Another two-part "not a Bisect (tm)" travel compsand

General Discussion
1

Ok, I’m totally remiss in not having documented this build…  But it’s similar enough to my other projects (and simple enough) that I can probably describe it.

 

Here’s what I started with.

 

I’ve been riding it for a couple of years, it’s held up really well, so I thought it would be a good candidate for to be a bisect-ual spec board.

 

Started with some proboxes, used a forstner bit to cut 7/8" holes into it, then trimmed the end of the bolt from a “Titejoint” setup to make it short enough to fit:

 

 

Implanted those into the board probox style, then sliced the whole thing in half (no photos).

 

Once I had the board halved, I took my homemade  CF tube (made by molding CF sleeving from solar composites over an aluminum pipe with two layers of wax paper so it would slide off), and cut teeth in the end of it to make it like a really long holesaw.  After carefully marking my position, I bored into both sides of board using my CF tube, making the hole oversized for adjustment.

Roughed up the finish of the CF tube using some 40 grit, then set it in place with some gorilla glue.  After gluing in to both sides of the board, I assured alignment by using the already-positioned clamps, and by spacing the halves with a few chunks of 1/8" plastic so there’d be a gap for me to saw through the CF tube once the GG was set.

Then I sawed through the tube and all the GG foamy overflow, and faired the ends of the tubes back down to the cut face of the board halves.

I roughed up some sheets of 1/8 ABS plastic with 40grit, smeared them and the cut ends of the board with epoxy thickened with milled fibers, then placed the board halves face down on the plastic sheets (sitting on a sheet of glass to keep them flat) and pressed down to squeeze out all the excess.

 

The edges of the plastic sheets were trimmed with a laminate edge trimming bit.  The hole for the CF tube was cut out using the same bit, inserted into a hole drilled for access.

Then it was just cleanup work.  pretty simple, really…  Ha!

I didn’t wind up using the original 7/8 inserts that came with the titejoint clamps.  They were slightly too tall for the maximum hole depth I could cut in a probox, they would have stood proud of the board surface (I thought about grinding them down, but that would have taken off the zinc coating, inviting rust), so I milled my own inserts out of 7/8 aluminum tubing (LOVE my tabletop harbor freight mill!).  An added benefit is the inserts are a press fit and stay in the probox holes.  Only the bolt and nut from the titejoint clamp comes out.  Much cleaner.  Lighter too.

 

Sorry about the lack of build photos, I was trying to push through to get this one done to replenish my hobby kitty (it’s for sale if anyone’s interested). But if you have any questions or want any clarification, please feel free to ask.

 

Here are the finished photos:

 

2

excellent.  Maybe we can talk Robin into factory production of proboxes like that!  Given the airline costs to bring surfboards these days, a lot of guys might be interested.

Thinking I may have to saw one or two of my boards in half now!!  mix & match would be fun, two boards of the same general shape mid-board… tail 1 & nose 2, etc.

 

 

 

3

Outstanding!  Is there any flex at the joint?  Any change in ride characteristics?  A board like this would solve so many problems for me. 

 

Is it the aluminum rod that takes the bulk of the force while riding?

4

 

shwuz

You win! You never cease to amaze me with your thinking and quality of work.  I can see the thread train wrecks of guys trying to replicate this right now. "Hey, I just sawed my favorite board in half....does nay body know how he lined up the two peices and got them to snug up tightly....and made it water tight....err, how did you drill the tubes straight?" 

 

As for Jefleopold, Jeff yes the do kill the overall ride quality. it would be like some one sticking an aluminum in da butt and telling you to run around a track....yes you can do it, but not as well as with out the rod in the butt.

 

But that's not the point.  Shultz just made an important discovery......he just saved us 1,000's in board shipping costs. I'm going out to start sawing boards in half right now.

 

This is just the injection this site needed!!  Now we don't haver to respond to "How do I handle guys that drop in on me"....or Who's you favorite surfer from the 80's"

5

Brilliant, Jarrod.  Lets keep advancing this.  I am simply not going to pay $400 RT to take a board on an airplane.
One thing for everyone to note is that your boards and mine have all been compsands/bamboo.  I think this important since it gives you an edge in the skin tension between halves.

6

I also note that you are using two clips on the bottom and one on top.  Same here. On the one I posted a few months ago, I have found it to be rock solid even w/o the CF tubes.  I think this is because the bolts are good and tight and the board (fish) is thick in the middle giving a lot of bearing area between the halves.

7

Seriously had me laughing out loud at your comments, resinhead!

I had to pleasure of discussing this stuff with an actual mechanical engineer a few days ago (husband of one of my patients), and I asked him about what he thought about the whole thing.  The only thing he suggested was some sort of pliable material between the faces, like a very thing sheet of rubber, to preload the clamping bolts.  I told him I was using ABS plastic as my face plates and he said that might be just enough pliability.  I did ask him if he thought there was some way to do away with the center tube entirely, and his thought was only if the you could somehow drastically increase the surface area of the clamping inserts.  With the ones I’m using, there’s no getting away from using a center tube, the shearing forces where the proboxes mount in would be just to great under a heavy load.

