good stuff mike
id love to see and have a go on one day
if i ever get up that way
not to mention rags
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secret ingredient see below;)
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Yep keep it simple
I just can’t buy into this idea (unless your talking about building techniques). Rarely is building a composite structure simpler than building an object from a single material since there are so many more potential variables to take into account. I think that when you start removing structure (like going with 12mm rails) you allow the “secret ingredients” to start influencing the ride of a board. A light board is only a biproduct of a good design. I believe that the springer is key to influencing the boards ride. You can select springer material and springer shape that will give you the ride that you want (you want a stiffer board then use a thicker springer made out or a material that doesn’t what to flex, you want energy return shape the springer like a bow (thick in middle & thin at ends) and use a wood like ash or yew). The glass only holds the board together.
Hi Dan
Its not a springer, its a way of changing the stiffness and panel flex of the top sandwich panel
Think about this ,if you increase the sandwich thickness you increase the stiffness of that panel,but do you want the whole panel to be stiff all over?
No! so if you increase the thickness just where you want less flex that would work?
Maybe! But how much area do you increase the thickness over and how much do you increase the thickness by?
Ah ,maybe thats the secret!
Rather than me telling you the answer, which may be right for you or may be not, how about I set you on a path where you can decide for your self.
Look into composite yacht construction, the area you want to look at is panel strength and flex control
This was a big problem in yachts like open sixtys and whitbread sixtys with panel panting in slaming loads which would lead to delamination or shear failure of the core
The fix it solution is so easy that it really is just comon sense.
Now use this new found info and make up your own mind as to how and where to you could applly it to the inner side on your sandwich
What you find may work better than what im doing, which is why i dont want to be specific at this time
Many minds all trying differing things will eventually make better surfboards
Let me know how you go, sorry im not trying to play with you by not coming out with my solution I just would like to see what others come up with once you have the starter.
I am keen for everyone to share the best end results.
Mike
The fix it solution is so easy that it really is just comon sense.
well i guess some of us have it and some dont…
I completely agree with what your saying, but your path shows complexity - not simplicity. Although the construction fix might be simple the design concept behind it isn’t. I agree with the importance of the deck spring, but it creates construction problems for me and the springer easily addresses this problem. Meecrafties balsaless bottom (I bet you didn’t know you had one of those) helps to shift the focus to the deck. I primarly surf longboards so I don’t think that the deck skins can develope the desired spring (but then again I could be wrong).
Dan
Allright its a top hat,look inside any composite boat in the bottom you will see a grid pattern and on the topsides things boatbuilders call stringers
A top hat is just a way of putting a extra glass parrallel to the sandwich but at a greater distance away from it
This in effect makes the sandwich over that small area much thicker therefore stiffer
I have placed strips of balsa 20mm wide by 3mm thick diagionally on the under side of the deck balsa
They form a grid pattern.they do not cover the entire surface
Yes i do join my balsa sheets together prior to glassing which makes attaching these very easy
I do the balsa first so that when glassing the underside the glass goes on to the balsa not onto the foam
If you apply resin to the foam directly you will never get the weight reduction that can be achieved
The balsa sheet is then placed on top of the blank lightly push down all over ,remove the balsa sheet ,there, the imprint shows where the extra bits go
Route these out,build a little guide jig takes about ten mins to build the jig
Place the prewet glass on to the balsa sheet over the extra strips
Bag as per normal
The extra time to do this compared to just doing a plain balsa sheet 12 and a half mins (timed)
How big, how wide, what pattern grid,its up to you
It works, its easy to do, its easy to tune in steps with each new board and its repeatable with accuracy over and over again
You say that deck skins cant develop the spring you require,I would say that at this stage you have embraced the advances that sandwich construction can give you over traditional construction.
I would encourage you to continue to develop the sandwich rather than throw the springer , which is a relic from the traditional board,into support something which can
be developed to do the job better.
Meecrafty is doing this allready by achieving the flex he wants with just the skins.
Also cast your mind back to some Bert posts re the rail bands or perimeter stringers and how they assist twist control of the board vs the traditional stringer system
If you use the entire skin surface to control flex it links all parts of the board control system together
So to sum up i would say that my system is anything but complex when conbined with my construction system.
Wouldnt it be easy if we could all be in one place for a day and each see how every one is doing things!
Cheers Mike
Very interesting idea of the grid. I could see how it would add some desireable characteristics. It sounds like you are saying you make a basket weave. If so, how do you handle the added width where the wood crosses. However, I think what you are accomplishing is similiar to the springer (it is placed horizontal inside the foam and is not tied to the board) and diaganal running balsa. I think that we are approaching the boards from different angles. I think of the board as something to store and return energy. I really appriciate you putting all this information out. Its been re-energizing to my intrest in composites.
