I have read a few posts here that seem to suggest that rocker can change after lamination- was it Mike Daniel? My question is; to what extent does lamination change the rocker? Does this only happen with certain glass weaves or weight? Is this a nominal amount or something to be taken into consideration when shaping?
I don’t think about it when I’m shaping. I just make sure I do the single layer bottom first, as normal, and make sure the cloth is not laid down at an angle… the warp has to be straight, end-to-end. If it’s at an angle, I think it can twist the blank when it cures and shrinks. I believe that once the single layer is down, it adds stiffness to fight the pull of the double layer deck when it cures and shrinks. (I do put down the deck layers at slightly opposing angles.) Also, I make sure the blank is flat and level when curing just in case that might present a twist factor too.
Maybe alot of this is driven by fear and nonsense, but that’s what I do. An ounce of prevention, you know?
Yes, I did point out that rocker can and does change when hand-lamming on T-racks. Poly shrinks as it cures. Epoxy not as much. But don't tell anybody, all the guys who are using CNC to get ''accuracy'' and then glassing the old way don't want to hear about this.
What I do to minimize surprises is to have my racks the same distance apart as the glassers when I check my blanks rocker, it gets me real close.
So generally, does the double layer on the deck shrink and pull more curve into the rocker? Are we talking like a 1/16" or something much greater? Or is it the rack span that is more influential?
I've measured both increases and decreases in rocker. I'm not sure what effect rack distance would have, unless you were weighting the board during cure.
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Yes, I did point out that rocker can and does change when hand-lamming on T-racks. Poly shrinks as it cures. Epoxy not as much. But don't tell anybody, all the guys who are using CNC to get ''accuracy'' and then glassing the old way don't want to hear about this.
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aaahhh! maybe that helps to explain why pros will get 10 "identical" boards and only 1 or 2 will be "magic"... hmmm
No, that doesn't have anything to do with it :)
How significant were the measurements? Are these changes not even worth worrying about?
It's only significant if you're one of the ''status quo'' companies talking about the ''accuracy'' of your CNC PU/PE.
Howzit Mike, I remember a few threads concerning shrinkage of both poly and epoxy and I think poly shrinks about 6% and epoxy anout 3-4% if I remember right. I think the thread was more about how the shrinkage twisted the blank and not about changing rocker. Aloha,Kokua
On one hand I say it's a really good question with some really good comments.....I'd like to hear more...
On the other hand.....well....I've fixed some really thrashed surfboards....guys love their boards...The thrashed boards...the ones I can see are a little bit twisted....a little bit water logged....why worry........
I read some stuff on Swaylocks....yeah....right in the middle of my first stringerless longboard project with wood skins....
...Too Much Stress......
My board is fine...I don't need this ....A little rocker change...a little twist,,,no worries...really....Low Tech Lab..
I love Mike D...He helps me online...he helps me a lot......What I see as no big deal matters to Mike D....
A little twist...a little rocker change...Guys like Mike watch out for that stuff...
Just keep in mind what level you are after.....and how many boards you will need to glass to catch up to Mike D and Kokua.........
Ray
This was a problem that reared its ugly head when 1/8th inch stringers, and stringerless boards became the rage, circa 1969. Solved the problem with a combination of processes. Something I'll cover in detail in a workshop, in Feb., or Mar.
I can't imagine doing a stringerless on T-racks. Setting the rocker in the bag on a fixture eliminates rocker deviations and twist.
Get a good stringer in a good foam blank. Otherwise; yes a deck lay-up can affect final rocker and even twist. Someone mentioned laying out the bottom layer straight, warp etc. That is correct. You don't have to worry about the deck though if you use E in combination with Warp. Any combination of weave "crowsfoot" etc combined with E or S will be less likly to twist or pull rocker.
Thanks for all of the comments guys. Im concluding that this issue insignificant for a backyarder like me and probably most folks. Case Closed!!
one of my all time favourite shortboards had a 1/4 twist in it for most of its life, the thing was otherworldy to surf,real ‘stuck to your feet’ stuff, maybe a lil twist isnt always a bad thing?
If you don't mind going through 10 or 12 boards to find one that's twisted ''just right''....
I'd rather move on to more reliable and consistent methods of building surfboards.
Wouldn’t the amount of twist/change in rocker ‘caused’ by glassing on T racks
be related to how stiff your construction is? Like the compsand guys
are vac-ing the skins on with a rocker bed then hand laming afterwards.
Fairly stiff construction, do they get change in rocker? Greg was promoting the T-Flex as not
needing a rocker bed for the vac stage or glassing?
My question to you Mike if your glassing a stringerless blank, just fiber no HD skins do you reccomend doing the whole process on a rocker table?
I would like to hear more about this subject.......
I did a repair job on an 11 foot log last month. Very nice board. Pro build not backyard. Tripple stringer. The board has a slight twist. I thought it was my racks so I took it out into the yard to get a better view....Twisted....
I think long surfboads twist over time..with age...that's an opinion not a fact...I have no proof......
Stingray