Quantcast

Greetings from an aspiring designer!

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

L

Liras

Guest
Hello everyone! :)

I have scored thousands of hours in WWII aviation combat games over a past few years and I got hooked forever... Since then I've been learning, building and flying model airplanes (crashed a lot of them) and now comes the moment of truth: can I build a real airplane? I'm on my final year in high school and there are only 66 days left to freedom. And when it comes, I wanna be ready. I want to grab my plans, buy some Aircraft Spruce and head down to the garage to begin my epic quest. In reality though, designing and building your own plane is VERY difficult. I went through lots of engineering books, some really great, some a bit worse and managed to get a good idea about aerodynamics and conceptual design. This is the easy part.

I came up with an idea for a plane so simple to build that even a child (like me?:)) could do that. It's slow, has no engine, ridiculously low wing-loading, open-cocpit and is quite blocky to be honest. This is called a microlift glider. I did all the preliminary calculations, sketches and a fancy 3D model! Conceptual design is done according to my dev plan. Great, isn't it? I attach my design spreadsheet and the 3D render.

Well, to be honest, I'm stuck now. Almost completely. I have to do some more detailed design. I'm not so worried about the primary structure, but all the little details, bolts, washers, fittings, etc. And the control system.... omg. I don't even know where to start (wait, I know, I'm gonna have electric flaps!) But seriously, I've been searching through the entire Internet and I could only find references for the easily done conceptual design. I don't have much support here, in Poland, where I live, so I thought maybe you guys could help me out?

Any suggestions?
Thanks for all your advice,
Liras
 

Attachments

don january

Well-Known Member
Log Member
Joined
Feb 10, 2015
Messages
2,908
Location
Midwest
First thing I'd suggest would to look into any glider groups you can find beings this is a powerless aircraft. Then you need to look at your design from the inside out. How will your tail group mount, how does the wing mount. Do you have enough room to build a larger wing? Also you must see what the availability for a tow to get you off the ground and to altitude. And first and foremost I recommend going out and getting some flight time in a craft like you want to build. Good luck to you and welcome to the Forum.
 

lr27

Well-Known Member
Joined
Nov 3, 2007
Messages
3,822
It seems like you're willing to do your homework, which means you're much more likely to survive this project. So that's good.

I see you've picked the USA 35A airfoil. It looks suitable, but have you calculated the trim drag? It's possible to find relatively high lift, thick airfoils that have smaller pitching moments.

Do you really need flaps? More weight and complication, though I suppose they could also be used as air brakes, as long as you kept the speed up. If you fly too slow and need to stretch the glide, raising the flaps will mean you drop. So I think that requires a bit more skill and thinking from the pilot, compared to, say spoilers or perhaps no glide path control at all. Your wing loading is so light that the glider is quite slow already.

What happens when the aircraft flips over? The pilot's head protects the airframe? Might be better if it was the other way around. You might consider a canopy that incorporated a support structure to protect the pilot. The canopy ought to reduce drag for a better L/D.

I mention the Sky Pup too often, but the specs for it are very similar except it's a bit heavier due to the engine. I imagine a Sky Pup with the engine removed and the pilot moved forward would make a good glider. It's supposed to have an L/D of 12:1 even with the engine. The wing area and span are similar. It's constructed of wood and extruded Styrofoam. It's been around for many years, and still has a good reputatoin. It appears there's been at least one successful conversion to low wing. One disadvantage is that it has no ailerons. But that could also be seen as an advantage, especially if you're the one building it. I imagine that, with a bit less dihedral and a little redesign, it might be ok with ailerons. Another downside to the Sky Pup is that you have to buy the plans! However, I think you could base your design on it, or at least pick up a lot of details. The plans are thorough.

There are other plans on line. Plans for the Woodstock sailplane and the Carbon Dragon, both by Jim Maupin, are on line someplace, and likely have some useful details for you. Both use some carbon fiber, and would probably be better converted to carbon pultrusions instead of hand layup carbon tow. But the basic construction is wood. I'm sure there are all sorts of other designs to look at. Don't limit yourself to gliders and sailplanes. Well engineered ultralights will have details similar to what you need.

I don't know if you're aware of the EAA, but they have a bunch of publications which I'm sure would be helpful to your design. https://www.eaa.org/en/eaa-shop/media/aviation-books#/?filters[0].key=category&filters[0].value=%7BD04C4C17-2FE7-43DE-BE89-1C45683AA355%7D Also, the FAA (Federal Aviation Administration, part of the US Government), has lots of technical information on line. For instance: https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/ and: https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.list/parentTopicID/0/display/current/changeNumber/0/currentPage/2/sortResults/false/sortColumn/dateIssued/sortOrder/DESC
Magic NACA Archive:
http://naca.central.cranfield.ac.uk/ Lots of good stuff here. Anything from 85 year old airfoil tests to conical camber for supersonic aircraft.
NTRS server:
https://ntrs.nasa.gov/ It may be difficult sometimes to sort through all the overly technical stuff, but you'll find some useful publications too.

I think, if you haven't seen it already, you'll find ANC-18 useful for information about the design of wood aircraft. Available in a number of places on the net, including on HBA.

Poland has a long history of sailplane designs. Check some of them out here: https://www.j2mcl-planeurs.net/dbj2mcl/planeurs-machines/planeurs-selec_0int.php Does that sort of activity go on in another part of the country, or near where you live? I'm guessing that Poland has equivalents for many of the information sources I pointed out above.

Keep us up to date on your project!
 

Chris Young

Well-Known Member
Joined
Feb 19, 2013
Messages
90
Location
France
I would suggest you buy the plans for a "similar" airplane, such as the Volksplane, and study them asking yourself why the designer put that there and not there, etc... THen you will get a better understanding of the whys and hows of detailed design. Best thing to learn is still to actually build one, if you can afford it.
 

BoKu

Pundit
HBA Supporter
Joined
Aug 15, 2013
Messages
2,796
Location
Western US
...If you fly too slow and need to stretch the glide, raising the flaps will mean you drop...
I've got about 700 hours in two different types of flapped gliders with no spoilers or airbrakes, and I can say that this is just [redacted] not true. When you raise the flaps, you just raise the nose at the same time, and you don't "drop." Just like when you lower the flaps you lower the nose at the same time. Just like Cessna 150 drivers have been doing since Eisenhower was President.

--Bob K.
 

BBerson

Light Plane Philosopher
HBA Supporter
Joined
Dec 16, 2007
Messages
14,011
Location
Port Townsend WA
But if you are already too slow, is raising the nose a good plan for a low time pilot?
 

BoKu

Pundit
HBA Supporter
Joined
Aug 15, 2013
Messages
2,796
Location
Western US
But if you are already too slow, is raising the nose a good plan for a low time pilot?
If you're slow and need to "stretch the glide," you are NFBSK'd regardless of how many hours you have and what the glidepath control handle is connected to. Your best bet is to lower the nose and deal with the situation as best can be done.
 

lr27

Well-Known Member
Joined
Nov 3, 2007
Messages
3,822
If you're slow and need to "stretch the glide," you are NFBSK'd regardless of how many hours you have and what the glidepath control handle is connected to. Your best bet is to lower the nose and deal with the situation as best can be done.
But, in that situation, you're still better off with spoilers, because putting the spoilers back in immediately improves your sink rate. Plus spoilers don't let you get that slow in the first place.
 
Top