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Has anyone increased AOI on a PA14, PA12, Wag 2+2, etc?

RVBottomly

PATRON
Asotin County Washington (KLWS)
I keep coming back to looking at building a Wag Aero 2+2. I'm not averse to a super cub, but for some peculiar reason I just like the looks and potential of the PA-14 style craft. I'd probably make it a two-place, anyway.

I've studied the Wag drawings and the Northland drawings. I've also read all sorts of threads on angle of incidence, thrustline, etc. I think I have a handle on the basics.

It looks like not a big deal to raise the forward spar butt hinge 1" when building the fuselage. That would match the super cub's 2.5" rise over 31 inches between spar attach points in relation to the horizontal reference.

I'm wondering if anyone has done this, either to a PA 14, Wag 2+2, or maybe a PA 12? If so, is there an improvement in short field performance?
 
yes

but they do it making different FRONT wing attach fitting on wing... I don't remember the links to the threads and the pictures here... can somebody supply those?
 
Can’t remember the tail number. The PA-14 that Crash rebuilt had a PA-18 AOI. I have a lot of 14 time with the stock AOI and I go the same places with it as an 18, 12 or an 11. Just have to adjust to the reduced visibility of the 14 and if you change the AOI the tail will be higher in cruise creating more drag and slowing you down. Where I operate might be a little more conservative than the rest of you but after thirty years of flying I love all of the Cub models and keeping the shiny side up is my goal, just depends what you are trying to accomplish.
 
Yes, my PA-12 (homebuilt) had it done. I now have Super Cub performance :lol: with Super Cub speed :cry:.
 
Can’t remember the tail number. The PA-14 that Crash rebuilt had a PA-18 AOI. I have a lot of 14 time with the stock AOI and I go the same places with it as an 18, 12 or an 11. Just have to adjust to the reduced visibility of the 14 and if you change the AOI the tail will be higher in cruise creating more drag and slowing you down. Where I operate might be a little more conservative than the rest of you but after thirty years of flying I love all of the Cub models and keeping the shiny side up is my goal, just depends what you are trying to accomplish.

Greg dropped the rear spar attach 7/8" on that -14. I tried to do the same when I was building my -12 but ran into roadblocks. Dave C had pictures of a riser for the front spar attach, maybe from Ron K's exp -12? That provided adjustability, too, if I recall correctly. I have no idea how the tail compensated for the wing change. Before I bought my BCSC kit I contacted Javron about a -12. I wanted the AOI altered to match an -18 but Jay wasn't interested. Another route for that mod would be to talk to Airframes. They had 3 and 4-place -18s sitting out front last year. They know how to build them.
 
If you adjust the AOI of the wing you have to do the same for the tail.

Right. That makes sense after looking at the profile drawings together. The horizontal stabilizer travel specified for the PA 18 is different from what I see on the PA 14.


Yes, my PA-12 (homebuilt) had it done. I now have Super Cub performance with Super Cub speed .

That sums up pretty succinctly the info I was looking for!


Greg dropped the rear spar attach 7/8" on that -14. I tried to do the same when I was building my -12 but ran into roadblocks. Dave C had pictures of a riser for the front spar attach, maybe from Ron K's exp -12? That provided adjustability, too, if I recall correctly. I have no idea how the tail compensated for the wing change. Before I bought my BCSC kit I contacted Javron about a -12. I wanted the AOI altered to match an -18 but Jay wasn't interested. Another route for that mod would be to talk to Airframes. They had 3 and 4-place -18s sitting out front last year. They know how to build them.

Interesting that Jay was not keen on changing the AOI. I guess a 3 or 4 place -18 might be less a can of worms to draw from the start than trying to change an existing airframe. I don't know.

It just seemed like a Wag 2+2 might be a nice start for a side-by-side 2 place super cub with room for bikes in back.

I know, just build a super cub and be done with it....
 
Lots of -18 drivers wish they had the speed that -12s and -14s have. if a stock -14 AOI provides you with adequate landing and takeoff performance why mess with it?

Think about the history of Cruisers. Small engines, cleaner gear, flatter wing. Then guys started adding more power. They needed more AOI to help control the forward CG. But mods evolved over time. Short engine mounts, improved flaps, bigger failfeathers, extended gear, and bigass tires. You can get more AOA than you need for short ops these days without messing with AOI.

