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Leading Edge Slats

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Posted

I borrowed a slat panel that Randy Apling is making out of carbon fiber for the cubs and fabbed a mounting pattern for my Avid wing out of 1/8 plywood. I made it with 3 mounting positions so I could move the leading edge of the slat up and down.  Randy says the best spot on the cub is with the hook line where the convex top and concave bottom meet under the leading edge of the slat at 5.5" ahead of the leading edge of he wing and 3/8" above the bottom of the wing.  With the Avid undercamber wing I think it might need to have the height of the leading edge a little different so I made the mounting plate with the 3 holes so I could adjust it.  It looks like it fits pretty well but the large amount of washout in the Avid wing really shows.  With my new wings I plan to reduce the washout to 3/4" so It should lay on the wing a lot smoother.  The opening is limited to 3" with pins when mounted.

 

The last set of pictures is with it on a cub wing so you can see the comparison; not that much different.  I think it will work on the Avid wing OK.

 

OK, what do you guys think?  Am I crazy for thinking seriously about doing this?

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Posted

Wow, Is the idea to run them full length?  I have been noodling on a set up like the Highlander STOL, but I don't think their slats increase the chord nearly as much as what you are trying.   Are you going to try and split the flaps and ailerons?

It seems like their flaps are at least as important to performance as the slats.  

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Posted

I don't think it's crazy at all. It's called an experimental aircraft for a reason! I've always wanted to build a set and see what they would do to enhance performance. I saw a set on a CH701 years ago that was spring loaded so that it would push it when the aircraft gained speed and then deploy again as you slowed down for a landing. It was a very simple set up and other than figuring out what springs to use would be easy to build and reduce drag as the upper cruise speeds.

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Posted

David, He makes them in 4' and 3.5' panels for the cubs.  On a square tipped cub it would take 3-4' panels and a 3.5' at the tank end.  On a round tipped cub I am not exactly sure what the combination is.  Some leave the inboard 32" without the slats and they retain more rate of climb (the slats increase angle of climb but reduce rate of climb).  With my extended Avid wing at 13.5' to the last full rib before the tips I could run 3-4' panels and leave 1.5' inboard without slats or use 2-4' and 1-3.5' and leave 2' inboard without slats.  I have not decided on it yet. 

 

I have not thought about splitting thet flaperons at this point.  I would like to complete the extended wings and fly it like that, then add the VG's, then the slats, then VG's to the bottom of the wing (which I think might be even more important with the slats on) and see what the affects of each are.

 

Kenneth, These slats just work with the wind pressure and angle of attack. As the angle of attack increases the wind gets under the wing and starts to flow through the slats which causes them to open automatically and as the angle of attack decreases, they lay back down on the wing.  Most I have heard of work this way without manual deployment so I am not sure what the advantage of the manual deployment might be.

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Posted

Randy,

     My first suggestion would be to only put 1/2 inch of warp in the wings - I think there has been a lot of proven info on that.

By not having slats on the inner part, you may not need any warp, since the root should stall first anyway.

 

     The next concerns the rear opening of the slats - On the Z-701, the plans call for the rear opening of the fixed slats to only be 1mm.    I questioned this with Chris H's son and he said that is correct.  

     Donno much about the moveable slats, but if the rear gets too high, then I would think the airflow would just go out and up and not follow the surface of the wing as much - guess your engineer has it all figured out better than I do.

     I will share any info I can on the flaps/ailerons - you may come up with something better than Wittman's design.

EDMO

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Posted

Please keep us posted on the slats vs. VG's. I have been doing a ton of thinking on this one.

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Posted (edited)

Slats vs VGs:   Check out the comparison articles in Kitplanes or Sport Aviation about the Zenith 701 or 750 with slats or with VGs.

EDMO

Edited by Ed In Missouri

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Posted

Ed,

My question about those articles, which I've read several times over the years is this: The Ch701 has VERY thick cambered wing, and I really wonder how much that has to play into the factor. I'd love to experiment with it on an Avid, try the Slats first, then remove and install VG's, then possibly have both!

