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Lowrider LSA

Mark,

Thanks for the comment...I'm trying to inspire myself while unpacking from my move, buillding a green house, an extra bedroom, getting a boat ready for the Spring and function testing a variety of fly fishing gear...among other things. Glad I'm retired so I have time to do all this stuff!!

Don,

When I first joined the EAA chapter here one of the first safety lectures was on emergency landings. One slide was entitled "Avoiding potato bugs" which of course live in the ground...something I've avoided running into for 45 years next month. Low and slow suits me just fine...fly safe!!
 
OK, Let's talk gear length....I keep seeing recomendations to use a +3" extended gear on cubs to gain a 1.5" advantage in prop clearance. I really don't see that as a major benefit depending upon what engine/prop combo is mounted and where it's mounted on the nose. If I go with an 0-320 I will most likely mount it as close to the firewall as practical to keep the CG where it should be. That will reduce prop clearance to some unknown degree. If I go with an 0-200/C-90 that will be less of an issue. Either way, I'm planning stout mains and a beefy tailwheel. I don't want to mow knee high grass and I understand that tires are also a big factor in prop clearance. I'm planning on 21"x6" or larger but may end up with 6.00x6" for weight.

Questions:

Is there something magic about 3"?

Why not 4" or 5" or 6" or more?

How much extra stress does the extended gear place on the fuselage bottom longerons and mounting points?

Is it better to gain prop clearance with tires than extended gear?
 
Laid out and welded the rudder with the TIG...sure is slow compared to the MIG or the gas torch. It does allow very percise heat control and as my (and #2 son) experience increases we are able to do acceptable welds, I believe.

Any thoughts on previous post????
 
OK, Let's talk gear length....I keep seeing recomendations to use a +3" extended gear on cubs to gain a 1.5" advantage in prop clearance. I really don't see that as a major benefit depending upon what engine/prop combo is mounted and where it's mounted on the nose. If I go with an 0-320 I will most likely mount it as close to the firewall as practical to keep the CG where it should be. That will reduce prop clearance to some unknown degree. If I go with an 0-200/C-90 that will be less of an issue. Either way, I'm planning stout mains and a beefy tailwheel. I don't want to mow knee high grass and I understand that tires are also a big factor in prop clearance. I'm planning on 21"x6" or larger but may end up with 6.00x6" for weight.

Questions:

Is there something magic about 3"?

Why not 4" or 5" or 6" or more?

How much extra stress does the extended gear place on the fuselage bottom longerons and mounting points?

Is it better to gain prop clearance with tires than extended gear?

Isn't the slight advantage to angle of attack during take off as one of the reasons given ? A slight change in angle of incidence would make more difference when building but a long tail dragger is at a disadvantage AOA on the ground.

A longer prop is much more efficient at low speeds.
 
I beieve there is a slight advantage in AOA with longer gear but my reason for wanting it is prop clearance. I am concerned about the increase leverage due to longer gear and that is one of the questions I have....is it really worth it?

I will follow Mr. Calkins' suggestions regarding AOI.


We laid out and TIG welded the horz stabs and elevators today and we're still waiting for the ribs from Avipro to finish up the rear control surfaces.


Any other throughts on extended gear?
 
I beieve there is a slight advantage in AOA with longer gear but my reason for wanting it is prop clearance.

Any other throughts on extended gear?

My opinion is that the real advantage of extended gear and especially when combined with tall tires is that allows you to takeoff and land at a higher AOA while keeping the tail wheel off the ground. High AOA means slower landing speeds and resulting shorter ground roll. On takeoff it facilitates getting the tail up, but not so much that it reduces desirable AOA when it is needed.

This probably isn't much of an issue unless using unimproved landing areas.

Prop clearance is another benefit but not the most important IMO.
 
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Lowrider do have any pictures you can post.



We laid out and TIG welded the horz stabs and elevators today and we're still waiting for the ribs from Avipro to finish up the rear control surfaces.
 
