Hello,

My head has been spinning for a while now, trying to absorb and process the information overload. I have read and re-read every thread I could find in an attempt to understand some of the dynamics involved with sandwich construction, one thing that I have though about alot is the rails, specifically in the balsa sandwich method. It seems to me that alot of the control/ flex is attributed to rail/ perimeter stringer design.

I don’t know if someone has already tried this, but here is my idea.

I was thinking of laying the rail pieces on an angle at say 50-60 degrees.

While flexing, I picture the two rails loading up against each other, I think it could provide some of that elusive snap as it releases. But this is just an idea…

Josh

G’day Josh!

Getting onto a subject I am pretty interested in here

Keep in mind the following is from a purist’s perspective on wood tension and bending… I am still learning about how this applies to sandwich board design myself.

I am wondering how you expect to maintain a 60° face behind the rails. Remember you will be bending the wood in three dimensions (at least) - in this case two planes. Try taking a piece of half-round and bend it simultaneously in and up while maintaining the 60° face you are talking about. Hard, isn’t it?

Notice how the timber responds. Doesn’t really like it, does it? It wants to go back to it’s original shape… Or torque. Now, we can overcome this with vacuum bagging - by shaping the foam appropriately and marrying up the timber to the foam in the join. However, it’s just the fact that it’s glued to the foam the prevents it from springing back into shape. So the wood is still under tension, even though it doesn’t look like it.

If your rails are pre-stressed in a particular direction (or directions), then flexing further in that direction (or one of those directions) will cause a snappier return to the opposing (original) direction. Bert must use this in his Burgers - whether consciously or not. This is an important part of the flex and return factor. And there are a number of ways that we can exploit this in construction.

When pre-stressing I’d recommend someone new to this area start by pre-stressing in one direction only… But how do that and achieve the shape that we want? Traditionally we use chemicals or heat to bend in one plane and apply our dynamic tension to the other only. Personally I am a big fan of steam bending, it’s simple and safe and I can do it in my own kitchen using a pot of water on the stove with a tea-towel, some clamps and a jig.

And for best results I’d suggest that you (A) don’t violate wood fibers (grain) and (B) try to keep your pre-tensioned curves as even as possible (wood usually breaks where it bends most). These rules can be broken to some extent, once you have gotten a feel for it.

Anyway, really just my own thoughts and blathering Hope someone gets some mileage out of it.

-doug

PS. There are some neat ways to make “spring” snappier - a fairly obvious one being reverse bending… But there are ;D

The prestress sound like a good idea for a snappier return. However attaching the rails at that angle seems very hard to do to me. If you want more snap I have a better idea(IMHO of course). Secondly, if you pretension something like this it will after some time begin to give and the pretention noodles out.

Here is an idea of prestress, preloading, whatever you call it. The bows below are from top to bottom increasing in efficency(providing everything else is equal). The topmost three will almost look the same when they are stringered, the last one being slightly different in the tips. It’s easy to see that the preload is increasing from A to D.

Now look at a snowboard and it’s ‘reverse rocker’ or what is called camber in a snowboard. Basically it’s a preload, giving it more tension. This tension also helps keep the board stable by keeping the contact points on the snow with a little more force. Eventually this camber wears out, the board noodles out and it’s no good.

So how can we use this in a surfboard? Since there are limitations to the shape a surfboard can be, why not use a horizontal stringer? A ‘bow’ or snowboard within the surfboard? www.surflight.com does it, http://www.nevsurfboards.com/surfburger.htm does it. The question is just HOW. How do you foil your stringer, how wide should it be, how do you put it in the board? What do you make it of? And, do you preload it?

I think you should be able to preload it. If it is installed inside the board after the board has gotten it’s bottom skin and rails, the board should keep it’s shape. Otherwise the preloaded string could possibly flatten the rocker too much.

regards,

Håvard

Haavard,

I have been thinking about the exact same thing. Only I have been thinking about what is called a recurve bow which takes your version D and tweaks it just a little farther. See picture. Plus I have been wondering what would if you used a recurve bow under your feet placed perpendicular to the stringers of the surfboard.

Look at Bert’s concave deck boards and you see the recurve bow shape. See picture.

