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( 2.9 / 200 )Drilled the holes and glued them in.
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( 2.7 / 140 )Based on design calculations for the strut and root attach fittings, I had two choices - use five 1/4" bolts in bare wood, or use three 1/4" bolts in 1/2" phenolic bushings. Since drilling holes in the spar makes me nervous, I went with the option that required less drilling. The problem was that I did not have 1/2" phenolic rod - only 3/4". A few minutes with a lathe solve that issue, and I am now ready to install the bushings into the spar.
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( 2.9 / 94 )I got a shipment of GL2 birch ply that should keep me busy for quite a while. I have been trying to find an inexpensive source for the plywood, and I think I've done the best I can do - Plywood and Door Manufactures Corporation in Chicago, IL. They sold me the 1/16" 50"x50" sheets at $23 each, plus shipping. With the freight, the cost was still well below that charged by the usual suspects. I had the plywood one day after I ordered it.
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( 2.9 / 111 )I glued in the leading edge stringer as well as an additional lamination on the wing tip bow. The reason for the extra lamination was that after shaping the nose area of the tip bow, there wasn't enough area for the leading edge skin to attach. The extra 6 inches of lamination along the underside of the leading edge gave 1/4-inch of glue area for the skin after shaping. That should be sufficient for the low stress joint.
I am trying a new (actually old) adhesive - Weldwood Plastic Resin. I really like T-88, but it isn't available locally. I can get it in St. Paul, MN at Rockler, but they only carry the very expensive 8-oz. kit. I can currently get WPR at the local Ace Hardware store, and it is MUCH cheaper. I think the plastic resin works fine, though I can see where it would be unforgiving of gaps.
Speaking of locally (well, kind of local) available products, I stopped at McCormick's Lumber in Madison, WI this weekend to get some 1/16" birch plywood. They were out of the plywood, but they did have a very nice selection of Sitka Spruce. The quarter-sawn rough-cut boards were 1"x9" in lengths from 14' to 18'. I didn't have to go into the stack more than a few boards to find one that will make some nice longerons.
Yes, the spruce is more expensive than the lumber at the local lumber yard (we do still have a lumber yard in Eau Claire, in addition to Menards) - but I haven't had much luck finding wood that I would make a spar or longeron out of. The structural grade douglas fir at Lyman Lumber was one exception - I found a few 2x10s that I could have used. Each timber could have yielded a couple one-piece longerons or caps, maybe double that with scarfing and laminating. That douglas fir was better than half the cost of the nearly perfect spruce - not worth my time to save so little.
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( 2.8 / 10 )I sprayed the leading edge ply with near-boiling hot water to soften it, then used a dozen cargo straps to pull it into position around the leading edge ribs on the wing.
The radius is pretty sharp for the 1/16" bias-ply birch. It took a fair amount of coaxing to get the skin tight to the ribs, especially from 2" to 6" back from the nose on the top. In the image above you can see where I needed to use some oak boards under the straps for extra pressure in that area.
On the strut-braced wing with two struts per wing, the leading edge is not normally load carrying - the chordwise moment is directly carried by the struts. So why use the expensive 45-degree plywood? The primary reason is because the bias-ply holds shape better between the ribs with less tendency for warpage. The other reason is that it does offer some degree of structural redundancy. Even though the skin cannot resist the moment from all the design flight loads, there is a good chance that it would be sufficient to resist 1G loads in the event of a rear strut failure.
1 hr.
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( 3.1 / 9 )I cut and fit the nose stringer. The 12-foot stock I had was just a few inches short of extending from the root rib out to the wing tip bow, so I scarfed on a short extension.
I also ripped the 45-degree birch ply into wide strips for the leading edge. These strips were scarfed end-to-end to make one large piece for the leading edge skin. The plans call for two butt joints in the leading edge skin over heavier nose ribs with cap strips. Aside from the PITA scarf joints, I feel that the one piece leading edge skin will be easier to build and will form a smoother leading edge.
It is interesting to note that the 45-degree birch ply has a very pronounced sheen that the 90-degree ply does not. The 45-degree ply is mil-spec, whereas the 90-degree stuff is GL-2. I'd wager that the mil-spec material is more sensitive to needing the surface scuffed. Testing that I did with the GL-2 ply and epoxy didn't show much difference in bond between scuffed and un-scuffed.
2 hr
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( 3.1 / 9 )With a little gentle application of a heat gun to soften the glue along with a sharp razor, I had the starboard skin of the rudder removed in about a half hour. As I suspected, the interior of the rudder had not been varnished. Strictly speaking, that enclosed area doesn't require varnish. However, varnishing the interior does help with dimensional stability of the plywood skin as humidity changes, thereby preventing oilcanning and warping.
