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Wingtip Stall Fences

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Posted

I built a couple of wingtip stall fences the other day for my new wings; since I want to see if they will make any difference, I made them so I can take them on and off over my nav lights.  It will be a while before I get to test them but figured it was easier to build them with the wings on the bench than on the plane.  When I get a chance to test them I will post what the results are.

Hope to be covering the new extended wings with Oratex within 2 weeks.

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Posted

Very nice work, I would like to know what the dollar amount you have in the coverings.

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Posted (edited)

Randy,  I think if Kitfox had some really great "Bragging Rights" for the new "cool looking" wing and fences, then we would have seen some magazine articles on the testing and comparisons between those and the Riblett wings, like same plane, same pilot, same weights, with BOTH KINDS of wings and STOL FIGURES and CRUISE SPEEDS - Of course, they not only added fences, they used a different airfoil, and that might have made most of the differences?    

  Maybe you can give us some figures when you test yours both ways?  Good luck and Best Wishes - Glad you are trying something that has only been talked about.  EDMO

Edited by EDMO

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Posted

Jwhetnall, I have a pricelist for all the different Oratex components if I know how to attach it, but might need some instruction from Leni or Joey to do that.  The material costs to do just the wings was about $2000 without the glue and tapes.

Ed,  I kind of shaped them after the Kitfox fences they have on the new STI; but I had no dimensions to go on so used the eyeball comparison approach.  They are about 34" long and 7" wide at the widest point in the back.  I couldn't make them the full chord of the wing because I used the stock Avid wing tip bow but I installed the nav light fairings as far forward on the wing tip as I could reasonably support them so they would hold the front of the stall fence secure.  It will really be interesting to see if they work.  A fun experiment.  Like you, I have not seen any information pro or con on the KF fences.

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Posted (edited)

Just Aircraft has had them for years. If nothing else they sure do look good.

I think the ones that go in the middle of the wing would be the best. That would keep the airflow going strait over the wing In the right direction for better lift.

Edited by TJay

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Posted

Suber

 This is what I did with my extended STOL  wing, used wood  spacer on the outer rib to screw the fence in to the rib 

Will forward and picture later onIMG_0616.thumb.JPG.c8042254aa55f4a853bdf

IMG_0617.JPG

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Posted (edited)

Just Aircraft has had them for years. If nothing else they sure do look good.

I think the ones that go in the middle of the wing would be the best. That would keep the airflow going strait over the wing In the right direction for better lift.

TJay,  The fence in the middle of the wings is used to prevent boundary layer separation, usually located about 2/3 of span - Much the same as VGs.  Some older planes had them and others used a notch or step in the leading edge or other designs.  EDMO

Edited by EDMO
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Posted

Sioux,

Did they seem to make any difference with the tip fences?

I might try the mid wing fence too after flying this for a while. 

Also might try leading edge slats but that will be a lot more expensive test.  My concern with them is if the angle of attack will make them unusable without going to some long travel gear.

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Posted

Sioux,

Did they seem to make any difference with the tip fences?

I might try the mid wing fence too after flying this for a while. 

Also might try leading edge slats but that will be a lot more expensive test.  My concern with them is if the angle of attack will make them unusable without going to some long travel gear.

Randy,  I don't know how many noticed in the video of the Kitfox STi, but they also had VGs the whole length of the wings - I would bet that they did more good than the fences for STOL.  Zenith also replaced their slats with VGs and got similar performance.  Didn't want to cover up your questions for Sioux, but had to put those two facts on here.  EDMO

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Posted

Thanks Ed.  yeah, I still plan to install VG's the full length.  Since I built the tip stall fences so I can easily remove them it will let me compare them with and without pretty quickly and easily.  Since I took over half of the washout out of these wings I plan to install the tip 1/3 span with VG's a bit forward of the rest of the wing. I noticed Dakota cub is doing that.

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Posted

I have been doing some thinking about slats also but a friend of mine that has them on his S7 thinks that without more HP they would not do that much.  He has his 912 pumped up to 140 HP.  Bruce is the owner of Back Country Super Cubs so he has a lot of experience with slats but none with the Avid.  He could be wrong but for the amount of work and expense involved I have been somewhat dissuaded, but the thought lingers.  It sure is fun flying the BCSC with them and the 35" tires!.  You can drop them in like a bomb.  The one I flew most had the Dodge gear, can't think what he call it but it does have lots of travel for sure but the 35" Bushwheels absorb a lot of the impact.

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Posted (edited)

I have been doing some thinking about slats also but a friend of mine that has them on his S7 thinks that without more HP they would not do that much.  He has his 912 pumped up to 140 HP.  Bruce is the owner of Back Country Super Cubs so he has a lot of experience with slats but none with the Avid.  He could be wrong but for the amount of work and expense involved I have been somewhat dissuaded, but the thought lingers.  It sure is fun flying the BCSC with them and the 35" tires!.  You can drop them in like a bomb.  The one I flew most had the Dodge gear, can't think what he call it but it does have lots of travel for sure but the 35" Bushwheels absorb a lot of the impact.

Paul,  My Maule 4C had the STC Atlee Dodge "Bush Gear" on it with the Hydro -? shocks ???  My memory is shot!  Cant remember how much weight it added, but it was a lot and was so strong you couldn't hurt it.  Best thing ever for Piper and Maule, IMO. 

Randy,  Your new "extended" wings - are they standard Avid 29'10", or longer?   EDMO

Edited by EDMO
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Posted

Paul, for sure you can't beat HP.  I think the slats would work regardless of HP when landing though, but like you say, may require you to drop like a bomb in order to utilize it.  I have 30" tires which help a lot but I have also bent a few axles.  Not a big deal to change out but I know that is the weak point in my setup right now.

