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Shaved Slat Brackets
If you've seen my Slats and VG's post, you know I definitely prefer the VG's/no slats configuration on my 750 since I really don't need extreme ascent/descent angle ability into obstructed strips. Aesthetically, it bugs me to have the "naked" slat brackets protruding from the leading edge. They're so prominent and with the empty mounting holes, I typically get the question "What are those for?" or "What attaches to that?" In other words - a plane that I really tried to finish-out looks unfinished!
On a really boring winter day, I knocked-out some non-functional trim pieces that mimic the leading-edge profile but at least gave the brackets something to attach to! (You can see them in the "Slats and VG's" post.) I have had a good time with them as when asked about them by someone without a clue, I look at them with a straight face and say "those cut down on sonic boom propagation." Good for a laugh!
However, I've now decided all the trim pieces do is call even more attention to the brackets since they are so prominent. The easiest solution would be to shave the brackets off flush with the leading edge and call it a day, but that means (a) there's no going back to slats, ever, and (b) I've got a nice paint job on the wings and even with careful masking and taping, it might be tough to really cut those brackets down flush without damaging the finish and/or leading edge.
I think it's unlikely I'll ever put the slats back on, but in the event the plane had to be sold (over my dead body!), a potential buyer might very well want that capability - especially since the slats are hanging right there on the hangar wall! It has been suggested that perhaps the most-practical and "cleanest" look might be to just trim the existing brackets back to less than an inch or so and follow the leading-edge profile. Before cutting them back, one could template the portion of the existing bracket that protrudes from the leading edge so as to later easily make an "intermediate" bracket to link the slat bracket on the wing and the bracket on the slat (thus restoring the slat to its proper position relative to the wing) if the slats are to later be reinstalled.
I would locate pilot holes on the "intermediate" bracket template to be able to later accurately locate them on the wing bracket, but I don't think I would even bother to drill the holes in the wing bracket to keep a clean look - they would be easy enough to do later if the slats were going back on. In reading Zenith's construction standards, it looks like for .063 the "potential" holes in the wing bracket and the pilot holes in the "intermediate" bracket would need a minimum radius edge distance of 10 mm.Due to these brackets overlapping, I'm thinking that means the wing bracket should be trimmed to a final height of 20mm to allow for the mounting holes - real or potential - to have the proper edge radius both fore-and-aft.
20 mm height seems a good compromise as it retains the potential to reattach the slats and makes shaving the bracket easier since the cut will be well above the leading edge skin - easier to mask and protect. Also, if carefully masked, all I'll need to do is touch-up the cut line with paint. Yes, they'll still be protruding, but not nearly so much.
I posted this to solicit input - positive or negative - and to see if I'm creating a problem that someone else has thought of. If I cut those brackets down, I figure I've only got one chance to do it right!
Replies to This Discussion
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Permalink Reply by Ken Ryan on
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If you do this, you're still going to have brackets sticking out of your leading edge. I fail to see where you have gained much, aesthetically. Besides, having the brackets is a good conversation starter, and opens the opportunity for discussion of slats/no slats. If you really want to "fix" this, what you need to do is to remove the leading edge skins, remove the brackets, and then replace the skins with ones that don't have slots cut in them. But I would just leave it the way it is, and not let it bother me. You never know what the future will bring. You might one day find yourself wanting those slates.
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Permalink Reply by John Austin on
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If you do this, you're still going to have brackets sticking out of your leading edge.
True, but only protruding 20mm and following the leading edge profile. To me, that will at least have less visual impact than an angular shaped bracket with empty mounting holes several cm long. But again, it's just opinion. I might very well have never installed the brackets if I was doing it over again, but I bought a partially-completed project and the brackets had already been installed - also, at that time, it never occured to me that I might not use the slats!
But, as you say, one day it might turn out the slats are to go back on ... that's what leaving the shaved-down bracket will allow with a suitable adapter/"intermediate" bracket. So, a compromise aesthetically, but not functionally.
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Permalink Reply by John Edwards on
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John , Thank You for bring up this subject again on flying with no slats. I have talked with a few 701/ 750 folks without slats and using VG's. They seem to say the same things. No reason to fly with slats when they cant tell a difference in TO or Ldg distances and about a 20% savings in fuel.
But , slats sell. I ordered my wing skins without the slot cut for the slats several years ago.
Perhaps with posts like yours, more people will come to recognise that the 701/750 has a well designed high lift wing that just works with VG's and get off their high horse and realize there is more than one way to achive the same goal.
