Advice of DIY Repair

I'm about to undertake my first serious DIY repair and have used the following video posted by Paul van Bellen for inspiration.

I've sustained a number of hits on the front of my windfoil board and have so far been covering up the cracks with squeeze out of the tube epoxy. I've now gone out and bought all the gear mentioned in the video (Westsystem expoyx, qcell, fiberglass cloth, primer filler, spraty putty, etc.) and ready to take the plunge.

I've covered the board with masking tape and sanded the cracked areas with 80 sandpaper. What I've noticed is that there are different levels of damage and I'm not sure if if all merit the full fiberglass + epoxy + qcell treatment

In below pics:
Pic 2 - this is the worse damage, my plan is to follow the steps in the video
Pic 5 - 2nd most concerning damage, Is the black stuff the carbon layer? Should I sand down more to create a V and then apply steps in video?
Pic 4 - I'm on the fence about what to do here. Can/should I get away with something simpler (adding only epoxy or just painting for example)

My questions:

1) Not that I'm seeking perfection but in order to avoid a lumpy finish is it advisable to sand down the surface to "make room" (V shape into the board) for the new fiberglass/exoxy/qcell. In other words should one inflict more damage to the board in order to come out with a smoother finish?

2) Given the extent of the damage, should I simply just apply one long strip of fiberglass from one side of the nose the other. Any pros/cons to doing this. Hoping this might help avoid a lumpy looking finish.

3) What does the spray putty do exactly and why in the video is it applied after the primer filler? Should one ever apply the spray putty first?

4) The video didn't really show the painting stage. What tricks does one use to ensure as clean/straight lines on the paint. I've got masking tape on there but would be surprised if that will do the job.

Thanks in advance for any advice.

Pic 1


Pic 2


Pic 3

Pic 4


Pic 5

If I'd do this repair, I would indeed dig deeper, as you suggest. But more importantly, I would extend the area to go past any cracks that can be seen in the fiberglass. In your pic 2, that would mean going all the way to where the tape is. In pic 4, the crack seems to go at least to the tape, so I'd remove some of the tape. Maybe that seems like overkill, but I have seen repairs that were too small, and needed to be re-done a while later.
I'd also use 2 layers of fiberglass, so I don't have to worry about sanding down a bit too much. If I wanted to reinforce the nose to make future similar damage more likely, I'd certainly consider 3 layers, and use large strips that cover the entire nose at least to where your tape starts. The extra weight is minimal and outweighs not having to do repairs again.

boardlady.com/repairbasics.htm

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Manuel7 said..
Is the damaged area soft when squeezed. You want to inject foam if so.

Then you sand down below level as you'll be adding layers of fiberglass and resin. You'll sand down then use filler, sand again and paint.

Thanks Manuel7.

The surface isn't soft but when I squeeze the board in the area of Pic 2 there is a little bit of movement (I can compress the sandwich slightly and then when I let go it pops up again).

Having to insert foam sounds like a new rabbit hole I'm uncertain I'm ready to go down so keen to avoid if possible.

Agreed. Stop overthinking it. Sand all the paint off the nose. Then 3 layers of 4 oz over the whole lot, make them progressively bigger to save on filler

Fill over with resin and q-cells, or auto bog

Sand.

Then watch the painting video.


(For any continuing unbelievers on nose softness - like the whingers on Yoochoob - if it is a little soft around the crack, that's natural and you don't need to go nuts rebuilding the sandwich. In the middle of the board you would, as its highly stressed. Heel dents, you would. Etc.
However the nose is not stressed at all. You can glass over soft (ish) bits. Think about it....... Spend days cutting out large areas, reshaping styro, heat forming PVC foam, vac bagging it on, blending it out, then glass and carbon and fill and paint. Etc. Then the rounded, small diameter, very hard mast hits it again at 60kph. Will it fare any better than the above nose with 3 layers of glass over? Nope.

Thanks all for all the great advice. I finally took the plunge today and applied the fiberglass and epoxy to the sanded nose section. It's all dried now after about 3 hours and for the most part I'm happy with it. The area of concern though is the area which had the most damage (down to the exposed sandwich). When I push down on this section it's not solid like everywhere else on the board, it sort of squishes down like there's a gap between the sandwich and the fiberglass I've applied.

Have I buggered this up or will the qcell harden this up?

I'm not after perfection but the squishy feel doesn't seem right. Any advice appreciated.

Just out of curiosity: What exact resin did you use? Mine will not be hardened in 3h. Maybe it is not sticky anymore, but it will take 24-48h to harden. Better leave it as ist is and wait.

as said, epoxy takes a while to harden after 3 hours that will still be very soft.
That area does look a little low, some smaller lengths of cloth over that gap in the sandwich, to bring the level up to the rest of the rail will help a great deal.

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cleverku said..
On reflection I think the error I made was to apply a large piece of fiberglass to the nose rather than start small and build from there.

Hopefully smooth sailing from here on. I'll make sure to post pictures of the finished product to seek praise and admiration

I remember reading online that Boeing and Airbus have opposing views on how to feather in, in their case, carbon fiber for a repair. I don't recall which was which but one recommends starting with small pieces and building to bigger pieces and the other just the opposite. ie don't worry too much about this.

Edit: mansbergeraircraft.com/Aircraft Composite Repair Design Paper.pdf page 5

"Two different methods of scarf joint lay-ups are currently being used. In general,
military specifications and Boeing use a lay-up starting with the smallest ply down first and
building up to the largest ply last on the outside. Airbus and many European aircraft
manufactures use a reverse method and start with the largest ply down first and the smallest ply
on last. In the Airbus method the orientation of the laminate schedule must be reversed and the
lay-up becomes a mirror image of the original skin. "

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cleverku said..
Quick update on this. As many suggested the epoxy just needed a bit more time to set. It's pretty solid now that I've given it 24 hours. Though feeling firm to the touch, the area in question does make a different sound when tapped. Not sure how to describe, more of a higher pitched "tapetty" sound than a lower pitched "donk" sound. I'm inclined just to leave it as is and move on to the next steps, I'll likely need to fix it up again soon following my first catapult anyways. On reflection I think the error I made was to apply a large piece of fiberglass to the nose rather than start small and build from there.

Hopefully smooth sailing from here on. I'll make sure to post pictures of the finished product to seek praise and admiration

What you are saying then is that the repair does not sound "hollow" like the rest of the board, I think. In my experience, that is common because the repairs I make tend to have a little bit more layers than the original layup.

looks great! Now you'll be really upset next time the mast/boom crashes into it.
My thoughts on a tapered build up.
I normally aim to put on more cloth than needed, so the outer layers will get sanded back. so it's better these layers are the short ones, other wise you'll loose tension strength when the full length fibres get sanded away.

Then of course, if you're filling in a valley, fibres across the valley will be pulled up under a tension strain. So there are reasons for doing it both ways, for best tension strength the fibres need to be at least straight or better, convex. So I'd start the base of the valley with short lengths, then use full lenghts approaching the surface level.

So I've made arguments for both cases, maybe go for a hybrid