Decalage angle

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Eugene

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So, during landing, stub is not doing anything for us at all. 100 % of down pressure is providing by elevator. Stub is more or less level at that point.

From what I understand, in level flight stub is providing 100 % of down pressure to counter balance forward CG, wing moment and high mounted engine moment. Elevator is not doing anything if trim is in neutral position.

If above statement correct, here is my question: let's assume that airplane designed perfectly and 10° on stabilizer really needed at 100% power and most forward CG situation. If I decide to prove this to myself and change negative angle on stabilizer by moving leading edge up by 2° or so = in the exactly the same situation I will need to dial more trim or apply back pressure on the stick to stay in level flight. Then after landing I will need to put everything back together. Where is danger by doing so? What can potentially happen? Is there something I don't see?
 
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Eugene

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Need help to understand something -

Lets say we have aircraft that is doing very good on 100 HP with 1° AOA - 1000 lb. - 100 MPH. With 50% power and same 1000 lb. we going about 70 MPH with 5° AOA.

Let say we need to replace engine and no money for 100 HP. So, we installed 50 HP and started flying with 5° AOA at 70 MPH and 1000 lb.

So, one day we change wing incidence by 4°, so fuselage will be level again and we can see over the nose at our new top speed. This way coffee inside of cockpit will be level again.

Here is my question: How this aircraft will fly if we install 100 HP engine back and forget to change wing incidence back to 1°?

We all know what will happened if we pool power back on aircraft, with 100 HP, that was designed fo 100 HP.

What we normally never experienced, is what will happened, if you doubled up power on aircraft with geometry for 50 HP.
 
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Eugene

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FA84F8C0-BA66-4AC7-86A2-344021484BAA.png

As example this could of been same production aircraft model with 4 different engine options.

In order for all of them to fly with level floor inside of cockpit, they must have different wing incidence

So, every time you go for bigger engine = you will go faster = but you also need to change your wing incidence.

Or different: - every time you change something (MTOW or HP) , so your speed is changing = you need to match your AOA to wing incidence, so floor stays level.
 
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Eugene

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We are in the middle of a snowstorm. So, I can’t go flying for real. End up flying on paper. Top airplane is standard Skyboy. Bottom airplane, this is what I have right now. They telling us that wing is doing all flying and fuselage just hanging down below. So, my my fuselage is hanging at different angle. It looks like visually that it is better angle to go through the air. Maybe not, because wheels hanging down at more aggressive angle = Making more drag this way. There also will be less down pressure on horizontal stabilizer. Will be probably OK for solo flight, but with two people a lot of trimming will be needed, possibly. I tried very hard to make those angles correctly, to simulate real life situation.
 

Eugene

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I am ready to go. All done for test flight. BRS installed. Just waiting for spring. Trying replay in my head what will change on my first flight. Trying to get ready.IMG_0707.jpg
 

BJC

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Part of getting ready is to know under what circumstances you will deploy the BRS and exactly how you will deploy it. That is not something that you want to have to decide when things go wrong.


BJC
 

Eugene

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https://drive.google.com/file/d/1u4-VeiMaF0l3x3xXeqi8O7ldjpzuZ2Vu/view?usp=sharing

Screen Shot 2018-04-02 at 13.27.37.jpg

This is bottom #3 connection on strut #66 of this picture. I found this when working on changing wing incidence. Whole tail boom was moving up and down in flight. I believe this movement resulted in "flatter". It wasn't elevator flatter, but whole tail was moving. All fixed now. No more rivets. I put it all together with bolts and nuts.
 

Eugene

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Not sure if you can see on this picture, that this bolt was working very hard during last 1000 hr. This is upper location of same #66 strut right under engine mount. Its all fixed now with 8mm bolt vs 6mm.
 

Eugene

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IMG_0411.jpgIMG_0403.jpgIMG_0402.jpg

My struts were made on different days of the week. So, they were different by 3/8". Rear struts were made on same day = no problems there. This would explain why trim tabs on my wings were bend out of shape in opposite directions. All fixed now.
 

Eugene

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IMG_0608.jpgIMG_0609.jpgIMG_0610.jpgWith new wing incidence during landing or takeoff at about 15.5° AOA this little tail wheel will touch the ground and hopefully protect. If that ever happens.
 

Eugene

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If this experiment works, little side benefit will be possibility to install bigger diameter propeller. Maybe I can go back to3 blade vs 5 I have right now. I heard somewhere that every blade lows propeller efficiency by 5%.
 

Eugene

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I definitely found myself in a experimental aviation. It is unbelievably cool that you can do anything you want without asking anybody for permission and be perfectly legal. I tell everybody that I have my own flying motorcycle. Except it is side-by-side and has a very good heater with full incloser = Ultimate Paradise!!!
 
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