This is good stuff…

Doug, I have also considered some of the possible issues with complex bends and prestressing the timber. I think laying out the rails this way would be a challenge but not impossible. I am trying to grasp some of the effects of this approach and I have some crude experiments in mind to try and sort some of this out. I think it is possible to find a good combination of rail thickness/angle that would promote flex. If say the rails were cut out of a wide piece of balsa, possibly even layered, then there wouldn’t be as much stress from trying to match the rocker contour. I don’t think the bend would equal much more stress than bending the balsa along the traditional 90 degree edge, but I do think the rail would flex more this way.

I like your idea of steam bending, I am not familiar with this process, could you elaborate.

Haavard, I too have been thinking of the springer and I think looking towards snowboard construction is a good place to start. Again, HOW is the question, I remember seeing a thread on snowboard construction, I’ll look for it. This approach adds so many more variables. One of my big questions is, say I did figure out how to make a springer, and that I even determined a good starting point for size, preload etc. How would you attach it to the inners of the board? maybe as part of the deck sandwich? Or attached to the underside of the deck but freefloating on the bottom to promote flex/allow for shear…

Even before I discovered swaylock’s, I wondered why we didn’t see some of the current technology used in boardbuilding…

Josh

This is one way to do it.

I’m not necessarily advocating it but I’ve got six my belt to still test out…

You glue a 1" sheet to a 2" sheet with the “springer” in between.

You can alter the thickness and width of the springer as needed.

Preshape the bottom sheet first on a flat table then glue or vacuum everything togethor.

If you lam on the bottom sandwich while doing this you’ll never lose the rocker and shaping the deck will be a breeze…

Again this is just one way maybe not the best…

I’m currently rethinking putting the “springer” to be under the non attched lam sandwich since that’s where the flex will occur… And yes them Bert thin concave deck flat bottom shapes make a nice preloaded bow…

And Jim Richardson’s stuff is way way more sophisticated than this attempt… More like a fancy torsion boxed ski.

Hey Guys!

Haavard - I never suggested that angled attach was a good idea. True, I never came directly out and said “no” - but if you read between the lines you’ll get the picture that I think it’s too hard for what little return you will get. Glad to see you are starting to reference highly-stressed timber designs (bows). Have you made any selfbows? I have - gives you a really good feel for the properties and limits of wood. Just reading the theory will help anyone wanting to unlock the secrets of “burgers”, IMHO.

The recurve/setback in your illustrations is correct - it does increase “snap back”. All else being equal. With one exception. Your illustration comes from vol 1 of the Traditional Bowyers Bible. In vol 2 (or maybe 3) Tim corrects that design statement. The order should be A, C, B, D - total tip displacement to stringing is the critical factor (i.e., how far the wood moves). As for your snowboard - I have made bows with an identical profile to your contact point/camber model In the bowmaking world it’s called a static recurve. Similar principles.

Those four words (“all else being equal”) are critical! If the timber is thicker or wider or other important design concepts have been incorporated things change. And sometimes the change is an order of magnitude different!

Hhhmmm… In a bow the tips (as in your illustrations) bend (flex) down, past the handle. In the snowboard profile the ends bend up past camber. The direction of flex is different. So in a bow to increase “snap” we prestress/preload upwards and with a snowboard we pre-stress downwards (again - ref your piccies).

Your “how” questions and comments are interesting and I’d like to follow on with some lines of reasoning in open discussion here. The ends of a surfboard (from side view) bend up and we want them to recover in the opposite direction. Assuming we are using wooden rails we can improve snap starting with flat “rails” and bend them into top view profile (they are still flat form side view). Then vacuum bag them onto the blank. When we remove the whole lot from the vac bag it will tend to spring back into flat shape somewhat, but not completely. Now bag on the top and bottom veneers. The board will now recover to it’s original flat shape to a much lesser extent. How much? Well, that’s hard to tell and will require some experimentation. Don’t like to guess, but I’d say probably around an inch at each end (I could be way off). So using this technique will require your “bottom template” to have more rocker than the final product will have. The same concepts apply to using various stringer designs underneath your top and bottom skins.

To increase the effect we use rails which bend TOWARDS THE FLOOR before laying up

Bart - That is a recurve… More accurately it’s a composite recurve. Unstrucng those suckers for a “C” away from the hand of the person holding it! They go through incredible flex just to be strung. Not surprisingly they are made of horn, wood and sinew and are the earliest example of human composite material use and manufacture I know of.