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Wouldnt it be easy if we could all be in one place for a day and each see how every one is doing things!
But this is the next best thing! I dont think that I’m ready to abandon the springer (since it produced the first board that I’m happy with), but I think your “top hat” idea will be incorporated into my next board. I already know how I think I’ll use it. If you wouldn’t mind could you post a picture of the grid?
Hi Dan
Here is a couple of phots
I made two of these boards one with and one with out
Both are the same other wise
The one with just seems nicer and has a smoother easer flow about it when you ride it
It just seems it will go where ever you want it to with out ever stalling or stoping
Yesterday at Rags I found that i could do a hard bottom turn then go streight up the face and spin it at the top over and over with out any pauses
The wave at rags you can do six or seven of these in a row so it is interesting to link the same turns and experiment with trims etc
I had a surf again tonight in very different conditions yet it still did the same things
I guess the bottom line is that it just very easy to surf on it nothing within reason feels at all hard to do
mike
Variations around the same basic ideas… stimulating. What do you think the link between the perimeter stringer and respectively top and bottom skins should be? I would say there should be a strong link between the top skin and the perimeter stringer and a loose link between the bottom skin and the perimeter stringer, to allow flex. Top skin + rails should be stiff, bottom skin should be elastic.
Here is where it gets interesting
top is in compression bottom is under tension
both are are individual sandwich skins combined they are effectivly a single sandwich structure
Its much easier to control things in compression than it is when in tension
the over all shape and the core structure are the variable features
it is a flexible sandwich panel
most sandwich panels are designed to limit flex
most have core compresive strength as a key factor
we have a core with poor compresive qualitys which is ideal for our use
lets explore the functions of our poor compressive sandwich skined sandwich panel
the link betwwen the top and bottom skins via the perimeter rail bands
my solution only has glass on the outside of the rails
if i put it on the inside it locks every thing up
it becomes too strong and defeats the objective
its funny pu/pes try to make them strong enough so they dont break to easy
sandwichs seem almost impossiable to break so all the effort is in trying to make them closer to that edge where they might just break
Mike
wonderful reading guys
egads
fin systems are heavy
my latest board with futures is about 400 grams heavier than the last one
admittedly its got double 4 oz all over and i aint sanded it yet
so i might loose a bit there
its 2.7 kg
which is heavy for this construction
i was hoping for 2.3
oh well
this is a travel reef board so its all good with the extra strength
heres a quick preview before sanding
couldnt resist sorry
i know the artwork is crap
hey mike,
im looking at your shapes and they are almost identical to what im riding…havent seen a rocker shot yet tho…got any?
now regarding that performance feel youre getting…i’d be really interested in looking at the rocker…i’ve had similar observations and there’s definitely more to it than just construction…dialing in the right rocker for one’s arcs and wave face curvature is where the majic lies (performance wise)…also, when you make’m this light, you can maintain way more speed going up the face so when you bank into a top turn you have more speed before, during and AFTER (AFTER is the holy grail IMO)…so its easier to link your turns, making combos much easier
anyone have berts pic where the tail foam is lifted off the rail/bottom balsa?
Its much easier to control things in compression than it is when in tension
hmm…i used tension control to promote flex on my last one…
sandwichs seem almost impossiable to break so all the effort is in trying to make them closer to that edge where they might just break
ditto…way to go there you da man
Not to derail this amazingly stimulating conversation here (and it is!)…
But how about some “easy” methods of getting the rails on? Or am I just doomed to piece them together like a jigsaw and tape like a madman?
Schwuz- If you still have your templating offcuts, that’s the only real shortcut. Connect pieces of balsa on end to the length you need. Superglue works fine for that. Leave them wide enough to cover your whole thickness/rocker scheme. If you have like 5" of nose rocker, you don’t have to use 5" wide balsa, just cut a butt joint at an angle to tip the front rail section up…
Make 3-4 pieces to length for each side. Epoxy or gorilla glue onto the edges of your blank, wood glue between each 2 pieces of balsa.
Now go to your U-shaped shaping stands. Drop a 2x4 in the bottom of the U. Next, one of your rail offcuts, then a stack of rail balsa, still wet. Then the blank. The other rail stack, the other offcut, and the other 2x4. Big bar clamps across the whole mess - some on the top & some on the bottom to even out your clamping. 3-4 hours later, you’re all set. Plane the balsa to deck & bottom, then start cutting rail bands.
Otherwise, you’re in tape city, baby, one layer at a time.
