Laminated SS V2 (Pic heavy)

Discussion in 'Show off your homemades!' started by knifefightermike, Jul 18, 2013.

  1. knifefightermike

    knifefightermike New Member

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    In my first SS thread I showed the laminated AL/Cherry/Oak slingshot I made, and the frame hits I got because the forks are so low. After shooting it a bit more and getting the hang of the twist technique, and seeing more beautiful slingshots here, I designed V2.

    Here is the new design on paper next to the old one.

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    I used vellum (tracing paper) to copy the design onto the cardboard. I just pressed down hard with a pencil and the impression of the line is left behind. Follow the line with a pencil, then a marker to make sure you are happy with the shape. You can see I decided the knobs should be a little bigger once I transferred them over.

    I used a sharp scissors and a razor blade to cut the shape out of the cardboard.

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    I transferred the design to aluminum plate then used the drill press to rough the shape out. A dremel cutoff wheel finished cutting between the holes. Then I roughted the shape down close with the a bench grinder. Notice how I put a dashed line outside my cutout line. That makes sure I stay away from the line with the rough power tools. I will finish close with the belt sander and files.

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    Checking the Aluminum blank against the cutout. All good.

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    Next I found the pieces of wood I wanted to use and cut them roughly to shape. I mixed up a big batch of JB Weld and stuck them all together in a stack and clamped them in the vice to dry.

    [​IMG]

    The fidgety part is making sure all your pieces are where you want them before really applying the pressure. They tend to slide around a lot. It helps to make sure your epoxy coat is even and thinly applied. I use JB weld because it is the strongest 2 part epoxy mixture available to me, and also because I happen to have some in the shop already. ;) I like the way it looks between the layers anyway, when you clamp it like this it makes a thin gray line between the layers that I think looks cool.

    It looks messy now. This is the part that most builders don't like to show because it looks so messy and sloppy before you clean it up. It's like, is there a better way to do this that doesn't make such a mess? (Yes, vacuum bagging. ;) but that's more expensive.) So you don't want to show and admit maybe you don't know what you're doing. But for a regular guy in the garage or home shop, don't worry about the mess because you're going to grind it all off later anyway. Just make sure it's thin and even and you clamp it really tight.

    So now waiting 24 hours for everything to fully dry before going back at it with the power tools. I'm going to edit this post and add more pics of the process as I go, hope you guys find it interesting! :)


    Edited to add: I did rough sand the wooden pieces on the faces that would have epoxy, I know the outer ones look like they're varnished but that's just the outer surfaces. :eek:

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    Rough Shaping
    (Hope you're ready for a lot more pics! :) )

    So here is the stack, 24 hours later and the epoxy very dry, straight out of the vise.

    [​IMG]

    And the other side:

    [​IMG]

    Note the circular marks on what will be the knobs, that's from the small clamps used to attach those separate pieces. Both clamps popped right off because they're filthy and rusty. If I had newer clamps, I would stick a piece of wax paper in between the epoxy and anything bits I didn't want stuck. But it's a good objective lesson, because think about the pieces you're laminating together: if they aren't clean and dust free, they might not stick together and you run the risk of them popping apart later. That's part of the reason I "butter" pieces completely before putting the faces together and then slide them back and forth against each other before pressing them in the vise, that helps make sure the epoxy is well worked into the wood grain or into all the scratches on the metal so things stick. Here's the side view of all the layers, you can see I got good squeeze-out all along every seam, that's something to look for when checking your lamination job, it's a sign that the epoxy is evenly distributed.

    [​IMG]

    This is probably as good a time as any to throw in some more comments about using JB Weld. Everyone should take note of LW's post below:

    So not only does JB weld have superior adhesion when working with metal parts, it's better suited to the temperatures transmitted through the metal from the high friction tools. Here's another reason to use it: most epoxies are UV sensitive, they yellow over time and delaminate with prolonged exposure to the sun. JB Weld won't do that. The older it is, the harder and more like steel it becomes. It's easier to see if you have good coverage and squeeze out with the gray JB weld than with clear epoxies. Drawbacks are that it takes a long time to set, but if you know epoxies, you know that the longer the cure, the stronger the bond. With JB Weld (and all epoxies really) you can essentially do paper-mache with wood and metal (or fiberglass or pretty much whatever you want - from linen micarta to GRP (fiberglass) sailboats.)

    (Steps down off soapbox.)


    OK! Next I use a sharp coss-cut saw (9 TPI) to rough out the shape. I want it close so I don't spend forever with the sanders and rasps. Here's where leaving the extra bit of metal around my desired shape starts to pay off.

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    I cut along the sides but avoid cutting on the outer faces of the blocks so I can maintain the squareness of the sides. The inside of the forks is hardest to do, take the saw and make a bunch of angled cuts, alternating cuts from one side/fork towards the other, removing the wood in lots of little pieces. Basically, the more you can get out now, the better. The saw is fast, filing is sloooooow.