If you're starting with an airframe and are thinking about mods that make sense? Move the upper longeron up to the top and enjoy a huge cargo area and access door. That's the best feature of the BCSC airframe.
 
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Lots of -18 drivers wish they had the speed that -12s and -14s have. if a stock -14 AOI provides you with adequate landing and takeoff performance why mess with it?

Pretty well said. I admit I've been going back and forth--the vacillation is starting to hurt my neck. Usually by evening I'm back to "keep things simple and stock, unless there's a real good reason otherwise."

If you're starting with an airframe and are thinking about mods that make sense? Move the upper longeron up to the top and enjoy a huge cargo area and access door. That's the best feature of the BCSC airframe.

I've been kicking that around a lot. I've just enough engineering background to know that I'd be dangerous if I tried to change something like that on my own.
 
I still believe a cub flys on angle of attack. Increasing angle of incidence makes it fly nose lower not slower. Wing will still stall at same angle of attack. Induce drag might change which is part of the reason a 12 will cruise alittle faster.
 
I increased the angle of incedence on my 2+2,no decrease in cruise speed,but great visability over the nose with full flaps and slow, I'm a fan
 
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I increased the angle of attack on my 2+2,no decrease in cruise speed,but great visability over the nose with full flaps and slow, I'm a fan

That got my interest. How much of an increase?

When I look at the Northland PA 18 drawings, front spar attach point is 2.5 inches higher than rear spar attachment.

On the 2+2 drawings, the difference is 1.5 inches, over the same 31 inch span.

Did you put it at the PA 18 angle, or something else?
 
..It just seemed like a Wag 2+2 might be a nice start for a side-by-side 2 place super cub with room for bikes in back.

I know, just build a super cub and be done with it....
It seems that you are just wanting a wide -18. Years ago (about 1980) I saw a PA-18 at a Merrill Field airshow which had been converted to a 4 place by cutting the fuselage down the middle and pushing the sides outboard. I was under the impression that it was approved on a field approval. Consider studying your Northland drawings with the idea of increasing the length of the fuselage cross tubes. This will give you the side by side seating in the front with a large baggage area. Just keep in mind that with two up front you will likely run into a forward CG issue. Perhaps you will need some removable ballast for when no baggage is carried. Make provisions for this at the tail.

Perhaps some of our Alaskan friends know this plane?
 
Lots of -18 drivers wish they had the speed that -12s and -14s have. if a stock -14 AOI provides you with adequate landing and takeoff performance why mess with it?

Think about the history of Cruisers. Small engines, cleaner gear, flatter wing. Then guys started adding more power. They needed more AOI to help control the forward CG. But mods evolved over time. Short engine mounts, improved flaps, bigger failfeathers, extended gear, and bigass tires. You can get more AOA than you need for short ops these days without messing with AOI.

I agree. Extended gear, big tires and a proper CG make the Cruiser family very capable, along with all the right mods of course. I don't know anything about the 14, but a lot of bush modded 12's are very nose heavy. People will tell you their plane isn't, but just look at the position of the trim when you walk by. That tells the story pretty well.
 
The 4 place Supercub is a STC. Kirk Ellis flys one (the hulk) and is usually in the top 5 at Valdez. Airframes is making the fuselage. Best done from scratch because you end up upsizing a lot of the tubing. I believe it can have yoke or stick.
DENNY
 
It seems that you are just wanting a wide -18. Years ago (about 1980) I saw a PA-18 at a Merrill Field airshow which had been converted to a 4 place by cutting the fuselage down the middle and pushing the sides outboard. I was under the impression that it was approved on a field approval. Consider studying your Northland drawings with the idea of increasing the length of the fuselage cross tubes. This will give you the side by side seating in the front with a large baggage area. Just keep in mind that with two up front you will likely run into a forward CG issue. Perhaps you will need some removable ballast for when no baggage is carried. Make provisions for this at the tail.

Perhaps some of our Alaskan friends know this plane?

I was thinking similarly. When you put the Wag 2+2 drawings next to the PA-18 drawings, they look very similar, except for the width. The Wag design is a foot longer in the tail--I suspect that addresses the cg issue, too.
 