My opinion is that the real advantage of extended gear and especially when combined with tall tires is that allows you to takeoff and land at a higher AOA while keeping the tail wheel off the ground. High AOA means slower landing speeds and resulting shorter ground roll. On takeoff it facilitates getting the tail up, but not so much that it reduces desirable AOA when it is needed.

This probably isn't much of an issue unless using unimproved landing areas.

Prop clearance is another benefit but not the most important IMO.

I am not convinced that longer gear "...facilitate getting the tail up..." for takeoff.
 
Larry,

I have fallen down on my photo responsibilities and I will try to fix that tomorrow. I'm not terribly qualified at picture posting...you would think a COM IA MEL CFI could handle something so simple...well...not so much.

It seems I have a leak in my new TIG setup....Thursday of last week I refilled my argon bottle and this morning it was almost empty. Took it to the argon store and explained the problem and they said it must be a leak. I assured them we have not been welding 24/7. They gave us a loaner bottle and leak checks all around in the morning.


Dave,

I must agree...moving the main axles forward would put more weight on the tailwheel and require more tail lift to get it up so it would seem forward extended gear would slow take off. Does it make enough difference to make forward extended mains a bad idea?
 
I am not convinced that longer gear "...facilitate getting the tail up..." for takeoff.

I didn't mean to say that longer gear made it easier to get the tail up. What I meant to say was that longer gear allows the pilot to get the tail off of the ground during the takeoff roll but still keep a decent amount of AOA in for maximum lift.
 
I didn't mean to say that longer gear made it easier to get the tail up. What I meant to say was that longer gear allows the pilot to get the tail off of the ground during the takeoff roll but still keep a decent amount of AOA in for maximum lift.
Raising the tail wheel just clear of the ground (1/16" or 1/8") will not make an appreciable difference in the AOA. No need for a longer gear.
 
Raising the tail wheel just clear of the ground (1/16" or 1/8") will not make an appreciable difference in the AOA. No need for a longer gear.
I guess I'm still not making myself very clear. What I'm trying to say is that on rough ground it is desirable to get the tail wheel off of the ground quickly on takeoff to keep from banging it up and get the tail feathers out of the brush, water and flinging stones and other stuff like that. But in raising the tail the AOA is reduced (we agree). With longer gear and taller tires the tail can come up and the plane still have desirable AOA. river_tailwheel.jpg
 

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This is what you need to get out of the rocks and brush while protecting the tail:
300px-Pitcairn_Autogiro_NASA_GPN-2000-001990.jpg


Or how about this: Pitcairn PA-18
Pitcairn3.jpg
 
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First pic is horz stab and elevator, second is front and rear seats and third is vert stab and rudder with another horz stab...that elevator is not together yet and still on the welding table. The ribs I ordered from Avipro will replace the 3/8" tube once they arrive from Mexico...apparently there is only one truck coming North every 3 months...wonder what it would cost to have an undocumented visitor to handcarry them?

Spinner,

I think I understand what you mean. My interest in the extended gear (longer and further forward) is to get prop clearance and I'll most likely use a few extra degrees in AOI to get good takeoff AOA. The protection of the tail is another issue...prop and wheel thrown debris can be really tough on the tail and fuselage underside in the rear.

I'm trying to "balance" the use of a beefy tail wheel against the added weight at a far back arm. I don't know the answer yet...thoughts?
 

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Spinner....I getcha.

Skywagon........length matters in my opinion...I havent disagreed with you for.....like...ever.
 
Dave,
When I had a Cub in Alaska, no one had thought of extending the gear, yet. Gar Aeros were the tire of choice. Around here there just is no need for anything more than just a set of large tires. We don't have the large unrestricted landing spaces that you are privileged to use. So as a result, I have never tried long gear. I would be leery of moving the axle forward in order not to increase the weight on the tail wheel. Thus, requiring more speed to lift the tail out of the rocks. I would also be concerned of the extra leverage arm between the axle and the lower longeron. More of an upsetting tendency? And, possibly a requirement for stronger gear fittings? So as you can see, there are a lot of questions that need to be addressed. Perhaps you already have those answers? ..... I know that we are on the same page.
 
