Scarfing Balsa Rails

General Discussion
1

This is actually a two part question. The first is that I’ve looked into buying long balsa stock and resawing it down to size then cutting the rocker into it. Its just too expensive and wastefull. Is it possible to take three 3 foot by 3 inch pieces of 3/16th stock, scarf them together at the joints with epoxy, then cut out the rocker. Now I would sandwich the pieces together to the desired thickness. Does anybody see any problems with this approach? What would be the best way to cut the scarfs.

My second concern is wrapping the rails around the foam in order to form the rails. I’ve though a lot about how Bert mentioned that contour mats were a starting point that allowed him to go to a new level. It would seem to me that making adjustable forms (jigs) and preshaping the boards parts then attatching them with epoxy would be a better way to work (sort of an anticontour mat). When I think about attatching rails strip by strip to the board itself it seems like it would create a giant mess, and it would be extremly difficult working with both sides at the same time. What do you think about making an adjustable rail jig ( think of a piece of plywood bent like a frown with adjusting blocks to push the plywood into different shapes). This appoach would supply lots of clamping opportunities (maybe even vacuum bagging) and let you work one rail at a time. You could even preshape the bottom edge of the rail so that the skin attatches the way you want.

2

Scarfing works fine. You set your tablesaw blade at 45* and then set your miter fence at the angle off 90* you want to get some curve in. I’ve used 85* for one side of the cut & 95* for the other with fine results. If you’re thinking of gluing that all up to make a solid wood board, its going to be heavy. Of coure before you glue it all up, you could chamber out all the middle pieces and just leave the rail ones solid for shaping. Its still a lot of balsa. Mine is $5.51 / bf and that’s about the cheapest I’ve heard…and you don’t need to glue wood-wood with epoxy. Wood glue is fine.

Yes, adding the rail pieces strip by strip is tedious. But it does work. If you come up with a better way, I’d be very interested in seeing photos & descriptions…

3

I’m getting very close to the point were I can give it a try. Trying to get a handle on all the components of a surfboard and how they fit together seems to require hours of staring at the wall before it starts to make sense. What got me thinking about a better way to build the rails was the frustration (bordom) you expressed at building your rails. You seem to have extremely good woodworking skills and if it doesn’t work well for you it probably wouldn’t work in a production setting like Bert’s.

4

You’re right, I can’t imagine doing it with any kind of production speed. Although I did find:

On the longboard, because of the length & rocker, each rail strip took 3 separate pieces, end-to-end. To get 4 pieces thick - enough to shape a nice egg rail on a thick board - on each side, that meant separately gluing on 24 pieces.

On the 6’ fish, because of much less length & rocker, each rail piece was continuous. So 8 pieces total. And since my garage was around 62 degrees, I had enough ‘open time’ on yellow glue to wet out & lay up 2 pieces at once. I think clamping is actualy easier with 2 at once, since the glue between the two pieces holds them into the curve better than glue on one piece alone. Like building a bent piece of wood out of thin pieces glued together rather than trying to steam or water bend it. So it was only 4 lay-ups with glue & tape. Do one side, tape, flip the board in the racks, and do the other. Go put it in the bathroom with the spaceheater…wait 2 hours…do the next layers.

Much more tolerable process, but I’m 99% a longboard guy, so I’m not about to build 6’ boards just to make the rails easier :slight_smile:

I think I’m going to try CMP’s way next, of shaping the rails onto the foam blank instead of cutting them off square, then laminating the veneers around the curve. The more time I spend with the vac bag, the more do-able this seems.

I might even layout all my veneer and a layer of glass and brush in the resin and let it cure overnight. Maybe even in a vac bag on a flat table. Almost like a prepreg. I’ve found, in test pieces, that balsa with a layer of glass on one side only can be put into incredible curves without cracking. Once its cured - but within 24 hours for good epoxy bond - I’d brush more resin into the weave, slap it on the blank, and back into the bag. I doubt the veneer would crack at all that way, and I think that’s closer to what Bert’s doing…although the underside of his balsa apparently has some profile (I missed the phamous photo) and maybe he uses a foaming agent in his blank-to-prepreg resin to help fill any voids…

5

Yea doing the balsa perimeter rail wrap is a b*tch especially if you plan on doing it all by yourself.

Just finished my first and I’m still cleaning up the mess… wood shifting and wrap breakage. patching and sanding, patching and sanding…

I did all my layers using titebond along the whole board all at the same time over lapping each joint 1-1.5".

took 3 layers of 1/4" balsa for the sides and 3 layers of 1/8" balsa interlaced with 3 layers of 1/8" cork to build up the nose and tail curve wrap. Almost impossible to hand bend the 1/4" around the nose or tail without a jig like Paul Jensen uses.

