I have shaped a grommy board and it is a stringerless blank, I have shaped this one very flat thru the centre and out the tail, its 4'11" x 17 1/4" x 2 1/8", tail rocker is only 3/4", looking to get maximum speed and drive from flatter rocker, have added a serious single concave that rins thru the guts and alsmost to the tail...now am about to glass it up and have been toying with the idea of using carbon running down the centre on the bottom but tapering it to nothing about where the fins will be...keen to hear anyones experiences or thoughts on this ???
With only 3/4" rocker in the tail, I wouldn’t do anything to stiffen it up. I did a stringerless once that I thought was too flexy in the tail. I later added two layers of 5 oz 6" wide carbon tape in the last two feet of the board. There was a noticeable difference.
Since were all about the experiment here, do it first without the carbon. If you want to change it sand down through the hot coat to the top of the weave, and add it later. A single flat layer of carbon wont do much. Two layers you will feel. Do the rails, and it will be a C channel, and do more still.
but by having the carbon run down the centre and tapering to a very thin point about the fin area and then having nuthing but standard glass in the last part of the board, it should allow the board to twist and flex more in the tail , I am happy for it to stay stiff up front and give alot of drive but some additional flex in the tail would be good ... glassing it with epoxy and thinking of using up some Innegra I have left for front and back foot patches.....have 4 diff kinds of carbon ribbon, think I'll use the standard all carbon ??? anyone use the blue poly mix ???
Hi, sounds reasonable… Have a look at the pic below looks like Kellys new baord has something similar although it has a stringer which would negate most of the effect of the carbon i reckon, looks good though:)
Ive wondered about routering a strip of flat timber into the blank to control flex , you could thin the timber out towards the tail that way too, timber would flex for ever too … something to try on my next board!
I swear I didnt get my idea from that and I havent seen that before...but I wonder if he has a weak point there with the carbon finishing so suddenly and the plugs as well ? thats why I am tapering mine slowly to a fine point...... and dunno bout the stringer also.....my test pilot is a little ripper and he weighs about 37 kgs so less likelihood of breaking it I guess but its not about keeping the board in good nic, its more about seeing if theres some performance benefits here and to take them and work with them.......like the idea of the timber, maybe we can help each other out with feedback and info on the boards .....
here's a few pics of the shaped 4'11"...this board will be trialled by a grommy I shape boards for , he surfs really well and his usual board is a 5'2" x 16 7/8" x 2 ", rounded square tail, thruster...so this one is 3" shorter, 3/8" wider at wide point and wider thru the tail area, its also 1/8" thicker ( but he has grown since his previous board so the thickness increase is needed for his growth and weight increase as well as for design reasons ).... the tail rocker reduction is a major difference, its been reduced by 3/4" of an inch... as well as the carbon tapering for flex in tail, I am also going to do some different sets of fins to try, mainly a set of more upright front fins,best way to describe them is half way between the ks2.1 template and the H2s', they'll be hand foiled and have quite a bit of flex in them...
[IMG]http://i403.photobucket.com/albums/pp114/pridmore73/411DDbyron016.jpg[/IMG]
[IMG]http://i403.photobucket.com/albums/pp114/pridmore73/411DDbyron012.jpg[/IMG] very flat thru the tail, should be drivey and fast
[IMG]http://i403.photobucket.com/albums/pp114/pridmore73/411DDbyron018.jpg[/IMG] the concave is about double the depth of his current boards
[IMG]http://i403.photobucket.com/albums/pp114/pridmore73/411DDbyron013.jpg[/IMG] quite a wide pod for this size board too, extra planing area for small and weak waves... he is also getting right into airs....
gone with 1 layer of 6 on the deck with 2 oz Innegra patches under the 6 for front and back foot strength, the blank is quite a lightweight one....4 oz bottom with tha carbon ribbon...
Cool, looks like a nice board… Im trying to find stringerless blanks here but not having much luck I dont really want to cut a stringer out of a good blank!
