Project Bush Demon

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BJC

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Oct 7, 2013
Messages
14,906
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97FL, Florida, USA
This is the first time I have ever attempted to design a full sized plane. I am sure you can tell from the name, I am working on a back Country Bush plane. I have several thoughts and ideas for STOL performance. I am for the most part a Arm Chair designer, I don't have any engineering in my back ground, so if i ask dumb questions, please forgive me.
I have bought plans for a J-3,
I am going to go the carbon fiber route. Use of honeycomb sandwiching, and adding supports such as bulk heads and longerons. I can make the fuselage in two pieces, and join them with rivets, and a adhesive to seal them solid.
Arkan:

With all due respect, you are not ready to begin designing an airplane.

Hang around some with EAA members / builders, learn the lingo, learn what standard practices are, learn about airplanes in general, learn to fly, learn basic aerodynamics and structures and systems, then begin your study of how to design an airplane.


BJC
 

Arkan

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Joined
Jun 6, 2021
Messages
83
Arkan:

With all due respect, you are not ready to begin designing an airplane.

Hang around some with EAA members / builders, learn the lingo, learn what standard practices are, learn about airplanes in general, learn to fly, learn basic aerodynamics and structures and systems, then begin your study of how to design an airplane.


BJC
Oh I am sorry, I thought that was whT I was doing here, learning. exchanging ideas, and putting together a course of action.

I have read through a lot of the posts through out this forum. I have learned a lot, and continue to expand my knowledge. Now since you go back through and quote several of my old post, go back and remember why I started this design journey. So until I figure out what's happening with my health, like why I have lost 35 lbs in a month, why I am anemic and losing blood. Well I don't think learning to fly, or even building an airplane is option until this is remedied. But learning, drawing, researching, chasing possibilities down each rabbit hole, as I learn. Spending my time drawing ideas, researching materials, figuring out how to do something or potential problems with an idea, that I can do.

Now if I seem argumentative on a position, it is because I want to chase it to it's end.

So if I came to the wrong site for that, then sorry to waste your time. I will leave the site and never bother any of you again. But I am the type of person who needs a sounding board, someone some where to discuss ideas and thoughts. I guess I can talk about it wife my wife, who is cloister phobic and afraid of heights. She will listen, give me a standard that's nice or interesting, and I get no knowledgeable feed back, or talk to another family member like my dad who is almost over 80, no knowledge of planes or flying and just wants to know what my doctor had to say.

So sorry to waste your time with my lack of knowledge, but I came here to learn.

Enjoy your site
 

BJC

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Joined
Oct 7, 2013
Messages
14,906
Location
97FL, Florida, USA
So if I came to the wrong site for that, then sorry to waste your time.
You are at the right site. You are not wasting my time.

As for the build, I am going to go the carbon fiber route. Use of honeycomb sandwiching, and adding supports such as bulk heads and longerons. I can make the fuselage in two pieces, and join them with rivets, and a adhesive to seal them solid.
What carbon fiber have you selected, and what is your lay-up schedule? What safety factor are you using? Why do you need longerons?


BJC
 

Arkan

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Joined
Jun 6, 2021
Messages
83
What carbon fiber have you selected, and what is your lay-up schedule? What safety factor are you using? Why do you need longerons?


BJC
I am still researching the carbon fiber, sandwich materials, and epoxies. I know there are several weights, weave design, and applications. the Sandwich materials range from Aluminum to Aramid honeycombs, and in a full design, i am sure it is going to be a mixture of materials. For instance i have been thinking on actually laying Kevlar over any mounting areas where i have metal mounting to the fuselage for it's abrasion resistance, that and when i actually mount them, either using a thin piece of rubber or silicone to dampen any vibrations.

the longerons will give extra added strength over the length of the airframe. I don't have an engineering degree, so I tend to over design.... i see the bulk heads running the width, and my mind goes to the length, so adding structure in that direction makes sense to me. I am not talking steel, but rather in the design, adding sandwich material to the inside of the outer skin and laying over it. I am talking like a four inch wide sandwich material running between the ribs. so say in the corners, just below the rivet line from the upper and low pieces of the fuselage. this should keep flexing between the ribs at a minimum and keep the rivets from busting through or stress cracking from forming.

As for a safety factor, honestly I have no clue, as I have said before, I don't have an engineering degree, I can only look at a structure, locate what i think are weak points and work my brain to figure out a solution. I keep telling my self when I look at things to K.I.S.S. (Keep It Simple Stupid) it, but I am also one of those who likes to challenge conventional design and thinking. If someone say this will not work, my next natural thought is why will it not work, what is the problems, and how do you over over them.

