i bought a longboard 2nd-hand (9’6, 74L, polyester, pu-foam). it was kind of cheap (150€) and i knew it had a problem. the guy did a fix himself and explained a lot but i still have some language problems so i did not get it totally.
What i understood is: the board got a big impact and had a crack from side to side on the top deck.
i used it for 3 month but now i realized that there is kind of a crack opening on the upper side next to the fixing. the patch that he put is only about 10cm wide and goes from side to side and over the rails. on the point of the transition from the patch to the board it feels like he grinded a bit to much and removed a bit from the original coat so it became even thinner there. that is also the area where the crack appeared. when i got the board i put a big patch of 4oz on the bottom because there were a few crack lines in the polyester.
alright, long story short, i prepared the board for the fixing and realized that the fiberglass that he put was not very well connected so i could take it of with a bit of effort. lets say i more or less removed everything he did and i found out that the stringer is cracked but it is hard to see just when i put a bit of pressure to the board you can see that there is more space/movement on that spot in the stringer (perspektive from the top). the foam looks ok and everything else is in place i would say.
ok, i am learning to fix surfboards so some questions might sound very stupid. here it comes: do i have to fix the stringer? means cutting out the foam left and right of the broken spot and glueing support wood to it and fill the gaps with foam again? Is there another option? can i use pu-foam of the can to fill the gaps between stringer and foam?
and after i would fill the gap with polyester-micorballons putty, sand it down and then put 2 patches that go from side to side and around the rails. one smaller, one bigger. a bit of sanding again and finally hot coat with surface agent. would that work what i imagine? and if, how big should be the patches? does it make a difference if i put the smaller one first and the bigger on top or vise versa?
of course i will take the of with a vaccuum cleaner and wipe with acetone before adding new patches.
i would love to get some tips. here are a few pics.
How far down and across does the split in the foam go? If its quite deep and out to the rails you might be better off breaking the board and putting it back to together to ensure it doesnt break. Otherwise resin and q cell and two patches and around the rail to where it begins to crown into the deck. I like to put the smaller layer underneath and cut both in a oval shape rather than a straight line across the width of the board. For where the stringer is raised a small block plane should reach it or a razor blade instead if you’re careful. Nothing proud of the foam (stringer).
The short answer is yes you absolutly need to repair the stringer , I cannot see from your pics if the fiberglass is removed from both sides of the board but you would need to support the stringer the whole thicknes from the top deck to the bottom , the support pieces would need to be about 10 inches / 25 cm long and at least 1/4 in / 1cm thick , try to use some strong wood , yes you will have to remove the foam on both sides of the stringer but it should not be difficult with a razor knife , cut the wood to the correct size and glue in place with Gorrila glue or similar , follow the directions for using Gorrila glue its important , allow space to clamp the support pieces to the stringer , must be very tight , after you have done all this and alowed time for it to dry/set up , recheck the flex at the stringer if good everything after that is easy , let us know .
Yeah he did. Likely a wave broke on it when it was floating bottom up
He likely ground away too much of the original cloth and the repair was waaaaay too narrow. 10cm? Really? Probably a single layer too? Seriously? He hacked it, man.
I would inlay cloth in where the original cloth is missing or sanded away, to bring it up smooth as well… This won’t’ hurt the strength any and it will look best.
As suggested, I’d use two layers of 8 oz cloth, one more like 30 cm wide, side to side and well lapped over, then another on top of it that’s wider still. 50cm wouldn’t be bad. You may want to sand the edges of the bottom layer so the top layer lies smooth. And yes, if the bands are more of an oval than a straight strip., that’s good. You don’t want a side to side straight line where the board’s strength changes abruptly. With something like that the board is likely to break again right at the straight edge of your repair. Seen that happen more than once. A single layer of 8oz on the bottom might be a good idea too.
But first you need to make a jig or fixture so that while you are doing the job it stays put and the original rocker is preserved. . You mention you can flex the board now, so unless you set the board so it’s firmly held with the right curve to the bottom it’s going to be off, rocker ruined. A table plus some wood slats to hold the board and rocker will work well or a fairly rugged plank on top of your sawhorses plus some spacers will work fine. , I like to hold it down while I do the first layer with straps like you would use to strap the board to the top of your car.