Josh - I think the whole approach is a good idea. As I said above I think angling the timber will provide minimal benefits for a number of reasons. It may even be counter-productive (too much toquing sheer - even with modern composite materials the boadr could pull apart internally if one join is just a bit too dry). As for the “current tech” question… there are answers elswhere on Swaylocks Keep talking! We are all listening!

Steam bending, the way I do it, is easy! Get a big pot, fill it 1/2 to 2/3 and bring it to the boil. Put the section of wood you want to bend over the top when it’s boiling and cover with a wet teatowel or such. Let it boil merrily away for 30 minutes per 1/2 inch thinckness of wood. When the time is up pull it out and clamp it to your bend jig (the ends should be 1-2 inches overbent for every six feet of length). After a few minutes it will have “set” but you should leave it on until it’s cooled down. Resist the urge to put it somewhere cold or to put it in cold water for at least an hour. Obviously - your wood will need to reequalise with EMC before you encase it in epoxy :=D

oneula - Beautiful! I don’t think sophisticated always produces the best results. IMHO technique comes into it a whole lot. Of course, I have a whole bunch of questions Firsly - are your internal stringers prestressed (if so, how much)? What are your stringers made of? I also look forward to hearing what you think of the prestressed rails idea.

To noone in particular - At the risk of being shouted down… I think people will find they get best results pre-stressing if they do not use ply. If anyone disagrees I suggest they think a bit about the difference between solid timbers and ply then we can discuss

I have some other thoughts and ideas I am looking forward to discussing. But I don’t want to preempt things. I am really enjoying the diverse opinions, thoughts and perspectives. Great new (to me ideas) are coming through it.

Take it easy!

-doug

Quote:

You glue a 1" sheet to a 2" sheet with the “springer” in between.

You can alter the thickness and width of the springer as needed.

Preshape the bottom sheet first on a flat table then glue or vacuum everything togethor.

If you lam on the bottom sandwich while doing this you’ll never lose the rocker and shaping the deck will be a breeze…

[snip]

And Jim Richardson’s stuff is way way more sophisticated than this attempt… More like a fancy torsion boxed ski.

How about cutting the blank 1" thinner when hotwiring it instead, then glue on a 1" flat panel with wood in between on the rocker table? Seems easier to me(maybe I did misunderstand though…)

Is Jim Richardson the man behind the surflight? I think he needs the torsion box because the outer foam is so soft that he would get a ridicules twist if he didn’t have it. With outer glassing and sandwich, the twist is reduced. Even more so with parabolic rails, and even more with both parabolic rails and sandwich deck and bottom which in effect is kind of a torsion box.

regards,

Håvard

hey doug,

sorry if I came out a bit unclear, the comments about the angled rails was intended for josh, not you. Didn’t have to even read between the lines to understand what you thought about it.

I’ve never made a bow myself, I’ve used a couple though and got the medals and national records to show for it ;-). Gotta get a hold of that bow bible, that would be interesting. A couple of your comments got me thinking since the board has to have rocker, the stringer can be straight before it is preloaded. It’s like stringing a straight bow, when you do it, that’s also kind of a preload. It will have less effect, true, but it’s still better than no preload or in other words a stringer that easily conforms to the shape of the board when it’s installed.

I’d suggest taking a more or less straight piece of wood for the stringer. Attach the bottom skin and rails. Route a slot wide enough for the stringer and deep enogh for the stringer, plus a layer of EPS foam. Now vaccum bag the stringer into the slot with an oversized backing of foam while the board is in the rocker table. Remove the excess foam then bag on top skin, and laminate the deck on the rocker table as well. I doubt the springback will be very significant. Bdw. the skins are also preloaded as they are formed to tge board.

Also, you could o two or 3 stringers to load up against the fins, do a V or Y shaped stringer spring on the fins to help against torque, the variataions are endless.

You could obviously do the same with a stringer that already have a recurve or preload of some sort. But even so, I think the preload of a straight stringer would be a benefit. Secondly, no matter how much preload we put into it, it’s going to wear out since we cannot unpreload it like you do when you don’t ride the snowboard or you unstring the bow, however, this advocates for a more heavily preloaded stringer since some of the tension will wear out.