I thought by cutting a full template for the top and bottom I could pressure tape the rail wrap to the outline against the hardboard instead of foam but I was wrong… We had to eventually use that plastic office supply wrap to hold everything in and then strapping tape over that to keep the plastic wrap from releasing.

Basically you should get you blank to a semi finished shape with 90 degrees rails on the outline.

Then draw out your rocker profile on the 36" or 48" long 1/8" or 1/4" balsa strips.

You can cut 3-4 rocker profiles out of one strip to build up either 3/4" ot 1" balsa rail bands on the sides.

Remember that the thicker you go on the sides with the thick stuff the more 1/8" or 1/16" wood you’ll need on the nose and tail to match. That’s where I got the idea of using layers of cork in between the thin balsa strips ala PaulJ. It should also decrease the weight up front and back and putting more of the wood weight on the side rails where Greg L says it needs to be…

Benny knows I showed him pics of my little disaster already…

Thinking about it over this work week this is what I would do if I did it again…

First make a bending jig using a variable/non-variable wood rocker table

this is how I see it based on Paul’s pictures…

  1. cut three rocker profiles out of 1"x"6"x8" pineboards.

  2. nail/screw a 1/4x24x96 plyboard to these rocker planshape using one one the side and middle.you could connect these three board at the top and bottom with more pine for rigidity.

  3. draw your outline profile on the ply making it bigger to accomodate the balsa rail glue up AND rail compression wrap.

  4. drill holes in the ply every “x” inches along the outline that you can stick 6"x1/2" dowels into

  5. cut a rocker profile out of (2) 1/8" hardboard panels

  6. insert your blank down on the plywood rocker table between the dowel holes

7 working your way from nose to tail place and glue the balsa rail pieces on the rail and place the 1/8" hardboard rocker piece against the strips inserting the dowels to hold everything in place as you work your way down the board

  1. leave the board in the jig over night remove next day and shave down the wood rail for final shaping

as an alternative to the dowels you could use a thicker ply rocker base and just dado a groove along the outline on the base and insert the 1/8 hardboard into the groove as you work down the board from top to bottom or vice versa…

The key is to do both side rails at the same time.

A real lazy*ss cheapo solution, especially if you are going to wood sandwich over the rails anyway…

Is to just drywall screw/nail the balsa strips to the blank to hold them on place and take out the screws/nails when the glue has dried. You then patch the holes with spackle/epoxy/wood putty or what ever and finish sand it before you place on the deck and bottom wood sandwiches. You’re gonna wrap the rails with the top and bottom wood lams anyway. I don’t know if the lazyman technique would (or is it wood?) weaken the board’s structure later as there would be gouges in the foam going in from the rail. I’ve had boards buckle right at a poorly fixed rail ding many times…

Wood rails are the key to a strong shell over the foam and to maintain the flex but they sure are a b*tch to put on…

Sabs seems to just put on 1 thin layer on the rail as a perimeter to bind his top and bottom to and then builds up the rest of the rail after… Looking at Bert’s gouged out tail example(The one John Mellor keeps referring to) I don’t think this would have the same strength as bonding the top to a 3/4" or 1" rail band under pressure.

Hey John… I thiink Bert just goiuged it out to show us the rail band bottom lam bind… I don’t think he’s hollowing out the foam … But I could be wrong.

6

Why not EPS rails on a hollow wood board? Sounds like this would eliminate all that banding hassle. Somehow I assume that guys building balsa boards are using epoxy, though I didn’t see anything to confirm this. Or is using EPS on a woodie just caving in to convenience?

7

This is actually responding to both Benny and Oneula. Thanks for the input. The problems that both of you described are exactly what I envisioned. What I’m trying to avoid is becoming a giant gluey mess and leaving glue fingerprints everywhere. Thanks about the input about jigs and rocker tables. Its the only way I can see things coming together. The problem I have is that I’ve reached the point where I need hands on experience to work out the remaining bugs. With the cost of balsa I want to minimize the drama (as Bert would say).

Quote:

I’ve found, in test pieces, that balsa with a layer of glass on one side only can be put into incredible curves without cracking. Once its cured - but within 24 hours for good epoxy bond - I’d brush more resin into the weave, slap it on the blank, and back into the bag. I doubt the veneer would crack at all that way, and I think that’s closer to what Bert’s doing

I thought that might happen, but I hadn’t tested it yet (I just finished building my vacumm pump) When I read through Bert’s posts he seems to try an minimize chaos in the shop (for example, his dust collection system). What instead of using a wetout table then applying the cloth to the wood not make a curved (sort of like the boards shape in reverse) and lay the wood to the wetted glass. This would also minimize the about of resin entering the balsa.