Hopefully I'll have one very soon to do that with.

 

Randy,

Has he ever just installed a 3' section out towards the tip to see what it would do, much like the Stinsons that are built in. I like the idea of it being able to float and then push back against the wing in cruise flight. I might have to try this one! Let us know how it goes, I'm very interested in the end results.

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Posted (edited)

The Zenith Slats are a lot different than the wide-open "SLOTS" in front of the outer Stintson wings.....Stintson put those in to keep the ailerons working when the inner wing had stalled.

Our STOL method was to get up some speed in the old Stintson 108 and grab the flap handle and jank in about 20 degrees - gave some quick lift for takeoff.   It couldn't compete with the Avid / Foxes in STOL....

EDMO

Edited by Ed In Missouri

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Posted

Ed,

My question about those articles, which I've read several times over the years is this: The Ch701 has VERY thick cambered wing, and I really wonder how much that has to play into the factor. I'd love to experiment with it on an Avid, try the Slats first, then remove and install VG's, then possibly have both!

Hopefully I'll have one very soon to do that with.

 

Randy,

Has he ever just installed a 3' section out towards the tip to see what it would do, much like the Stinsons that are built in. I like the idea of it being able to float and then push back against the wing in cruise flight. I might have to try this one! Let us know how it goes, I'm very interested in the end results.

Kenneth, I don't know if anyone has just used a single panel on the outboard end of the wing.  He just said some left a wider gap at the inboard end and it retained close to the same climb rate.

 

Ed, I am surpised at the 1mm opening in the Zenith fixed slats, it seems like that would defeat the purpose.  The fixed slot Dakota cub wings are a lot more than that and most of the moving slats seem to open to 3" or so.  If you look at the videos of the Just STOL and the SQ2 you cannot deny that they work a lot more than just VG's.  The caution will be not to overdo it on landing and drop the plane in too hard. What I would really like to see is the lower stall speed for takeoff.

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Posted (edited)

Randy,

       When I got my plans for the 701, I questioned the figure that Chris had written for the trailing edge of the slot - It looked like a 7 to me, so I called his son who explained that his Dad writes the figure 1 with the top like you see it here, but it was a 1mm.  This could have been an effort to get a better cruise speed?  That was 20 years ago, so it may have changed by now?

       Stall speed for takeoff could also be slowed by 1.  adding 4 inches to leading edge, 2. making the flaperons wider, or converting to wide flaps, or extending wingspan - either of which increases wing area, which, along with weight, determines stall speed.  

Can you go on a diet, :lol:  or decrease your survival gear???     

   I think the Slats are more for increasing angle of attack before stall,  than slowing the stall speed, IMO, but I am no expert on this subject.  I think the ones doing this also depend on more horses to hang it on the prop?

The slats will somewhat increase the wing area and change CG a little, just like extending my leading edges 4 inches.....

EDMO

Edited by Ed In Missouri

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Posted

Speaking about slats, did anyone set the flaming bag of dog poo, slatted kitfox on Barndreamers?

A good parts plane at 1/2 the asking price...

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Posted

Post up the Slatted Fox - so we can see it too.

EDMO

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Posted

It's gone now.   :mad:

 

It was a IV-1050 from Oregon with a modified, high compression 912UL (95 hp) in it.  It had extended wings, full span slats, and the leading edge extrusions were deleted to fit the slats.

 

 

According to a conversation I had with a fine fellow looking at the plane (who wisely chose to run rather than walk away) there is quite an extended laundry list of absolutely scary problems with the motor and airframe.

 

The seller was asking $28.5k...

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Posted

I saw the pictures, The tires were enormous!!! I wouldn't have even called to look at it after seeing what all he'd done to it and that it was only a 1050 aircraft.