I am now able to access the trim actuator. It is a simple powered lead nut salvaged from something. The linkage to the trim horn consists of a leadscrew on one end that threads into the actuator. My problem with this setup is that there is no limit to the motion. In a trim runaway situation, the actuator would keep going until something broke - I'm fairly certain the motor has sufficient torque. This will be replaced with a standard MAC servo or equivalent.
I removed the light and associated wiring. I plan to use an LED tail light, but I haven't decided which one to use yet.
I also removed the sharp leading edge piece. Once the new skins are in place, the plan-specified rounded leading edge will be shaped. The rest of the workmanship appears above average.
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( 3.1 / 105 )The first part of the purchased airframe I decided to check out was the rudder. Falconar supplied plans for several different rudder versions over the years. This is the full-flying rudder that is slightly swept.
I am checking this part against Falconar drawing 119A 83 Iss. 5, sheets 1 and 2. Status of the components by callout number are as follows:
-1 - 1/4"x1/2" strips and 1/16" birch ply OK
-2 - 1/4"x1/2" strips and 1/16" birch ply OK
-3 - 1/4"x1/2" strips and 1/16" birch ply OK
-4 - 1/4"x1/2" strips and 1/16" birch ply OK
-5 - 1/4"x1/2" strips and 1/16" birch ply OK
-6 - 1/4"x1/2" strips and 1/16" birch ply OK
-7 - Obscured
-8 - Partly obscured, 1/16" ply OK
-9 - 1/16" ply, ash blocks, ply doublers, and 1/8"x5/16" strips OK
-10 - Upper nose ribs made from 3/8" pine block instead of 1/4" ply. This part is not subject to significant loads, OK
-11 - Starboard skin is delaminated from the ribs in numerous places. Skin extends further than necessary. Remove and replace skin and trim to plans shape.
-12 - 1/16" ply OK, though face grain isn't oriented as shown in plan
-13 - 1/16" ply OK
-14 - Cover not present. Will be made after rudder is fit to fuselage
-15 - Trim tab not to plans. A larger tab has been made that is hinged to allow for electric trim. A servo and linkage are present as well. Although the tab is OK, the linkage is unacceptable and the servo is suspect. The linkage contains a double link to "turn the corner", but is insufficiently constrained, so the flexibility of the pushrod allows uncommanded movement of the tab with only slight sideways pressure. A longer horn on the tab will solve the linkage geometry issues, but the servo will still need to be checked out.
-16 - Skin in radius area OK
-17 - Hinge plates not present
-18 - Eye bolt is homemade, not specified AN hardware. Finish is poor, with cut threads, no cad-plate. Replace with appropriate AN hardware.
-19 - Nut is not appropriate AN hardware. Replace.
-20 - Washers not present or not appropriate AN hardware. Replace.
-21 - Clevis pin not present
-22 - Washer not present
-23 - Cotter pin not present
-24 - Rudder control horn has poor finish with rough edges, insufficient hole-edge clearances, and sharp internal radii that are prone to cracking. Not attached with AN hardware. Make new part and attach with appropriate AN hardware.
Other issues not related to a part callout:
* The leading edge of the rudder has a rather sharp radius made by the addition of an additional wood strip. This will be removed and the leading edge reshaped to plans. In addition to adding unnecessary weight, this could change stall characteristics of the rudder.
* The light attached to the top of the rudder is not the correct nav light. Also, the wiring is not teflon. Replace the light and wiring.
When removing and replacing the rudder skin, I will have a chance to better view the internal components and give the inside a good coat of epoxy varnish.
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( 3 / 76 )So I picked up a Falconar F11 project a few months ago. I'm still working on the Ragabond, but the F11 could be flying a lot sooner. If you are unfamiliar with the Falconar F11, it is a design based on the Jodel D11. The plans are produced by Chris Falconar. As I understand it, Mr. Falconar used to sell English language versions of the Jodel plans, then began selling plans that incorporated his modifications.
Some of the differences of the Falconar from the Jodel are as follows:
1) The kink in the cranked wing is moved inboard
2) The washout is reduced in the end wing panel
3) The spar is simplified - washout is by rib geometry, not spar twist
4) The landing gear is spring instead of rubber puck
The project I acquired has the airframe largely complete. However, many items will need to be revisited. Here are some pictures of the project provided by the previous owner:
As you can see, a lot has been done. Most of the craftsmanship is good, some is excellent, and some will simply need to be redone. In general, the woodworking is fine but the hardware and control linkages are not.
Some obvious things I noticed were the wood stains on the rudder, red automotive-type light on the rudder, foam and fiberglass leading edges on control surfaces and wings, and more body filler than I like to see on the tail. These and and any other problems I see will be addressed as I audit the project against the plans.
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( 2.9 / 71 )
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