I’ve been thinking about how Bert mentioned that you can use lumber in a different direction in order to add more spring to a board. He mentioned that it was possible to tie the two rails together is certain point. So, here’s what I’m thinking. Use very springy pieces of balsa that are perpendicular to your skin balsa on the tail of the board in the area where the fins go. It would serve the added benifit of re-enforcing the fin boxes but keeping them isolated from the upper deck. This would help explain why on some of his pictures it looks like the skin is not rapping over the rails. What do you think? Would this work? Do you see any obvious problems that I am not thinking about?
Fin boxes?.. Yikes.
Running wood in that direction would be great for reinforcing the fins and would help stop the rails from twisting off (which Bert is also big on). I could see how not allowing the rail to twist off would force that energy to be transferred into longitudinal flex instead… aiding in the load up of energy and release out the tail.
hey dan… i don’t understand… are you saying run the balsa across the board instead of nose to tail? are you saying do this under the balsa skin? i don’t really understand “skin is not raping over the rails” do you mean on the bottom or the top?
check out the photo where he uses the d-cell to reinforce his boxes… looks like only one layer of balsa to me…
so much to think about…but i think for the weights he is getting that he is not adding much anyplace…
oh yah, my question on that photo is do you think he just “dropped” those reinforcements in or were they bagged on under the skin and they extend further then the boxes?
bert’s photo used with the best intentions…
I’m stretching my brain just as much as you guys to try and keep track of this stuff.
Here are some from Bert about s curve in tail.
-this board is still my all time favourite all round shorty, for waist to double head waves…
this pic below was my second surf on this board ,i think ive ruined this board , about 18 months back i put futures boxes in it , even tho i made fins identical in size , i think where it stuffed up was the elimination of shear movement and the general flex it had in the tail before i put the boxes in …
i tied the boxes to the deck and it stiffened the whole tail , it doesnt spring out of turns like it did before , for the last year ive only ridden it once , in super clean head high solid beachies (normally where it went best ), and it just wasnt the same …
so even tho i said it was my all time favourite , its not like it used to be …
i got 6 good years out of it , i will just retire it and make a copy of how it used to be …
------------------------------------------------------------------------hey jip …
yep it had glass ons before …i make all my own fins as im very particular about foils …when i made fins to fit the futures boxes the foils and templates were the same , there was some small differences at the base , but the fact the board was different was more to do with flex than anything else …
if you have glass ons or shallow boxes that dont tie to the deck your board can flex way more…
for your board to flex it needs maximum shear movement … when you tie the deck to the bottom you eliminate shear , so now you cant use flex as part of the equation …
stopping the flex in just the last 18" of the tail still meant it affected the overall flex even at the centre …
coz even if just the centre of your board flexes , itll still transfer load right to the tail …bend a book sometime and youll see what i mean … speaking of flex …
check out the boxes im making now …
im doing a rockered version , for obvious reasons …thinned it down so the box is lighter , but best of all ive got the boxes to flex , to reduce the load where the box contacts the board , and also to flex and move freely with the skin of the board …
ive pretty much had to make these if i want my boards to work well and be able to offer a fin system …
not taking anything away from all the other systems , its just that none of them are designed specifically for high performance sandwich boards …
also tubedog , your dead right about subtle changes …
move a fin 1/8th or tweak your tail rocker 1/8th in the wrong spot ,maybe pull your tail in 1/4 and youve ruined your board …
my boards havent really changed in over a decade , once you work out exactly what works for you ,after that it comes down to real small changes , most of which dont make it go any better , just different in different conditions
11 " nose as well …
hey dorian heres a few more pics from one of those sessions above …same board as the pic above …
doh , i really need to build this board again …had so many magic sessions on it , even tho ive got the flexing boxes now , i think ill just do set fins, keep everything the same and just build a copy with boxes , have two identicals and compare …
this was the only board ive ever owned that i couldnt fault …
you know how you always want more out of a board somewhere for some little reason …i think thats why i rode it as my main board for 5 years … mostly i just on sell a board if its not magic within a few months or even after a few days in some cases …
the whole time i rode this shortboard i had no idea what i would do in another board coz this one did everything i wanted …so i had no need to try something different …
ive based all my team guys boards on the same formula as this board and had the same response from all of them …
cant fault it …
crispy hard edges to … maximum release …
have fun i hope it works for you …
Yeh I was thinking of a layer of wood UNDER the layer of balsa on the bottom of the board. That photo you showed is what got me thinking. A while ago I was reading one of Bert’s posts and he mentioned that he used wood under his fin boxes (I’ll try to find the link after I’m done writing this). At the time I didn’t understand the significance. In the flex thread he talked about being able to tie together the two rails in key locations and in the process be able to take advantage of the springiness of the wood that was turned sideways (he didn’t mention sideways but he talked about directional bias of the wood and the balsa is much more springy against the grain). This method seems like it would kill2 birds with one stone; you support the fin boxes and put springiness where the board compresses under the stress of turning.
Heres one of the links that I was thinking about http://www.swaylocks.com/forum/gforum.cgi?post=162636#162636 but its not the one that had the illustration.
Instead of putting the wood 90 degrees to the longitude axis of the board I’d put two pieces of wood in 30-45 degree to the logitude axis towards the fins in a V shape. This would reduce twist when the fins have high load. Kind of like blade springs(Is that the right term?) You could also use 45 degree glassfiber weave in this area to get some of the same effect.
Dan, are you experimenting with horizontal stringer in your new board?
I think the main point of that link you posted about the boxes set in wood are 1) don’t tie your deck and bottom together with the fin boxes. 2) reinforce the fin area or you will get trouble with water leaking into balsa/EPS. That’s how I read it atleast.
regards,
Håvard
yo dan i think this is what bert and lee are talking about in that post…
i don’t know if your would be adding more springyness or just more stiffness by doing what you are talking about. but the setting the glass on 45degress is something i play around with…
look at how bert is glassing some of his team boads 1oz under 2over bottom 1oz under 3oz over deck, to me that is saying that the springy is there you just have to “unlock” it… of course i could be wrong 
just couldn’t help throwing in a photo of the two boards i am sanding tonight…
I have 3 Bamboo horizontal stringered EPS frankensteins experiments I’m finishing.
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Balsa rails attached to the stringer top and bottom balsa lam not wrapped 2.25 thick concave deck/Vee Bonzer singl;e
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Balsa rails not attached top and bottom bamboo lam not wrapped 1.75 thick concave deck/bottom single
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No balsa rails to stiffen double wood layer Balsa/Hardwood Veneer 2.75 thick thruster
We’ll see what happens
Nice work John you’re cranking them out now…
I’m going to work on adding the horizontal stringer next. The goal for this project is to go with the concave deck. I sanded it in last night and I’m really happy with how it turned out. I was afraid with the stringer and being new to concaved decks I might sand all the way through. I’m surprised how much more smoothly things are going this time. The perimeter stringers were soooo much easier once I preglued the strips. I think that I’m going to try and attatch the top and bottom skins at the same time. That should be good for a huge laugh!
By the way, does anybody have a good way to install future boxes in eps. I see that Bert used divynicil under the box area. I was hoping my perpendicular balsa idea might do the trick, but I would hate to mess up the flex or not have it strong enough.
jjp, your boards are looking great. you really see to have it wired. Now you need to share your wood trimming secrets!