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Riblett 66" on a Stretched Pacer help

A

aviweld

Registered User
I hope to find some real numbers from others that have done this same conversion. I am about to start putting the wings to airframe and establishing geometry. The Javelin plans seem to indicate 24" longer airframe with the same horizontal reference line, the same Pacer tailfeathers, and the same Pacer 6.5 degrees down and 1.0 degree up horizontal stabilizer travel.

D&E plans for the wing, without knowing what airframe it's going on, show the front spar attach bolt centerline as 1.063" down from top of spar cap, and for the rear spar, 1.567" down from top of spar cap. These will establish the angle of incidence for the wing ie. the angle between the horizontal reference line of the fuselage and the CHORD LINE of the wing.

This configuration is what is proposed and before I move forward I am really hoping to hear what others have used and what their results were. I will use PA-18 tailfeathers, and a IO-375 powerplant with Catto 86x40 prop.

What I want to end up with is:
Ability to trim the tail down for landing in most forward loaded configuration ie. minimum fuel, pilot only. In order to get the angle of attack required to fly as slow as possible.

So for now I would really like to hear how others have done this wing, tail, and stretch geometry and how it worked out.

If there is a better location to post this request, please advise. Thanks to all who can help.

Scott

Edit: The Javelin stretch doesn't say where the tailpost is vertically in relation to horizontal reference line. They just give add-on tube lengths and specify to keep tailpost plumb. Where does it end up??
 
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If you simply move the tail aft in the same horizontal plane as it was on the PA22/20, your finished plane will sit more level on the ground, very little deck angle, increasing take off distance. To get the same geometry as a Cub, you have to raise the tail as you move it back.
 
D.A.:Good Point. On a PA-18 the bottom of the tailpost is 1.5" ABOVE the top motormount boltholes (in level flight) while a PA-20 bottom of the tailpost is 4.5" BELOW the top motormount holes. The Javelin plans I have don't say exactly where the tail ends up. They just give lengths of tube to add to top and lower longerons. The lower add-on tubes are longer than the top ones so it must be raising the tail as well. Someone better with math could figure out how much higher it is: 61.75" lower longeron add-on, 43.875" top longeron add-on, while keeping the tailpost plumb.
 
Try to contact Rick Davis and see what he did: http://www.mykitlog.com/Rick Davis

I would be careful using D&E drawing unless they have been updated by the guys in FL recently. The old drawings were full of errors. Best is to learn what angle of incidence you desire, then build for that. The D&E wing fittings are completely different than Piper.
 
Call mark at Dakota Cub. Wonder whatever happened to his stretched pacer? Does he still have it. Very nice plane.
 
I have been trying to reach Rick Davis. Looks like he moved to Soldotna and I haven't been able to get in contact with him. Anyone have current contact info? His Davis Special is very nice looking. The angle of incidence I need only comes from wind tunnel testing or by trial and error. I would like to avoid as much of the error part as I can.
 
tempdoug said:
Call mark at Dakota Cub. Wonder whatever happened to his stretched pacer? Does he still have it. Very nice plane.
Click to expand...

Recently sold (too many airplanes, not enough time to fly all of them). Getting or has already gotten a new engine in Washington by the one and only Mike Butterfield and Yakima Aerosport. Then she will be off to Alaska where we hope she'll get to prove her worth and utility!
 
Talked to a guy in B.C. that builds Bushmasters and he puts the tailpost in the same place in relation to the HRL only back 23.5". Haven't been able to reach Mark at Dakota Cub yet.
 
I know a lot of guys have simply moved the tail section back level with the original 22/20 geometry and I'm sure that works just fine for them and that's great. But if you want the same geometry (and deck angle) as a Cub, you have to move the tail section up as you move it back. Think of it this way: If you took a Cub and extended the fuselage 50 feet aft, the airplane would sit almost level. On the other hand, if you shortened the fuselage 15 feet, the nose would probably point up at 45 degrees.

Well, Piper had to take the same thing into account when they shortened their rag wing airplanes (PA15, 16, 17, 20 & 22). As they pulled the tail section in toward the nose, they also had to lower the tail in relation to the cabin to maintain normal nose up angle. If you take one of those shortened fuselages and just move the tail section back without raising it, you end up dropping the nose down. The airplane will sit more level on the ground, the same effect as installing a tall tailwheel spring or a shorter set of main gear legs, not what you really want for short field work.

