I recently picked up a 2nd hand Sonic 85 with a couple of very minor patches (knead-it on the nose and sola-rez epoxy on the rail and tail). Given a lack of wind I thought I would have a go at tidying them up (as well as seeing exactly what damage was underneath) Here are few photos of the spots after sanding them back. I reckon I need a couple of layers of glass on all the spots. Starboard guide suggests 2x100gsm cloth and I have some 120gsm plain weave glass and WEST System epoxy. Will 2 layers of this be enough to return it to factory strength?. Also, I've sanded a small hollow in all spots but have not yet got to foam underneath. Am I better to leave the factory layer(s) of glass if they are OK and just replace those that have been damaged? Pictures in order are rail closeup, nose, tail and rail again.

I would go the 2 layers(feathering the edges - top layer 1cm smaller) on each of the repairs but the nose crack i would vee out and fill with epoxy/microbaloons first. I repaired an isonic with a similar crack and there was no pvc foam in that area until about 1.5cm above the rail edge.
You can either do it in 2 steps or glass on wet - just overfill the crack and dab the layup with a brush to fair it out. Another option is to tape the layup to fair and reduce finishing time. Let me know if you want pics...
I have done plenty of these bread and butter repairs and am always amazed at how little and light the cloth used on soft moulded boards is!

Thanks for the reply Kimba. I figured the crack in the nose was going to need a bit of filling before glassing.

They're pretty shallow so two layers will sit proud. I'd sand it out a bit more first and go 3 layers.

www.seabreeze.com.au/forums/Windsurfing/General/repairing-board-advise-please/

Are the nose and tail dings severe enough to warrant a "structural" repair though? My thought was (and please correct me if I'm wrong) that you'd wet those out with a bit of resin then follow up epoxy based filler (resin and microballons maybe),sand smooth and call it done.

I wasn't really suggesting structural repair like replacing d'cell ....... but for the one that is mid-rail area (near Starboard logo) it is a hi stress area so you do want to reproduce the board skin as near as possible to avoid making it too strong or too weak and thus have an area that it is likely to break from again.

Just suggesting that if you don't remove enough material and blend / feather it in, then you have a lot of glass to sand away to get the surface back down to where it should be, and that is where many people stop and then have an ugly repair.
Much better to have the glass about 0.5mm lower than the surrounding area and then fill with epoxy and d'cell

I see.

Mark, the rail repair was my main concern exactly for the reasons you explain - it is in a high stress area. I appreciate the suggestion to sand it back to make the smoothing easier later on. However, if I am prepared to deal with the extra sanding will filling the shallow depressions with 2 layers of glass give the same strength as your suggested approach. I suppose my preference is to maintain as much of the factory glass layers as I can as long as it doesn't compromise the final strength.

Terry, really hard to say without seeing it. Lay a straight edge along it from one side of the repair to the other. As a rough guess if there is a good 2 -3mm of gap in the middle then I guess the depression is deep enough to put 2 layers of glass on.

If that depression is too shallow, you'll put 2 layers on and then sand most of it off to get the factory profile back - which means you may just have some Solarez and half a layer of glass.

It is really hard to tell how much material somebody else put on so I always remove all their repair and start over to be safe.

How likely is it that in forming a depression to put your glass into you'd actually go through and end up with a bigger hole? My impression is that the layers on modern boards are not very think.

Not a bad thing - as long as you don't remove any divinycell

Sometimes the glass around the dinged area can delaminate from the divinycell - just a bit - and you would not know until you sand thru it. I guess I mean the damage can extend further than the obvious dent.

So in one sense a bigger hole is better (bigger area not too much deeper)

Makes sense.