    You can do a lot with a big saw, just scribe the line you want to cut first, then use you finger as a rail to guide the saw and make sure it doesn't jump around. When you first start the cut, draw the saw towards you until the groove is deep enough that you can cut on the forward stroke like you're supposed to.

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    This is the point at which I stopped with the saw on the forks:

    [​IMG]

    Don't try and do a chisel cut unless you're sure the wood has a solid grain structure. My outer layer is some very old vertical grain cedar, which tends to want to split between the grain, leaving grooves in the surface below where I would want them to be. So I cut close but don't try to snap out or chip out those pieces in the middle, I just take it over to the sander and do the last bit there.

    Here's the basic outline done with the saw:

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    Starting to look a little bit like a slingshot.

    Next I took it over to the belt sander:

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    You can see I still haven't touched the faces yet.

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    Pretty quickly though it's back over to the vise and start work with the rasps. The belt sander is fast but not for close work and doesn't have tight enough curves to get in under the forks. So I switched to really heavy rasps, both round, half-round, and flat, and then to a half-round bastard file. Material should still be coming off fast at this point, we don't want to kill ourselves just because we're using hand tools, right? So no sanding and no fine file-work yet. Still only working the outline and making sure the sides cut square to those front and back faces.

    [​IMG]

    As you can tell, I've been clamping it in the vise to do the file work. It's always better to have the work firmly supported so all of your energy goes into cutting the piece, not supporting it. Sharp files are a must. So are handles on your files. Trust me.

    Last pic for today, close up of the back face. You can see where the pressure of the vise cause some of that grain spalling I was referring to earlier. It's OK at this point because there's still so much material to remove. Part of the reason to work the shape like this is to leave yourself those flat faces to clamp on while you do the brunt of the work. Once I'm there on the sides/outline, then I can start rounding and shaping the faces.

    [​IMG]

    Also notice that I cut with the bastard files all the way down until clean aluminum shows on the core all the way around. That's the main reason to leave extra material, to leave room for the overcut. Every shaping and smoothing layer removes material, If you cut right to your line before you start shaping, the slingshot will end up smaller than you wanted it to be.

    Hope you guys are enjoying it. Stay tuned, next up is shaping the faces and knobs. :D
     
    Last edited: Jul 19, 2013
  2. onnod

    onnod Im from Holland, isnt that weird?

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    good start!!
     

  3. Brazilviking

    Brazilviking Thread Hijacker

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    Watching and learning.... keep showing so I can see the outcome!!:D
     
    Last edited: Jul 19, 2013
  4. flicks

    flicks ...lost in the woods....

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    Carry on, good work so far! I am excited about the outcome.
     
  5. dannytsg

    dannytsg Senior Member

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    Nice work, looking forward to the rest of the tutorial
     
  6. LW

    LW New Member

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    Nice work, I'm curious about the result. :)

    That is exactly how I do it. For Laminating with a metal core I also us JB weld, because it is the only 2K epoxy which can withstand temperatures of 300 degrees and more. When grinding on a Belt sander there are very fast temperatures above 200 degrees. Normal 2k Epoxy is stable only up to 100 degrees.
    Laminating only from/ with wood are no problem with regular Epoxy.
     
  7. Would be nice and great Slingshot!

    Joe
     
  8. tokSick

    tokSick Senior Member

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    OK, this is inspiring...
    Are you planning to round the fork tips, curve them or leave them like the template( square)?
     
  9. knifefightermike

    knifefightermike New Member

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    Thanks for all the comments everyone!

    LW, I really appreciate that info about the JB Weld, I didn't realize that particular aspect. Thank you very much! Please note I quoted you in the original post. :)

    tokSick, the tips will be rounded cubes with grooves around and over the top for the bands and binders. That's a good question though; the outline shape really is for symmetry and rough cutting, you can see that on the laminated block, it's only in a few places you can even see the line anymore. So adding a lot of detail to the template is somewhat of a waste of time. Plus the template is 2D, for the outline, there's another whole template you could make for the profile shape, but even then I wouldn't include detail like the band grooves on the template. I know I want them, so I leave enough extra material to cut them when the time comes. If I was doing a drawing for someone else to manufacture, they would need to be in there. So the template or drawing should, to a certain degree, reflect what your capabilities are shop-wise... don't put in curves you can't cut or grooves you can't make, you should already know how you're going to make it before you do the drawing, know what I mean? I know that's way more than what you were asking, but there ya go. ;)
     
  10. Thistle

    Thistle RESIGNED

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    You're correct, it does look "messy" in the beginning stages. But seeing all of these steps and reading thru your build process is such a wonderful learning opportunity and great tutorial for the rest of us. It's really shaping up and looking super!
    [​IMG]

    Very exciting and looking forward to seeing the finishing results. Thanks for sharing this entire process [​IMG]