Not a stupid question, though you will get some stupid answers.No, you don’t have to fix the stringer. In fact, you would make the job far more complicated and real ugly for pretty much zero additional strength.
Look, when you think about it, did the stringer keep the board from cracking? Nope. Contrary to popular ‘surf science’ narrow stringers (under 20mm thick) don’t really contribute much to the strength of the board.
What do they actually do? Well;when a blank comes out of a mold it generally is fairly flat, little or no rocker. So it is cut right down the middle, the halves are bent to the desired rocker and glued to a stringer down the middle to hold that rocker. It doesn’t take much, which is how they get away with such a thin piece of wood. They also used glue impregnated paper at one time and that worked just fine.
The other function of the stringer is to give the shaper an easy centerline to work from.
The real strength is in the laminated glass on the foam… Fix that and your board is strong again.
One more thing about adding wood and so on. Remember I mentioned that you don’t want any abrupt changes in how stiff the board is, as the thing will break there? Yep. Don’t do it.
Well, I kinda covered that, but it doesn’t hurt to go over it again.
Don’t waste your time futzing with the stringer at all. Do make sure the rocker is good before glassing.
Fill the shallow spots with cloth. Sand flush with the original glass. Sand the original cloth/hot coat lightly to get a good bond with the new cloth. Get the dust off. I like a white cloth with a little acetine, Watch out, if you use colored cloth, well, the acetone can dissolve some cloth dyes and you get color where you don’t want it.
I would glass like this. Use 8 oz cloth for all.
Deck- a patch with curved sides, like a narrow oval, call it 30 cm wide tapering to 20-25 cm at the ends, rail to rail and lapped what, 5cm onto the bottom. Squeegee well, you don’t want extra thickness. Let that harden. Sand the edges if it’s too abrupt.
Carefully turn the board over, preserve the rocker.
Bottom patch - similar oval, lets make that 40 cm wide tapering to 30-35 cm, lapped onto the deck 5 cm on each end, squeegee and sand edges like you did with the deck patch.
Turn the board over. Your rocker is now set.
Now, a deck patch over top, make this one 50 cm wide tapering to 40 or so, again lapped onto the bottom. Hot coat with surfacing agent just as you describe, sand and polish as need be and there you have it.
to clear things. the bottom was not broken. there are a few lines but they look like that they are only in the coat and not in the fibre. i put a large piece (almost 50’') to reinforce before i started using it but unfortunately i did not go around the rails and i did not cut them oval. i do not remember if it was 4 oz or 6oz what i used. i will put another patch from the bottom as you say.
at home i have 4oz and 6oz and the supply i usually go doesn’t sell stronger than that. would you say 6oz is to thin? more layers? does it make sense to mix 4oz and 6oz?
the foam is totally fine as i see it. there is a ditch on the top but that is not even half a centimeter deep and mainly from foam that got removed with the fiber/polyester.
the movement on the spot where the stringer is cracked is very little, maybe half a milimeter. i would also tend to not fix it because i will take out quite a bit of foam that i will not be able to replace so precisely. i would try to inject a bit of polyester into the crack of the stringer from the top - good idea or just let it be?
i will pay attention to the rocker - thanks for the advice, in fact the first board that i ever fixed was a softy and it has almost a negative rocker now. it was not very good before but now it is useless
thanks a lot again. i will continue now. lets see.
Right, that’s why I figured it was bottom up and hit by a lip. The glass on the deck failed in tension, possibly there was some damaged glass there that was where it all started. Do enough of them and you get curious about what causes breaks, there’s usually a weak spot that triggers it. Anyhow-
6 oz will be fine. Maybe a little better, as the strength doesn’t change as much with each layer and it’s thinner so you can maybe get away without sanding the edges of each layer… Use one more layer, if you like, start with a narrower one as the first layer on the deck.
That’;s what it looked like to me as well, it failed in tension from the deck, no foam missing or permanently compressed, so you don’t have to make up for that to keep the rocker. I like Gorilla Glue white for that particular problem, but then your rocker jig gets REALLY important.
Ummmm- a little wood glue wouldn’t hurt. Or polyester, or epoxy. If you like. It’s more psychological than structural.
Ah, softies bent the wrong way make amusing tables.