Thank You again for your posts.
I will be putting a L angle bracket inside my wing skins that matches the wing profile and a big nut attached to that. I think something simple like a single rivet in the wing skin marking center point of those nuts will make it easy for someone to reattach slats in the future is they want.
Thnks again for you posts..
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Direct quote from Chris Heintz:
From a design standpoint, I have no objection to the removal of the leading edge slats (and their attachment brackets) and replacing them with VGs, but be aware that the take-off distance will be longer and the initial climb rate will not be as good (nor will your approaches over trees be as steep), and the cruise speed will only increase slightly.
My experience has been that the take-off/landing rolls are nearly identical with either configuration - certainly not enough to make any practical difference for my situation. However, my cruise speed increased 8 kts, which I consider significant! I'm not advocating everyone pull their slats off, but it works for me!
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Permalink Reply by Roger Wibbels on
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I left mine off too, although the nose skins came with the slot cut. I just put an L angle under the slot, and I'll use a little bondo to smooth it out and paint it.
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Permalink Reply by zbyszek Kedziora on
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No slats
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Permalink Reply by Joe Harrington on
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Ahh, the "no slats" camp is coming out of the woodwork! (including me..). I personally love the looks of the slats, especially on this aircraft; they fit with the ultra utilitarian look of the plane. However I have drank the VG koolaid. Every single member of our flying group that tried them (a dozen or so) strongly feel that VGs improved their airplane. Our scratch built airplanes did not have any slats or brackets included. I plan on testing without and with VGs as to determine any differences.
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Joe - As a fellow Kool-Aid drinker, I must ironically admit that I, too, really like the look of the 750 with slats - no doubt the distinct appearance has been a great marketing aid for Zenith! However, when I returned to reality, I was able to demonstrate objective benefits from removing the slats (8 kts increased cruise speed at same rpm) and then, by adding VG's, a 5 kts (indicated) decrease in departure stall speed vs no VG's. As far as slats vs. VG's landing and takeoff distance, I just can't see a difference!
Fortunately, I spend more time inside the cockpit flying my 750 vs. standing around outside looking at it! Now, if I could just get over that fixation about ugly slat brackets!!!
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Permalink Reply by Chris Aysen on
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John - Cut off the slat brackets and live with it. Something sticking out won't look good. If your fighting with this this much you must doubt your theory on slats vs VG performance OR you're not sure if you will sell at a later date; at which point put the slats back on. Now I'm sure this post will help you decide. HA HA.... I just like the look of slats but all-in-all probably not a whole lotta difference in performance. To me not having the slat look is not worth the little increase in speed. I believe you have to break 100 mph CRUISE speed to justify modification of the airplane. Simply because that is where you get a real cross country difference in travel. Zenith STOL designs just aren't meant for that. That's why there's a 650. Just my two cents.
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Permalink Reply by Rick George on
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That's why I have a RV4 sitting along side the CH750 -180 mph or 80 mph!
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Permalink Reply by Mark Maltais on
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I'm thinking the slats matter most when the 701 was a lower powered aircraft and that the difference would be noted there! Now with 100+ HP pretty standard on the 701/750 the plane has enough power to just climb with or without slats near it's max speed/angles anyways.
I'm sure if I would drop a 200 hp engine on the front my plane it would not cruise much faster, it's just too much of a brick to do it... That's my theory anyways, but I'll be keeping my slats anyways! ;)
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I knocked-out a couple of templates yesterday:
The steel template would be clamped against the existing slat bracket on the wing and used to mark a cut line. Pilot holes for mounting bolts have a 10mm radius edge distance. I'll probably cut close to my marked line, then clamp the steel template against the remaining stub of bracket to somewhat protect the profile as I file or sand the cut edge down to the line. With some careful taping, it should only take some touch-up of the cut edge. I don't think I'll even bother to drill the pilot holes in the stub bracket if and until the slats ever had to go back on (for the estate sale after I'm dead and gone! LOL!).
The aluminum template is the new "intermediate" slat bracket to bridge between the stub on the wing and the slats. The actual brackets would be .090 - same as the existing ones. I used my steel template's pilot holes to locate the proximal holes in this bracket. I'll use one of the cut-off's from the original brackets to pilot the distal holes where the slats are bolted. These new brackets could just be left bolted to the slats, so installation to the wing would still be just as easy and quick as it is now.
A lot of trouble for "decreased visual impact", but hey, it's drizzling freezing rain outside today - not like I could be flying instead!
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