As to longer......

...When Sullivan and crew did the 6 inch extended gear, every one that got them was in love with them....IT was THE BIG DEAL......A REVELATION!!!!

Word is.....The most famous Cub mechanic in the world got an idea in his head and spoke loudly the opinion that long gear did bad things to gear fittings and longerons. That opinion KILLED 6 inch gear from being as common as the Borer Propeller on Cubs. This same opinionated mechanic (whose flying days were long-behind when I arrived in Alaska) postulated that the long gear made the tail heavier and took more power to lift the tail on takeoff. (as if lifting the tail on takeoff is the "end all, best" technique). Anyway, My argument with this mechanic was the turning point in my dealings with him.....seems that he valued a good argument, and treated me better after I argued with him!

.......and.......I am a believer in 6" gear on a Cub,,,even with 35's!!

...forward sweep??? Depends on how much of your flying is with an empty or forward-CG a/c where the heavy-braking safety of forward gear is a comfort to some.

Hell...the best money spent on a Cub is for good instruction and lots of practice.....not parts-candy goodies!
 
AOA is an interesting topic. Lots of guys think taildraggers are the cat's meow for short ops but if you look at a taildragger's geometry they have an AOA disadvantage. While a trike sits relatively level at rest the application of power allows the tail to drop and in concert with the main gear being aft of CG center? They get a real AOA boost. The only thing we can do with taildraggers is to lift the airframe at the mains and/or reduce the height at the tail. Not many guys out there are bolting skids to their tails and in fact most add enlarged tailwheels. That alone reduces available AOA unless you add height at the mains. Slow speeds in ground effect allow most of us to bump the tail before the plane stops flying. Not a big deal for the vast majority of us in average ops but in theory? Tall up front/short in back offers the best AOA and therefore the slowest potential operating speed where contact with the ground is an issue. My best soft field technique demonstrations came in nose draggers. Watch a good 172/182/206 driver and see how slow they can make those planes fly at initial take-off AOAs. It never fails to impress me. Food for thought.
 
AOA is an interesting topic. Lots of guys think taildraggers are the cat's meow for short ops but if you look at a taildragger's geometry they have an AOA disadvantage. While a trike sits relatively level at rest the application of power allows the tail to drop and in concert with the main gear being aft of CG center? They get a real AOA boost. The only thing we can do with taildraggers is to lift the airframe at the mains and/or reduce the height at the tail. Not many guys out there are bolting skids to their tails and in fact most add enlarged tailwheels. That alone reduces available AOA unless you add height at the mains. Slow speeds in ground effect allow most of us to bump the tail before the plane stops flying. Not a big deal for the vast majority of us in average ops but in theory? Tall up front/short in back offers the best AOA and therefore the slowest potential operating speed where contact with the ground is an issue. My best soft field technique demonstrations came in nose draggers. Watch a
good 172/182/206 driver and see how slow they can make those planes fly at initial take-off AOAs. It never fails to impress me. Food for thought.

low rider be careful your or you're going to end up with a 1200 pound empty weight el essay
 
As to longer......

...When Sullivan and crew did the 6 inch extended gear, every one that got them was in love with them....IT was THE BIG DEAL......A REVELATION!!!!
.......and.......I am a believer in 6" gear on a Cub,,,even with 35's!!
...forward sweep??? Depends on how much of your flying is with an empty or forward-CG a/c where the heavy-braking safety of forward gear is a comfort to some.

Hell...the best money spent on a Cub is for good instruction and lots of practice.....not parts-candy goodies!

Agree...knowing your plane is first and foremost and flying with a GOOD CFI is where it begins.

OK...6" extra length is good and further forward may be good depending upon what type of flying you are doing. What are the disadvantages other than extra leverage on the gear which is probably very difficult to determine in real life and what is the appropritate "beef up" to do on the longerons and gear mount points?
 
