I’ve been checking the archives and couldn’t find an answer. Amazing though what you can find. The speedneedles in 04’ look insane.
I’ve been thinking of putting my vacuum bag back into operation and am tired of waiting for the elusive “parabolic blank”. It’s like trying to find a menehune. So in the spirit of Sway’s I’m going to make my own. I’ve worked with Dcel and corecell enough by themselves but I want to use it for a stringer or stringers in eps. I was thinking of doing one with 1/8" stringers that follow the rail and another with the stringers in a vee shape, narrow at the nose then wide at the tail. I know that someone has tried it before and I was looking for any comments.
I’m thinking that the high density foam might be too flexy for 1.7 lb. eps as a perimeter stringer but then again I’m guessing. I also have some .5 oz uni carbon veil that is equal to 4 oz E that I was thinking of trying as a sandwich between the foam and the stringer to give it some twang. Also the reason I decided on the 1/8" corecell is I was going to cap the deck stringer to stinger but leave the rails with just the eps. Any thoughts would be appreciated?
I’m not so sure about the terminology on this stuff. Segway Composites offer “Contour Stringers” (“Parabolic Curves”) on some of their EPS blanks. They have different densities available. I’m not sure if all stringer options are available in all foam densities - on their website they show 1 lb density core with 3 lb density rails. I do know Ken is a very helpful guy and if he’s around can probably hook you up with what you need.
Thanks, that is the bible that everyone refers to. I have access to Marko blanks and will be using them as a starting point. I understand the advantages and disadvantages of the 1 lb. EPS and I’m going to try something a bit different with a denser foam.
I’ve read the post before and will be trying a similar technique to do perimeter stringers with corecell and a deck cap of 1/8". Just waiting for the blanks.
I’m not so sure about the terminology on this stuff. Segway Composites offer “Contour Stringers” (“Parabolic Curves”) on some of their EPS blanks. They have different densities available. I’m not sure if all stringer options are available in all foam densities - on their website they show 1 lb density core with 3 lb density rails. I do know Ken is a very helpful guy and if he’s around can probably hook you up with what you need.
I was really impressed with the amount different blanks that they have. I don’t think anyone carries them in Hawaii and their perimeter blank is pricey.
Check Drewtangs posts. He is doing something very similar and may chime in. His D-cell perimeter stringers also use bass wood…
I built an 11 footer (4.5 inches thick) with a 4 pound EPS stringer about 4 inches wide down the middle. Not broken yet, but remember it is 4.5 thick, so that helps exponentially.
I think, in hind sight (re my 11 ft’er) that foam at just about any density isn’t going to help much in tension (bottom of the board). Try it and let us know how long it lasts.
Thanks for the input. It is a bit of a hassle to get the PVC or corecell foam here. We have a local supplier of exotic woods that has balsa, bass, and some other stuff I don’t even know the names of. I even know a kiteboarder/surfer that grows his own balsa and has made a board with it.
I’ve read over the data sheets for the end grain skrim balsa in comparison to the high tech foams it pretty much blows doors on the foam. Never the less I was just looking to try something that was a bit different. Also the limiting factor is that I’m going to be using a higher density foam.
Still waiting on the blanks. I’ll post pictures when I start. Thanks again.
Check Drewtangs posts. He is doing something very similar and may chime in. His D-cell perimeter stringers also use bass wood…
I built an 11 footer (4.5 inches thick) with a 4 pound EPS stringer about 4 inches wide down the middle. Not broken yet, but remember it is 4.5 thick, so that helps exponentially.
I think, in hind sight (re my 11 ft’er) that foam at just about any density isn’t going to help much in tension (bottom of the board). Try it and let us know how long it lasts.
Thanks, I’ve eye balled Drewtangs posts. Very nice boards. The theory that I’m going to run with is that yes foam is not a good controlling medium for tension. E glass provides the best for tension flexion. High density materials like Dcell and Corecell and materials like coremat and aeromat provide the best for compression. So E glass on the bottom probably 5 oz. warp and then a mix of the other materials on the deck. The center stringer while functional just doesn’t seem right from a performance standpoint. Having the stringers closer to the rails makes more sense.
I’m liking balsa skins with E cloth for lively panels; endgrain balsa (hidden) for perimiter weighting & skin-edge reinforcement; d-cell rails for compression resistance & snappy response off the flex of the panels…
I’m liking balsa skins with E cloth for lively panels; endgrain balsa (hidden) for perimiter weighting & skin-edge reinforcement; d-cell rails for compression resistance & snappy response off the flex of the panels…
Sorry for the low quality phone photos…
Wow! I like your construction schedule. I was thinking along the same lines of having a deck material that was similar to the perimeter stringer material. My concept was to have an I-beam effect. Deck cap to perimeter rail, but without the rail wrap to allow flex. I’m impressed you went all out.
You did what I have yet to try. Sorry but you’ve got my full attention. What is your core weight? Did you glass under the balsa skin and if so what weight? How much glass on the deck? How thick was the end grain you used on the stringers and how did you get the end grain to create such a long stringer? Most importantly was it worth all that work for the ride quality?
Its all just one piece at a time for me. Stick with the same basic shape & change one material at once.
Last one was 2# core, 1/16" balsa top & bottom skins, bottom got 1 layer 4 oz E inside & out; top got one layer inside & 2 layers out. Endgrain perimeters before the skins, 1/2" of solid balsa rails outside the skins:
That one rides great, down the line, very responsive, nice & stable to walk it, but it’s almost too flexy. If I do a left-go-right take off into a more than square bottom turn, it mushes under my feet a bit more than I like before it snaps back.
So on this next one, I replaced the 1/2" of solid balsa exposed rail with 1" of d-cell, hoping to stiffen up the flex-back without any weight penalty. Same skins, same endgrain (photos of that in the recent “wood orientation” thread) and same glassing schedule.
Ride quality? Just put on the bottom hotcoat yesterday, haven’t fin boxed or sanded it yet. But I’ll let you know
Its gonna get a bit of a finbox variety too, in case its too stiff to feel good as a single fin. Found this gem from Austin on the ProBox site, and that’s what mine will get for boxes too…
