Fairings, more

62 posts in this topic

Posted

Made a couple of more fairings.  Built some gas cap fairings which I would really classify as vortex generators, which are similar to KF fairings.  The other fairings were for the gap of the HS.  I should add that the gas cap fairing from KF are cheap and I would have bought them but I was making the other fairings so it wasn't much more work to go ahead and just build them.  

Binding bolts or sex bolts were used to mount the fairings on the HS VS location.  The fairings were attached after painting and when I jumped into the plane the fairings limited the up elevator travel so a little more carving was required to make it function.  I flew the plane with just the HS fairings and did not see any speed change that was noticeable but the response of both the rudder and elevator was better well seemed better.

The gas cap fairings on the other hand picked me up 2-3 mph and may have lowered the stall by 1-2 mph.  I will need to get a little more time on the install to be positive.

i am looking at the junction of the struts and the wing next.  It is obvious by looking at the fabric on the underside of the wing that area can use some work.  I know John did some work in that area with good results but I don't remember what he said he gained.  Haven't figured out how to make a fairing that looks good and still works as of yet.

So a couple of steps closer to my 120 mph cruise at 5500 rpm, it is within easy reach now.

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Posted

Looks good Paul, do you have a picture of the gas cap fairings from the side?  Thanks,  JImChuk

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Posted

No I don't Jim but I will try to remember to take one next trip to the airport  

 

 

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Posted

I bet fairing the back side of that cap will give you better results too.

:BC:

 

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Posted (edited)

I know you are right about that Leni And it is on my mind.  Looking back I wish that I would have installed recessed caps while building, would have been much easier then. Maybe just a simple ramp or stingray style.  Guess I wil have to make a couple of foam models and try them out.  Someone in NASA has probably came up with an answer that was tested in the wind tunnel if I just knew how to find it.  I will dig out my copy of "Speed With Economy" and see if there is anything in there.

Edited by wypaul
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Posted

I have this if its any help. 

image.png

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Posted

Thanks Buck, sure is good info.

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Posted

What model is your airplane & what wing?

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Posted

It's a MK IV with the heavy hauler wing. Located in Casper.

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Posted

It's a MK IV with the heavy hauler wing. Located in Casper.

so you have the under camber rib profile? What engine?

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Posted

912ULS

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Posted

Wow, 120 mph is amazing for the HH wing Paul.  I didn't think that was possible.  I may have to try a few more things  Of course it's hard to make wheel pants for 30 tires, lol., but I guess every little bit helps.

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Posted

Randy, 

 Sounds like ud need some "Bell Bottoms"

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Posted

Ha ha, yep, and big ones!

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Posted

Jim I did finally remember  And I'm installing the Williams Aviation strut cuffs.  His fairings are thin, vacuum formed, and light weight.

 

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Posted

Finally had a chance to fly with the Williams Aviation strut cuff fairing, the front two at least.  The results were disappointing, no noticeable gain in speed.  These fairing are thin and flimsy at best and a pain to try to install.  I cannot recommend them.  The fairing behind the gas caps were installed today so report will follow tomorrow's flight.  Like the cuff fairings these are also thin vacuum formed plastic but due to the smaller size and shape they are more acceptable.  Now if there is gain l will be Ok with them.

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Posted

Fuel cap fairings showed an increase of 1-2 mph.  I'm now at call it 117 mph IAS, 3 to go.  Looking at working on the cabane next which maybe enough to get it over the hump.  I would say the fuel cap fairings from Williams are worth while but just as easy to fashion your own from foam and glass.

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Posted

I had thought about building a fairing that would completely enclose the cabane.  It would attach to the belly of the plane like a belly pod.  Most likely out of fiberglass.  I think it would cut down on a bunch of drag, and the area behind the cabana could maybe become a baggage area if built right.  JImChuk

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Posted

I had thought about fairings but after looking at 21X12 tires hanging out in the breeze, figured what's the point.

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Posted

I am really skeptical about putting a few fairings on an Avid and getting 10 or 15 mph more cruise out of it. Physics argues otherwise.

Drag goes up by the square of speed, so if you want the same power to get you from 90 mph to 100 mph (let alone the 120 mph someone posted here!), you have to cut the drag by 20%. How many gas caps does it take to equal the drag of that big wing? Or the fuselage cross section? Or those long double struts?

To get to 120 mph, you have to drop the drag by almost 80%. 

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Posted

:lmao:

Tell Kent Paser about physics, I'm having a hard time staying civil here.  I'll make a video for all to see. Yep I'm talking IAS, no I didn't make a CAS chart and yes my IAS is fairly accurate.

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Posted

I had thought about building a fairing that would completely enclose the cabane.  It would attach to the belly of the plane like a belly pod.  Most likely out of fiberglass.  I think it would cut down on a bunch of drag, and the area behind the cabana could maybe become a baggage area if built right.  JImChuk

That thought has crossed my mind Jim.I read somewhere about a pilot adding a belly pod to a Super Cub and picking up several miles per hour.  It would be a fun project to build out of carbon fiber,  if I were Mike Patey it would have been done by now.  Have you watched his latest video on building the CF fuselage covering for his latest project?  I'll see if I can post a link and do an edit.

Also the pod sure would be nice when I head into the Backcountry camping again next summer.

Casper was just chosen for one of the three sites next year by the AOPA for their fly-in's. Maybe some of this group will make it up here for that.  I'm going to get a hold of the flying Cowboys and see if they are interested in doing a STOL Drag for that.

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Posted

I had thought about fairings but after looking at 21X12 tires hanging out in the breeze, figured what's the point.

I have the 21" tires and there are several points for me.  I can now keep up with my buddy's  Kitfox Four when we are traveling to the Backcountry in Idaho, while flying in the Backcountry by pulling the throttle back a bit I won't have to head out to get fuel as often and it's fun when non-believers tell you an Avid won't go that fast!

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Posted

Hey, go for it! Makes little difference to me since I didn't get mine for speed anyway. 60-65 is just fine for me since most anywhere I go is an hour or less. I live in the mountains so going to the mountains is walking out the backdoor, or flying a pattern around the strip.

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