"Speed" Pacer.

[cook11]

So I am leading towards rebuilding my Pacer for cruise speed rather than trying to make it land on a postage stamp. So I am wondering what has been tried on Pacer to improve its cruise speed. Again my experimental Pacer has stock wings and fuselage length. The motor is a Lycoming 0-320 E2D rated for 160hp. Below is a list of items that I would like to do to the plane to make it better:

-Grove aluminum landing gear with either the streamlined gear legs they offer or aerodynamic gear leg fairings possibly resembling the Pacers original profile.
-Wing strut fairings. Is there anyone who makes the wing strut to fuselage fairing like the one used on the Mystery Pacer?
-Miss Pearl fairings "Wing root, flap/aileron hinge"
-Flap/aileron gap seals
-Rudder/stabilizer gap seals
-Negative flap setting "not sure if it will make a difference in cruise speed"
-Overhead flap handle with electric trim
-RV-6 cowling and plenum
-Zero degree engine mount
-FAB intake system K&N filter
-Carb inlet closer to prop blast
-James aircraft RV-10 "6.00 x 6" wheel pants.
-Tailwheel fairing.
-Minimize cooling drag through efficient baffling.
-Exhaust system either 4 pipe or 4-1 along with augmenter. Not sure if cowl flap are required.
-Rake the windshield more.
-Windshield to fuselage/wing fairings
-Strobe lights streamlined into the wings
-Remove the humpback look.
-VG's "Stolspeed"
-Beef up tail structure "Need ideas on this"
-Wing tips "I'm thinking Stewart gives you the best increase in cruise"
-Pilot weight loss!

Already have on the Plane:
-AeroVolts lithium battery "big weight loss"
-API 6" tailwheel with stinger "weight loss and less drag"

Quite a few of my ideas come from Tailwind and BD-4 forums.


Anyone have any other ideas?

Thanks!

[yarddart]

I would duplicate younkins airplane with a few changes but I think he had a pretty well dialed in

[CamTom12]

-Grove aluminum landing gear
-Wing strut fairings. Is there anyone who makes the wing strut to fuselage fairing like the one used on the Mystery Pacer?
-Miss Pearl fairings "flap/aileron hinge"
-Flap gap seals
-Negative flap setting "not sure if it will make a difference in cruise speed"
-RV-6 cowling and plenum
-Zero degree engine mount
-RV-style "6.00 x 6" wheel pants
-Exhaust system
-Remove the humpback look
-VGs

My Racer has the above listed mods. Others have talked to Roger about the landing gear, it seemed like he thought it was an exceptional amount of work. It sounded like he wouldn't do them again. They are clean though.

Roger hand-laid fiberglass fairings at nearly every junction on the airplane. I saw his pictures, and other than being tedious for a perfectionist, it didn't seem like it would be that hard to do it yourself.

I think Roger purchased the flap/aileron hinge fairings. They're pretty tight fitting. I heard a birdie tell me the original design was by Younkin?

I've also got a reflexed flap setting. Once I get my baffle seals replaced and can do high power runs I'll let you know if they make a big difference at higher speeds. Initial observations show they're probably good for approximately 3-5 mph at 130 mph indicated, but I haven't done any real testing yet.

I haven't installed the wheel pants yet to see how much of a difference they make. I need to do that and check it out.

The exhaust is pretty sweet, I'll post who makes it when I get home to check the paperwork. It's a 2-into-1. Sounds real nice. It looks efficient, but Its the only exhaust I've had on the plane so I can't make any comparisons.


If you have any questions I'll be glad to answer. I didn't build this beautiful plane though, so I might have to phone a friend to get some answers.

[mmoyle]

Changing to a zero thrust line will change the cruise angle to nose down and will require the vertical stabilizer to be off set to the left about an inch. I'm going to make wing strut fairings from 3003 fifty thou in two pieces. Fit the halves and weld the seam....then more planishing work to make the weld disappear......but that's way down the road...
Mark M


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[Steve Pierce]

Changing to a zero thrust line will change the cruise angle to nose down and will require the vertical stabilizer to be off set to the left about an inch. I'm going to make wing strut fairings from 3003 fifty thou in two pieces. Fit the halves and weld the seam....then more planishing work to make the weld disappear......but that's way down the road...
Mark M


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Do you think the thrustline modification will work on a short wing? Because of the difference in the angle of incidence of the wing and my experience Super Cubs with a higher angle of incidence that the modification did not work on I am curious to see.

