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wsimpso1

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Besides doing wing overs directly above an airport, are you going to explain what is going one here?
 

flyrite

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Mar 22, 2015
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lyons, ga. in the usa
Been contemplating for Years of how to get more elevator performance. Because of my mount being a Pusher (High thrust line), When I would be a high alpha I would have full back stick and the wing still flying. When you would hang it on the prop By bringing in power,, It would push the nose over before the wing stalls.
Sooo, Because the Monster stays at the edges of the Performance envelope, I hated giving up any thing, I pondered How to solve this problem.
Because the tail on my plane is stock J-3. I was intending to buy Super Cub feathers. They are drop replacement without any changes to anything. Would add weight, But give me more power through more surface area!
Got to thinking of trying a different solution. Test flew the mod today. Couldn’t be more happy! Not only did it enable the ability hang it on the prop even when the wing lets go , It still has back stick still available! Also lightened stick pressures considerably.
Built a mount and put it in clean air up to 95 mph on the roof of my vehicle while allowing it to free fly. Recorded it all with the go-pro.
Any mod is capable of hurting you. But any that you tie to the elevator is much more capable of going south quickly. After the first WHITE KNUCKLE flight testing It on the plane that lasted 30 minutes. I then got to put it through it’s paces feeling it out.
I call it the .....SERVOVATOR !
It’s on it’s own mount hinging at around 30% , Connecting to the elevator at 8”s behind the hinge line!
To clarify....Total weight added for both sides....7.5 lbs, Convinced it is lighter than what the Super Cub tail would’ve added. If not, it’s still worth performance per pound trade off!
Also adds character to the Monster. Will be adding the other side shortly.
 
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proppastie

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Total weight added for both sides....7.5 lbs,
so that little piece of extra tail weighs 3.75 lbs ....did you use a bathroom scale....but if true did you do over the weight and balance,...... make it tail heavy I would guess you will have more aft elevator left
 

wsimpso1

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First, let's get the details out. It looks like its hinge line is directly above the elevator hinge line. And its hinge line is 30% of its chord. Then you hooked its trailing edge to the elevator so they move together. Have a got it correct so far?

First, kudos to you for conceiving, building, and then flying a change to the airplane that your seem to LOVE. That is an accomplishment unto itself.

I am curious as to how much analysis and evaluation of failure modes went into this... I will elaborate below.

Pros and cons:

Pros:
It is an increase in elevator area, and will increase pitch authority;
With the hinge line behind 25% c of the device, it will have negative hinge moments, and so decrease elevator control forces - well maybe that is a pro, maybe it is a con;
It will shift your neutral point aft a tiny bit.

Cons:
It is a pretty small added area with lots of edges, so is fairly high drag per unit increase in tail authority;
It has biplane effects - since the high pressure zone of the base tail is also the low pressure zone of the new device, it is less effective (on a per unit area basis) than the base tail;
The struts and bolts and everything hanging on it add more drag than the gadget itself does;
It had better be way secure in flight - if any of it comes loose, but it stays on the airplane, the bird will likely be unflyable;
If the control rod comes loose in flight, it may or may not flutter, but it will definitely be tough to control;
That weight increase all the way back at the tail will likely shift your empty CG aft as much or more than the shift in your neutral point.

In short, we know it works, but you have added substantial weight and added to the danger of the craft.

A slightly bigger set of tail feathers (as you were thinking) will probably be as effective, give that improvement with lower drag, and without adding new failure modes. Now that you have demonstrated to yourself that a modest increase in tail authority converts the airplane for the better, why not just buy or build that Super Cub horizontal tail and put it on. I am sure it will have less drag, is likely to add less weight aft, and is less likely to cause us to read about you in an accident report. If you fly the Super Cub tail feathers, you can always tailor the control feel by modifying the balance horns.

Billski
 

bmcj

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Apr 10, 2007
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Fresno, California
Just a thought... instead of your new external surface, is it possible to somehow hook your elevator input to your stab trim mechanism so that it self trims with the elevator movement to give you more authority?
 

proppastie

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it does look interesting sort of like a spade for the elevator.....or the anitservo tab on the all flying tail of the Cherokee.
 

flyrite

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Mar 22, 2015
Messages
55
Location
lyons, ga. in the usa
Boyz......Soma you Fellers are just to smart for this Ol boy!
Shoot I’m still try’n to figure out that ol Bernoulli thing....I mean...If’n a contraption is ‘Sucked’ off the ground then I be think’n of Mount’n a big vacuum cleaner over each wing!
BUT...If’n it’s pushed off the ground...,I’m’a think’n a big backpack blower!!!
What say you Fellers....Which way should I go ????
 
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