I’ve been thinking about one thing. Bert always show us the board flexing while standing on the bottom of it. Ok, so it’s easier and more practical to show it that way, but it’s not the way it flexes when you ride it. So it got me thinking since he could so easily flatten it out, maybe it is heavily preloaded in the other direction?

Yeah, plywood is a probably bad idea. It’s normally the grains of each layer running perpendicular to each other. That’s why it bends so easily. Also the wood quality is usually low. I also doubt the glue used are made to withstand thousands of flex cycles. I would guess for a surfboard you would use balsa to keep the weight down. I doubt the weight of an ash or yew stringer in 6’ length and 2" width with the proper taper for a bow would be acceptable in a surfboard.

How do you suggest the stringer is laminated and foiled knowing bow tech? Bdw. what did they use in ancient times to glue laminated bows?

regards,

Håvard

flex bias , interesting concept …

regards

BERT

G’day Havard!

sorry if I came out a bit unclear, the comments about the angled rails was intended for josh, not you.

Didn’t have to even read between the lines to understand what you thought about it.

NP Sorry for the crossed wires, mate.

I’ve never made a bow myself, I’ve used a couple though and got the medals and national records to

show for it ;-).

LOL! I am not that great a shot - good enough to put dinner on the table, that’s about it. I prefer shooting long wooden bows. Which I also love making… Though this boardmaking thing is rapidly taking over

Gotta get a hold of that bow bible, that would be interesting. A couple of your comments got me

thinking since the board has to have rocker, the stringer can be straight before it is preloaded. It’s like

stringing a straight bow, when you do it, that’s also kind of a preload. It will have less effect, true, but

it’s still better than no preload or in other words a stringer that easily conforms to the shape of the board

when it’s installed.

Spot on! There’s something called a deflex bow. It’s the opposite of the standard modern recurve - the tips of the unstrung bow point back towards the archer holding it. Those designs shoot like a straight stave bow 10+ pounds of draw lighter. The more tensioned wood is the more vigorously it wants to spring back to it’s original shape. Too much “snap back” in a surfboard wouldn’t be good. But too little makes it feel unresponsive. There’s three volumes of the TBB (Traditional Bowyers Bible) and one or two chapters in each is incredibly enlightening regarding the way wood behaves under stress and tension.

Another important factor in how easily wood bends while retaining tension is thickness and, to a lesser degree, width. Wood twice as wide is twice as hard to bend. Wood twice as thick is EIGHT times harder to bend. So shaving a small percentage off thickness may drastically increase the ability to bend. This should mean that wooden rails can be fairly highly pre-stressed (snap back more sharply) but not be too difficult to bend by tuning their thickness and width.

I’d suggest taking a more or less straight piece of wood for the stringer. Attach the bottom skin and rails.

Route a slot wide enough for the stringer and deep enogh for the stringer, plus a layer of EPS foam.

Now vaccum bag the stringer into the slot with an oversized backing of foam while the board is in the

rocker table. Remove the excess foam then bag on top skin, and laminate the deck on the rocker table as

well. I doubt the springback will be very significant. Bdw. the skins are also preloaded as they are

formed to tge board.

I reckon that’ll work for a centre stringer. I am going to pursue the wooden rails-as-stringers approach tho Yep - the skins are pretensioned, but the effect will be minimal - because they are so thin. Take a wood shaving and bend it - bends easily and doesn’t recover. A 4x4 won’t bend without great force, even then bends very little before it breaks, but spans back incredibly fast (if it doesn’t break). A 2 inch wide, 0.25 inch thick slat bends easily and snaps back readily.

But I have changed my mind about something I said that the whole board will recover away from rocker an inch or so after the skin is applied. Well, I have changed my mind - I realised last night that the mechanical bond interface (where the skins are “glued” to the stringers) will counteract this a lot. We see this in composite bows and Perry bows. That might be less pronounced in your “buried” stringer (because it’s only bonded to the skin on one side, to foam on the other and foam gives easily compared to wood).

Also, you could o two or 3 stringers to load up against the fins, do a V or Y shaped stringer spring on

the fins to help against torque, the variataions are endless.

Yeah! You could do virtually any combination of pre-tensioning strips under the skins. That should mean any area can be given almost any combination of flex, resistance and snapback desired.

You could obviously do the same with a stringer that already have a recurve or preload of some sort.

