Month: November 2018

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Stacking them up

Nothing new, but last night I gathered up all 47 full ribs and stacked them up, carefully aligning the cross pieces for the main spar, aft spar, and nose spar.  I was a little concerned about the amount of variation I might find, considering the ribs came out of two jigs over a period of 20 months.  I was very happy to see that there’s no more variation than could be attributed to wood thickness.  Less than 1/64″, probably under .025″ anywhere along any of the ribs.  Then I stacked up the dozen false ribs I have done so far, same story. 

Wait – 47 full ribs?  Yes, it seems somewhere along the line I must have lost count and built one extra aileron rib.  I’ll either keep it around as a wall hanger/test piece, or maybe stick it under the wing walk for a little extra support.  I’m not sweating it.

This exercise has also reinforced my idea to build a sled for the table saw to lop off the ends of the ribs for the leading and trailing edge pieces.  They are very highly consistent, as they should be, so I think that will save time and make subsequent assembly steps easier.

The bad news is — my T88 epoxy is junk.  I refilled the dispensing syringes and the resin looked a little “off”, not perfectly smooth and clear as it usually is.  Maybe a little cloudy and with a different texture.  I mixed up a small amount and glued up some test pieces.  Where I glued the flat sides two sticks of capstrip together, the joint held well and pulled apart well into the wood.  However, where I had glued a couple pieces of geodetic brace into the slots, the glue joints failed allowing the braces to pop out without breaking.  The glue also was not clear and hard, as it should be, but had an almost grainy or mealy texture to it.  I don’t have any trust in the remaining glue in those bottles.  I’m certainly not going to risk using substandard adhesive to save about $20 worth of epoxy!  Into the trash it goes.  I have two new bottles here, and half a dozen new 60cc syringes on the way from Amazon.


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False ribs = true :)

Well, I set up the second jig for three false ribs.  I’m only making two at a time on that one, though, plus one on the first jig, so three at a time.  One of the three setups on #2 is just not quite “there” enough to suit me.  To be honest, I don’t really know how much difference it makes if there’s a 1 to 2 mm variance in the shape of the lower or upper surface of the airfoil.  I’m getting the ribs all as close to identical as I possibly can, but I know I’ll need to do some minor true-up work once they are all ready for assembly to the wing spars.  What I think I’ll do is stack them all together on some scrap wood cut to match the size and shape of the spars, then use a long sanding block to true everything up.  That’s a while of, still. 

In the mean time, I’ve got around a dozen or so of the false ribs done, and am cranking out 3 per day on the days I get any work done.  Now, however, I’ll have to take a day off to hot-soak and bend some more capstrip.  I’m out of the pre-bent pieces.

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Minor milestone – the last full rib

Sitting in the rib jigs right now are the last aileron rib (#16 of 16), and the sixth false rib.  After the glue cures on these, I’ll modify the second jig to fit as many false ribs as possible.  I think I can fit three on it for sure, possibly four – but that’s doubtful.  I’d like to start cranking out four false ribs at a time.

So I guess it’s time to go start shopping for the best plank or two of white pine I can find to get started on the laminations for the tail surfaces.  Pretty sure Menard’s will be my source for those; the stuff I find at the other big box stores is more suited for a dog house or the pulp mill than anything else. 

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Bending wood and building ribs

I got two false ribs glued up last night and pulled them from the forms today.  The new razor saw arrived yesterday afternoon, so that was nice to have.  I’m leaving all of the ends of the top and bottom capstrips a little long.  I am planning to just build a sled for the table saw out of MDF, with dowel pins or wood blocks to locate the ribs for the four cuts I’ll need, referenced to the main spar and rear spar.  That’s one cut for the nose, one for the trailing edge, and two for the tail ends of the false ribs.  That can wait until all of the ribs are finished, maybe later depending on how cold & crowded it is in the garage.  They really don’t NEED to be trimmed until I’m ready to assemble the wings, so that may be a while yet.

I figure I’ll get two, maybe three false ribs out of a pair of capstrips that would make one regular rib, so I’ll have plenty of opportunity to use whatever method I do finally end up using to pre-bend the wood.  Over the past couple of nights I’ve tried a couple of methods of bending capstrip.  The other night I ran a bucket of the hottest water I could get from the tap.  It was probably 140 F or so, coming from a bar sink just a few feet from the water heater.  I put half a dozen capstrip pieces in there, let them soak a couple of hours, and put them on the bending forms.  That seemed to work well, with no broken pieces.

Last night I added a gallon or so of hot water to the bucket, just to top it off some more.  The water would have been lukewarm at best.  I soaked another half dozen strips for 12 hours or so.  Of the six, one snapped as I was bending it in the form.  That’s about what happened the last time I tried soaking in cold water, so obviously that’s a waste of time and good spruce.  Won’t make that mistake again.

