stringer bump
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stringer bump
so....lately some of my boards after being finished and surfed a few times have developed a noticable bump where the stringer is, on deck and bottom. This is not because i didn't get my stringer shaved down enough when shaping, my boards after being finished were fine, it is just after they have been used that the problem occurs.HELP!!!
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Re: [astevens] stringer bump
I have had a similar problem on my first few boards. They were both 2lb EPS with RR Epoxy. I have heard a couple of theories on why this happened:
1. Air travel. These boards went on trips, I was told it was possible that due to pressure or temperature changes, the foam may have expanded, then contracted below the stringer line. Don't know if this is true, but it's a theory.
2. You think you planed the stringer flush, but actually you didn't.
3. Leak? Perhaps some water got in and caused the foam to contract?
The last few boards I have done, I used the Greenlight Gore-Tex venting leash plugs. I no longer have the problem with the "elevated stringer". Now, this could be because of the vented leash plug, OR, because I haven't traveled with these boards yet, OR, because I was more careful about planing the stringer flush everywhere, OR, because the boards have no leaks.
Take your pick. Not sure of the cause, but all I know is that I don't have the problem anymore.
Good luck.
Re: [astevens] stringer bump
Thanks for the help. problem is, this is poly construction,not eps, I did take stringer material down too, and there are no leaks cause its 7 days old. It seems like the glass and foam sunk below the stringer level. It even happened in my single concave.
Re: [astevens] stringer bump
Stranger than that... I have an Ice9 blank glassed with RR epoxy, that the stringer sucked INTO the foam. After a year, the stringer is considerably lower than the foam on both sides, on both the top and bottom, but only in the thinned out nose area of the board. Very weird. Any ideas?
Re: [astevens] stringer bump
OK. You stumped me. The only thing I can think of is just really making sure the stringer is flush, or slightly below the foam. Run your hand side to side across the board when you're done shaping. It should be flat as can be.
One other idea: maybe you were pressing to hard with the squeegie when you were laminating and crushed the foam a bit? Just a thought.
Re: [astevens] stringer bump
what kind of blank was it?
do a search I remember a similar topic
I heard some blanks decompose rather abruptly
Ken
Exotic Designs Surfboards
Re: [kensurf] stringer bump
Its pretty rare, but sometimes foam blanks shrink. Even good brands can do this on occasion. It sucks, but I dont' know any way to predict which ones will, and I've never heard of such a method either.
I had a really nice fish shrink under one rail, but not the other?
Re: [nj_surfer] stringer bump
nj_surfer, in your case, I would guess the foam likely swelled a little rather than the stringer shrunk.
As for the "proud" stringers (original subject of this thread), I would think the foam degraded/collapsed. I've seen this as well.
Re: [astevens] stringer bump
Yeah guys I really don't know what this is from. I've never really had this happen. I'm using the same blanks(U.S. blanks red density) as I always do. I have never really had this happen so early on in a boards life, It sucks, but whatever. Nj surfer i don't know what is up with your board problem, but I'm not the guy to ask when it comes to ice9, so sorry. thanks everyone for the help though.
Re: [astevens] stringer bump
I was thinking that temperature made the wood shrink (always embarrassing) but the foam stayed the normal thickness????
Re: [astevens] stringer bump
Heat makes the Ice 9 blanks swell, I let a customer try my board made with an Ice 9 blank and she left it in the sun and her van in the summer. when she returned it everything was swollen except where the stringer is, it looks like a minature channel running the length of the board
Tom
www.mahadysurfboards.com
Re: [astevens] stringer bump
I had an Ice9 cane blank shrink around the stringer near the nose on both the bottom and deck. The poly glassed board was in an unzipped board bag in the bed of my truck. It may have expanded before it shrunk, not sure, but the stringer is now raised. Sold all the rest after that, can't risk investing that much time into a board if I can't travel with it or leave it in the back of my truck for a few hours.
Re: [astevens] stringer bump
This happened to me too. I made a board with RR epoxy and a PU blank (US Blanks) and it was fine for about 1 year. Two weeks ago I noticed a ridge along the stringer at the nose, top and bottom running about 12 inches down. I did travel with the board over the winter. I'm certain there are no leaks. All the other boards I made don't have this problem, but they were glassed with polyester resin.
Re: [nj_surfer] stringer bump
I was thinking that temperature made the wood shrink (always embarrassing) but the foam stayed the normal thickness????
Did the board get hot at all? I had a board back in the early 80's that I forgot about being in the car one hot summer day. When I remembered, all the wax had completely melted off the board and the foam had expanded, leaving a noticeable "ditch" where the stringer was. The board was too hot to take out of the car without burning myself, so I threw it in the yard and ran water on it to cool it off. Permanent damage, but the board still went good.
Re: [surfthis] stringer bump
Possibly... Can't say for sure. But that sounds like a good explanation.
Re: [astevens] stringer bump
Use of water as a ''blowing agent'', seems to predispose a blank to shrinkage, thereby raising the stringer. Some is good, but more is not better, as it relates to lighter foam. This was a problem as foam went lighter in the 1969-1972 time period.
Bill Thrailkill
Shaper since 1958