Once I have my ideas, on paper, in one unit and a design, i will work on a lay schedule. I am assuming you are referring to how each part will be layed and in what order. that is something i will figure out before i ever try to build.

I am going to be completely honest, My health situation has me scared, I don't know what is going on, the Doctor doesn't seem to know and I am doing everything in my power not to dwell on my fears. I am looking ahead, moving forward, and yeah I'll get through this, I am going to learn to fly, I am going to build me a plane, and I am going to start doing the things in life I always wanted to do. Learning to fly and having a plane at my disposal would give me the freedom to do those things. it will bring into reach distant places and adventures. I have always wanted to go fishing for Salmon in the pacific north west. Fly out to Moab and explore canyonlands nation park or Arches national park. Maybe take a weekend and fly down to the Gulf for some deep sea fishing like I used to do when I was in High school. (graduated HS in the Florida Keys) I realize somewhere in my life I lost the spirit of adventure. I fell in to the work eat sleep routine, and this health scare has opened up my eyes again to wanting to live life to the fullest. I have always loved being in the outdoors, Fishing Hunting and camping. I love going to new places and experiencing new things. In High School in the Keys I sailed boats, went Scuba diving, fished, and enjoyed so much, but after dropping out of college, I worked, came home, and went back to work. OH I bought boats and toys, but never make time to enjoy them.... Now I see time wasted, and how I let things get in the way actually living. I made a living, but didn't live. Every time I got into something I enjoyed, I let it go due to costs, waste of money, in my mid twenties I raced dirt track cars, add up the cost one year and sold off my car. I don't know, now I look at wasted time, lost chances, and I look ahead to how to change that, how to move forward and start to live again. So designing this plane, working out the problems, helps me move forward. I don't know what hurdles, problems or issues i am going to have to over come to do this, but i am going to find out and find the solutions.
 

blane.c

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Joined
Jun 27, 2015
Messages
5,902
Location
capital district NY
You are trying to make up for the lack of knowledge by using additional material in places it may or may not be needed. This will cause the airplane to be overweight in areas not needing the material causing even more weight to bear on underweight and weaker areas. You cannot do this and expect a aircraft that is safe and its performance will suffer as well.

There are many threads on this forum that discuss just about anything you can think of about aircraft and are good starting points for your quest for knowledge.

I suggest you begin reading, you have a tremendous amount of reading to do.
 

rv7charlie

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Joined
Nov 17, 2014
Messages
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Location
Pocahontas MS
Arkan,

I don't want to put words in BJC's keyboard, but I suspect that he is seeing something similar to what I've been seeing, and it may just be terminology & 'failure to communicate'.

I'm confident that the smarter people here are happy to answer any and all 'what if I...' questions; that's how we all learn. It's harder to answer when the questions are framed as statements, like,
'I am going to go the carbon fiber route. Use of honeycomb sandwiching, and adding supports such as bulk heads and longerons. I can make the fuselage in two pieces, and join them with rivets, and a adhesive to seal them solid. '

If you ask that as a question (as in 'can I do X?'), then several people a lot smarter than me could easily answer (with a 'no', in that case). But if you just make the statement, then it feels like you're not asking for opinions on whether it's a good idea, or *why* it isn't a good idea.

Looking at plans/designs of existing, successful a/c is absolutely the best place to start. But it's worth considering that when we start out with no engineering background and no piloting or a/c maintenance experience, the the chance of us coming up with a safe and successful construction technique never found in an existing successful design is pretty close to zero. Because a lot of smarter people than us, over a lot of decades, have already thought of, and discarded those ideas as unusable.

So ask away. Like, 'has anyone ever riveted together fiberglass structure?'. And the answer is, not much, because glass doesn't handle the point loads of fasteners very well; it works much better if it's bonded over a wide area. (My redneck description; an engineer can give you the answer in more technical terms.)

Hope you get an answer to your health issue soon, so you can get on with building/flying.

Charlie
 

Victor Bravo

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Joined
Jul 30, 2014
Messages
10,521
Location
KWHP, Los Angeles CA, USA
Arkan, the one thing you are not fully grasping here is that the vast majority of people here are "spring-loaded" to help, first by preventing someone from winning the Darwin Award, and then second to exchange ideas and have fun. The reason is that several of us here have seen people hurt, killed, or otherwise financially harmed by following a misguided path.

So when this group sees a nice guy heading down the wrong path in terms of what will or won't work in an airplane, our gut reaction is to immediately pull the guy of the road before he gets run over, and then later explain to him about cars and roads and distracted drivers.

So what you're seeing and feeling here is just the abruptness of the gut reaction - "Oh no, there's another nice guy about to step on a rattlesnake, push him out of the way and we'll brush the dust off of his clothes later".