I agree. Extended gear, big tires and a proper CG make the Cruiser family very capable, along with all the right mods of course. I don't know anything about the 14, but a lot of bush modded 12's are very nose heavy. People will tell you their plane isn't, but just look at the position of the trim when you walk by. That tells the story pretty well.

Amen to this, my horizontals live on the longeron for landings. As for my 2Cents, I have a lot of time in my 12 and a little in an 18. I would take the increase in AOI and lose airspeed in a heartbeat just for the over the nose visibility on approach. Yes the longer gear and big tires help take off AOA, but do nothing for approach to landing, the nose is still way high.
 
I agree. Extended gear, big tires and a proper CG make the Cruiser family very capable, along with all the right mods of course. I don't know anything about the 14, but a lot of bush modded 12's are very nose heavy. People will tell you their plane isn't, but just look at the position of the trim when you walk by. That tells the story pretty well.

My -12 with a Charlie center 0-360 needs the EW CG to be 13.5"+ with 9# lead in the tail, 1306# EW. If not that far back it is nose heavy. I think many are just not making the adjustment to get CG right. To afraid to add a little weight in the tail. It would be almost impossible with my plane to run the CG to far back even filling the extended baggage with 40# of stuff. This set up is great now that I have added weight as needed. I fly day in and out and have 25# tools, tie downs, ropes etc in the far end of my extended baggage. Wish I had the increased GW as this would have eliminated the lead in the tail because of the added tubes.

Before I did this I ran out of nose up trim and the nose fell out of the sky, now trim is back 1/3rd from rear and have great control and can consistently land short and TO at 1750# 900MLS in 250'
There is the need for the extra weight, you just need to add it.
 
Yeah, there's no arguing with facts as far as the AOI/deck angle goes. I have 31's with 3" gear and if I really want to drag it in, I give it 5 turns up trim (still about 4-5 turns from full up). With a touch of power I touch down tail first by about 6". Visibility directly over the nose isn't great but still a hundred times better than a 185. I have my 12 rigged and balanced really well (washout 1.8°/ CG upper 13's, don't have the exact# right now) and I wouldn't trade it for anything. With regard to cruise speed, I can't help but think the 12 got a fair bit of it's advantage from fairings and internal bungees. I wouldn't think the fuselage angle would make much difference, in and of itself. With a Mac 82-42 I cruise about 93 @ 2450. Airfoil bungee covers, naked gear.
 
My empty CG is 12.6, and like Perry says you can see it in the stabilizer position. I get about the same airspeed with 31s, standard length covered gear, airfoil bungees and the same prop. I'd bet that with a more aft CG it would do better.
 
I still believe a cub flys on angle of attack. Increasing angle of incidence makes it fly nose lower not slower. Wing will still stall at same angle of attack. Induce drag might change which is part of the reason a 12 will cruise alittle faster.

You would think wouldn't you. Personally I think there is a little more to the geometry of a plane than just pure angle of attack.
 
I still believe a cub flys on angle of attack. Increasing angle of incidence makes it fly nose lower not slower. Wing will still stall at same angle of attack. Induce drag might change which is part of the reason a 12 will cruise alittle faster.

So how does the 3-4 degrees of nose-down thrust from the Piper engine mount on an -18 enter in?

Seems to me that effectively increases angle of incidence.
 
I subscribe to the theory earlier that the fuselage on the Cub rides higher and is more draggy that way.

At any given airspeed and pressure altitude, the angle of attack will be related to the weight. The heavier you are, the more lift required, and the more induced drag.

Get a heavy Cub up to 8500' and observe where the wing is with respect to the horizon. You might find that the thrust line at that point is perpendicular to the relative wind. Maybe.
 
I subscribe to the theory earlier that the fuselage on the Cub rides higher and is more draggy that way.

At any given airspeed and pressure altitude, the angle of attack will be related to the weight. The heavier you are, the more lift required, and the more induced drag.

Get a heavy Cub up to 8500' and observe where the wing is with respect to the horizon. You might find that the thrust line at that point is perpendicular to the relative wind. Maybe.

I'm trying to follow--you mean if you have the zero thrust line mod plus increased angle of incidence, it would make the thrust line more vertical under heavy loads?

That makes sense enough, I think.

FWIW, I'm not pursuing the idea on my project. I'm thinking of going with a stock wing incidence, but with Keller flaps.
 
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