Tag: Wood

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Generic update

Yeah, it’s been a long time, no updates, and so on. I bought a few more pieces of capstrip from ACS to finish out the last of the false ribs, but honestly the lack of any place to assemble wings or build the tail surfaces — or really any other parts of the plane — has had me less than enthused about getting much done. I’ve got a tall stack of full wing ribs and an almost-as-tall stack of false ribs sitting on a bench on my basement, doing nothing.

From time to time I check Barnstormers to see if another Celebrity pops up for sale. Occasionally one does. The two that really gnaw at me? A gorgeous, Rotec radial powered Kitplanes Magazine article centerfold that was advertised for probably less than the engine would cost me, and one a couple hours’ drive from here with no engine that was listed at about $5K or so. In both cases the timing just was not right (hell having not frozen over quite yet).

Now I’m contemplating a run down to St. Louis. The purchaser of Celebrity serial number CE165 – one later than mine – had apparently never started building, and a crate with the complete wing kit is for sale. The seller is asking a fraction of the cost of a new kit, and it appears to be complete. I did some plotting, and even just ordering the wood for the wing spars – not the entire wings, mind you, just the spars — would cost more than he’s asking plus my gas for the trip, and that’s before I pay LTL freight costs to have it shipped from Aircraft Spruce. Plus it’s a complete wing kit, with all the pre-cut plywood pieces, laminating strips for the wingtip bows, trailing edge pieces, all of the bits that would add cost and time and aggravation to a scratch build. I can’t pass it up. I’d also have a full set of plans that I could sell to help defray a little of the cost.

A friend with a large woodworking shop has offered to let me continue building there in his shop — heated, air conditioned, lots of space, plenty of power tools, and this all feels almost too good to be true. I’ve just got to make a 13-14 hour round trip with a pocket full of cash.

Stay tuned, I guess.

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A few more false ribs

I glued up two more last night, and will do two more tonight. That will make 18 down, with 20 19 more to go. I’ll typically take some time at lunch to cut out the cross brace pieces and get everything set up. Then after work I’ll mix up some T88 and glue the ribs up, then let the glue cure overnight. By the next morning I can pull them out of the jigs and start again.

I’ve run out of cross-brace stock that’s been sanded down to 3/32″, so I’ll have to stop while I retrieve the small shop vacuum from the project house where it is now and run some more 1/8″ stock through the drum sander. It’s a pain, yes, but it has to be done.

I’m already debating where to go from here, once all of the false ribs are finished in a few weeks (maybe). I could start on the tail, but that will require a 4 x 8 work surface. The wing spars will require a longer bench, at least 12′ long. I may instead start working on cutting out the large number of nose ribs that will be needed, and the other high volume plywood parts. It’s awfully tempting to set up my CNC router again for that part, but I doubt that I will. I’d have to translate the outline from the printed plans into G-code for the router, and quite frankly I think by the time I got that right I could cut them all out by hand. I’ve seen a couple of guys use a router and a flush cutter to route the nose ribs from a pattern. I’m a little concerned about the radius on the inside corners where the nose rib glues to the false spar. I figure I could either sand a matching radius there, or touch up the corners of the nose ribs with a bandsaw or something. I’ll cross that bridge when I get to it.

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Spar web update

For anyone else who might be in the same predicament, the fine folks at Homebuilt Airplanes came up with a couple more sources. B&D International carries 5′ x 5′ sheets of Finnish birch aircraft plywood, and will cut and ship UPS. Boulter doesn’t carry as wide a variety, but might be good if you’re closer to the east coast than the west.

The price at B&D is higher than Aircraft Spruce. If you price it by the square foot, it’s not terribly higher. 13%, on the 1/8″ sheet I need. Not terrible.

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Spar webs

The plans and BOM call for plywood spar webs, cross-cut, 60″ long. The webs are butt-spliced mid-wing, with what seem to me to be fairly narrow blocks of spruce on either side.

Problem is, you can’t buy 60″ wide sheets of aircraft plywood in the US. Aircraft Spruce has ONE size, and not a size I need. Everything else I’ve found is in 48″ wide sheets. And since the web needs to be crosscut, it’s not as simple as just buying a 4′ x 8′ sheet. I’ve contacted Fisher Flying Products as well as another supplier in Canada. Fisher’s tab will be roughly $340, the other place was pretty reasonable for the plywood but wanted over $500 for crating and shipping. To put that in perspective, ACS will sell me the plywood I need for about $100, delivered.

The question is, can I make 48″ long spar webs work in a way that is at least as good, or preferably stonger and better, than the original design? I am no engineer. Especially a mechanical engineer. I’m certainly not qualified to make such a call. Fortunately, I have someone local who is an engineer, and is qualified to help make that decision and recommend another way to do it — if there is one. I’ll be taking the wing plans to the February EAA chapter meeting to go over them with him and see what we can figure out.

If that doesn’t work out, Spruce does sell 5/32 ply in 61″ x 61″ sheets. The spar webs are specified as 1/8″ for the main spar, and 1/16″ for the rear spar. I could just make both webs 5/32 with a slight weight penalty. The plywood would weigh 3 to 5 pounds more, but I’d probably also need to trim 1/32 to 3/32 from the spruce stiffeners, so that might make up for some of it. Again, I’ll need to consult with a real engineer to see if that wold work or not. Ending up with a plane that’s a couple pounds heavier but significantly stronger is OK. Ending up with a plane that is in any way less strong or less safe is absolutely not. And if the ribs need to be modified a little to clear a beefier spar — I’m OK with that.

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Tempus fugit

Another year draws quickly to a close, with what feels like not a lot of progress on this project. I have a tall stack of ribs, but really nothing else. I had hoped to have a good start on the tail surfaces by now, but haven’t even started on them. We’ll need the basement for a family Christmas party, so no laying a 4×8 sheet of MDF over the island down there to start laminating pine. No worries, though. I have located some nice clear pine boards at Menard’s that will rip down nicely into 10′ long lamination strips. I have an order of Finnish birch ply queued up on Aircraft Spruce’s web site, ready to place the order once I’m sure I have all the stuff on there that’s going to be expensive to ship. As soon as we’re finished with the post-party cleanup, I’ll have the basement available to work in through the rest of the winter since the garage will just be a bit too cold for epoxy.

I also got a great idea from one of the guys on the Biplane Forum. I’ve been pondering how to store the wing ribs. I think I’ll build short pieces of main and rear spars out of pine and non-certified plywood, just to assemble all the ribs and clamp them together. That way I can surface sand them all together, and maybe if I’m lucky use that assembly to run them through the table saw for trimming as well. Maybe.

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Musing.

Haven’t done much in the past few days, mostly because I’ve had the workbench cleared off to fix a recalcitrant robot vacuum.  I did unroll some of the plans and take a good long look at the tail surface sheet.  Sixteen feet or so of paper, mind you…  not the easiest thing to manage on a 6′ countertop!  I wish that had been split into two sheets. 

It looks like I can build the entire fin and rudder out of pine and plywood, so that’s my next project, I think.  I’ll go look for a suitable 10′ length of pine at Menard’s that can be ripped down into decent quality lamination strips.  Once the saw is set up for that I’ll make as many as I can, since I’ll have a bunch of other laminations to do as well for the wingtips and fuelage.  Then I’ll look at what to do for the elevator and stabilizer spars. 

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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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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.