Zenith Aircraft Builders and Flyers
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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
Replies to This Discussion
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Permalink Reply by Tony Renshaw on
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I want to install gear and strut fairings on my Cruzer and whilst a lot of R&D has gone into their production, I don't see too much benefit with the amount of work required to make these ones fit. I think the issues of separating into pieces, even creating a lip should have been solved for the product to be saleable, it seems half baked. Great modelling for sure, sophisticated, but the fitment lets them down in my opinion.
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Permalink Reply by John Austin on
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I'm mostly with you on this, Tony!
What you are provided with is a basic shape that has slightly oversize edges to allow for trimming. No instructions are provided and as you point out, you have to decide where to separate the pieces to allow for installation and where and how big to make cut-outs for gear legs and struts. And, of course, no lips or joggles are provided since you have to make the cuts first and then glue-in lips as required. Complicating this in the case of the STOL 750, the twp struts approach the fuse-struts-landing gear leg fitting at an angle, so where they intersect the fitting depends on how much of the edge of the fitting you trim off - it's a really complex 3-D problem. Believe me, I thought long and hard on where to cut that fairing! The strut/wing fairings are not so difficult, however. Also, I think they could be made from thicker material - they seem almost "delicate," but ABS plastic is fairly tough and I must admit that so far, I see no evidence of cracking - time will tell as to the true durability, however. Lastly, I honestly believe that the problematic landing gear/fuse/strut fittings had never been actually installed on a STOL 750 - so far, I haven't found anyone who has installed them before I did!
OTOH, I guess the vendor could argue that the parts need to be oversize and require trimming and cutting to allow for variations in the airframe construction, but if the plane is constructed anywhere close to plans, I don't really think that would be an issue. I suppose the biggest "pro" argument is that if you've ever purchased certified aircraft fairings, the whole Zenith set is ridiculously inexpensive relative to what a single certified fairing would cost.
I had some down-time due to a prolonged wait for a new engine, so I didn't mind the hours required too much, but this definitely is NOT a project for an impatient builder! LOL!
(BTW, the Cruzer gear/fuselage/strut fairing will be much easier to fit as there is only one strut intersecting the fairing!)
John
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BTW, if anyone is interested in seeing an actual installation of the wing/strut and landing gear/struts/fuselage fairings, I'll have my 750 STOL at the Homecoming fly-in - just look for the Gecko Green 750 ... it's hard to miss! LOL!
John
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