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Posted (edited)

Question about wing theories:  When you bank an airplane, the wings have less lift, so your stall speed goes up - Sooo - When you increase the angle of attack, then that is like banking in a fore/aft mode, and the wings would have less lift again, so wouldn't the stall speed increase after reaching a certain angle, even with slats? 

     Note that I said "banking" - not "turning" where centripetal force would play a part. 

     I think this is where the fowler flaps have the advantage - increasing wing area while keeping wing surfaces flatter.

Another:  When you lower your stall speed so slow that the wind has more control than the pilot, then you are not in control - and the earth may come up and smite thee for thy discretions ?

Thinking - Thinking....

EDMO

Edited by Ed In Missouri

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Posted

Thanks for the ideas; a lot of ways to get there like you said.  Weight; yes, planning to pull all the insulation from my floor area and just leave it on the firewall, also the aluminum heel plates.  Thinking about pulling the plywood floor and putting in carbon fiber foam core board but that is a lot of $/lb.  Still thinking of changing to a LI battery and moving it to the firewall and pulling out all the cable to the rear battery location.  Maybe drill some lightening holes in my landing gear steps.  Am adding some wing area with the extended wings and reducing the washout will help some but extended wings, increased spar stiffners and larger lift struts will add weight as well as the slats.  Only trying it will tell for sure.  Fowler flaps are impressive but are well beyond the level of modifications that I want to do.

 

On the banking /turning; my understanding is the turning adds angular acceleration and increases the felt load on the wing from the added centrifigal force.  The banking causes the lift vector acting perpendicular to the wing to be at an angle off of vertical so the vertical component of the lift vector is reduced.  All other factors being constant; I have not experienced any increase in stall speed as angle of attack is increased.  I had not thought that the wing angle of incidence was changing the vertical lift vector.  Better ask Barnaby W.

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Posted

Randy,

 

Any more development on this? I'm very curious about it's functionality. Any updates would be great.

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Posted (edited)

Randy,

      I said the 701 had 1mm gap at the trailing edge of the slats - It could have been 1cm, which sounds more reasonable - Someone with a 701 / 801 manual might know.   Chris uses sillymeters on all his drawings, and it don't take much to confuse me.  I can easier relate to either .039 or .394 inches.

EDMO

Edited by Ed In Missouri

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Posted

No new developments on this yet; I need to get with Randy (he's been in HI) and see what he thinks of the fit up.  It looks like I should be able to mount the brackets then add or remove the slats as desired and leave the brackets in place.  It is a pretty expensive proposition so would like to know also if they didn't add any real benefit to my wing, if he would be willing to let me sell them through him at a discount to someone wanting them for their cub since they are the cub slats and they would just need the cub brackets.

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Posted

Randy,

      I said the 701 had 1mm gap at the trailing edge of the slats - It could have been 1cm, which sounds more reasonable - Someone with a 701 / 801 manual might know.   Chris uses sillymeters on all his drawings, and it don't take much to confuse me.  I can easier relate to either .039 or .394 inches.

EDMO

Even a cm is pretty small but at least they would be doing something it seems.

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Posted

Randy I was thinking about this thread last night and couldn't remember what had happened with your testing. Did this idea fade away or just never get posted when you did try it out?

Randy,

      I said the 701 had 1mm gap at the trailing edge of the slats - It could have been 1cm, which sounds more reasonable - Someone with a 701 / 801 manual might know.   Chris uses sillymeters on all his drawings, and it don't take much to confuse me.  I can easier relate to either .039 or .394 inches.

EDMO

Even a cm is pretty small but at least they would be doing something it seems.

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Posted

Bonjour,

je possède 2 avids flyer speedwing et suis  intérréssé par les becs de bord d'attaque et  j'aimerai savoir si

des essais en vol ont été effectué sur un avid flyer car faire des becs demande pas mal de travail et si des VG

ont des résultats proche ce n'est peut-ètre pas la peine de ce compliquer la vie.

Si parmi les amis pilotes une réponse peut m'aider a faire un choix Merci d'avance.

Marc Comte

 

 

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