[piperrocks2013]

So I am leading towards rebuilding my Pacer for cruise speed rather than trying to make it land on a postage stamp. So I am wondering what has been tried on Pacer to improve its cruise speed. Again my experimental Pacer has stock wings and fuselage length. The motor is a Lycoming 0-320 E2D rated for 160hp. Below is a list of items that I would like to do to the plane to make it better:

-Grove aluminum landing gear with either the streamlined gear legs they offer or aerodynamic gear leg fairings possibly resembling the Pacers original profile.
-Wing strut fairings. Is there anyone who makes the wing strut to fuselage fairing like the one used on the Mystery Pacer?
-Miss Pearl fairings "Wing root, flap/aileron hinge"
-Flap/aileron gap seals
-Rudder/stabilizer gap seals
-Negative flap setting "not sure if it will make a difference in cruise speed"
-Overhead flap handle with electric trim
-RV-6 cowling and plenum
-Zero degree engine mount
-FAB intake system K&N filter
-Carb inlet closer to prop blast
-James aircraft RV-10 "6.00 x 6" wheel pants.
-Tailwheel fairing.
-Minimize cooling drag through efficient baffling.
-Exhaust system either 4 pipe or 4-1 along with augmenter. Not sure if cowl flap are required.
-Rake the windshield more.
-Windshield to fuselage/wing fairings
-Strobe lights streamlined into the wings
-Remove the humpback look.
-VG's "Stolspeed"
-Beef up tail structure "Need ideas on this"
-Wing tips "I'm thinking Stewart gives you the best increase in cruise"
-Pilot weight loss!

Already have on the Plane:
-AeroVolts lithium battery "big weight loss"
-API 6" tailwheel with stinger "weight loss and less drag"

Quite a few of my ideas come from Tailwind and BD-4 forums.


Anyone have any other ideas?

Thanks!



My AME friend/teacher Ed rebuilt a Piper Pacer many years ago. He never did all what you are going to do. But he was into speed and effiency and other interesting components in many aircrafts more then anything and his work was recognized all over the industry from Bombardier to Cessna across the Us and Canada. Anyhow enough bragging about the great guy :) He always told me the biggest secret to a speed airplane is the leading edge. Make well sure your leading edge is perfect! No dents should be perfect smooth - think it be hard to hide the rivets, not sure if you can use flush rivet- something to look into. As you know this already make sure you rig the plane perfect and follow the instructions and mostly make it light! Ed's Pacer/ converted Pa22/20 with a 160Hp Full Power Cruise 2500' average temp day was reading close to 150mph and 135 at 2400 RPM. He can't recall but he is sure his prop was the stock 61 or 60.

Side note story he told me a guy with a Cessna 210 got new paint job and afterwards his cruise wasn't much above 150. (It use to cruise around 180) They tried everything you could think of and no go! Finally Ed looking at the leading edge and notice slight hump and took closer observation and grabbed a pick and started picking on the new paint job. Should of seen the owners face!!! Anyhow to there surprise there was masking tape for some reason left on the leading edge during the paint process. Ed got all the tape off and sanded the leading edge to make it smooth again. Jumped in the 210 and right away got his 180 ++ back. Moral to the story any rough surface no matter what wing we have will affect the performance greatly. Why do you think frost, kills ????? Hope that helps.

[CamTom12]

Why do you think frost, kills ?????

Because it creates a rough airfoil surface, which creates a very turbulent boundary layer, which requires more energy to keep the boundary layer attached, which leads to airflow separation.