You ARE in the right place to discuss airplanes and strange designs and new ways to solve old problems. You ARE 100% welcome here.

However, you also must not be surprised or offended if some of the folks seem gruff or impatient with someone who is just starting out and is making many of the same oversights and misunderstandings as we all have made already.

OR... the "short version" is... if you're an experienced rancher, and someone buys a ranch next to your ranch, and you really want to help them not make the same mistakes you made - but they just can't quite see the difference between the bulls and the horses - would you raise your voice and be rude to them in order to prevent their horses from being gored?
 

Arkan

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Joined
Jun 6, 2021
Messages
83
VB if you want to help and educate, that's cool, but some people come across in a way that feels and seems more like a personal attack. It takes years to properly design an aircraft. But every design starts with a vision, a thought, and before you put even pen to paper in design, you need to know your materials, and an idea of how it will all come together. The problem with some people approach on here, instead of helping direct someone's idea, helping, teaching or guiding them to the right answers, they criticize the idea entirely or dismiss the person cause "they have a lot to learn." Well no Sh**! that's why I came to a home builder website instead of applying for a job at Boeing. The biggest problem is you could read every piece of literature ever printed on aircraft design and construction and still have a lot to learn. As with any other knowledge field, the day you stop learning, get out, because your going to kill your self or someone else.

So I will continue to research, maybe even do some material testing, and test a few other ideas. Maybe after I figure out and learn more I will have gained enough knowledge to share.

But in my research I have found multiple aircraft made entirely of composite material, the quickie was hand laid fiberglass over a foam core and was one of the fastest kit planes of it's time. Arion lighting uses carbon fiber fuelage and a fiberglass constructed wing, DarkAreo, and Elixir out of France. And I am sure many others. So my ideas has merit, it is the process I have to learn and figure out.

Since a composite build design will be extremely different than say a tube and fabric design, the design process is going to be different way different.

I toss out ideas looking for feedback, and it feels more like I get criticism than help. So honestly I don't know where to go from here, except on my own.

I know I have a lot to learn, and I will find the knowledge, make my designs and plans and maybe one day they will be good enough to share with you all.
 

Arkan

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Joined
Jun 6, 2021
Messages
83
So I have been researching airfoil designs and I think I have settled on the Clark Y airfoil. that with a flaperon and leading edge slat, should give me great stol performance.
 
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Arkan

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Joined
Jun 6, 2021
Messages
83
Okay quick update... I am still researching like mad, but we finally got answers on my health issues, In October I had a Bone Marrow Biopsy. the results came back and i have a Blood Cancer called Myelodisplastic Syndrome. Short quick version of what that means, my bone marrow is not producing mature red blood cells, it releases them premature and they either die before entering the blood stream or shortly after. The only chance for a cure is a bone marrow transplant. I go to UAMS in Little Rock on the 14th to discuss treatment options on the 14th, so please keep me in your prayers.

On plane design, I have been running a Comparison between the PA-15 and the Piper J-4 Coupe. but trying like hell to find some accurate cab measurements. I they look similar from all the pictures and i know the PA-15 had a shorter wingspan at 29ft, while the J-4 Coupe was 36ft. the J-4 actually had about 100lbs more usable payload. So I keep researching, sketching ideas, and so forth. I am still planning on a carbon fiber build. I know a lot of you don't like that idea, but is still the direction i am heading in this design.

toss out the idea on the ClarkY wing as well, honestly Piper used the USA 35b with a slight mod. I think i am going to keep Pipers Original Airfoil, I do want to add the deployable leading edge slat, but i am still on the fence on Traditonal Flaps and Ailerons, vs. Flaperons. I know KitFox, Zenith, and other good Stol Aircraft use the Flaperons, with good results, but with traditional Flaps and Ailerons have advantages as well. I could use some help on making this choice. maybe someone with flight experience who has flown both types and can give me more information on how they handle in flight.

I have decided not to get too stupid with the Stol ability of this design, I want to balance in some cruise ability as well, target cruise speed at this point I am aiming for around 100.... I know the original J-4 and PA-15 had 65hp, so I am thinking on 100 hp engine, and gaining that balance with the prop, I am thinking a ground adjustable prop might be the answer here, and of course reducing drag anyway I can in the design.

Anyway, hope to get some good feedback form you guys.
 

rv7charlie

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Nov 17, 2014
Messages
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Location
Pocahontas MS
If you want decent (not even fast, but decent) cruise speed, find a different starting-point a/c from the early Piper J-x planes. Why? Compare a J-3/J-4 performance envelope to something like a Taylorcraft or Luscombe from the same era. Then compare any of those to a modern design like the Bearhawk LSA or Patrol. BTW, HP is a *very* poor bandaid for bad aero.