That's my 2 cents worth and maybe you want change :). I think stretched pacers are awesome, on my bucket list for sure. If Chris and I build one, we're just going to reproduce the Cub geometry.
 
I concur with D.A., I extended the lines , bottom longerons aft and up so as to continue the angle of the tail to wheels at 11.0 deg. That places my rear HRL 1.5" below the PA 20's line. I also moved my rear stab brace up and forward about an inch. I cut the entire empennage off at the 113.5" top station, and the 95" bottom station and reman the rest for a -4deg front stab. I have copied the Bearhawk type tail feathers and rudder, along with the balanced (weighted) elevators, trim tabs set up. Just finished my motor mount, 4" more than stock. placing the prop flange at 54" from WLE, 0320 E2A, reman the MLG to the bearhawk, Maule type, set tread at 84". The Prop M74 hub center sets at 51" from the floor level. I have not yet built the wings, however I will be going back to the US36b type, span in the ball bark of 36'.
 
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The pink line shows the HRL below the tail feathers, the date on the frame photos is wrong, taken last weekend. Picture 092.webp
 

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Jim and D.A.,
I understand you are saying that to get a similar angle of attack or "deck angle" while sitting three point, as a PA-18 you need to raise the tailpost in relation to the HRL. And I completely agree that is true. However from your description, Jim, I'm still not sure where your tailpost is in relation to the original PA-20 horizontal reference line, which is a line from 3.5" down from the top motormount boltholes at the firewall rearward to 1.0" above the bottom of the tailpost. If you level your airframe longitudinally with a level on the straight section of longeron below the front door area, that should put the firewall plumb. Then if you drop down 3.5" from the centerline of the top M/M bolt holes, and run a level string back to the tailpost, you will know where the bottom of the tailpost is vertically in relation to the HRL. I am fairly certain that the three outfits that build stretched Pacers,(Javelin, Bushmaster, and Producer)keep the tailpost at the same relationship to the HRL as the original. If that is not true, I would be very grateful for a correction. Would also like to hear if anyone has tried a variation of that geometry and how it worked?

Also, Jim, I believe the Champs use the same -4 degrees for the fixed horizontal stabilizer and it works for them. That is ,of course, relative to their HRL. I am also going to chop off the tail same as you, and fabricate my own, but I am going with a jackscrew trim. Will be adding a left-hand door plus large Maule-style baggage doors.
 
No, although I have all that Blanton stuff, I used the frame trussing from the bearhawk, and just some common sense. Also the motor mount is set on 0 center line, and 1/16 of an inch lower at the prop hub.
 
My HRL the pink string is level with the rear wing fitting @26.5" down and the front wing fitting @28" down and the 82.5" station @21.5"down, the end at the tail is level with the tail spring bolt. I would not just use the hole in the door frame or the fire wall to level the plane, you must consider the wing AOA on the Pacer, its not the same as the PA 18. I hope this helps.
 
That's great Jim, I always find when you start talking about HRL's and AOI not everyone has the same definition so I try and be as specific as I can. I was planning on going with joysticks as well. I'm waiting on my tubing before I start hacking and slashing.
 
aviweld said:
...Will be adding...Maule-style baggage doors.
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Are you talking about the left hand doors that seem to open up half of the side of the fuselage? I'd like to see details of that also. Is that on the Bearhawk plans as well?
 
D.A.,
I believe the later Bearhawk plans include that style door. My Bearhawk plans do not, but I have Maule drawings that I will use as a guide to design the doors.
 
I don't want to take over the thread. I see back a ways,John Scott asked about the numbers of stretched PA20/22's that might be out there. I am going to go and start a new thread re; that subject. Ed Lowry
 
I have already stretched my airframe. I used the Blanton plans which put the tail back 24.25 inches. TheBlanton plans called for an ugly joggle for the additional length. I cut myairframe just aft of the baggage area and again just ahead of the cross tubethat holds the jack screw. From the baggage area the bottom longeron isstraight. The result that I am now measuring is that the bottom of the leafspring mount bracket is 4.5 inch below the top engine mount holes. With theairframe leveled per the pacer instructions and the use of a plumb bob digitallevel a water level these are the readings I am getting.