But even so, I think the preload of a straight stringer would be a benefit. Secondly, no matter how much

preload we put into it, it’s going to wear out since we cannot unpreload it like you do when you don’t

ride the snowboard or you unstring the bow, however, this advocates for a more heavily preloaded

stringer since some of the tension will wear out.

I guess a good rule of thumb is - if you have to bend it to glue it up you are pre-tensioning it (just keep in mind thickness, width, etc “rules”). The more you bend it the more you pre-tension it. So yes - a straight piece is going to pre-tension. I am going to disagree with your second point In a raw wood configuration you would be right - that’s why wooden bows are traditionally unstrung when not in use. But in the composite world things change! A huge number of modern composite material bows are never unstrung except when the string is changed. And they do not suffer any loss of cast or “noodling”. The secret to why is actually in the material interface and fibreglass layering outside the wood. But that interface layer becomes very important - you do NOT want a dry join

I’ve been thinking about one thing. Bert always show us the board flexing while standing on the bottom

of it. Ok, so it’s easier and more practical to show it that way, but it’s not the way it flexes when you ride

it. So it got me thinking since he could so easily flatten it out, maybe it is heavily preloaded in the other

direction?

I reckon that’s probably right (if I read you correctly). While he’s simply demonstrating the flex present it suggests a certain level of snappy recovery (or you will surf a noodle). There is a relationship between flex and recovery, but it’s a fairly fluid one. And with composite construction we mitigate some of the insurmountable hurdles involved with all-wood construction. That’s why Bert can bend his boards back in the OPPOSITE direction to the way they flex without doing serious structural damage to the “flex systems”.

Like I said earlier - in theory we can put whatever flex and flex resistance we want in any vector or plane. Work out how you want your flex to work and introduce the appropriate design flex slats. Look at the board in any perspective you like (top/side/front/end) and work out what directions you want flex and how much. And how snappy you want it to recover. Then work out the slat system that implements it

I am visualising a skeletal frame of slats, stringers and rails implementing perfect flex and recovery :=D

Yeah, plywood is a probably bad idea. It’s normally the grains of each layer running perpendicular to

each other. That’s why it bends so easily. Also the wood quality is usually low. I also doubt the glue

used are made to withstand thousands of flex cycles. I would guess for a surfboard you would use balsa

to keep the weight down. I doubt the weight of an ash or yew stringer in 6’ length and 2" width with the

proper taper for a bow would be acceptable in a surfboard.

You have the right idea!

It’s an interesting area in it’s own right People often talk about grain without really understanding what it is. Grain is, in reality, a 3D lattice - wood fibre embedded in organic resins. Chop down a log. Look at the clean-cut end. The rings are the end of the wood “threads”. These threads are where all the integrity and strength of wood comes from (the “resin” is pretty week). Imagine making a composite “log”. Get a whole bunch of long fibreglass threads, resin them up, lay them on top of each other in a bundle, roll the cylinder into shape and wait for them to set. Next we’ll “make” a “plywood” log. Get the same number of fibreglass threads, chop them into itty-bitty bits, resin them up and roll them into a cylinder and wait for it to set. Now, which one is easier to break and why That’s the real secret to “grain” and wood integrity. That’s why splitting a log from end to end produces strong wood than cutting it form end to end with a saw.

This is very relevant to composite board construction using timber. And yes - lightweight woods will be a must. I have been wondering for some time whether anyone has tried using spruce? It has the highest strength/weight ratio of most light timbers. But too much strength may be a bad thing.

Bert? have you tried any spruce species??

Idea! We can use different timbers for our “slat skeleton”! This gives different strength/weight ratios for further flex tuning and weighting. And we can use heavier timbers throughout for big guns

How do you suggest the stringer is laminated and foiled knowing bow tech? Bdw. what did they use in

ancient times to glue laminated bows?

Old composite bows are constructed of horn, wood and sinew - held together with animal glue. Those animal glues (hide glue) are strong! Put a line of it on glass and as it dries at shrinks… And pulls pieces of glass off! The Achilles heal of animal glues is moisture (they aren’t water proof), so old composite bows were often wrapped in a moisture resistant layer of some kind. Composite bows have been around for at least 3,000 years. One was aged using radio carbon dating and by looking at the layers of earth it came out of. Simpler wood/sinew composite are almost certainly 500-1,000 years older again. In wooden composite bows the glue (interface) layer is critical.