Stay positive on the health issues, and get at least three opinions before picking a path forward. Hate to make the tired joke, but there's a reason they call it 'practice'; medicine is an inexact science. My wife has CLL (another blood cancer), and she's gotten a wide range of medical recommendations, from pretty bad to quite good. She's managed to pick the good, and has an excellent oncologist, so she's been living with her 5-year-life-expectancy disease for almost 30 years.

Oh, and don't mess around and let Covid kill you before you get any treatment. In case the docs haven't mentioned it yet, many blood cancer patients don't respond to any of the vaccines, so they get no real protection from them, and they're particularly vulnerable if they get it. I'd certainly want to know whether I was protected.

Charlie
 

TFF

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Memphis, TN
The PA-15 is the sports car. After WW2 facelift airplane. The J-4 was a stab at Taylor for leaving in 1935. All the pipers are pretty much parts bin airplanes. Mix and match and call it a new airplane.
 

Arkan

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Jun 6, 2021
Messages
83
If you want decent (not even fast, but decent) cruise speed, find a different starting-point a/c from the early Piper J-x planes. Why? Compare a J-3/J-4 performance envelope to something like a Taylorcraft or Luscombe from the same era. Then compare any of those to a modern design like the Bearhawk LSA or Patrol. BTW, HP is a *very* poor bandaid for bad aero.
It is amazing how I had what I thought was a clear idea in the beginning of this design process, but the mission through research changes a bit in my head. I want a high wing plane with the ability to land "Off Field," but i do not want to get too hung up or crazy with the "off field" portion. At the same time, I still want the ability to fly say to Idaho, there are some Off Field places maintained for fishing and camping in the back country there, and taking a weekend or planning a trip to have that back country adventure, without getting stupid on the STOL or Back country limitations on design. finding that balance I guess we all look for in design for our mission. For instance, I love those Alaskan Bush Tires, and the look and stance they give a good airplane. Same time, if your running out of a paved runway airport, and don't get off field, they suck, due to cost and tire wear. (just an example)

I actually looked at Taylor craft a while back, the J-4 did not really compete well with those, they were better aircraft, not till say 1940, Piper was closing the gap between the designs, but WW2 kind of stopped all civil aircraft production for the war the following year, I think the PA-15 was them revisiting the J-4 concept, they looked almost identical other than wingspan. I would have to check but I think the nose to tail length was shorter on the PA-15 as well.

Stay positive on the health issues, and get at least three opinions before picking a path forward. Hate to make the tired joke, but there's a reason they call it 'practice'; medicine is an inexact science. My wife has CLL (another blood cancer), and she's gotten a wide range of medical recommendations, from pretty bad to quite good. She's managed to pick the good, and has an excellent oncologist, so she's been living with her 5-year-life-expectancy disease for almost 30 years.

Oh, and don't mess around and let Covid kill you before you get any treatment. In case the docs haven't mentioned it yet, many blood cancer patients don't respond to any of the vaccines, so they get no real protection from them, and they're particularly vulnerable if they get it. I'd certainly want to know whether I was protected.

Charlie
As for my Health, yes, I have three different Doctor already on the case. I trust my first two Doctors, and will be meeting the third for the first time on the 14th. I am being very careful and weighing all the options. I have not been able to work in a month, and that is driving me insane. I get to do too much and I get lightheaded and Dizzy, so walking around the hospital all night is not an option, I would go from care giver to patient by the time my shift ended. I do what I can around home, and i am actually going flying (RC'S) later today. As for Covid, I caught it last month, I thought i had allergies mixed with a head cold, but my doctors tested me, and then sent me immediately for the Monoclonal Antibody treatment... Two days later I felt fine, just have a slight sinus congestion. by the end of my Quarantine, I was climbing the walls feeling trapped in my own home. I also know that with my condition, immunities don't last, so I am being careful.
 

Riggerrob

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Joined
Sep 9, 2014
Messages
2,585
Location
Canada
VB if you want to help and educate, that's cool, but some people come across in a way that feels and seems more like a personal attack. It takes years to properly design an aircraft. But every design starts with a vision, a thought, and before you put even pen to paper in design, you need to know your materials, and an idea of how it will all come together. The problem with some people approach on here, instead of helping direct someone's idea, helping, teaching or guiding them to the right answers, they criticize the idea entirely or dismiss the person cause "they have a lot to learn." Well no Sh**! that's why I came to a home builder website instead of applying for a job at Boeing. The biggest problem is you could read every piece of literature ever printed on aircraft design and construction and still have a lot to learn. As with any other knowledge field, the day you stop learning, get out, because your going to kill your self or someone else.

