I have mentioned this before, and so it goes on. Just trying to work out if it’s my own error in construction or not.
All boards I have made for my eldest son (pretty heavy, and heavy footed with it) have these circular compression dents. At first I thought it was putting boards into the water too soon, so I started giving it the full 2 weeks minimum. Then i used UV cure and still did the 2 weeks. Still got the circles on boards. So the last board i went way overboard (I always make boards strong and heavy) and this time I used quad axial glass plus 6 oz on deck. Was told this should be bomb proof. But again we have the circles. He just jump and stuff on the board so it could just be his weight and style, but if anyone thinks it coiuld be my fault in the build, please let me know!
Heel dents are completely normal. I have a carbon/kevlar board with classic density foam that still gets heel dents in it… not as many as a normal board but it still gets them. I would say that maybe your hot coats may be a little thick which is making it shear through the fabric a little but it could just be the darker color of the board which makes it stand out a little more.
Thanks very much. Heel dents - so that’s what they are! He does pound on his boards a fair bit, all these youngsters seem to be hooked on “pumping”. I keep saying “chill out dude, let it flow”, but what does this old codger know?
It’s the resin not moving as much as the cloth and foam. PE resin is comparatively stiff and brittle. You could try using vinylester - that resin is both stronger and more flexible than PE and you glass the same way with it. But the real fix would be switching to epoxy and post curing it. IMO
I’m not savvy to the technical explanation of it all, but I do know that post curing an epoxy lamnation is one way to push the lam into a full cure and maximizing its physical properties. It’s a heat cure where you’re exposing the glass job to an extended period of moderate heat followed by a cool down period. The heat-cool cycle prompts a higher degree of crosslinking in the structure.
If you google the term there are a bunch of articles on it. Some of the glass shops that do epoxy have “ovens” that they bake the finished board in as a means of bringing the temperatute up enough to get that excellent finished cure. The oven’s aren’t the only way to do that - you could stick the board up into the rafters of a hot garage or stick it in a tent covered to black plastic tarp or trash bags, or stick it in a hot van on a summer day. You just need to be mindful that you don’t overheat the board to the point where the foam starts to break down. I’m almost positive we’ve had threads covering this topic on this forum before - this is where I learned about it.
With all that said even an epoxy glass job hat hasn’t been heat cured will still be 2-3x stronger and more resilient than a PE glass job.
No real need for post curing these days. The polymer cross linking works very well in modern surfboard epoxies. However, it will not hurt the board and may get you an even tougher shell.
The location of most of those dents indicate to me that it is not from your son’s heels, but his knee slamming into the board when he pops to his feet.
Does he have a bit of a belly and is a regular foot? I do, and all my boards show this same damage in the same place, no matter how much glass I use. Its worse when I am more out of shape.
I never really noticed my knee slamming the board each time getting to my feet, until the glass cracked enough to cut my knee. I was mystified how i got cut, until I saw some skin and hair sticking out of the deck. The sheer excitement of catching a wave would dull all other senses, and erase memory of the knee slamming incident. It was a bad habit learned early on. Slamming the knee into the deck on popping up was a way to get the board into the wave and down the face in stiff offshores. It is a bad habit I still retain 35 years after learning to surf. Every board I own gets reinforced there, sooner or later. I surf so much better when I am aware of this tendency and avoid the short term tripod on pop up. If your son is still young enough to unlearn this tendency, then by all means nip it in the bud now.
Backside rail grabbing/pigdogging for the barrell can also place the knee in this same area.
Those dents right at the stringer will take on water, starting the delam and board destruction. Hidden under the wax they often get bad well before they are noticed and the delam has already begun.
My custom boards were always glassed triple 6 oz with a third deck patch not just under the backfoot, but up past where my knee would slam the board getting to my feet. Now I ride hollow wood boards and this area is heavily reinforced inside the board, and it is still not enough as the cedar gets soft and splits with enough knee slamming, even glassed on both sides. I layer more and more glass over it, carbon patches hold up way better in my experience, but when the wood needs to be routed out, i replace it with a harder stronger wood
I hear that epoxy is stronger, I’m not sure epoxy is all that much stronger than poly, but it is more flexible. So it doesn’t tend to get those brittle glass cracks that let water in.
What a great post, thanks very much. I think you may be onto something there. He doesn’t have a belly (I don’t feed him enough for that :0-D) but he is stocky and def on the heavy side.
So I better get it back on the stands and do some work on it? What would you recommend? Just rub the areas back to glass, resin and patches until it’s flush and smooth?
He loves the board and so he should as it took 3 times as long as any other I have made for him. The pin lines underneath has made me allergic to pin lines for a while!! So it would be nice to keep it dry and prevent any delams if poss.
I would first sand the indents back, then use a hair drier to gently heat the area. If there is water within it will seep into the sanding scratches. Do not cover until it is dry.
I do not worry about sanding deck patches flush. I am more concerned with not sanding away strength.
I’ve been using the poor man’s vaccuum bag trick. some ziplock freezer bags placed tightly across the layers of saturated cloth and a squeegee pulling the cloth tight from the middle to the edges and removing all excess epoxy. I use tape to confine the resin and put some paper towels at the edge of the tape to absorb the extra resin. When the resin thickens I use a new razor blade, cut inside the tape and remove it, leaving the plastic over the repair. When the epoxy has cured i peel off the plastic and take a rozor blade and knock down teh edges. wax the board and go surf.
The poorman’s vaccuum bag trick can get much more saturated fiber applied for less thickness, and I really enjoy the no post sanding required factor. But keep in mind I am not seeking perfection.
Whats also a good feature of the PMVB trick is it pulls the cloth super tight across the indent, and with no extra resin, which does not really do anything for strength.
I’ve not tried this with PE resin.
If there is still water in the ding then it will blow bubbles through the patch. If you do this in rising temperatures it can blow bubbles under the patch while it cures. I prefer to warm the area of the board first and work as the board is losing temperature and will suck resin into the ding as it cools and contracts.
most epoxyies used for surfboards are slightly flexible than poly (young modulus, ie stiffness modulus) and have double elongation to break. So everything equal if you use epoxy instead of poly on this board you will have bigger dents but no spider web. there is a nice demo of this somewhere in kazuma instagram. for same foam the only way to reduce dents is to increase skin stiffness = increase material stiffness (carbon instead of glass) and or increase thickness (more layers and or a sandwichskin tech to keep weight down). remember each time you double skin thickness with same stiffness range material, you x8 overall stiffness. by compacting lam and reduce thickness, vac bag is worst to reduce dents, better is to introduce air to increase volume and thickness= foaming resin . Windsurfs are build with sandwich skins and lot of carbon on ultra soft eps, they don’t dent even if they take way more loads. But be carefull stiff skins+ stiff stringered foam = stiff board.
For low dents surf,sup and kite, i use 1 to 2mm light wood sandwiched between layers of glass and some carbon for dentless, on mid density eps core, it work. i use foaming resin microsandwich tech too which reduce significatively dents on cheaper, classic look dented boards that surfers like.
i sandwiched a skin a wood layer on a old pu pe repaired long boards for an really heavy guy, no more dent and break for 5 years of heavy used.
Hi Helter. I would say that is not normal on a newer board. Over time all boards get pressure dings. It looks like the foam is crunching around the stringer. Perhaps you are not getting your stringer flush with the foam before laminating or cutting too deep into the deck foam where the foam is softer. Mike
