Mysterious pressure dings on bottom side of rail

Once again, seeking some wisdom from this great community after coming up short in my searches. About to glass my 4th board, and want to make sure that I’m following best practices when it comes to the strength of the layup just below the rails. I realize the solution may be obvious, but just in case there’s more to it, figured I’d ask :slight_smile:

On 2 of the 3 boards I’ve built so far, after just one and two years of use, they both have 20-30 small pressure dings about the size of a fingerprint on the bottom surface, most of which are about 1-3 inches inboard from the apex of the rail, and most of which are in the six feet that makes up the middle of the board lengthwise. They are also mostly on the left side. The cutlaps are 2 inches, so about half of the dings are in the cutlap where there are two layers of glass, and half are just inboard of the edge of the cutlap where there is only 1 layer of glass.

These are noserider style longboards of PU/PE construction (the one in the photo is stock density foam (blue), and the other one not shown is ‘cruiser weight’ density foam (green). The glassing schedule for both is 1 x 6 oz on bottom (plus fin patch) and 2 x 6 oz on the deck (plus 6 foot long 6 oz. deck patch starting at 12 inches from the tail) - cut lap style lamination with first deck layer ending at rail apex and second deck layer wrapping onto bottom by 2 inches. All the glass is E-glass. When shaping I minimized foam removal on the deck, so the bulk of the foam removal was on the bottom surface, exposing some softer foam from what I understand about PU blanks.

I have a theory as to how the dings got there. I usually store the boards on the floor with the right rail down against the floor on a towel, bottom of board facing towards me. To pick up the boards I grab the left rail with my two hands with 4 fingers on the deck side and the thumb on the bottom side. Squeeze and pick up. The boards are pretty heavy at 18 lbs for the 9’2” and 21 lbs for the 9’10”. The funny thing is I never feel like this method results in a pressure ding from my thumb or fingers, nor do I see one occur while I’m picking it up (although my son uses them too), but alas, they are there. Assuming my theory is right, I have started lifting up the board from the bottom rail to keep things from getting worse.

Assuming that theory is true (although please share any other theories) then I wonder why has it not happened on a few other boards that I did NOT build, namely an old Bing, and an old Hank Warner Throwback - clearly a testament to their solid construction. I bought them both used, so have no idea of the glass schedules on them. Their weight is in the same general range as mine for their sizes. These have been stored the same way and picked up the same way for the most part, and I’ve owned them both over 20 years. I realize the dings I speak of make little difference to the performance, but I’d like the boards I build to be top notch in durability and aesthetics.

Has anyone seen similar issues, and if so what you would suggest to make this part of the board stronger? I’ve read about letting both layers of deck glass wrap around the bottom (slightly staggered) as opposed to cutting the first layer at the apex of the rail, but not sure if that’s a good idea. Or I could add another layer of glass on the bottom perhaps. Thank you all in advance for any guidance or ideas you’d like to share.

I have had very similar marks on a few boards. I deduced that many were from jogging around to the point, which is a km or two, with a bag on my back. The buckles and the contents of the bag, flippers and hand plane, bouncing against be board, also where the leggie sat against the board during the same process. This could have been avoided by bigger laps and a 6 oz and not a 4 oz bottom lam. This is just my board and what I found. it was from a stripped and recycled blank and glassed in entropy epoxy. I found that epoxy can be a little more prone to depressions, especially if its over soft foam. As in foam that’s been shaped a fair way in from the outer crust.

Thanks sk8ment. I do frequently walk a long way carrying my board as well.

every time I loaned my board to kimo, they came back with … he works hard landscape gardening, strong hand tool musscles, i told im to wrap his arms arround the board on push throughs, I dont lend him my boards and encouraged him to make his own. when you are pushing through a big srong wave ,do you tend to grab hard/ 3’’ laps? over six foo affected area? my guess strong unchecked gripping… …ambrose…

How do you transport it? might come from there…

This was my thinking as well. I get those same little dents from strapping my boards down, in warm weather the epoxy softens a bit, and the straps will make a little indent.

I think you get these from holding your board to tight when going under waves. This might be why you get it on some boards but not all. It just depends on how hard you squeeze on any given wave. Most times these dents are right where you hands go when you’re on the board paddling.

Thanks for your thoughts on this Ambrose, Huck, Mike and Billy. In my case, it’s not the transport since it goes inside my truck 95% of the time. I think it’s a combination of squeezing it when I lift it from the floor to load it into the car, and also like Billy says, probably I get some pressure dings when I grab the rails for turtling or ducking through waves.

If anyone’s got methods/ideas for beefing up the rails, I’d love to hear about it. Maybe I’ll do my next board in 7.5 oz. volan instead of 6 oz. On my recently completed board (pics attached) when doing the deck lamination, I did cut the middle layer of 6 oz cloth past the apex by an inch or maybe a bit more, but I’m not too hopeful that will protect it from these pressure dings made by finger tips. But this board is for my daughter, so maybe her grip won’t be as damaging as mine. Time will tell :slight_smile:

ditto! and as huck has mentioned, epoxy if not post cures has a low Tg, whhich means it will deform on a nice californian summer day. where you pressure hold it with your fingers.

conspicuous cut lapsas far as fingers reach
reinforce oh and let the board cure.
hump said two weeks the strength increases
200% but thats just a boat builder I know stuuf
comment but riding them the day after the get glassed
they ars SOFT.
and whatt’s Tg ? temperature ? gradient?..Aoe

The Glass Transition in Epoxies. The glass transition, Tg, is the temperature at which cured epoxies go from being rigid and glassy to being rubbery and more flexible. Most of us think of cured epoxies as being pretty hard (Shore D) materials; and they are, due to the crosslinked nature of their molecules.