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  1. #1
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    Default Cubism competition 2022 - Labr@

    Still trying to decide on a suitable project at this stage. I have a list of ideas but none of them stand out as a preferred option at this stage.
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

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  3. #2
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    Maybe start on a couple of ideas and see which one stacks up better, As long as you take photos along the way and eventually post progress, who's to know?

    Good luck!

  4. #3
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    So, only a bit under 5 months to go and nothing cut but at least now there is a plan. I'm thinking of doing a box with a drawer that opens a tambour top. It's been done before so not overly interesting as stated however there are a few things that I want to try to incorporate. First is to have a marquetry design on the tambour - again, done before, but with the marquetry design cut into slats using a knife so it is not interrupted by saw kerfs. Second is to have the face of the tambour flush with the box sides.

    This will introduce some design challenges. Normally a tambour that sits closed in a convex shape has curves on the front of the slats so that it can go into a straight slot when opened. With the marquetry design on the front this will not be able to occur with normal construction so a mechanism needs to be designed to allow it to happen. Having the front flush with the sides will have its own issues but also I think it will make the opening problem more difficult to solve.

    So in case I can't work all this out in time the backup plan will be a folding stool for the shed. Some preliminary mud maps indicate that I can easily accomodate a good height for the stool and still have it fit into the large cube when folded.

    So that's my clever plan.
    It's taken about 20 % of the available time to come up with it....
    And of course time spent on the stool in parallel with the box will make the box even more difficult to finish....
    And I need to develop a way to solve the tambour issues then build a test piece...
    And come up with a marquetry design....

    ....errr, maybe not so clever
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  5. #4
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    Have been thinking about the issues with the proposed flush surface marquetry tambour and many ideas for solutions to the problems have occurred to me. However I have trouble putting these ideas into a clear plan or design that I know will work.
    The way forward is to do some proof of concept trials and work out the details from these.
    The first of these is underway and consists of 15 short slats that will be experimented on. Here they are sitting in a former that represents something similar to the shape that I want to make.

    P1120063 crop [800x600].JPG

    Upper sides will be cut for the former and these will be used to hold the slats down. The slats will then be sanded smooth and veneer applied. That is as far as the plan goes at this stage - further steps will go in the direction of whatever inspiration takes hold on the day.
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  6. #5
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    Popcorn is on standby…..
    Nothing succeeds like a budgie without a beak.

  7. #6
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    My previous post showed the tambour slats in the former. Since then I have sanded them, glued on a layer of canvas and then a simple piece of marquetry. This was a trial to determine if I could make a kind of “reverse” tambour with the canvas on the front instead of the back but covered with veneer.
    The reason for making it like this is so that it can curve both ways while having a flat face with the marquetry pattern at the front.


    There was a concern that trying to curve the premade marquetry piece would cause the insert pieces to pop out and I wanted to see if this could be prevented. There was also the question of how to slit the veneer to match the slats. The slitting would need to be done from the front and there was a danger that the canvas would be cut as well.


    I made a negative of the former with clearance for the slats and veneer so that this could be used to clamp the veneer in place for glueing.
    The marquetry piece was clamped in the former overnight to see if it could be prebent to shape. It took some of the curve and this helped make the glue up easier. The canvas was glued onto the slats first and allowed to set. Then glue was spread over the back of the marquetry and it was clamped in the former overnight with 2 layers of leather under the top former to take up and shape mismatch.


    It came out of the former looking fairly good.


    To make the slit in the veneer I first made a nick in each side in line with the slat joint and then ran a knife along a steel rule lined up to the nicks. Had to apply masking tape to the back of the rule to make it a little less slippery because it was moving too easily on the first few cuts. To avoid cutting the canvas I tried doing 6 or 7 light passes with the knife and then flexing the piece to tear the last few fibres and it worked well.


    The piece is not perfect because I didn't do the slat chamfers very well. They need to go all the way across and there were a few that didn't. This means that some joints are restricted in the range of bend. The slits are also more obvious than I hoped for but the veneer has held to the curved faces of the slats so it will feel quite smooth when in place. Despite this I'm calling the experiment a success because the piece will fit the shape I want for the closed tambour as well as flexing enough to go around a 45mm rad as well as straight.

    Prepared for the canvas glueing.
    P1120064 [800x600].JPG

    Final glue up
    P1120083 [800x600].JPG P1120092 [800x600].JPG

    Nicks at edge for lining up straight edge.
    P1120097 [800x600].JPG

    Range of curve
    P1120105 [800x600].jpg
    Attached Images Attached Images
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  8. #7
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    Just to recap, the main design goals are
    1 Box with drawer and tambour openings.
    2 Tambour to have marquetry design with no gaps.
    3 Tambour to be flush with face either side.
    4 Drawer and tambour connected so that they both open together


    No 1 is straightforward and No 2 is shown to be achievable.