Ed,  These wings end up being the same length as the Magnum wings which will put my Avid+ at about 33'-2".

Randy

 

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Posted (edited)

Paul, for sure you can't beat HP.  I think the slats would work regardless of HP when landing though, but like you say, may require you to drop like a bomb in order to utilize it.  I have 30" tires which help a lot but I have also bent a few axles.  Not a big deal to change out but I know that is the weak point in my setup right now.

Ed,  These wings end up being the same length as the Magnum wings which will put my Avid+ at about 33'-2".

Randy

 

Randy,  The extra 3'+ wingspan should help your STOL a lot, IMO.  I believe that with the .065" wall spars I would have moved the strut fittings outboard more than standard Avid and made new struts, but with 5' JUST inserts you might not need that - Or, do you have .083" wall spars?   Good posts on the wing building.  EDMO

Edited by EDMO

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Posted

Ed, we did move the struts out.  He has a whole thread on the wing extensions etc.  It has been well thought out, well engineered and well built.  I know the struts are extended, I welded them for him :lol:

:BC:

 

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Posted

Im sure its to late to removing existing plywood wing inserts and replace with a longer one now that the wings are cover and painted. .I am wishing I had done this when I did my wing extensions but never thought about it. Did think about extending the struts but wasn't sure about having all the rivet holes from the old location in the spar so in the end just left it alone ,

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Posted (edited)

Im sure its to late to removing existing plywood wing inserts and replace with a longer one now that the wings are cover and painted. .I am wishing I had done this when I did my wing extensions but never thought about it. Did think about extending the struts but wasn't sure about having all the rivet holes from the old location in the spar so in the end just left it alone ,

I think that Suberavid has new spars, so no holes to worry about.  If I had strut fittings already on the wings and wanted to make the struts longer I would leave the old spar fittings riveted in place and maybe just remove the outer part that connects to the struts.  Then you have to make sure you have an insert in place above the new fittings too.  EDMO   

Edited by EDMO

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Posted

Thanks Ed,I will keep working on it ,in the mean time its flying fine with the new wings and I know of one other aircraft flying with the same setup,just wont be packing out any moose :)

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Posted

Thanks Ed,I will keep working on it ,in the mean time its flying fine with the new wings and I know of one other aircraft flying with the same setup,just wont be packing out any moose :)

I would bet that Suberavid made the longer struts out of 1" x .049" or .058" wall.  EDMO

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Posted

Wow. a lot of discussion on the wing tip stall fences on Barry's magnum build thread.  I hope I can provide some real numbers with and without the fences on these wings soon; and with no other change in the wing, such as removing the wingtips.  I agree that it would be hard to determine what worked and what didn't if the wingtips were removed when installing the fences.  Plan to start covering this weekend!

Willis, installing new or additional spar inserts in the wing after it is built will be a challenge.  Jack and I were discussing how to do it last weekend and didn't come up with any real great solutions.  Be sure to post if you come up with a good method.  It was certainly easier to do while I was building mine.  I was going to install the longer and stronger inserts anyway, but would not have extended my lift struts until I read about the experience Chris was having with his.  This forum is a real value !

It sounds like you aren't experiencing any excessive wing flex with yours that affects the flaperons, correct?

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Posted

Hi Randy , no problems at all with wing flex and the flaperons. The only problem I have with the flaperons is them freezing up when water seeps into the hinge area. I throw on some lock de-icer and then some silcone lubricant and it solves the problem. I think a person could extrend a really long recipricating saw blade to cut the old one out  but with all the rivet in the spars not sure how I could get the new one in. Do you know if the old inserts were usually epoxied in place or just a tight fit?

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Posted

I believe I am experiencing wing flex that affects flapperons when flaps are deployed.....the more flap deflection the more stiffening of the controls. My next project is to see if it is going to be possible to replace the existing spar stiffeners with longer ones. i bought a small inspection camera to help with the evaluation. I should begin this project in the next week or so.

First step will be to determine if I can do it without ruining something. Already have the wood picked out from A/C Spruce P/N 02-00236 which will allow for 60 inch stiffeners. The plan is to laminate two 5/32 pieces into 5/16 thick beam 60 inch long and hopefully slide it into the existing position by just drilling out the rivet(s) that secure the current 18 inch stiffener. If it doesn't look like I can pull it off I won't try as it is not worth ruining the wings. I do believe there is significant improvement to be gained if it will work though. 

I have run the flapperons through full travel with and without someone standing at the wingtip and pushing up until a tire almost comes off the ground, and the flaps definitely stiffen up as they are deflected with the wing under load.

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Posted

Chris,It will be interesting to see how you make out on the stiffeners, I can only deploy the flaperons about 1/2 of the full travel ,otherwise I run out of elevator,I haven't notice any binding with that amount. I have the model C elevator so hopefully next project will be enlarging it with trim tab. I had the plane loaded with 26 gal of fuel and 2 people and didn't notice any extra binding so far

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Posted

Hi Willis!

The binding or stiffness happens more at the extremes of flap deployment. Regular flying around, even steep turns do not deflect the ailerons enough to notice what I am talking about. I notice the stiffening when the flaps are at greater deployment.

What is your weight and balance? I find that the typically far forward w&b of the Avids really affects elevator authority. I have some weight in the back of my Fat Avid and it helps immensely! I put 10 LB of lead way back in the tail which brings the W&B into the middle of the range and it lands much better than at the forward limit. Everything works much better in the middle to rear of the CG range.

Chris

 

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Posted

The  weight is 755 Lbs, I cant remember what my cg was but you were right about it being forward, I finally added 10 lbs of weight to the tail wheel bolts today and it made a huge difference, pretty much can let go of the stick and it flys pretty well level and the deploying the flaps is quite a but less nose down now as well. Thanks again Chris for the advice :BC:

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