Elevator balancing for tube and fabric tail

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Geraldc

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I wonder if you might be able to get a yacht mast builder to design a tapered composite boom to replace your alloy one?
With the America's Cup racing the technology has become quite sophisticated.
The forces on a mast may be similar, I don't know.
Contact . These people may be able to put you in touch with the right people.
 

Eugene

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I wonder if you might be able to get a yacht mast builder to design a tapered composite boom to replace your alloy one?
With the America's Cup racing the technology has become quite sophisticated.
The forces on a mast may be similar, I don't know.
Contact . These people may be able to put you in touch with the right people.
Looks like I found someone and looks like we are going to do it. But he was telling me, to make sure I understand, that to do it this way will cost money and time. And I do understand that will be no flying for me for next 2-3 years. For some reason it's not very sad news to me. I will be working towards something beautiful and that's important to me. Building is fun, but flying is boring.

I was making sure that we don't have easier solution. Something any Skyboy owner can do and improve his airplane.

Understanding problem was very very important and Bill was big help on this. Thank you!!!
 

wsimpso1

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I was talking to designer of this airplane in Russia. He was telling me that 3- tube structure is turned out to be pretty flimsy. On top of everything else they end up using many cables to stop tail from side-to-side motions. He was telling me this is not very good idea to go this way. He claims that aircraft turns into very draggy machine because of that and he call it "flying farm".
Eugene,

Is this the same guy who took a decent 50 hp machine, doubled the power, shrank the tail plane, kept the already too flexible and too heavy tailboom because he thinks it works fine? Or are they different guys? And the other plane with a too flexible back end - when he found it to flexible, why did he not improve the clamping at both ens and maybe bump the tube size one step? Was the original design just too perfect otherwise, or had he already bought the tubes? It seems to me that these guys (this guy?) have only demonstrated that they do not know how stiff the system must be, do not know how to make it that stiff, and upon finding it too flexible, sold it to customers anyway instead of revising the design to work. They are proof that you can start with a known and proven approach to a problem and still screw it up.

Why talk to them? They have done you badly. Their track record is one of screwing up known good schemes. Please get your criticism of design revisions from someone else.

As to its drag, the current tailboom has drag too. Simple calculations can be used to get reasonable estimates of the drag for each design.

I am talking about learning a little engineering from the sophomore year of study, do some analysis of the current scheme, estimate loads, strength, stiffness, and weight. Then you can scheme out a new aft fuselage, defining its loads it can see from the new tail planes, make a guess about how stiff it needs to be off the original boom stiffness (my initial target would be 4-6 times stiffer than the original boom), try different tube sizes in the calculation until you get to adequate strength and stiffness, then compute weight. I am willing to check your work at every stage so your work does not go all wonky.

But listening to the guys who have made and sold bad airplanes? Why bother with them?

Billski
 

Eugene

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Eugene,

Is this the same guy who took a decent 50 hp machine, doubled the power, shrank the tail plane, kept the already too flexible and too heavy tailboom because he thinks it works fine? Or are they different guys? And the other plane with a too flexible back end - when he found it to flexible, why did he not improve the clamping at both ens and maybe bump the tube size one step? Was the original design just too perfect otherwise, or had he already bought the tubes? It seems to me that these guys (this guy?) have only demonstrated that they do not know how stiff the system must be, do not know how to make it that stiff, and upon finding it too flexible, sold it to customers anyway instead of revising the design to work. They are proof that you can start with a known and proven approach to a problem and still screw it up.

Why talk to them? They have done you badly. Their track record is one of screwing up known good schemes. Please get your criticism of design revisions from someone else.

As to its drag, the current tailboom has drag too. Simple calculations can be used to get reasonable estimates of the drag for each design.

I am talking about learning a little engineering from the sophomore year of study, do some analysis of the current scheme, estimate loads, strength, stiffness, and weight. Then you can scheme out a new aft fuselage, defining its loads it can see from the new tail planes, make a guess about how stiff it needs to be off the original boom stiffness (my initial target would be 4-6 times stiffer than the original boom), try different tube sizes in the calculation until you get to adequate strength and stiffness, then compute weight. I am willing to check your work at every stage so your work does not go all wonky.

But listening to the guys who have made and sold bad airplanes? Why bother with them?

Billski

No, two different guys. My airplane was designed and built in Czech Republic.


Guy who designed and build airplanes on picture below is Russian guy. He was really helpful for me in the process of understanding my problems.

9FCD85EB-6727-4AD5-A355-97061322946E.pngD7AD8867-290D-4C7A-ACE7-62AB47ED0C3B.jpegD2C92189-7442-4444-AF73-6CC1D6E910C5.jpeg65C636A0-F686-405F-A785-B7A865B37823.jpegCAEDAAB3-9C11-4511-95A2-2CDA16A9A9F1.jpeg9F4C8109-4578-49DF-A47F-0EC034FAF743.jpeg
 

wsimpso1

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No, two different guys. My airplane was designed and built in Czech Republic.