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Well, that was dumb.

I was filling the 60cc syringes I use for dispensing T-88 epoxy in an exact 1:1 ratio.  Typically I overfill them a little, then stand them on end tips up to let the bubbles rise to the top, then squeeze a little back into the bottles to get the amounts in each syringe evened out.  Yeah, it’s a little picky, but it lets me easily keep the ratios exactly the same.  Anyway, I got a little distracted, and accidentally squirted about 4cc of hardener right into the half-full bottle of resin.  Oops.  All I could do without making things worse was let it sit.  I thought about trying to scoop it out with a long handled spoon, but decided all I’d really do was mix it in.  I figured either I’d end up with a hardened mass on top that I could scoop out later, or it would ruin the entire remaining half bottle of resin.  That would be about $22 worth of epoxy…  not the end of the world, but it would kinda suck.  I was hoping the hardener would not slowly sink to the bottom, ruining resin as it went.

Well, I got lucky (or science worked in my favor).  Today there was a gooey layer of semi-cured epoxy sitting on top of the resin.  I was able to scoop it out using a chunk of scrap spruce.  Assuming things don’t go south in the next few weeks until I need to refill the syringes again, it looks like things will be OK.


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Ready for ribs

Well, the work bench is cleared off — well, at least enough to get both jigs on it.  I’ve got a couple dozen sticks of geodetic brace stock shaved down.  The epoxy syringes are filled.  All I need now is a razor saw and a steam setup.

Yes, I have a razor saw.  Somewhere.  I pulled it out during the kitchen remodel, and I remember seeing it in a box of tools we were using, but now I can’t find it.  It’s a Zona, good quality but inexpensive.  A new one is on the way.  Two, in fact; one medium and one fine tooth.  I also have a steam box that I built for the capstrips, but I’m unsure whether I’ll use it in the basement.  It takes bench space (which I now don’t have down there), and drips water out the end by design.  I’m thinking about ways I can use it vertically.  I had looked at rigging up a piece of pipe or something with a heating element for hot water, but it looked like an awful lot of extra work considering I’m over halfway through the ribs.  I’ll probably need it for the tail and wingtip bows as well, but I’m not entirely sure yet how I’m going to steam 6 to 9 foot long strips of wood.  Tonight I tried soaking half a dozen capstrips in a bucket of hot water for an hour — we’ll see how well that worked. 

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Back at it…

Well, I thought it had been a lot longer since I did any construction, but I see it was only back in February.  I really wouldn’t have been surprised to find that I’d gone an entire year without building anything.  But, I’m getting ready for winter and more building.  To be honest, I’d had second thoughts recently about even continuing with this project.  Sometimes it seems like such a massive undertaking, especially when I see pictures of guys attaching the wings and getting flying wires made and rigging done…  only to tear it all apart again and then start covering.  Covering!!  How the hell an I ever going to cover this beast?  But then I decide that maybe I’ll keep at it after all.  Hey, it’s relatively cheap…  so far…  as hobbies go.  It keeps me occupied for as long as I care to work on it, and nothing bad happens if I let it sit idle for a while.  Even a long while. 

Over the past few days I’ve been working on getting my absolute pit of a basement workshop cleaned up at least enough to be able to move around and use the workbench.  A new water softener installation, a kitchen remodel and a few other household projects meant there was a lot of mess left over, and a whole lot lot of crap got just piled everywhere.  Most of it’s cleaned up.  Not enough, really, but at least enough for me to be able to take stock of where I am.  In hindsight, I suppose I could have, you know, looked at my blog posts, but where’s the fun in that?

I need 26 normal wing ribs, and they are all done.  I need 16 aileron ribs — the same as the normal ribs, but just missing a couple of cross pieces.  Of those, I have built ten, so there are six left to build.  Then there are 34 false ribs — just stubs from teh leading edge back to just behind the main spar.  I’ve built one of them, so 33 left to build.  Those should be quicker to build, since there are only about a quarter of the geodetic braces to cut and glue.  Unfortunately, each will still occupy a full rib jig — so two at a time is still the limit.  Unless…  maybe after the aileron ribs are done, I can tear down one of the rib jigs and rebuild it to do several false ribs at a time.  I think keeping one rib jig intact would be good, just in case I should ever need to build more ribs for a repair or whatever. 

I’ve got a bunch of geodetic brace stock sanded down to the correct thickness.  Enough for sure to do the rest of the aileron ribs and get a good start on the false ribs.  I’ll probably do half a dozen more, then put the oscillating sander away and maybe knock out a few ribs.  I’m starting to get a little fired up again.