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![]() It doth often trouble me to Think That in this Business we are all to Learne and none to Teach... -Robert Cushman, 1619 The Chugger Project is an on-going series of experiments using inexpensive, commonly available materials to build a simple single- place airplane. As the work progresses, drawings and photos are placed in the Files archive of the 'chuggers' Group on Yahoo. Text and periodic progress reports are posted to my blog. It's important to note that the primary purpose of these experiments has to do with materials and methods. For the structure I've simply scaled up (or down) from proven designs. In doing so, I've tried to give credit where due, although that isn't as easy as you might think. Bernard Pietenpol used parallel wing struts on his Aircamper ...but so did Claude Ryan on the NYP. The scaling is necessary because the inexpensive, commonly available materials I'm using do not enjoy the same ratio of strength-to-weight as for aviation-grade materials. Pete Bowers' Fly Baby has a beautiful empennage. By adapting Pete's empennage for the 'chugger' project, I'm paying homage to a past master but in doing so I'm taking advantage of an invaluable training- aid. Pete's tail-feathers incorporate no less than nine built-up spars of box- and C-section designs, as well as curved laminations. For the novice builder, the empennage is their Trade School. Fabricating the tail-feathers provides a No-Fault opportunity to acquire the skills they will need to build the wings and fuselage. Clearly, the Fly Baby's empennage is more complex than the relatively simple structures found on a Volksplane or Jo-Del but when scaled for the Chugger , none of the components are especially large, reducing these training materials to table-top dimensions. If fabricated from locally available materials such as door skins and Box Store lumber, the cost of this training exercise is only a few dollars. In fact, if the goal of the novice is merely to learn how to build a wooden airplane, there is no reason to build the entire tail, making the cost even less. While the parts-count of the Fly Baby tail makes the structure fairly complex the required skill-level is delightfully low. Most of the parts are duplicates, allowing you to take advantage of stack-sawing. For example, the six shear-webs needed to produce the spars for the elevators and horizontal stabilizer may be cut-out at one go. The same holds true with the four shear-webs needed to produce the stern- post and rudder spar. The diagonals in the horizontal stabilizer are identical, left to right, so they too may be cut-out as a stack. The only singleton is the shear-web for the diagonal brace in the vertical stabilizer. That means all thirteen shear-webs can be produced from only four patterns. Once the shear-webs have been stack-sawn, Pete recommended attaching the spar-caps and filler-blocks to them. In effect, the shear-webs become your patterns. Since you're dealing with straight edges here you need only apply a bit of glue (to both surfaces, please), tack a piece of scrap to your bench-top to act as a back-stop, press the pieces firmly against the bench (don't forget the waxed paper) and tack them together with a pneumatic pin-nailer. Thanks to the use of the pin-nailer the work took only a couple of hours Then comes fitting the filler blocks, which takes longer – a couple of months longer in my case, thanks to some health problems that had me lolling around various doctor's offices instead of working in the shop. In October 2007 I received a comment from Mr. Corrie Bergeron who is building a Fly Baby. Corrie pointed out that there were other, equally accurate methods of fabricating the empennage spars and diagonals than the one advocated by Mr. Bowers. Rather than make the shear-webs first – and use them as patterns – Corrie fabricated the guts of the spars first – and used the guts as the pattern for the shear-webs. Since I'd already tackled the project using Pete's method I attached Corrie's comments to the appropriate article in my blog http://bobhooversblog.blogspot.com/2...gers-tail.html Once back on my feet I was anxious to finish the tail surfaces, hoping to carry the job right through to covering. But before doing so I recalled the words of Robert Cushman and thought it only fair to give Corrie's method a try, allowing readers of the blog to draw their own conclusions. Accordingly, I made up a simple jig for the spars of the elevators and horizontal stabilizer. This may verge on heresy but I found Corrie's method offers several advantages for a novice builder – or for any builder without a shop full of tools. Pete's method of stack-sawing is dead-simple and superbly accurate... if you happen to have a band-saw and a big belt sander. But for the boxed spars, after attaching the spar-caps and filler blocks in the recommended manner you're faced with the chore of figuring out where not to varnish on the other shear-web. Corrie's method offers greater latitude for the novice builder. I've not posted any photos of the two methods as yet; I'm trying to learn how to embed video in the blog. When I do, it may appear that I'm changing horses in mid-stream when in fact I'm merely showing that even an old dog is capable of learning a new trick – and of giving credit where due. -R.S.Hoover PS – Robert Cushman was one of the Pilgrims |
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