Firewall/lugs plumb
tail post plumb
wing attach points bolt hole to bolt hole LE 3.5 deg up
floor under fwd seats +- .5
tail post 4.5 under top engine mounts
stab trim 1.6 nose down 8.4 nose up

I am unsure if these measurements will get me that slow landing aircraft.
My plans have been to use the Riblett 66" wing and I have been doing researchon building a full span LE Slot. This will require I build my own nose ribs for that wing. For now I plan on using modified pacer landing gear with a third gear leg and PA-18 v-cabane, Pa-18 tail, cub jack screw,

I would appreciate any input especially on the subject of angle of incidence and stab trim

Levi Wood
V6stol




aviweld said:
Jim and D.A.,
I understand you are saying that to get a similar angle of attack or "deck angle" while sitting three point, as a PA-18 you need to raise the tailpost in relation to the HRL. And I completely agree that is true. However from your description, Jim, I'm still not sure where your tailpost is in relation to the original PA-20 horizontal reference line, which is a line from 3.5" down from the top motormount boltholes at the firewall rearward to 1.0" above the bottom of the tailpost. If you level your airframe longitudinally with a level on the straight section of longeron below the front door area, that should put the firewall plumb. Then if you drop down 3.5" from the centerline of the top M/M bolt holes, and run a level string back to the tailpost, you will know where the bottom of the tailpost is vertically in relation to the HRL. I am fairly certain that the three outfits that build stretched Pacers,(Javelin, Bushmaster, and Producer)keep the tailpost at the same relationship to the HRL as the original. If that is not true, I would be very grateful for a correction. Would also like to hear if anyone has tried a variation of that geometry and how it worked?

Also, Jim, I believe the Champs use the same -4 degrees for the fixed horizontal stabilizer and it works for them. That is ,of course, relative to their HRL. I am also going to chop off the tail same as you, and fabricate my own, but I am going with a jackscrew trim. Will be adding a left-hand door plus large Maule-style baggage doors.
Click to expand...
 
Hi Levi,
Great to see another stretched Pacer in the works. Very interesting about a slotted Riblett wing. I have not been able to get any feedback on AOI and stab trim, and those are key to a good flying airplane. The measures you have look right to me if you follow Blanton plans. But he didn't use a 40' Riblett 66" chord wing, and that may change what is required for AOI and trim. If you use an experimental wing you can put the fittings where you think they will work best with the perfect AOI. Let me know if you figure out where that is. I am welding on my airframe. Making changes to accommodate the one-piece aluminum spring gear and doors. Wanted to get that done before the tail stretch. Keep us posted.
 
Airwrench on this sight otherwise know as steve has built 13 producers and is the expert. He is building my pa-14 right now. I would talk to him. Let me know and I'll connect you.
 
Aviweld

I was looking back at old post on stretched Pacers and found this year old stuff but nothing new. Are you still building? Just trying to see who is still building ........ I have 2 in the works and was wondering if anyone else is still building in these times..
 
Hello all,
Preparing to hack into a PA-20 frame to build a stretched pacer with 66" riblett wings.

From what I gather the stretch should go something like this:

-Stretch should be roughly 24"
-The bottom of the tailpost should be about 1.5" above the HRL


I am planning on jigging it up square and rebuilding the tail from scratch, From what I have read this is the best option.

Does anyone see any problems with this plan?
Thanks



v6stol said:
I have already stretched my airframe. I used the Blanton plans which put the tail back 24.25 inches. TheBlanton plans called for an ugly joggle for the additional length. I cut myairframe just aft of the baggage area and again just ahead of the cross tubethat holds the jack screw. From the baggage area the bottom longeron isstraight. The result that I am now measuring is that the bottom of the leafspring mount bracket is 4.5 inch below the top engine mount holes. With theairframe leveled per the pacer instructions and the use of a plumb bob digitallevel a water level these are the readings I am getting.

Firewall/lugs plumb
tail post plumb
wing attach points bolt hole to bolt hole LE 3.5 deg up
floor under fwd seats +- .5
tail post 4.5 under top engine mounts
stab trim 1.6 nose down 8.4 nose up

I am unsure if these measurements will get me that slow landing aircraft.
My plans have been to use the Riblett 66" wing and I have been doing researchon building a full span LE Slot. This will require I build my own nose ribs for that wing. For now I plan on using modified pacer landing gear with a third gear leg and PA-18 v-cabane, Pa-18 tail, cub jack screw,

I would appreciate any input especially on the subject of angle of incidence and stab trim

Levi Wood
V6stol
Click to expand...
 
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