Zenith Aircraft Builders and Flyers
750 STOL Fuselage/Gear/Struts Fairing
For a while now, fairing kits for the 750 STOL have been available from Zenith, Mark Pensenstadler (kitplaneenthusiast.com) , and North American Aerospace Holdings (the manufacturer). I initially purchased from Zenith the upper fairings for the struts and jury struts - they all fit quite nicely except the forward strut fairing needed a revision and Mark Seaver at NAA quickly came up with a new version (similar to the Cruzer's) which fit great. I should point out that although a couple of knots extra cruise speed is nice, I had no expectations of turning the 750 STOL into a speed demon, but the fairings do give the plane a more "finished" look.
Obviously, the junction of the fuselage, struts, and landing gear is the "draggiest" area on the plane (talk about "flat plate drag" - this junction literally has a flat plate!) that could definitely benefit from a fairing:
So, I purchased from NAA the fairings for this area:
If you think about it, this fairing requires an extremely complex fitting installation - you've got two struts entering the fairing at angles to each other, and, where the strut openings in the fairing need to be located is dependent on the distance the opening is from the fuselage! On top of this, the struts' opening will need to be in the correct location fore-and-aft in relation to the gear leg opening.
I'm thinking one work-around as far as the strut openings will be to cut out the flat area where the struts pass through completely off, cut a flat piece of ABS to accommodate the struts, and once the fairing is located on the gear leg, glue the strut flat plate to the fairing. Clear as mud, correct? LOL!
Another question I have is how much does the gear leg flex? Can you just run the gear leg through the opening (once you've cut the end off), or, does the entire underside of the gear leg portion of the fairing need to be cut away to accommodate downward flexion of the gear leg?
Finally, where would be best to make a cut to allow the fairing to be flexed open to install around the struts and gear leg? Cut it in half vertically (maybe between the two strut openings?), cut a slit horizontally at the aft end of the strut opening (and a slit between the two strut openings) and either at the aft end of the gear leg opening or the underside of the gear leg opening?
As you can see, this is really a quite complex 3-D problem, to put it mildly! Has anyone successfully installed one of these fairings on a 750 STOL??? (Cruzers don't count as they only have one strut which greatly simplifies the problem!) Pictures of a successful installation would be worth a 1,000 words!
My gut feeling is that it might take a few mangled attempt$ before one gets this right! :(
John
N750A
John Burns
I am looking forward to your detailed instructions before I make my purchase.
I am interested in the fairing for the horizontal stabilizer to fuselage. Do you have that one too?
May 2
John Austin
Thanks, Scott! I simply templated the fairing with a piece of thin poster board and transferred it to some ?0.020? aluminum. The curves of the "hump" were formed by rolling the aluminum over an appropriate diameter tube to make the correct curves - just takes patience and a lot of trial fitting! Tip: to get the fairing edges to lay down flush against the underlying skin, use an edge roller to slightly turn-down the edges. This eliminates a lot of "waviness" in the skin edges and stiffens the edges considerably. The black vinyl edging is used where there is a possibility of fretting. I elected to rivet this on and left an inspection hole (which I now have a matching green plug to close it off with) where I can insert a borescope to check the torque paint on the bolts attaching the HT to the fuselage.
John
May 3
John Austin
If no one else has installed this (successfully!) yet, I've thought of a new approach to fitting it so the location where the struts penetrate the fairing is a close-fit and also in proper relationship to the landing gear leg penetration:
My new idea is to initially cut the fairing horizontally across the "chord" of the airfoil-shaped area where the struts go through and cut-out the opening for the gear leg:
The leg opening would then need to be cut on the underside to allow the resultant flaps to be deflected so the lower-half piece can be slipped onto the gear leg. Then, slide the lower-half piece up the gear leg till it hits the underside of the struts and start cutting-in the fairing around the underside of the struts until the lower-half piece fits against the fuselage.
Next, bring the upper-half of the fairing down from above the struts, cutting-in as you go until it conforms to the top side of the struts and matches-up with the lower half.
Once all this is done, one could then secure the fairing in several places to the fuselage and glue tabs to the fore and aft portions of the fairing to allow screws or rivnuts to hold the two halves together. This would also facilitate inspections as you would only have to remove the upper fairing fuselage screws and the screws joining the two halves to remove the upper half and inspect the strut attach bolts.
I like to "think out loud" and post this so if anyone sees a flaw or better approach they can point this out and maybe save me a co$tly mi$take! LOL!
John
May 3