Not quite sure of your question. Do you mean laminating the stringer as in layering multiple pieces of wood to form the stringer? Or as in how it’s layered to the foam? As for foiling… I am guessing you mean width and thickness tapering of the stringer for foil.

Unless my logic is fundamentally flawed I think we are heading in the right direction to unlock the “perfect board” aspects of flex. Course I have never been wrong before - not more than once a syllable ;D And if we are right there is a HUGE amount of experimentation and finesse that can be involved in this.

Damn, gotta get my vac bagging setup finished

Regards,

Doug

Hey Bert!

Hhhmmm… “flex bias”… Isn’t that bais to flex in one given vector rather than other vectors? Interesting term.

I’m sure I recall you mentioning something about that before

-doug

Quote:

Old composite bows are constructed of horn, wood and sinew - held together with animal glue. Those animal glues (hide glue) are strong! Put a line of it on glass and as it dries at shrinks… And pulls pieces of glass off! The Achilles heal of animal glues is moisture (they aren’t water proof), so old composite bows were often wrapped in a moisture resistant layer of some kind. Composite bows have been around for at least 3,000 years. One was aged using radio carbon dating and by looking at the layers of earth it came out of. Simpler wood/sinew composite are almost certainly 500-1,000 years older again. In wooden composite bows the glue (interface) layer is critical.

Not quite sure of your question. Do you mean laminating the stringer as in layering multiple pieces of wood to form the stringer? Or as in how it’s layered to the foam? As for foiling… I am guessing you mean width and thickness tapering of the stringer for foil.

The animal glue being water solutable explains a thing or two. I was wondering why the traditional Sami bows were wrapped in birch bark…

Re: center springer versus rail springer, I think the problem with the rail is the tuning. Since this is an outer part of the board there are limitations to what you can do to them without changing other aspects of the board. If you’d like a softer flex, but the same rail thickness, what do you do? The internal springer is more easily tunable and does not effect the shape of the board in any way. Althoug the stringer would only press against the foam, the foam would press against the skins so I think it would load up pretty quickly. You could also make supports of high density foam or woodat the tips for a more direct response. Just make sure it’s not glued to well together or it might be rigid, eliminating shear.

Since I cannot get 8’ of balsa in one piece I would have to laminate the wood in one way or another to make up an 8’ stringer/springer. Furthermore, I would think that I’d need a layer of glass on each side(ecpecially on the tension side) of the laminated stringer for reinforcement or balsa would break way to easily. This layer of glass with epoxy could be used to install the stringer also.

Regarding foil/taper. I’m not even really sure where I want the board to flex the most, but I’m leaning towards a nice curve with apex at the center of the stance (or with a slight setback). I’ve been pretty much set on a FU center fin box, but I think it will screw up the flex in the back of the board. Secondly, you would have to take into account the thickness of the board and how the pressure from the water is distributed on the bottom of the board when doing the taper of the springer. The stiffness of the board is also related to the cubic of the thickness. However, by creating a deck concave some of this thickness is removed making the initial board more flexible. Also, the fins regardless of which fins system you use(or glass ons) is going to stiffen up parts of the tail. All this needs to be considered when designing the stringer taper. Or drop taper and prestress/bend the wood instead is possibly an option.

All these variables…

regards,

Håvard

Regarding foil/taper. I’m not even really sure where I want the board to flex the most, but I’m leaning towards a nice curve with apex at the center of the stance (or with a slight setback)

i agree. but im adding some more tail flex…like this…

bottom is before, top is after

heres another sexy foil curve…

I think Bert uses pre treated (RTI)- maybe pre-curved wood for the rails in 18" to 2" pieced unjoined. Found this stuff on ebay which may be useful, as Bert also uses foaming epoxy

Falcon Grip - (used to be called “Talon”)

• and it really does ‘GRIP’!

this is really amazing glue! its technically known as a “Foaming P.U. Glue”

Very strong and will bond to almost anything - and also acts as a gap filler!

use it straight out of the bottle as a fast setting strong glue /b>

NO MIXING!

its like a Cyano, PVA, Epoxy and a filler all rolled into one!