Guy who designed and build airplanes on picture below is Russian guy. He was really helpful for me in the process of understanding my problems.
My apologies.

I want you to upgrade your thinking. When somebody who professes to be an airplane designer tells you something did not work so well, you have get them to tell you what it would take to make it right... It is easy for any moron to tell you something sucks, but a smart airplane designer would also have some ideas about how they would make it work great.

Remember that anything can be made to work, but it can cost a lot of money or effort or time or make the thing heavy or even all of the above. We are trying to find a good solution that is light and stiff and strong and does not ground you for years.

If you want to do the composite route, I still think you ought to do it with somebody who already has a track record. Sort of like why folks should do HVAC with your shop instead of the guy who has seen some Youtube videos on how to do it...

Billski
 

poormansairforce

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Why don't you cut the tube off behind the last brace and build an 12"? square tapered aluminum fuse section that clamps/bolts around the tube stub. The bottom of the fuse fairs into the bubble on the bottom of the cockpit.
 
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Eugene

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My apologies.

I want you to upgrade your thinking. When somebody who professes to be an airplane designer tells you something did not work so well, you have get them to tell you what it would take to make it right... It is easy for any moron to tell you something sucks, but a smart airplane designer would also have some ideas about how they would make it work great.

Remember that anything can be made to work, but it can cost a lot of money or effort or time or make the thing heavy or even all of the above. We are trying to find a good solution that is light and stiff and strong and does not ground you for years.

If you want to do the composite route, I still think you ought to do it with somebody who already has a track record. Sort of like why folks should do HVAC with your shop instead of the guy who has seen some Youtube videos on how to do it...

Billski
My thinking is already upgraded and this is exactly what is driving everybody crazy. My whole life I was thinking that 2×2 should be = 4 and not 5 or 6. With other words everything should have an explanation. There is a reasons why good airplanes flying so good. Bad airplanes flying this way for a reasons as well. Because I don't know those reasons, I like to talk to smart people and ask them questions. I did this my whole life and solved many problems. If I couldn't fix something at work in 15 minutes I never hesitate to dial technical support number. Those guys sitting on the phone and solving problems for 24 hours. It will take me 100 years to accumulate that kind of knowledge. So can I buy myself some books and learn how design airplane? And can I do that after work with a simple 30 minute reading before I go to bed? How long will it take to get to 4 year college degree level? There is all kinds of people out there spend many years at school studying this and they still don't know what is the right thing to do for my airplane. Am I really that smart?

Very hard to find knowledgeable people who are willing to talk. Skyboy designer as example gets very upset with me. He thinks I am trying very hard to make him and airplane look bad. Nobody had ever complain but only this stupid Russian, who thinks that he is smarter than his team of 12 engineers who designed this aircraft.

Nobody really wants to spend time to figure out your problems. Good and knowledgeable people are very busy doing bigger and better things. Plus different knowledgeable people with long list of accomplishments usually will give you different recommendations. That was by itself huge surprise for me. Sometimes very conflicting recommendations about what to do with this aircraft. Here is example, Peter Garrison was telling me that 10.2° decalage is OK and nothing to worry about. Everything I learned so far doesn't support that. So, how can I argue with Peter Garrison? I like to believe that this guy knows about airplanes thousand times more than I do at this point. And just about yesterday I didn't know difference between angle of incidence versus angle of attack.

And because of this conflicting recommendations I keep thinking that may be best thing to do is to find easier solution that even I can understand and calculate. Sort of like "if you wanna get it done correctly you have to do it yourself". Or here's another one "if you can't please everybody, you have to please yourself". Yes, I don't need to talk to anybody about how to convert my whole house to in floor radiant heat. I can just do it end it will be done right. But there is many years of experience and some schooling behind this confidence. Will I ever get this kind of confidence level for designing airplanes??????????. I really don't think so.

I will keep on trying and eventually I will get somewhere. I hope

Sometime ago I found this Russian designer who was willing to talk and got curious about what is wrong with this airplane. We spend a lot of time communicating back-and-forth using email and pictures, text messages, Facebook and so on. I wasted so much of his time, makes me feel guilty. He is pretty busy person with all kinds of projects and I am constantly sending him my questions.
 

Eugene

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Why don't you cut the tube off behind the last brace and build an 12"? square tapered aluminum fuse section that clamps/bolts around the tube stub. The bottom of the fuse fairs into the bubble on the bottom of the cockpit.

After I cut tail boom off, I will see 4 attachment points that I will need to get to. I need to grab #2 under engine mount. Otherwise, like Bill said, there is not enough vertical difference between old tail pipe #1 and two brackets #3 and #4. And the only way I can see it's possible if it is going to be a composite structure.

Propeller in the way, there is no more options. Any kind of space frame will needs to be attached to the wing and be made out of tubes. And after its all done, my dream of reducing drag on this airplane is out of the window.