    No 3 requires some testing and the trial piece has been rebated on the front side at each end of the slats in preparation for a trial.
    IMG_20220702_160929 [800x600].jpg IMG_20220702_161803 [800x600].jpg

    The potential problem here is that the part of each slat running in the channel is offset from the side that does the pushing and pulling. Thus the friction could result in a twisting effect and cause the slats to bind.


    No 4 is proving a bit troublesome due to the fact that the overall shape I want requires the tambour to travel further than the drawer. To deal with this some experiments are being done to try and find a simple mechanism to double the tambour travel when the drawer is opened.


    There are probably several ways to do this but I wanted to keep it as simple as possible so came up with something that has only 1 moving part (the drawer) apart from the tambour. The test rig gives the travel ratio of 2 to 1 and works well with no load. However, under load the tambour has a proportional mechanical advantage over the drawer. This multiplies the amount of friction so the entire rig slides along the bench when the “drawer” is pulled and pushed. Non slip feet may solve this but it would be better to have the internal friction reduced.
    The photos show a cobbled up housing with a small section of tambour between a “drawer” on the left and load on the right. A piece of abrasive taped to the bench reduced the tendency of the rig to slide.
    This is in the "drawer open" position with load up against housing.
    IMG_20220705_211053 [800x600].jpg
    Here is the drawer pushed to the right by 60mm and load moved 120mm. (Edit: ...and of course the idiot machine has turned the photos 90 degrees so left and right are now up and down . Anyhow, I'm sure you can work it out.)
    IMG_20220705_211000 [800x600].jpg


    If it can't be made to work then a handle can be installed on the tambour so the tambour will be the driver for the door. This is more likely to work because there is a 2 to 1 mechanical advantage that will reduce the friction effect significantly.
    If this doesn't work then they will be set up to operate independently.
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  9. #8
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    Can't believe it's nearly 3 weeks since my previous post .
    Anyhow, I decided to make a working model out of mdf and veneer so that concepts and design goals could be tested more thoroughly. Made it to the stage where there is a deeper channel at the top and rear so the tambour panel can be hidden when open. It runs OK in this. The idea for the front was to have veneer strips glued onto the front of the box such that they overlap the ends of the tambour slats, thus creating a channel for the slats to run in and also being just thick enough to be flush with the face of the tambour.

    IMG_20220720_150645 [800x600].jpg IMG_20220720_205216 [800x600].jpg IMG_20220720_210354 [800x600].jpg IMG_20220724_122124 [800x600].jpg IMG_20220724_211920 [800x600].jpg IMG_20220721_210907 [800x600].jpg

    I'm just about ready to pull the plug on this (design goal 3) because to have the panel sit flush at the front would require practically zero clearance in the channels and there is already more friction than desired.

    At this stage it's looking like the finished product will have the smooth marquetry tambour but not flush and not opened by the drawer action.
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  10. #9
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    To cut a short story long, I had some serious indecision about what timber to use for the box walls and how to make the slots accurately. In the meantime I went on with some small boxes, did some dog sitting, took a holiday and came back having lost interest in the tambour project.


    By this time I also had a serious commission to do – serious because it's something SWMBO wants. So now I'm working on a box in red gum with marquetry panel lid. Dimensions are 260 by 190 by 120 mm high.


    Of course the red gum I have has squirly grain and is prone to tear out. Having rough cut some pieces it was necessary to use a scraper plane but the small one I made a while back has a second rate blade and is a bit small for this size box.


    Luckily while we were caravanning I came across an old coffin smoother with a good blade – similar to the blade I used in the plane challenge, and from the same shop – so was able to knock up a larger scraper plane. This one has a 90 degree bed and meranti body with a sheoak sole insert for better wear.


    I also bought 2 water stones to replace the wet/dry paper on glass that I've been using for years and now wish I'd done so ages ago. The process with the water stones is quicker and a lot less fussy so I am sharpening as soon as there is a hint of bluntness.


    So now the aim is to try to finish the box by the end of Oct and if that can't be done then I'll just enter the plane .


    Scraper plane 2.jpg Scraper plane 3.jpg

    Coincidentally, I found a dead seahorse on the beach this morning and take it as a sign that abandoning the tambour project was the right decision.
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  11. #10
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    Time is running out and there is still a long way to go. Have been doing the marquetry in short sessions, often late at night, and had lots of frustration with trying to make small pieces fit. It's amazing how far a tiny piece of carefully shaped veneer will fly when the tweezers slip .

