of pictures:

The board is unpainted; the colors are just a bit of pigment added to the top layer. This leaves the glass layer semi-transparent, so you can see every little issue underneath. Leaving the board this way should help us spotting any issues (like delamination) before they become a major problem. Perhaps more importantly, it also let Nina use the board a few days earlier.

The board is about 80 to 85 liters, 5 feet 5 inches long, and 26 1/2 inches wide. The weight is and shall forever remain unknown. The color scheme (with the foil) reflects the nationality of builder and rider :-)

Sunday, October 4, 2020

Foil Jibe Rig Flip and Bubbles

Time for an update on my two current favorite topics - the foil jibe and Nina's wing board. As you'll see, both have been quite frustrating, but there is hope. Let's start with yet another foil jibe crash video:

This is one of my better tries, since at least I stay up on the foil the entire time. But the ending is quite typical for many of my tries: the rig ends up on the outside of the turn and a bit behind me. From there, I can't get it back to where it belongs before I crash. Often, the board starts turning back into the other direction; in the worst crashes, the inside rail comes up, and I fall to the inside of the turn, towards the foil. 

I started a discussion asking for tips how to fix this problem on Seabreeze. I got tons of tips, but none of them really clicked fully. Eventually, I found a tutorial video that shows exactly the same crash (at 5:51 in the video). Right now, the link does not seem to be working, so I just show you a screen shot instead:

Letting the mast go so far to the outside puts so much weight on the wrong rail that the board just turns back. Heroic efforts to pull the rig towards you don't work either on the foil - they just make the crashes more spectacular. 

I knew that this was the problem, but I did not realize why this was happening in most of my jibes (in some other crashes, I would pull the sail too far to the inside of the turn, so both sail and I ended up falling to the inside). Then, someone on the forum pointed out that in the good jibes in the video, the foiler moved the mast to the outside of the turn just before flipping the sail:
The mast is quite far on the outside - the left arm is fully extended to the side! But he manages to complete this jibe without any problems. This is very different from my jibe tries. I always tried to keep the mast to the inside of the turn the entire time. To make sure the mast would not go to the outside before I released the clew hand, I moved my front hand to the mast early, and did not move my back hand further towards the clew.

Then I remembered something I learned a long time ago in ABK camps: for the rig to flip "weightless", it needs to rotate around its center of effort, and not around the mast! The top of the mast is making a circle in the air as the rig flips when it flips this way, and there is no pull. But if the mast is pointing straight up (relative to the board surface), then the clew swings around, and the swing weight makes the flip "heavy" - you have to muscle the rig at the end.

In the session in my jibe crash video above, we had pretty good wind around 20 knots. My GPS showed that I was usually going at 10-12 knots when dead downwind in a jibe try, to I still had 8-10 knots of wind in the sail (and a bit more ifI flipped too early or too late). That made the sail flip quite quickly, which in turn increased the apparent weight, and made the rig "escape" from me to the outside of the turn.

The funny thing is that I remember my very first jibe tries on the foil: they were my best tries. I did not foil through, but I sometimes kept enough speed that the board never stopped planing, and I could get back up on the foil right away afterwards. But then, I started thinking and looking for advice ... and things started going downhill.

The one bit of advice that messed me up in particular was "keep the mast in front of you" or "keep the mast to the inside of the turn". In the "How to Strap to Strap Gybe - Windfoiling" video from Sam Ross that I talked about in August, Sam says "keep the mast upright and in front of you", and that does seem to work well for him. But he is on a faster foil in less wind, so his apparent wind during the sail flip is close to zero. That means the sail rotates slower and with a lot less power - it never escapes to the outside.

Thinking about this made me realize that I have a similar problem with the heli tack on the windsurfer in planing conditions. I can do heli tacks all day long in light wind, including one handed and (sometimes) no-handed versions, and pausing in clew first position. But the windier it gets, the more problems I have with the rig flip. In 15 mph, I may still get some dry heli tacks; but in 20 mph or more, my success rate drops close to zero. The problem? The rig flips too quickly and with too much power, so I end up off balance and cannot bring the rig back into sailing position. The cause? In more wind, I tend to power the sail up to much, which forces me to also lean the mast more to windward. When I then start the flip, the sail does not rotate neutrally! Do you see the common theme here?

So, next time I get a foiling session, I'll work on letting the sail rotate in a neutral position. I'll just have to put an Andy Brandt voice yelling "level the clew before the flip!" into my head! Somewhat counter-intuitively, letting the mast move to the outside of the turn right before the flip should make it easier to get it in front of me at the end of the flip.

Now to Nina's wing board (the "bubbles" part of the title actually referred to some problems I ran into with it, and not to my foil jibe crashes). Here's a picture of the issue:

After trying to "hot coat" the board to seal the little gaps in the fiber glass, I got tons of bubbles, where air escaped from the board while the epoxy was setting. I've had this happen before in repairs before I learned to only glass and seal when temperatures are dropping. So I concluded that I had not waited long enough for temperatures to go down. Out with the sander, and then try again ... with the same result. Maybe temperatures are changing to quickly outdoors, where I did all the work? Move everything into the house, measure temperatures, and try again! This time, I started late in the afternoon, and temperatures outside had dropped for hours before. Nevertheless, bubbles again! This time around, I could even see that some of the bubbles had tried to shrink again - they had little indentations on the top that must have happened in the middle of the night, when the room cooled down and the board finally did, too. 

These tries to seal the board had kept me busy for a few days, but I had gotten nowhere. So I finally bit the bullet and sealed the entire board with acrylic putty, which has a work time of 2.5 minutes. It stinks like hell, and is a PITA to work with, but I coated the entire board. This time, it worked, although I could see that the cool down overnight had pulled the little putty plugs in a bit. Some of them had little round dents in the top that had been absent in the evening. Since there were more than 100 of those little holes in the board, and any single one of the plugs coming loose could lead to delamination, I feared that just painting the board would not be good enough. So I added another layer of light glass to the bottom and the rails to be safe. Since Nina actually wants to use the board, rather than just see me work on it, we decided to just tint the epoxy for this glass layer and the top coat layer. That means she can use the board at least a couple of days earlier. Since the top layers are semi-transparent, it also means we can still see the core and the glass layers, so if the board should show some of the delamination issues that XPS core boards are known for, we'll have a chance to see them early. Now, all that remains to do is  (yet another) round of sanding, routing out glass covering the tracks and the carrying handle, and putting a leash plug in. Hopefully, the board should be ready for her in a couple of days. I am even 99.9% sure that it still floats, despite all those layers of epoxy that I ended up putting on. After all, I tried to sand most of the stuff off every time before trying again! Whether she'll be able to carry the board, which now feels rather "solid", to the beach may be another story...