IMG_4095.jpegIMG_4099.jpegIMG_1881.jpegIMG_1882.jpeg
 

Eugene

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Is there a way to brace under the main boom with two smaller tubes and jury struts?
View attachment 98684
View attachment 98685
Is there way? Well we can create some kind of way, but will it be enough? Boom is 120mm. So we need another 120-150 mm to be effective ? Skyboy designer was trying to do something like that on picture below. We are talking about additional reinforcement for existing tail boom? Right?

29597615_2003983436296829_2958575404343485028_n.jpegIMG_3532.jpeg
 

ScaleBirdsScott

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Yeah, I too like the idea of a pair of extra tubes running below, then just fabric cover the whole thing as needed. Cheap. If it doesn't provide the extra rigidity then go with the composite method.
 

wsimpso1

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Why don't you cut the tube off behind the last brace and build an 12"? square tapered aluminum fuse section that clamps/bolts around the tube stub. The bottom of the fuse fairs into the bubble on the bottom of the cockpit.
The current tail boom runs from the front of the airplane all the way to the tail. And it is flexing at too much of an angle even as it comes out of the brackets. My guess is that the tube is near strength limits with the current tail size and arm. To make the tail bigger and the arm longer, he either has to beef up the boom or mount the new aft fusealge with its mounts spread out. One place will probably be where the brackets are, and then two or three others...

Billski
 

wsimpso1

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So can I buy myself some books and learn how design airplane? And can I do that after work with a simple 30 minute reading before I go to bed? How long will it take to get to 4 year college degree level? There is all kinds of people out there spend many years at school studying this and they still don't know what is the right thing to do for my airplane. Am I really that smart?
OK, first, an airplane design book may not be the way to go. And the full Bachelor's degree educate people in way more than just this topic. Electrical circuits and thermodynamics and fluids and it goes on and on. Way more than you need for this if you have an engineer to check your work as you go. PM me...

You need to figure out how big your tail will be and how long the arm is, which comes from tail volume, and you are already on the way;

Then you need to figure out how big the tail loads can be. Search online for "CFR 14 Part 23" and Old version. You will find a BIG government document that you can download or search. You want to find the section on simplified tail loadings. Tail loadings as are based on wing loading and design g's. Loadings are just how many pounds are being supported on each square foot of surface;

Then you need to be able to design a truss. My favorite is "Mechanics of Materials" by Timoshenko and Gere. I bought it for classes while I was still a Sophomore in Engineering school. New does not mean much. Most of the information in the book was already old when I was born, so a used text book will do. There are chapters on beam theory and trusses. You can get this book cheap enough, find the chapters, and go through them carefully. Do not try to eat it in one gulp. It is taught in engineering school a few pages per lecture, three lectures a week, with the students doing home work problems as they go. This is doable.

Billski
 
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Eugene

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OK, first, an airplane design book may not be the way to go. And the full Bachelor's degree people in way more than just this topic. Electrical circuits and thermodynamics and fluids and it goes on and on. Way more than you need for this if you have an engineer to check your work as you go. PM me...

You need to figure out how big your tail will be and how long the arm is, which comes from tail volume, and you are already on the way;

Then you need to figure out how big the tail loads can be. Search online for "CFR 14 Part 23" and Old version. You will find a BIG government document that you can download or search. You want to find the section on simplified tail loadings. Tail loadings as are based on wing loading and design g's. Loadings are just how many pounds are being supported on each square foot of surface;

Then you need to be able to design a truss. My favorite is "Mechanics of Materials" by Timoshenko and Gere. I bought it for classes while I was still a Sophomore in Engineering school. New doe not mean much. Most of the information in the book was already old when I was born, so a used text book will do. There are chapters on beam theory and trusses. You can get this book cheap enough, find the chapters, and go through them carefully. Do not try to eat it in one gulp. It is taught in engineering school a few pages per lecture, three lectures a week, with the students doing home work problems as they go. This is doable.

Billski
I found a book already. So, hardest part is over? Rest is easy?

Thank you for having confidence in me! I will do my best.

F887F9F9-69EE-4B92-AEBC-65D5A6F0A684.jpeg
 

Eugene

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You need to figure out how big your tail will be and how long the arm is
Billski
OK, presently tail arm is 2.2 MAC and Vh = 0.34

If I make tail arm 2.5 MAC my Vh will get to = 0.4

If I increase elevator size back to original design (about 2 sq ft more) and keep tail arm 2.5 MAC horizontal tail volume will get to Vh = 0.43

If I try to get to tail arm of 2.75 MAC this will be increase from 10.8 ft to 13.75 ft and with larger elevator horizontal tail volume will finally get to Vh = 0.48

So, how big my tail should get? Anything bigger than what I have will be an improvement.

Wing area = 138 sq ft
Wing chord = 5 ft
Horizontal tail area - 22 sq ft
Horizontal tail arm - 10.8 ft
 
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