    Did the veneer application to back of panel last night to see how well the process would work and it came out OK. The marquetry panel was glued onto the substrate today and will be out of the “veneer press” later today. I will need to remove the veneer tape holding the pieces in place before I can tell if it has turned out OK. The worry is that there will be gaps I hadn't seen or that the pieces will not sit flat in the background veneer.

    Here is my unhigh tech veneer press:
    Veneer press.jpg



    Then I just have to finish the box, and the lid.
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  12. #11
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    The marquetry panel came out slightly bowed and with a few gaps. After sanding there were larger gaps so some repair was done.

    The lid is going to be made separately from the box by putting a frame around the lid panel so 4 strips of redgum had to be grooved to fit the panel edges. Did this with a small plough plane (recent purchase). The pieces were not large enough to hold in a vice while using the plough plane so the plane was put into the vice and the pieces run across it. This was time consuming and resulted in sore fingers but apart from some damage near the ends it turned out OK.

    A bottom panel was made by applying some karri veneer to 3mm MDF.

    The pieces for the sides were then taken to final thickness and sanded. Next will be putting grooves in these to take the base.

    IMG_20221029_175304 [800x600].jpg IMG_20221103_165951 [800x600].jpg

    This is where it's up to.
    P1120362 [800x600].JPG
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  13. #12
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    Decided to cut the box sides to length and mitre the ends. Used the router table with a 90 deg angle bit for this as I still have not worked out a way to reliably do mitre corners on box sides using hand tools.
    P1120368 [800x600].JPG

    The lid frame was a different case. I made up a little 45 deg jig with rare earth magnets to hold my Japanese saw blade at the correct angle and then cut them to length. This was not overly accurate but cut them close enough to clean them up with a sanding block on a 45 deg shooting board.

    So then last night I glued up the lid and left it clamped overnight. Here it is after I took the heat gun to it and disassembled the darn thing because of the corner gaps. The pieces were a tight fit to begin with but with the glue added they became immovable fairly quickly. I had it clamped face down to a piece of MDF to make the top faces of the frame pieces align vertically so could not see what a horror it was until unclamping.

    IMG_20221109_113507 [800x600].jpg

    Anyhow it is cleaned up and ready for round 2 now. Have made the fit just a little less tight and watered down the PVA a little. The plan is to glue 1 edge piece at a time with all the pieces clamped in place. Hopefully this will enable better control of the assembly process.
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  14. #13
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    The second go at glueing the frame on the lid went OK.
    IMG_20221110_110442 [800x600].jpg
    Then I cut 4 strips to fit inside the frame for locating the lid on the box. I must have been using the saw jig properly this time because these fitted straight off the saw .
    Once glued up the assembly needed a bit of levelling on 2 corners but otherwise was good. It was slightly too big to fit into the box but this is what I wanted so it could be gradually trimmed until a good fit was obtained.

    IMG_20221111_205224 [800x600].jpgn IMG_20221111_212403 [800x600].jpg
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  15. #14
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    The box body glue up went quite well. Assembled it dry and taped all the corners then unrolled, applied tape inside to minimise cleanup then applied glue and clamped it with my high tech band clamps.

    IMG_20221111_134124 [800x600].jpg IMG_20221111_142541 [800x600].jpg

    It came out of the clamps sitting flat and with the corners mostly good. Will need some cosmetic work in a few spots. This is the worst area and I am confident that I can make it presentable.
    IMG_20221111_213921 [800x600].jpg

    The continuous grain matches upp well all round, although with the squirliness of this timber I'm not sure if it was worth the effort.

    IMG_20221111_214310 [800x600].jpg IMG_20221111_214459 [800x600].jpg

    The locating rim in the lid was trimmed and the lid fits with a slight rock, not much - just enough to be annoying that it isn't perfect .

    IMG_20221112_131126 [800x600].jpg

    So now there is just final tidy up and finishing - which will take far longer than it should as usual .
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  16. #15
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    Well, the last statement of my previous post was off the mark. Despite finding myself standing in a puddle while tidying up the final assembly and then becoming saturated while going three rounds with blocked stormwater pipes it only took a day to clean up, apply shellac and then rub some wax on.

    With previous boxes I always brushed on diluted shellac but this time I used a rubber, like the ones used for French polishing, and it gave a more even coat.

    The mitred corners were gone over with a burnisher. This achieves two things - it softens the edge and also closes up any tiny gaps. Also used the burnisher to soften the other edges of the box.

    Quite pleased with the end result.

    P1120391 [800x600].JPG P1120374 [800x600].JPG

    Will do some more coats of wax before handing it over.
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

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