8

The rails see the greatest longitudinal stress when you turn, so it is a logical place to put the stiffest/strongest element in a board. Wood bends well, and is stiffer than foam, so perimeter stringers have their advantages. Some prefer to put the stringer a few inches inside the rail to get the same effect but be a lot more convenient. So, center foam 1# EPS, rail foam 2# EPS, and wood stringer in between. Best performance is with the stringer as the rail, but might be too time consuming for some.

And if you’re going to wrap it all in wood veneer/sandwich material anyway, you’re not going to be able to tell easily if the rail is wood or not.

9

I’ve been thinking a lot about what I would need from a rocker table. I thought about the pine shaping struts but it would require me making one each time a made a board. One key feature would be the ability to deform the rock at certain point (for example kicking up the about of rocker over the last foot of the board. Maybe use some type of dowel system to create the tail and nose height then some type of block that would pull the plywood into the required rocker shape.

10

You can build a permanent one with some two large metail bars down the middle and some adjusting bolts like the one in the sailboard vacuuming video but that’ll take up a lot of room in your shop like it does in the video.

Just get a couple 10’-12’ 10 gauge electrical channel conduit from your building supplier and sometye of flexible hing on both side for the bolts to go thru. Affix one conduit to the table base and one to the table top 1/2"-3/4" ply or plastic sheeting down the middle. Put some wheels on it and you’ll have what they showed in the video.

Big space take though…

We are trying to construct a more portable version you can tear down easy to hotwire cut EPS foam blanks on.

Metal posts holding top and bottom profilers affixed to a twin bed frame(?) to run your hotwire along each side of the EPS block you’re cutting…

Cut bottom rocker move block up cut toprocker … do next one adjust thickness etc… or

re-adjust to next template and cut the next shape.

11

I haven’t seen the sailboard building video. Is it something that is online (if so do you have a link?)

In one thread (I forget which) Bert was talking about tail blocks. There was one block that was different from the rest and he mentioned that it was because he cut the rail short. At the time it didn’t register what he meant, but know I think that he was suggesting that he preforms the rails. Look at the board with the foam scooped out (that pictures famous by now). Look at how the wood is joined together. It makes a lot more sence if you follow this order of construction:

  1. Prebend the rails

  2. Attach the rails to the foam. At the same time attach the tail block.

  3. You now have a chunk of foam supported on all sides.

  4. Shape the top and bottom of the board. You can put in contours if you want (Maybe this is why Bert is looking at the shaping machine),

  5. Preshape your top and bottom skins in some sort of wetout rocker table. The shape does not need to be perfect since as Benny says, the balsa seems to bend a lot with one layer of glass.

  6. Take both skins out of the vacuum and sandwich the railed blank. Put together with a layer of glass. These could be held together with tape so that they would easily slide into the vacuum bag (no need for a rocker table since the rails are holding the boards shape).

  7. Suck the board together. The balsa will conform to any V’s or concaves you put in.

I think this is why Bert can peel back the skin in that photo. For better or worse, this is the technique that I’m going to use on my board. I would appriciate any suggestions (or at least punch holes in my theory so I can try and patch them). I think I might order the balsa tomorrow.

12

Guys, if you want say 1/4" rail stringers, buy 1/8 (or 3/32) and stagger them on square EPS rails using 3M 78 (or light 77)…then cut/shape to your liking. As blakestah mentioned, an offset p-stringer is much easier…

13

Nah

Bert already showed me via PM.

He does it the same way…

Like Meecrafty says just glue them up to square rails and shape the wood rails first them bring the foam down to the wood.

You just need to prep and stage everything better so you can slap it all togethor in some methodology.

I guess if you did it enough it would become second hand.

picking the right sized wood is a start pre-cutting and possibly pregluing some of it would help like the basla+cork combo since that would still bend nicely.

I wouldn’t use epoxy glue since it would cut badly trying to smooth out the rail wood-foam blend.

To me it’s just alot more work than not using the rail band… (We’re gonna test BB’s theory anyway…)

With CMP like I told Benny we’re actually lapping each wood layer sheet under and over on the rail so there’s some added thickness there anyway. You do the bottom first with a little going up the rail taper sand the edge and then over lap the top sheet over the bottom edge and sand smooth.