So I will continue to research, maybe even do some material testing, and test a few other ideas. Maybe after I figure out and learn more I will have gained enough knowledge to share.

But in my research I have found multiple aircraft made entirely of composite material, the quickie was hand laid fiberglass over a foam core and was one of the fastest kit planes of it's time. Arion lighting uses carbon fiber fuelage and a fiberglass constructed wing, DarkAreo, and Elixir out of France. And I am sure many others. So my ideas has merit, it is the process I have to learn and figure out.

Since a composite build design will be extremely different than say a tube and fabric design, the design process is going to be different way different.

I toss out ideas looking for feedback, and it feels more like I get criticism than help. So honestly I don't know where to go from here, except on my own.

I know I have a lot to learn, and I will find the knowledge, make my designs and plans and maybe one day they will be good enough to share with you all.
Dear Arkan,
Different materials work best in different parts of the airframe.
For example, Glastar kitplanes are made of composites, sheet aluminum and steel tubing. They use composites on parts with complex curves, like wing tips, engine cowlings, and cockpit doors. Glastars have sheet aluminum flying surfaces (wings, ailerons, flaps, horizontal stabilizer, elevators and rudder) because they only need simple curves and rivetted sheet aluminum is the quickest way to build those components. Finally, steel tubing is used in the most heavily-stressed areas like engine mounts. The cockpit has a steel tube roll cage surrounded by a light-weight composite shell. Steel tubing is best for carrying loads around all those openings: windows, doors, etc.

Steel tubing is widely used in the fuselages of high-wing airplanes. If you ever see a deHavilland of Canada Beaver bush-plane stripped, you will notice that the fuselage structure is mostly steel tubing forward of the wing. Beavers only have light-weight sheet aluminum fairings around the cockpit. Beavers have out-lasted the next dozen bush-planes because they are strong and easy to repair.
 

Riggerrob

Well-Known Member
Joined
Sep 9, 2014
Messages
2,585
Location
Canada
VB if you want to help and educate, that's cool, but some people come across in a way that feels and seems more like a personal attack. It takes years to properly design an aircraft. But every design starts with a vision, a thought, and before you put even pen to paper in design, you need to know your materials, and an idea of how it will all come together. The problem with some people approach on here, instead of helping direct someone's idea, helping, teaching or guiding them to the right answers, they criticize the idea entirely or dismiss the person cause "they have a lot to learn." Well no Sh**! that's why I came to a home builder website instead of applying for a job at Boeing. The biggest problem is you could read every piece of literature ever printed on aircraft design and construction and still have a lot to learn. As with any other knowledge field, the day you stop learning, get out, because your going to kill your self or someone else.

So I will continue to research, maybe even do some material testing, and test a few other ideas. Maybe after I figure out and learn more I will have gained enough knowledge to share.

But in my research I have found multiple aircraft made entirely of composite material, the quickie was hand laid fiberglass over a foam core and was one of the fastest kit planes of it's time. Arion lighting uses carbon fiber fuelage and a fiberglass constructed wing, DarkAreo, and Elixir out of France. And I am sure many others. So my ideas has merit, it is the process I have to learn and figure out.

Since a composite build design will be extremely different than say a tube and fabric design, the design process is going to be different way different.

I toss out ideas looking for feedback, and it feels more like I get criticism than help. So honestly I don't know where to go from here, except on my own.

I know I have a lot to learn, and I will find the knowledge, make my designs and plans and maybe one day they will be good enough to share with you all.
Dear Arkan,
Different materials work best in different parts of the airframe.
For example, Glastar kitplanes are made of composites, sheet aluminum and steel tubing. They use composites on parts with complex curves, like wing tips, engine cowlings, and cockpit doors. Glastars have sheet aluminum flying surfaces (wings, ailerons, flaps, horizontal stabilizer, elevators and rudder) because they only need simple curves and rivetted sheet aluminum is the quickest way to build those components. Finally, steel tubing is used in the most heavily-stressed areas like engine mounts. The cockpit has a steel tube roll cage surrounded by a light-weight composite shell. Steel tubing is best for carrying loads around all those openings: windows, doors, etc.

Steel tubing is widely used in the fuselages of high-wing airplanes. If you ever see a deHavilland of Canada Beaver bush-plane stripped, you will notice that the fuselage structure is mostly steel tubing forward of the wing. Beavers only have light-weight sheet aluminum fairings around the cockpit. Beavers have out-lasted the next dozen bush-planes because they are strong and easy to repair.
 
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