Back when, there were some roto-molded ‘popouts’ called Aitkens. Cheap and very hard to damage. They would mold the shell out of a hard-ish plastic then inject foam into the cavity, like a lot of the early windswurfers. Which was all well and good, but roto-molding plastics means you have to use thermoplastics to do it, which soften again with heat. And some of them got negative rocker. We were using them as rentals and the renters would have them on the beach on hot days, and sit on them. Negative rocker. The good thing was that we could warm them up ( putting a black plastic bag on the surface) in the sun and make the rocker anything we wanted.
ehhh, yeah that was a bit stupid and full of wishful thinking in my last post.
i realized that i should check again the foam and yep, it is also broken. does not look compressed to me. there is a crack. what i can see is that it starts on the right side in the middle between stringer and rail and goes to the left side half hight of the rail. i did not dare to take of the fibre on the rails yet because it will become a lot more unstable and i have to mount it to a table. it is laying on 2 trestles now.
was a bit dump to think the stringer can break without the foam transformed.
does that change your opinion, doc?
injecting gorilla glue in the crack?
@deanbonkovich: what does breaking the board and putting it back together means?
the bent-the-rocker-the-way-you-want boards sound nice. i could imagine a lot of people would still be happy with a more resistant board. but i guess they are a lot heavier. were they like the boards from bic?
i am a bit confused now. would like to set it up in a way that i don’t have to be all the time extra cautious because i think it will break with a wrong movement.
@deanbonkovich: what does breaking the board and putting it back together means?
If there is a split in the foam beginning from one of the rails across the centre of the board your board is well on its way to snapping. From there it can be better to put the board on your shaping rack and press down on the middle to break it in half and then treat it as a snapped board repair. Just patching over it doesn’t help if its at that stage. If its not don’t break it :).
You’re thinking the right way, don’t take off any glass that isn’t actually loose and flapping. Not now, not later either.
Ummm, no, not dumb at all. It’s not a full-thickness or full width crack, if I was rushed I would have ignored it and maybe added a little more cloth. The stringer didn’t break so much as tear a little. It’s fine as is.
Gorilla glue, definitely is the way to go. The white stuff , because it is polyurethane foam that will expand to fill the crack. Dab the area with a damp cloth (water) first as that catalyses the glue. It will expand beyond just filling the crack, be careful it doesn’t bend your rocker. This is why you want to put a plank on top of those trestles ( sawhorses, we call them) and get out the straps to hold the thing nice and fixed.
Sand the excess, if you have some depressed spots where the old cloth ripped loose it’s good for that too.
Ohhhh, the Aitkens sucked. Really sucked. There are limits to what you can do with a molded product, more so/worse then. Very similar to the Bics. Another thing about those, the molds are expensive so you don’t make many, what you have is a lot of identical boards. Well, identical except for color, they came in either dead white, a dull chrome yellow or a disappointing light blue like an untalented painter would use for ‘sky’.
In any event, if you make your jig, strap it down, put in the glue, sand all that flush, do your first layer or two of cloth, it will be plenty strong enough to finish working on. And when you finish, it will be stronger than it ever was.
-crack in the foam is filled with the foaming pu-glue and also filled the missing lamination with pieces of fibre and resin. sanding sanding and wiping with acetone.
put first a smaller layer of 20cm (4oz) fibre on the deck and another of 30cm (6oz) on top. sanded the edges and wiped with acetone.
looks good so far. now i will put a 40cm layer of 6oz on the bottom.
i work with polyester resin which is a bit stressful and i am not sure if i squeegee enough. i put the fibre on the scale and i realized that i use almost the double amount of resin per weight than the fibre. everywhere i research it says just a bit more resin than fibre or maybe 1,5 times. is it way to much?
also the resin does not really stay sticky. sorry for all these questions but i really want to avoid that i have to undo the repair. that would be a nightmare
To insure that a board doesn’t snap or buckle a second time after your repairs; Rout two inserts, one on either side of the stringer. Use a 1/4" bit and insert two pieces 12" long. I usually use five gallon paint stir sticks. Depth of the routed slot depends on how deep you think the break or stress is in the foam. Sometimes I go below the deck and fill the slot with Qcell or a slurry of ground foam and spackle. Your stringer looks wide enough to rout down the center of it and place a 1/4" insert wood into wood. When you install a splint in a board like this the strength comes from the insert. So for the rest of the repair all you need do is fill, fair and cover with fiberglass cloth and resin to waterproof.