14

I appreciate your input. It definitely gives me something to think about. However, I’m pretty certain that I’m going to preform the rails. I’ll let you know how it goes. While I’m a total newb in regards to building boards I’ve done way to many projects to ignore “the system”. I find that I get my best results when I keep each step as small as possible. Both you and Benny have seemed to run in to the same problems putting together the rails. When I look and how excellent both your boards turn out I have to think their must be a better way (there might not be) because its definitely not a lack of skill that causes the difficulty. Maybe I’ll order enough extra balsa so that if I totally jack up the preformed rail I can give it a shot “the correct way”.

15

i like the way dan’s mind ticks over …

takes me 30 minutes to cut , glue , form and apply the rails to a short board , i used to have a guy work for me who could do 3 in an hour , the job was timed out so a mornings work was 3 boards railed , this guy would surf every morning , be in at 11 and have the boards done by lunch …

systems , takes time to try all the variables tho , eventually you got mchines doing the job …

systems …

regards

BERT

16

hi all,

i’ve been lurking around this forum for awhile and i’m particularly fascinated with all of the proposed layup techniques for balsa rails and skins.

‘Bert’s thread’ may not be the first or last on sandwich construction, but it certainly has all of you moving in the same direction.

and now me, as well .

i hope this doesn’t get me banned, but my interests are primarily sailboards and kiteboards.

correct me if i’m wrong, but the consensus for balsa rail layup seems to be:

cut the rocker proile from sheet stock then laminate multiple sheets around the core until the desired width is obtained.

yes/no?

What i would propose is to laminate the rails in the vertical direction instead of the lateral direction.

cut the inner plan shape of the rails and laminate up from the rocker table.

(on top of the bottom sandwich and alongside the core)

assuming you already went to all the trouble of making a rocker table/bed , it seems counter productive not to use it.

additionally, i believe this alignment will be more user friendly while vacuum bagging.

the laminations can be easily clamped against the rocker table, instead of the soft core, without the need of additional jigs and clamps to secure the perimeter.

once cured, the rocker is set and any shaping needed prior to laminating the deck can begin.

I admit this is not really an earth shattering approach.

In fact, i see it as the best way to mimic Burt’s recipe shown to date and maximize some of the inherent advantages of vacuum bagging

-bill

17

I think the main drawback to that would be the wasted wood. You’d either have to use very wide stock to cut in the curve of the template or you’d have a joint every few inches.

When I’ve laid up the rail pieces, even the rocker curve of a longboard prohibits use of one continuous piece. If you want one piece for the whole rail, you’d need it to be as wide as your blank was thick before shaping. You’d also need it to be a lot longer than your board or a stringer - think circumference rather than diameter.

I find it much easier to use pieces of balsa just a little wider than the board is thick, and cut a bit of an angle on the end of each to join the next one so they can follow the rocker. I hope that makes sense? The longboard took 3 pieces per length, 4 thick, so 24 rail pieces in total. The fish was flat & thin enough that I did do that one in single pieces, to to get the same rail width it only took 8 separate pieces.

Glue both pieces - outside of the board or the last piece of balsa and the inside of the next one. Start the attachment at the tightest curve, probably the nose, and bend it around taping it on until the edge of the rail piece passes the top or bottom of the board due to the rocker. Cut the piece there, cut an angle onto the piece you cut off, and continue on from there. It is tedious, but it also is sure to work, and with minimal wood waste.

18

good point,

my kiteboards have pretty straight rails

and the average length is less than 5ft.

not nearly as difficult compared to most surfboards.

-bill

19

One thing I’m trying is to pre-build (Glue) some 1/16 balsa+1/8 cork+1/16 balsa strips in the 48"x4" widths that you can template and cut to the rocker and bend around almost anything. You can alternate nose to tail then tail to nose glue ups to get the overlaps needed. It’s a 1/4" thickness but still pretty pliable… You could probably even pin or tack the rail band into the side of the blank to hole it in place during glue up.

Still slower in my opinion that slapping on both side everything at once working your way from nose to tail and taping or strapping everything down as you go. Messy though and it takes two sets of hands. but alot faster than letting the glue dry before apllying the next layer.

I also like your idea of glassing one side of the bals strip first before attaching it to the rail.

CMP thought it’d make sense to just lam the bottom with a big (1/2"-1") over hang and then use the lip as a brace to hold your balsa glue ups to the rail so you’d be glueing the rail bands to both the side rail and the bottom over hang. The vacuum pressure though might bend the lip extension over the rail during vacuuming kind of like how you do decks.

Any pic yet Benny of the fish?

I should have some pre-glass pics of the completed Bamboo bottom board

20
Quote:
Any pic yet Benny of the fish?

No, still haven’t finished the roll. I’m a technological luddite with some things.

But all it needs now is hotcoats & sanding. Lammed, fins, leash loop all done. Very light.