You get about 3-4 mins working time, and then its fully set in about 8-12mins

(Times depend on temperature and humidity)

Use it for Balsa, Plywood, Foam, -sticks almost anything!

I even know of someone sticking concrete breezeblocks together with it

Also -as its a moisture activated glue - if you spray a little water on it, it will foam up more and fill bigger gaps -

once its gone off its tough and can be carved or sanded to any shape

Fantastic for repairing foam wings too!

bonds totally with the foam and is stronger than the original!

use it for fitting Phenolic tubes solidly into wings

22 sizes and Bulk sales available - if you don’t see an auction for the size you want just email me!

i supose you can pretty much taper your tail foil to nothing with this kind of construction

i am going prettty thin at the tail on board No 4. as well.

tried a light glass job on no.3 and I am regretting it.doesnt seen to change flex characteristics at all

the board is the lightest ive ever picked up with about the same strength as a poly(but more springier).

i think id rather have a really tough board that is a bit heavier…(still way lighter than a poly)

Ill deffinately look more closely at board foil from now on. (changing it from traditional shortboard poly foil…thin tail/concave decks etc)

and try, not wrapping the deck skin around the rails

maybe approach the outer lam in a different way as well

one thing though no 4 has the rails tapered in width toward the tail and this has made the blank a bit more flexible

basically i have found that a blank with skins before its outer lam will flex and bend and sprinback etc… but as soon as you lam it ,it becomes stiff .

so i feel its more of a relationship between a lot of factors of which balsa stringers are only a small part…

its all relative to the weight of the rider anyway

i mean if you weigh 120 kg do you really want a board that flexes as per berts photos?

so WRTF

its basically individual tastes and weight of rider

I dont think that it is holy grail of surfboard design really

unless you are at a certain level of ability…

than im positive it would make a big difference…

flex for aerial surfing isnt really much use unless you can already do aerials…

I feel that weight and durability is the worth spending more time on as these are issues which are relevant to me as a surfer …(long walks and rocky bottoms)

is 1.6 kg the limit or has anyone topped that ?

i think sabs was doing .1.7kg

my board no 3 is under 2 kg…(4.4 pounds)i think its pretty light)

but id rather hell tough and weigh a bit more maybe 2.4 kg

cosidering my normal poopee is over 3 kg with fins system(and not very tough)

i think maybe not to push so far to the limits…

so FLEX hmmmmm getting there

what really trips me out is how simple it is to get a good result with epoxy composites

and im making lighter and stronger than a shop board

its only a matter of time before i get SHAPE sussed…

then look out local break(im alreadygetting more waves on no.2)…

yea silly i think your pushing limits there …

1.7 was the end of the line for me so far , with set fins …

that said tho , the board in question is over 6 months old and getting ridden by a QLD ripper virtually every day , and it was used as the trampoline for a few months as well …

shape is a must …

dont worry , ive built plenty of average boards this way , its not a recipe for a magic board , but will definatly get you a lot closer …

havard , you gota get one in the water , then tune up or down …

dont complicate things to much for starters …

keep the amount of variables down till you get a handle on what does what …

the springer is not essential unless you need it …

boosting , ultra front foot , heavy, large waves , or choppy ugly condititions regularly …

ive already found a huge difference between or east coast and west when it comes to flex …

on the east coast you can have way more and the board still loves it , so the power rating of the wave has a bearing to …

build it , then tune from there …

based on the feel to you …

regards

BERT

oh yeah you just reminded me…while were on KISS…no more balsa rails for a while…pretty sure i can get to where i want to go without’m…recent discoveries & results validate this direction…results tbd

oh and another thing…the core principle behind composites is strength to weight…if weight is no longer a concern its easier to build std epoxy boards like what Greg L does, but either no stringers or flexy stringers…much easier to build and they go off better than poopee with better durability…

…KISSSSSSSSSSSSSSSSSSS

on the east coast you can have way more and the board still loves it , so the power rating of the wave has a bearing to …

so less power east side? i’ve seen lots of footage of the east but almost none of the west so poor metal referrence…

speaking of west/east AU waves…i saw the most sick right hander video recently…somewhere on the west or SW AU…Taj and some other pros on perfect DOH TOH 10 second barrels…looked like a hybrid of jbay abd BDpipe…it was machine like…my jaw just hit the floor…whats the breaks name?