And back to the other conversation…
I’m pretty much convinced that Bert’s balsas have thin skins top & bottom. Like Dan says, I think he makes the skins first with the outer layer of epoxy + the balsa. Then, pre-wets the glass for the inside & bags on the bottom. The rail pieces aren’t long thin strips built up, but thick sections cut out at the proper curves & joined together. Those go on next, with no glass underneath. Then the top skin gets bagged on so it overlaps the rail. Once the skins are on, there’s no more exterior glass to laminate except around the rails, because the skins had their outside glass pre-applied. So the rails get 4" glass tape or something, to connect the outside of the top & bottom skins, but the insides aren’t connected by any glass.
DanB’s observations & experiments put a bright light on this & then I asked Bert about glass tape & he responded with a photo. Doing it in the order & lap sequence above, would insure a strong connection between the deck skin & rails, but not between the bottom skin & rails or between the core foam & rails.
I also think its unlikely that Bert uses many second layers of wood - either angled balsa under the deck or springers in the bottom - because his weights are just so light.
I assume, instead, that a strip of carbon fiber here & there tightens things up. In fact, I wonder if a 1/2 length (through the middle ) CF stringer epoxied into a halved blank would stiffen the middle & let the ends flex. I bet it would. You could just split your foam blank like for a stringer & epoxy in a CF strip for whatever part of the length you wanted to stiffen. On edge, it would add tons of rigidity with hardly any weight at all. I don’t think you’d even need to epoxy the foam fore & aft of the carbon, because the skins will keep it all together anyway.
Add flat CF pieces under the deck for the hand spots on pop-ups and the foot spots when surfing. Huge strength gains with virtually no weight.
In a production environment, using this system, you could have somebody making endless numbers of flat balsa skins, oversized, with the outside glass already on. Just waiting for a blank to be templated so the skins could be trimmed to the outline & bagged on. It would save a lot of time. Also, no taping or gluing of the balsa required. You use a wet-out table for the glass, lay out your balsa strips on top, and tape down a one-layer bag right to the table all around your skin. Pull vac & not only is the skin made, but your balsa gets good resin saturation (for flex without cracking, waterproofing, etc.) at the same time. You put your peel ply & absorbent on the balsa side, not the glass side. Its like infusing the balsa. You’d only need 1/16" balsa because you won’t have to sand it once the skins are on - the outer lam would be already done!
Nothing could be lighter & stronger, I believe.
"anyone have berts pic where the tail foam is lifted off the rail/bottom balsa? "
Found it…
What you’re doing with the “top hat” is very similar to what I did with the springer, but I see a lot more benifits to doing it your way. I’ve noticed similar types of performance gains, but your design seems to be a step forward. However, You are doing exactly what I said needs to be done - loading up the middle of the board with springy wood. I really like the diamond pattern because I bet it would help to load up the board on the face. I completely agree with what you said about the problem of building composite boards - if you aren’t careful they will end up being too strong. Its not until you remove structure (thinner perimeter stringers, light glass schedules, low resin usage) that you start gaining the benifits.
Schulz, the rails really do just get easier to build. Each time I’ve used a different technique - and each has benifits- but my main improvement is in experience.
thanks john…
i was just wondering if the foam floats…
…nah doesnt look like it
silly,
that is one sweet stick…i like everything about it…lemme know how she goes…
ok…onward
Hey Dave, here is the photo that you should have been asking to see…
This is from one of Bert’s newer boards (9 foot). Here’s the link to the write-up http://www.swaylocks.com/forum/gforum.cgi?post=181789#181789. I’ve been searching for this post for several months and suddenly it just appeared.
I just wanted to point out one quote from Bert’s explanation
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i wanted lighter and lighter boards , get to a certain point and lightness becomes rubberyness and also weakness ,you can go thicker sandwich , but that just adds stiffness without spring … the horisontal stringer allows me to go irresponsibly light (this board was 9’-2" x 24 x 2 5/8 it weighed 4kg or just under 9lb ) but still have spring , the board can bend and just like the pages of the book , can tolerate shear movement without stressing anything out , the bar works harder the more load you put on it , the closer it is to the neutral axis the better it works , you can even move it around for flex bias …
yeah i remember that one… ha! you could just sense it…he wants to sing so loud but he’d be giving the farm away if he did…just killing him inside…;)…the day just before he saw the light…plan B…dangle a carrot on the net and they’ll come…worked like a charm
yeah i suppose the h-stringer is good for longies…but i dont ride’m…mine are too stiff generally…except the last one…i prefer no stringers at all…zero, nada, zilch…
oh yeah almost forgot, thats some nutty stuff in the background huh?