[cook11]

Good points. I feel that by doing that cleanup of the airfoil and any parasitic drag on the wig surfaces will make a noticeable increase in the cruise speed of the Pacer. Combine the major reworking on the cooling drag both on the inlet and exit side, along with a more raked back windshield just like the Tailwind, Hiperbipe and BD-4 will make quite the mover. The raked back windshield will require it to go past the boot cowl and firewall. There are so many junctions on the Pacers airframe that require some nice compound curved fairings that I am certain if done correctly with all the other modifications may get the aircraft really close to the VNE of 170mph no problem. What is limiting the aircraft to a VNE of 170mph? Is it the airfoil? Wing structure? Tail structure?

CamTom12 did Roger install a zero thrust mount on the Racer for the RV-6 cowling to work?

Thanks!
Jon

[CamTom12]

CamTom12 did Roger install a zero thrust mount on the Racer for the RV-6 cowling to work?

Thanks!
Jon

I'm not sure, but I'll email him and ask.

[andya]

IMHO - a level flight 170 mph will take a wing other than the clark Y of the piper heritage and no struts for starters

[cook11]

Do you think the thrustline modification will work on a short wing? Because of the difference in the angle of incidence of the wing and my experience Super Cubs with a higher angle of incidence that the modification did not work on I am curious to see.

Steve this is a topic I have seen pop up from time to time.....I am not 100% sure whether the modification is even feasible or worth the re-engineering ....It seems that Piper is the only one "I'm probably wrong" that uses nose down on their mounts. I don't think Aeronca, Cessna, Funk, Luscombe, Taylorcraft, Rearwin, Monocoupe, Interstate had negative down thrust on their mounts. I am curious to know whether wing rigging will need to be modified due to the modified engine angle.

[cook11]

IMHO - a level flight 170 mph will take a wing other than the clark Y of the piper heritage and no struts for starters

It would be interesting to know how well a shortwing would go with the Taylorcraft NACA 23012 airfoil rather than the Pipers USA 35B airfoil. The Monocoupes were quiet efficient and fast with the Clark Y but again they had a small frontal area to them. I would be interested in talking to Callbie Wood the designer of the CF-4 Four Runner an enlarged four seat Tailwind which used the same airfoil and get an idea of what was involved with his design process.

[mmoyle]

Do you think the thrustline modification will work on a short wing? Because of the difference in the angle of incidence of the wing and my experience Super Cubs with a higher angle of incidence that the modification did not work on I am curious to see.

Yeah, don't think changing the thrust line will work if speed is what the builder is looking for. I think...ouch....decreasing the vertical axis to zero does the same thing on a Pacer or Tripacer as it does on some of super cubs modifications with a positive thrust line like we see at the Valdez short field competition. Like Cessna the Pacer/Tripacer horizontal thrust line is off set to the right overcome torque. For instance the 207 offset is three degrees. The Bearhawk has a zero zero thrust line, to compensate for torque the off set of the leading edge on the vertical stabilizer is 3/4" to the left. The Bearhawk also flys with a 2 degree nose down angle when light...heavy she flys level.


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[danP]

IMHO - a level flight 170 mph will take a wing other than the clark Y of the piper heritage and no struts for starters


Actually the Maule does close to it but with a whole lot more horse power.

[rsrguy3]

What was the 60's mantra? No substitute for cubes. Actually though on an experimental speed at altitude would be assisted by turbo normalizin plus you can ditch the muff.

[cook11]

Wittman BIG X
http://spirit.eaa.org/apps/magazines/eaa_articles/1965_01_18.pdf (http://spirit.eaa.org/apps/magazines/eaa_articles/1965_01_18.pdf)
http://spirit.eaa.org/apps/magazines/eaa_articles/1980_07_14.pdf (http://spirit.eaa.org/apps/magazines/eaa_articles/1980_07_14.pdf)

The BIG X looks very similar in profile to the Pacer yet its larger. Wittman airfoil with "V"struts, raked back windshield, no wheel fairings and cruises @ 150mph...on 130-150hp


CF-4 Four Runner
http://spirit.eaa.org/apps/magazines/eaa_articles/1974_08_11.pdf

[CamTom12]

CamTom12 did Roger install a zero thrust mount on the Racer for the RV-6 cowling to work?


I'm not sure, but I'll email him and ask.

No email back yet, but I did some rough measuring with a digital level today and it looks like there's a 3 deg nose down angle on the engine when compared to the bottom of the inboard wing rib.