Does anyone know the thread pitch on the cub jackscrew? I'm going to build something like that and I want to have it responsive to aircraft pitch changes so I can make trim changes quickly. If I can find a motor with the proper speed I will make it an electric trim with momentary 3 way switch.

Finished welding the rudder and vert stab and welded them onto the fuselage. I also welded a pair of 3/8" tubes on the stab and rudder that will take a 1/4" pin thru them to act as a rudder gust lock. Add a "remove before flight" flag and it's a surefire way to lock the rudder. I am going to add them to the horz stab and elevators too.
 
Does anyone know the thread pitch on the cub jackscrew? I'm going to build something like that and I want to have it responsive to aircraft pitch changes so I can make trim changes quickly. If I can find a motor with the proper speed I will make it an electric trim with momentary 3 way switch.

An easy and not too expensive way to get your jack screw set up is to just order it from D&E Aircraft http://www.de-aircraft.com/other.html Comes with yoke and jack screw. That's where I bought mine. P/N 335-019 Piper Stabilizer Trim Yoke $150

Tom
 
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Thanks Tom!!

I researched and ordered materials to build a yoke and motor driven jack screw last night. I went with an 8 pitch to try to get a slower and more percise trim. If I don't like it, I can change it to a 6 pitch fairly easily.

I mounted the horz stabs today and welded up the flying wire brackets pending arrival of parts for the jack screw. I'm using the McMasters-Carr geared motor that has been used successfully by others and a momentary on switch that I plan to stick mount which should make it easy to trim as flight attitudes change. I'm pretty sure I made a good decision on going wth the jack screw vs trim tabs by following suggestions from you folks.
 
DSC_0001.jpg

Not a terribly good picture but it shows the tail in place. Still waiting for my ribs to finish up the details.

Certainly not there yet, but I'm planning to use the Stewart System on the tail and fuselage when the time comes. Does anyone have any idea about where 2.7 oz Superflite falls in the covering weight scheme?
 

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.......and.......I am a believer in 6" gear on a Cub,,,even with 35's!!

...forward sweep??? Depends on how much of your flying is with an empty or forward-CG a/c where the heavy-braking safety of forward gear is a comfort to some.
QUOTE]

Dave,

I've been trying to rate the number of times I'll need to jump on the brakes hard and I'm probably not going to do that very often, but....doesn't the forward mounted gear also help however slightly in crosswind handling?
 
....doesn't the forward mounted gear also help however slightly in crosswind handling?

I don't follow your thinking here? Moving the main wheels forward, further from the CG, will require more tail directional control as in a larger rudder. Remember all of those WW1 movies of the early planes with their main landing gear way forward under the engines? They were always ground looping. Moving the wheels aft will improve directional stability on the ground. You just will need to be more careful with braking.
 
Sky,

You are correct again!! What I meant was once the tail is on the ground the extended gear would increase the wheel base and make it a "little" easier to steer. Probably not enough to make it worthwhile and it would also slow the turn. I'm thinking Maule vs 185.

I have been reading the posts on extended gear here and elsewhere and find that it is really a polarized issue...either you love them or wouldn't touch them. I have 1.5"
tube laying in the shop waiting for me to make up my mind. All the local Cub and Husky owners would like more prop clearance and are considering bigger tires, but you need to add 6" taller tires to get 3" more prop clearance. My IA says OK but wants to see gussets on the attach points just in case. Haven't talked to the DAR but it seems that extended gear is an accepted mod so he should be OK too.
 
My IA says OK but wants to see gussets on the attach points just in case. Haven't talked to the DAR but it seems that extended gear is an accepted mod so he should be OK too.
It is good to get advice from knowledgeable mechanics. But if you're EAB then you can do whatever you like without approval from an IA. The DAR that inspected my Experimental was from Post Falls. Same guy for you? My opinion on forward-shifted axles is that you can accomplish the same by shifting some baggage farther back, if maximum braking is what you want to accomplish.
 
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