Does the Innegra work really well, I have found I always pressure ding near the tail just in front of the deck grip from my toes on my back foot and was thinking some bigger patches around that area?
my first trial with Innegra wasnt very good, not happy with it but I am gunna give it another go, plus it may have been a softer blank, never can be totally sure...plus this time I am using epoxy and putting it under another layer of cloth, so may be much better hopefully....I reckon its the blank strength that prevents dents and depressions rather than additional cloth, but in saying that, we all add patches and it does make it stronger but if you get a good strong dense foam and dont take much off the top, then you can get away with much less cloth......I am also tinkering with some carbon combo variations as patches just to see how it goes and for optimum use on my shapes......
Hi Pridemore,
Just wondering how the board came out and if you have any pics etc?
I just finished shaping a board from a stringerless Pu blank and was thinking of doing something similar on the bottom, I have some Kevlar/Carbon tape thats 60mm wide that I am planning on glassing down the center of the bottom of the board, as you can see its already got some solid Balsa parabolic rails but I will add the carbon anyway if it makes any difference im not sure but it also looks cool:)
my glasser had a week off so its almost finished, mid week apparently...only did one layer of 6 with 2 oz innegra foot patches so was happy for it to sit glassed before he sanded it after a week away, bit extra cure time really helps imo.....team grom still doesnt know its coming, hopefully he'll be stoked and rip on it....also used a new epoxy resin, supposed to be much clearer and resistant of UV, we'll see ...previous ones yellowed too much too quickly....go great but resale isnt good....
will post info when I get it, and pics... I'm doin a few other little things to alter flex slightly too, might post and explain when I have pics of board finished.....
[IMG]http://i403.photobucket.com/albums/pp114/pridmore73/411stringerlessrockerdesigntrial001.jpg[/IMG] Richie Collins spray job.
[IMG]http://i403.photobucket.com/albums/pp114/pridmore73/411stringerlessrockerdesigntrial004.jpg[/IMG] you can see the Innegra foot patch....
[IMG]http://i403.photobucket.com/albums/pp114/pridmore73/411stringerlessrockerdesigntrial005.jpg[/IMG] glasser was not as neat with it as I wanted, had trouble cutting it but the idea is there still....did want to taper more so it doesnt create a weak spot especially near fin plugs...
[IMG]http://i403.photobucket.com/albums/pp114/pridmore73/411stringerlessrockerdesigntrial006.jpg[/IMG]
Looks good Pridemore , yes the carbon is a bitch to cut, im using Carbon /Kevlar which is even worse, in future tell your glasser to use a really sharp knife or scalpel and a heavy steel ruler and you should be able to taper it a bit more, but its probably quite hard to glass it nice and straight once it gets narrow.
Hope it rides well anyway, will post pics of mine once its done:)
Hi Pridmore, if you plastic tape the carbon , cut and glass it with the tape on the surface you can sand the tape off and it looks perfect.
Ive tried it with paper tape but the resin soaks in more than the plastic tape so the plastic tape is easier to sand off.
Heres what I just glassed up, Xps Stringer and Carbon/Kevlar tape on the bottom, might do it on the deck too to add strength or some foot patches maybe, Board is a bit of an experiment as its a little thinner than my usual and boxy rails so thought I might as well do a few trials on it…
ignore the black dot on the image to the left of the stringer, I think i actually managed to get a fly in flight with the camera!
I plan to use carbon on the bottom to stiffen the nose into the mid-section but leave it off the tail for flex. If done right, it should decrease nose flex into the mid-section.
Double post – my bad.
Now I know what the cloth strip is. Nevermind …
Not sure the kevlar portion of the weave is going to do much for you in the stiffness department.
Personally I'd do deck concaves to mess with flex. In my humble opinion laying carbon fiber length wise and not tying into any stringer will not add much stiffness to the design. And it won't add stiffness out on the rail line where it's needed. You still have a tortionally (sp) flexible board.
The bottom cured today nicely and i did some pretty basic flex testing, the weave tape definitely does something, stiffens it up quite a bit but you might be right if it was pure carbon it would do more. I will add some carbon to the deck when I glass that as there is no stringer or parabolic rail on this board.
Resin head, thats a good point I might do the carbon on the deck out wider from the center more towards the rail so it braces the whole front end and compliments the bottom strip… just messing with this really so itll be fun to see what happens…