Stingers are stiffeners correct? Can the skin then be anything else but the stringer (stiffener) on a stringerless surfboard?
Yes.
Take a look a the cerex thread in Errors and Bugs and the modern fibers thread.
Airplane wings have controled and engineered flex, without a strip of basswood inside. How do they do it?
“Airplane wings have controled and engineered flex, without a strip of basswood inside. How do they do it?”
Spars. Basically a stringer, typically located at the max chord thickness of the wing.
http://en.wikipedia.org/wiki/Wing_spar
Stringerless surfboards are more like a monocoque construction:
http://en.wikipedia.org/wiki/Monocoque
I especially like this quote from the Monocoque link:
“The skin added nothing to the structural strength of the airframe and
was essentially dead weight beyond providing a smooth sealed surface. By
thinking of the airframe as a whole, and not just the sum of its parts,
it made sense to adopt a monocoque structure…”
Lawless, I’m so confused! Airplane wings use spars. which are basicly stingers, and boards are monocoque, but then a source says “By thinking of the airframe as a whole, and not just the sum of its parts, it made sense to adopt a monocoque structure” which means stringerless boards are like airplane wings.
Tomorrow is the Fourth of July! Somebody pour me another Marguerita! Oh wait, I’m confused again! = )
I assumed you would read the link provided for context. Here is the entire paragraph I pulled that excerpt from:
“Early aircraft were constructed using internal frames, typically of wood or steel tubing, which were then covered (or skinned) with fabric[4] such as irish linen or cotton. Aircraft dope was then applied which tightened the fabric and provided a smooth sealed surface necessary to prevent excessive drag.The skin added nothing to the structural strength of the airframe and
was essentially dead weight beyond providing a smooth sealed surface. By
thinking of the airframe as a whole, and not just the sum of its parts,
it made sense to adopt a monocoque structure and it did not take long
for various companies to adopt practices from the boat industry such as
laminating thin strips of wood.”
That’s getting a bit away from the original question:
“Can the skin then be anything else but the stringer (stiffener) on a stringerless surfboard?”
Could be, guys are riding un-glassed foam boards. No need for a skin at all if the foam is dense enough. Body boards don’t have stringers.
But talking about more realistic applications for the average user, using light-weight foam as the core, you build the strength/durability into the shell instead of the blank. It’s just a different approach. Instead of putting your strength into the core/stringer, you put it into the shell.
They all work, it’s just what you’re after with the end result.
A little off topic but here’s one to think about- when I first started working a the boat builder I was shaping rudders. As I shpaed away I soon realized that the foma was not just foam, but had glass fibers blown into the foam. I was shaping outside with a t-shirt and shorts on on a hot day and was covered in what I first thought was merely foam dust, only to discover it was fiberglass.
Has anyone in the surf industry ever tried to add fibers into the foam they are blowing??
A stringer runs longitudinal, fore and aft…a spar is transverse ,across the stringer. A stringer is generally at the centreline of symetry or parallel to it , but can vary as in a wedge configuration or varius curves , but generally kept in symetry , to the centreline…
In the absense of a stringer , stiffness needs to be added to prevent excessive flex , or produce a specific required flex…can be done by stiffening the whole deck , or concentrating stiffness where required…
On a stringerless board skin must be the stringer if foam is too “floppy” to prevent skins buckling. The last aircraft wings (fighter aircraft) i can see have skeleton skins to prevent local buckling with best weight/strengh ratio.
Lawless, i know that bodyboards (good ones) have stringers inside that plays an important role for flex durability.
Llilibel03, ask bufo what he think about “fibers in foam”…
On one hand you have aviso with all in skin ( hi tech skins) and on the other hand you have hydroflex supercharger all in foam (periphery of foam).
Sorry for my franglish
The foam board is the stringer, A stringer is usually a higher density material of some sort to help prevent critical failure of the structure. This higher density stringer in surfbaords could be at center. lateral of center or any othe configuration to linclude horizontal between the foam layers.
So to answer the question, the whole board is the stringer. The fiberglass outershell is to compose a composite structure with a better strength to weight ratio and making the structure water tight.
Now my question is why would anyone care?
bb30,
The web of an I beam is the “stringer” . Stringerless boards are box beams. If a box beam shell is too weak for the given load the beam fails. So the outter web of a box beam (the rails) need to be stiffened since the inner web of the I beam has been removed when the stringer is taken out.
I can’t understand your point in your second paragraph.
Why would someone care? Is that rhetorical?
Resinhead, are you suggesting there is more than one way to make a surfamaboard??
Fucking heathen!
Words mean things. If you want to refer to a stringer as the 6 oz bottom and 6/4oz deck glass job then knock yourself out.