8

ok, one more thing.  Last time I traveled with it to CR I had no trouble getting in the country, but they objected to the tubes and hardware in my carry on as I was leaving the country.  They wanted to toss the CF tubes!  
ok, one more one more thing.  One end of my female tube leaked. Slowly.  I only figured it out when I saw a tube get sucked down as I vacc’d the water out.  Crazy.  Very difficult to fix.

9

I like that one Shwuz.I wonder if cutting it different would help do away with the rods.Perhaps instead of cutting directly in half,cut it in a V like a deck patch…

I’m glad we have Resinhead for comic relief around here!Funny sht.

10

Really Great!

 

What material didyou use for the end caps?

 

11

Perhaps somthing like a graphite or fiberglass tube that is somewhat flexible would help with the rigidity of the board instead of the aluminum.  The graphite tubes use for pushpoles for fishing might be perfect.  

12

My endcaps are a closely guarded trade secret, sorry…

Kidding, of course. They’re just press-fit “furniture caps” from the bins at lowes. They do finish off the tube nicely, don’t they?

The push pole is actually a great idea. There are tons of fishermen here, could probably find them easily. They should actually be stiffer than a similarly sized aluminum tube, and definitely lighter. Think I’ll look into that!

13

How is the tube supported in the foam?

If it is just a tube (in a tube) inside the low density foam, then I’m not a believer of the added value by the tube.

I’m interested in how the tube is supported.

14

Hans, on the Bisect the tube is anchored in the stringer.  On mine, sine I don’t use stringers, I cut a couple of  small rectangles of plywood about 6 inches by 2 inches and embed them perpendicular to the tube.  Then with a router I route the chanel into which the tube will lay, sizing it exactly to the diameter of the tube.  This provide a bit more bearing for the tube.  But, again, I think the key is the security of the clips and the bearing surface of the face plates.

I’m impressed with what Jarrod is doing because it offers a path to  a a retrofit.

15

Ok that makes sence to me.

This work is impressive indeed!

16

The tube is located so it almost reaches the bottom skin at the ends, so it's closely connected to the skin at the tips.  Also, from experience I know the gorilla glue will expand into the surrounding foam, so that makes for a much greater anchor surface area.  From what I've seen before, it probably reached the bottom skin and most of the way to the deck.  That's why I used the GG instead of just bonding that part with epoxy.

 

My next project after I sell this one is to make a jig for drilling out the hole for the tube, and one for slicing the board.  The drilling jig will allow me to use a forstner bit to cut directly into the stringer for retroing regular construction boards.

One thought on that, I'd love some input...   On a board with a stringer, wouldn't it make more sense to put the tube directly next to the stringer?  By drilling the stringer out, I'd think you'd weaken it and create a hard flex point right at the end of the tube, whereas if you attached it to the side of the stringer it would strengthen the system overall.  Also, if you were to do that, which side of the stringer would you place it for a regular-footer?

17

I think it would be best to put the tube in higher density foam. This will dampen the shocks and it will spread the load.

 

If I would do it, I would take out a rectangular box of foam (from bottom to deck) where the tube will go and fill it up with 2 component PU foam (density 50-80kg/m3).

Or maybe easier, fill a littlebit with foam, then glue in the tube (the tube in one part). Then fill the rest of the box and finish shaping like you normally would. When finished saw the board in half and the female parts are already in place and well aligned.

 

I haven’t made one yet, but this is how I would do it. This way it would also be easy to do a retrofit.

18

BITCHIN !!!

engineering award nominee.

 

the preload connector sounds

correct to insure alignment.

perhaps go to square stock

 between offset stringers

would up the engineering

to eliminate wracking present in

round stock inserts.

 

way cool go man go!

…ambrose…

19

Very nice board shwuz !

 

How did you cut the board : what tool ?  what jig ?

 

20

With respect to the tubes and wether or not they’re important : when I first built my three parts board, it had no tube, only some alignment pins, PVC face plates and 2 sets of bolts on each side.   Aligment was perfect and the junction was very tight.  The board was very rigid (100% carbon fiber laminate) and I thought i would not need any tube, that the load would spread on the face plates and skins.  It was true in knee to shoulder high waves but then when I started surfing the board in larger and hollow waves, the pressures were such that the system failed several times.  I had built it so that the weakest point would be the nuts (they bent), thus avoiding any severe damage : the nuts bent, then the bolts got released and sunk while the two parts separated.   I tried using stringer nuts, but then the plugs were starting to suffer …   Then I added some carbon tubes and it’s been working fine since then (several years surfing the travel board on my yearly 2 weeks surf trip to the caribean). 

I built my tubes so that they had nearly the same thickness as the board, and as you did, I added a small piece of wood to connect the inner tubes with the bottom and top skins.   Building the tubes was the easiest part of the project (given the fact that I had access to custom CNC cut cylinders of EPS), therefore, I wouldn’t bother trying to find ready made tubes that would probably be two small in diameter.   I also believe taht it is safer to have the tubes and the inner sleeves built from the same material.   You need a verry tight fit and with different materials (ex: aluminium tube inside a fiberglass sleeve), I would be worried that with temp changes they expand/retract differently and get stuck.  There’s also some serious corrosion problems when carbon fiber is in contact with aluminium.