Categories: all aviation Building a Biplane bicycle gadgets misc motorcycle theater

Fri, 01 Dec 2017

A Minor Setback

I have been slowly but surely building up my stack of ribs in the Charger project. I'm up to rib #33 (out of 44), with each taking about 2 hours, plus about 6 hours to produce all the parts to support every 15 or so ribs. So, slow but steady progress.

The wings are built up of ribs, some metal bits and pieces, and spars. These are the long pieces of solid wood that stretch out from the fuselage, and provide the foundation of the wings. The plans call for aircraft-grade Sitka Spruce, which basically means wood with straight, tightly-packed grain and a minimum of flaws and defects. The spars are a bit under 12' and a bit under 11' long, depending on whether you're talking about the top or bottom wing.

In June of this year, I placed an order for my spars with Wicks Aircraft Supply. I knew they would take months to actually ship, so I figured that by the time they shipped, I'd probably have all my ribs done, and everything would move along hunkey-dorey.

We have encountered a small snag in that plan.

Wicks called today and said that, effectively, they can't get high enough quality wood any more, and they're quitting the Spruce spar business. My order is canceled, so sorry, have a nice day. They were very kind about it, and I understand, but this still leaves me in a bit of a lurch. I still need spars.

Fortunately, I have some alternatives:

  1. Laminated Spruce: just because Wicks can't find any 12' lengths of aircraft-quality Spruce doesn't mean there's no aircraft-quality Spruce to be had. It just means that finding it in 12' lengths is no longer possible. Shorter, smaller pieces of Spruce carefully laminated with high quality glue can make up a spar, and there are distinct advantages. Laminated wood is stronger (see plywood vs. a plank of the same thickness), fails more gracefully, and is not prone to warping. Because it's made up of a lot of small pieces of wood, you get to preview the wood for defects that would be hidden in larger pieces. I can do the lamination myself, which sounds both enjoyable and inexpensive. Steen Aero Lab sells laminated spars, and I have a request in to them for a quote.

  2. Douglas Fir: Fir is about 20% stronger than Spruce, and is about 20% heavier (rough numbers from memory, don't hold me to them). I can't change the shape of my spars, that ship has already sailed unless I want to remake all 33 of the ribs and re-calculate a bunch of other stuff. So, I'd add 20% to the weight of the spars, which would amount to probably 5-10 lbs at a guess. Douglas Fir is much easier to find in plain old lumberyards, so I'd be looking at cheaper lumber, too.

  3. Aircraft Spruce still sells spars: the cost is about the same as Wicks, and at least on the phone when I asked, there was no suggestion that they would have trouble finding the wood I was asking for. I have a request for a quote in to ACS to see how long their leadtime would be, and what shipping would cost.

So I've got some options, but it's a bit disappointing that my well-planned order fell apart like this, putting me further behind on my construction plans than I already was. We'll see what Steen and Aircraft Spruce have to say, and that may determine the way forward.

Posted at 15:21 permanent link category: /charger


Categories: all aviation Building a Biplane bicycle gadgets misc motorcycle theater