Lots of ways to skin a cat. hundreds of thousands of surftechs are all stringerless. Most windsurfers are stringerless. Lots of sup’s are stringerless. Look at how any of those are reinforced. Not necessarly at the rails.
But I do think this topic is strange and quite the “load” in my opinion.
I think the stringer is the stringer.
bb30
I think you are misunderstanding me. Most of what I make are stringerless. In a stringerless board, there is no wooden stringer running the "spine " of the board. The deck and bottoms are not stringers.
If you take out the wooden stringer from the foam, then you need to stiffen it in some way. Either add more reinforcement in fabric to the rails. A “parabolic stringer effect” doesn’t necessarily mean wood.
Or bulk the deck and/or bottom lamination with wood, d-cell foam, or something to create a “leaf spring”
Or do nothing to stiffen. You with no stiffining other than a 4+4 deck and 4 bottom, you get a board that will do a great cutback, but a poor, sluggish bottom turn.
If I am not mistaken, wing ribs are placed parallel to the line of flight, adding shape to the foil and strength in the line of movement. They are similar to surfboard stringers.
A surfboard stringer is an I-beam formed of longitudinal beam and composite skins. It adds longitudinal strength.
The composite skins (fiberglass, etc) minimize parallel surface movement relative to the core.
The composite skins on a stringerless board must serve as an exoskeleton as well. The exoskeleton must be strong enough to withstand the forces it is subjected to (torsional, longitudinal, etc.).
Flex is affected by stringers and exoskeletons. Core thickness, density, minimum compressive strength and shear strength are also important.
…yes !..so do I…unless your into the flex , stringers are very practical… Ive always likened them to a boat keel, because they are (usually) the heaviest and thickest part of a surfboard , positioned nuetrally to give the board a natural balance from rail to rail. I have worked with some shapers who like to have weight around the edges , but personally ,I don’t totally agree with that…that said , stringers themselves can be made to produce some very nice twangy flex characteristics.
I would think that a stringerless surfboard is a sandwich construction
http://en.wikipedia.org/wiki/Sandwich-structured_composite
“… fabricated by attaching two thin but stiff skins to a lightweight but thick core. The core material is normally low strength material, but its higher thickness provides the sandwich composite with high bending stiffnesswith overall low density.”
What we call sandwich construction is kind of a double sandwich? (and what the sailboard guys call a double sandwhich is a triple?)
Aviso is closer to a true monoqoque construction IMO. I don’t know how much of the load on the deck is distributed through the rail to the bottom with normal surfboard construction, what I do know is that if you do remove the core, all strength goes out of it. I guess the deck channels along the rails on some board are monocoque feature?
To me it makes alot of sense to use a combination of these constructions. I think aviso proved that moncoque is doable, but not cost effective. Balancing the load between core, skin and stringer make for a cost effective board. Bdw. I still think that part of the stringers job is to prevent localized buckling, which in turn prevent breakage.
The stringer can also be the cause of breakage in lightly glassed modern boards. …if the stringer reaches it’s “snapping point” before the skins and core , it will take the core and skins with it , whereas a stringerless will flex far more before reaching the point of failure…Midgets stringerless boards of the 60’s were strong enough , but only because of a far heavier glass job than modern boards ,and far stronger foam.
Since 2004 I have been putting 10mil woven bamboo mat off cuts in the middle of my home made blanks, usually next to the 1" sheet which puts it closer to the bottom in the middle and the top at the nose and tail.
Dan Mann is now doing this with carbon fiber but I was inspired fom a post by Bert burger back in 2004 and my visits to Jim richardson’s surflite factory.
I like the idea of a horizontal stringer if you can insert it in an opposite camber to the rocker the better.
The centered horizontal springer with perimetter rails seems to be the ticket like what Bert did and firewire copied.using 1lb or .75 lb foam helps.
Jim’s carbon fiber glasses high density cores are conceptually the best idea of centered weight and spring with the lower density surround the core. Y doe this with his honeycomb nidacore stringer.
I think the strength can be added to stringerless boards through the rail better than through the top or bottom skin alone. The skins would only add a little stiffness.
I have numerous stringerless boards using very light EPS, 1 lb EPS, 2 lb EPS, Blue Dow Styrofoam, and PU for the core. They range from 5-10 to 8’. Some have balsa skins without solid wood rails or perimeter rails, they are just the balsa wrapped around the core. Others have just fiberglass and resin but a fuller wrap around the rails. Others have the full balsa perimeter rail.
I think the extra light EPS cores without the perimter rails have the most flex, but they could have been stiffened with more glass on the rail or rail channels.
I fixed a 10’ board that I had a major crease on the deck by stripping off the top and adding rail channels then re-glassing. It’s noticeably stiffer than it was before it was creased.