[yarddart]

There's a big X in the Hanger next to me it was thought to been used for drug running and was purchased cheap

[CamTom12]

No email back yet, but I did some rough measuring with a digital level today and it looks like there's a 3 deg nose down angle on the engine when compared to the bottom of the inboard wing rib.
Confirmed with Roger, he kept it as close to the stock engine angle as possible.

[cook11]

What limits the Pacer to a VNE of 170mph?

[yarddart]

Everything

[andya]

Not enough gravity pull :lol::lol::lol::lol::lol:

[Grantmac]

Reduce the dihedral and take out most of the washout. Sullivan tips are probably the most efficient. Get the gentleness back in the stall with VGs just on the section of the wing where the ailerons are.
Gap seals on all surfaces, fairings and get the cowling tight. Maybe look at building some airfoil into the horizontal stab to reduce required trim.
I'd not go crazy on the other stuff, it's a short wing afterall.

I'm willing to bet the VNE is limited by the aileron design, the tail construction is very similar to some much faster aircraft.

Grant

[cook11]

Granmac thanks for the input!

[mmoyle]

Kent White spent a week here fishing, helping to pour concrete in the hanger and instructed Marv and I on reverse forming of gear fairings. Hadn't planned on faring the gear on the Pacer....but it was the only airplane in the hanger...http://uploads.tapatalk-cdn.com/20160826/f2d149858ceb454820ce9e3bdc5b0eae.jpghttp://uploads.tapatalk-cdn.com/20160826/e34ee436cf8ff756745fc02c2bd94d35.jpghttp://uploads.tapatalk-cdn.com/20160826/d6cf99c30d5c8d8fd8c150e564b5004a.jpg


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[Clayton Harper]

Sounds like you might be an "RV Guy", and that's OK. Take a look at Tailwind speeds, that might be your limit.

[Zac Weidner]

Kent White spent a week here fishing, helping to pour concrete in the hanger and instructed Marv and I on reverse forming of gear fairings. Hadn't planned on faring the gear on the Pacer....but it was the only airplane in the hanger...


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Were you building aluminum wheelpants? How did those turn out? It looks like an interesting project.

[Curly]

Watched a lot of metal bashers in my time but seeing Kent White work his magic at Oshkosh was awesome. Now you tell me he fishes and can handle concrete. Fairly handy bloke to have around!

[mmoyle]

Yup...last pour in the hanger went very very well. Three hour overland ATV ride to the fourth oldest village site in the state...fishing was slow. Slivers should be in next week... http://uploads.tapatalk-cdn.com/20160826/4944c550d2535347863da60bbce8af53.jpghttp://uploads.tapatalk-cdn.com/20160826/813e928d8861feb21b46744fce30b217.jpghttp://uploads.tapatalk-cdn.com/20160826/3afec30f110f374a8331176ccabd2437.jpg


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[mmoyle]

Were you building aluminum wheelpants? How did those turn out? It looks like an interesting project.

Hadn't planned on wheel plants....they'd be awful big if I did....Will be making wing strut fairings for the pacer.


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[andya]

and lets not forget a post I saw on this sight some years back, "you can only push a swing set so fast" or something to that effect.
Younkin's Pacer probably had all the best features for speed.

[Agent Speights]

Just fly high.......... FL320 seems to work OK!

[cook11]

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Anyone on the forum familiar with this type of Cessna gear leg installation on Pawnee's? I have seen a few on the internet and apparently it was an STC. It appears to be a frame that is bolted to the stock landing gear mounts with C-180 legs attached.....

[dgapilot]

I did an annual on one last year. Yes, it is an STC. Don't have the number off hand but can find out.


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[Steve Pierce]

Worked a few Super Cubs with the fuselage tubing modified for spring gear.

[rsrguy3]

Wasn't someone advertising a cessna gear mod/stc for super cubs a long time ago in trade a plane? Too bad no one is making a nice carbon gear for weight and speed.

[Steve Pierce]

There is an STC and I have flown one. It is faster but not as good for rough landing areas. Cub Crafters did it on the X Cub for $300K plus.