I bought my cowling from Featherlite per Plans' recommendation. It arrived about 30 days later in a big box. It consists of three parts - the top, bottom and a stiffener for the top cowl. I measured the width of the lip at the forward edge of the cowl - it was not uniform. With a long sanding block, an electric hand sander and ~30 minutes, I have a uniform forward lip of 1 3/8" in width. |
Cowling Attaching FlangeI scrounged several 2" foam blocks (scraps) and cut them to appropriate sizes. With 3 to 4 dabs of 5 min. epoxy, I glued them to the firewall per Plan. Then I sanded their edges flush against the firewall.
I prepared 4 layer BID tapes with dimensions of 40" x 3.5" and 13.5" x 3.5" respectively. Since the foam will be cut out after the BID cures, I was debating whether to put packing tape on top of the foam prior to glassing OR micro the foam and glass on top of it. I tried the packing tape approach first and found that the plastic tends to bunch up at the aft end because the flange is tapered. I went ahead and microed the foam. The BID tape lay down directly onto the foam nicely. |
After cure, removing the foam was not too troublesome either. I used a small wood strip and marked off 1.5" along the entire length of the lip. Then I trimmed and sanded to dimension. |
Here's a picture of the lower lips. |
Aft Cowling TemplateThere is supposed to be a 1 1/4" spacing between the cowling and the engine gear hub per Plan. I made a template (out of a wood board) and bolted it onto the gear hub. This template helps to support and align the upper cowling prior to mounting.
With the template in place, I pre-drilled five 1/8" holes on the upper cowling lip at 7" intervals per Plan. Then I aligned the cowling under the canopy lip and match-drilled the holes. Note the clecos at the upper cowl...
Once I got the cowlings in place, I re-mounted both wings back on. I took the opportunity to re-measure the level of my wings to the fuselage. My right wing level (0.0o) and the left wing is 0.2o high to the fuselage. Since a thin washer adds 0.4o (per Plan), adding a thin washer will make the wing 0.2o low. Since the thin washer is 0.032" thick, I need to find one that is half the thickness. With the original thin washer between the wing and the spar (per Plan), I just need one that is 1.5 times the thickness of the thin washer. I found one in McMaster Carr. Will see how it turned out. |
Supporting LipsThe supporting lips along the wing root and aft strake were pretty straight forward per Plan. Here's a picture for holding the cowling level with the wing root. The first set of plies (5 layers) were easily accomplished. The subsequent supporting (single) layer, however, was a bit more challenging because it has to wrap around a sharp corner. It turned out that peel-ply (Per Plan) and patience did the trick. |
Installing the Lower CowlingWith the upper cowling mounted, I proceeded to install the lower cowling. It was a bit more challenging than expected because gravity is working against you. A bit of sag here, and bit of sag there...while you are stooping under the wings looking up. I tried many tricks (to hold up the lower cowling) which allowed me to keep the cowling in place for precise mounting. they included the laser cross-hair, a plum, masking tape on the plum line to establish the center and lower cowl lip position, and a cross-hair taped at the center of the engine.
I pretty much repeat the same as the top cowling except its a bit more shaping and preparation. The key was to pay close attention to the aft end of the cowling matching the gear plate and prop extension. |
So far so good...I still have to add the lip to the aft end opening and the trailing edge. That's next! |
I added the joining lips at the trailing edges per Plan. I did not separate the forward cowls by 8.5" per plan. Instead, I made my own separation measurement at the strakes. They turned out to be 8.3" - not much of a difference, especially since the cowlings flex quite a bit. Note all the dead weights I used to keep the cowl halves in place for glassing and peel- ply. |
Installing the Prop ExtensionMy prop extension arrived (from Saber Manufacturing) and it is a very nice machine part. I was alerted by Sam (the owner) that it has a very tight tolerance fit. I may have to rotate the prop extension, just to find the perfect fit. I tried all six possible positions with no avail. I finally slid all 6 bolts through the prop extension and allowed them to guide me along. It worked! I hand turned the bolts at 1-4-6-3-5-2 sequence (a slight turn at a time) until the forward face of the extension met the gear plate. |
Nut PlatesBetween the top and bottom cowl, I used a total of 49 nut plates to hold them to the fuselage, wing root and each other - that's a lot of nut plates. The Plan suggested camloc fasteners in some but not all locations. I figure if I have to remove a bunch of screws from those nut plates, I may as well get a powerful electric screwdriver and remove them all.
I picked up a nut plate installation preparation technique from the Cozy forum and decided to follow. Instead of mounting a nut plate on a flat washer, I made a flat base material (~8" X 10") out of 6 ply BID. Then I marked them to 1"x.5" rectangular tabs and its center locations. With my drill press, I drilled all center locations on the board at once. Using a nut plate as a template, I drilled all the rivet holes as well. Then I countersunk all rivet holes. Using the band saw, I cut out all the nut plate tabs for subsequent use. I spread wet flox on the underside of the nut plate assemblies and held it in place with the bolt through the cowling. Then I packed them with flox and laid 2 ply BID over it. |
After the nut plates were installed, I floxed in the stiffener. My stiffener fit onto the upper cowl very nicely - maybe one small gap at the forward edge. I filled it with flox and glassed all edges with 1 layer BID per plan.
Here's a picture of the cowling after all the nut plates and stiffener are installed. I did not use any camlocs at this time. |
Scoop LipThe scoop lip was not too difficult. I made a couple wood templates to shape the scoop. The top template was used to round off the bottom edge of the scoop first. Then I used the second template to complete the rounded 5/8" lip at the forward edge. I followed the Plan for making the rest of the air scoop. |
Here's a picture of the completed scoop lip. |
Oil Check DoorThe next step is the oil check door. Though it is pre-marked with the Featherlite cowling, I like to make sure the door is at the appropriate location before cutting. I tied a laser pointer along side of the oil check tube and project a dot onto the under side of the top cowling. By rotating the laser pointer around the oil check tube, a partial circle is drawn.
According to Plan, the oil check door is to be cut from the top cowling and re-used. Since the cut will be on a curve surface (especially the lower right corner), a poor cut around the corners will end up with a wide seam. I decided to make a backup door as insurance. I pre-marked the door location and covered it up with packing tape. Then I laid up 6 ply BID over the door area. Once cured, I popped it off for future use. The effort was pretty simple and straight forward.
I followed the Plans and completed the oil check door without much problem. I used a combination of my Fein Tool and Jig Saw to complete the cut. The seams are not perfect, however, the fill and sand stage will probably do the job. I did not have to use the backup door at this time. |