• Welcome aboard HomebuiltAirplanes.com, your destination for connecting with a thriving community of more than 10,000 active members, all passionate about home-built aviation. Dive into our comprehensive repository of knowledge, exchange technical insights, arrange get-togethers, and trade aircrafts/parts with like-minded enthusiasts. Unearth a wide-ranging collection of general and kit plane aviation subjects, enriched with engaging imagery, in-depth technical manuals, and rare archives.

    For a nominal fee of $99.99/year or $12.99/month, you can immerse yourself in this dynamic community and unparalleled treasure-trove of aviation knowledge.

    Embark on your journey now!

    Click Here to Become a Premium Member and Experience Homebuilt Airplanes to the Fullest!

Building Choices

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

etterre

Well-Known Member
Joined
Aug 30, 2006
Messages
313
Location
St. Louis, MO, USA
Sorry of the long post, but I'd really appreciate some advice from those who
have "been there and done that." I really want to build my own airplane for
what are probably all the usual reasons but I can't find a design that I
really like. So I'm currently pondering a one-off design for myself. :eek:
But that's a huge commitment and I'd like to be sure that my basic
assumptions are realistic. If they aren't, then I could be expending a lot
of effort for no good reason.

Here are the things I'm trying to balance:
1. Money - I don't have $10,000 USD (or more) to spend just to get started

2. My first child is due next week (and depending on how well that goes,
another one could follow in about two years or so...) But if I don't start
actively working toward my dream now, then it won't get started until my
wife and I are "empty nesters" - and I believe that I would deeply regret that
choice.

3. I don't trust most kit companies since I've read about (and seen) too many
of them go bankrupt and strand folks with partial kits (or no kit at all). The
ones I do trust (Van's, Sonex, and Zenith) don't make anything that really
appeals to me.

4. I want a "sightseeing" airplane that allows the pliot and all passengers a
good view of...well, everything - the ground below and the sky around me.
Comparable to what I imagine you would get from the OV-10 Bronco or OV-1 Mohawk.

5. I'd like to be able to use the airplane for the occasional trip with the
family and camping gear. This implies a cruise speed over 120 knots and a
cruise endurance of about 5 hours (4 + 1 for reserve)

6. I'd like to make some of those trips to backcountry strips like the ones
found in Idaho. This implies a takeoff roll of no more than 1500 feet as
well as extra performance to compensate for density altitude.

7. I want to build with composites because:
A. Fewer expensive tools to buy
B. Riveting is a rather noisy process that could alienate the family
C. Doesn't require recovering every few years like tube and fabric.
D. Holds up well over time - doesn't rot or corrode - doesn't dent easily
E. I can see myself building molds, doing layups, and obsessing about
sanding. But I can't see myself welding a fuselage together or assembling
wooden ribs for seemingly endless months.
F. Finished result just looks better to me

So I doodled on a few napkins and the picture that pops out has a 4 seat (+ bags)
fuselage like the Prescott Pusher but has twin tail booms like Vulcan's ION
(http://www.vulcanaviation.com) instead of the Prescott's T-tail. Yes, I realize
that a pusher has FOD problems but everything is a compromise. I won't subject
you folks to my lousy artistic abilities. If I was going to provide a decent
picture of it, I'd need to start putting together CAD drawings - but then I
would really get attached to the design...

So here's where I'd like some help. Designing a new airplane isn't even close
to being easy and I've made it significantly harder by trying to design
something different. But, after pondering a bit, I've noticed that there are
a few of my requirements that add just a little more functionality but drive
a lot of the difficulty. For example, if I compromise on forward/upward
visibility, then I'm probably designing an all-composite, high wing, tractor
without wing struts. If I compromise again and move away from 100% composite,
then I'm no longer designing - I'm building a BD-4

So where do you think I could simplify things? Here are the ones I've got
targeted (please add your own):

Is it realistic to think that the airplane would be usable for the "family
vacation?" How many of you have taken a mom+dad+kids trip in your own (or
a rental) airplane? How did it go? Would you do it again if you could?
Of those that haven't done it, how many would want to take a trip like that?
This is easily the highest cost assumption for me that may yield the least
benefit - maybe 1 or 2 trips a year for 10-15 years (If I'm really optimistic
on build timelines and family interest)

Any ideas on how I could reasonably compare the view from one plane to another?
Is it "safe" to assume that the forward visibility from a BD-4/Tailwind/Bearhawk
is going to be similar to a 172? Sightseeing/visibilty is a big consideration
for me. If it wasn't, then I'd probably have a set of plans ordered by now... :whistle:

Any rebuttals on my material choice? I've thought about going to some of the
SportAir workshops to "get over" my aversion to tube/fabric, but spending $$$$
to do something I don't think I'll enjoy seems downright silly.

Am I unreasonably throwing out the kit designs? The GlaStar planes could be
a good compromise fallback for me from an aesthetic and performance standpoint.
BUT the possibilty of being stuck with wings, a tail, and a bankrupt company
frightens the heck out of me. Why? At any point short of having the whole kit,
I don't necessarily have all the parts, information, or even legal license to
finish my plane. Why? Well, you never get a a real set of plans that specify
everything (I'd love to be wrong on that one) - so I don't have the information
(or perhaps even the legal right) to manufacture the things I don't have (short
of redesigning them). And now I'm stuck in a corner I don't like: I have to
accept the compromises of the original design while still doing a big chunk
of design work on my own. If I had the wad of cash to buy the whole kit
upfront, then those problems go away. So...how easy is it to find partially
completed kits? What sort of discount should I expect? Where would I look?
I've seen them on e-bay before, but I often wonder about how many tasks are
completed and if all the parts are really there...

Last one up is more about the process of design. Please poke holes here if
I've missed the point - the core problem seems similar to what I see in software
every day but I want to make sure I've got it right. I've seen it stated many
times that "if you make a change like that, you may as well re-design the
entire airplane." This is mostly because airplane design is a tightly coupled
process - each choice you make affects some other point of the design. One of
the "easy outs" I considered earlier was to buy a set of plans for a
BD-4/Tailwind/Bearhawk then dive in and analyze the structure to figure out
what kind of loads I need to design my replacement composite structure for.
After a whole bunch of "extra" work in re-design and build, I finally have a
plane built out of graphite, fiberglass, and epoxy. Here's the problem: I've
done a whole bunch of work, but I haven't really produced anything better than
the original. It's probably heavier, harder (overall) to build, and it isn't
more aerodynamically efficient. Why? Well, I carried forward all of the
compromises that the original designer made and then added some of my own on
top. For example, designer A picked airfoil B because they were using a wood
spar and needed a thickness of y to get a spar that would carry the loads. But
I, sadly enough, used a fiberglass spar of a similar physical size so that I
would still be using airfoil B, even though that means my spar is bigger than
it needs to be. And I have to do extra work to make sure that I haven't
created new point loads. And I have locked myself out of (perhaps) choosing
a different airfoil that would give me better performance while providing a
thickness that is closer to "optimal" for the construction method that I've
chosen.

Thanks for actually reading all of this.

PS - to those who think that the name or requirements might sound familiar:
Yes, I am the same etterre from the canard aviation forum. I have, however,
decided that benefits of having flaps are probably greater than the benefits
of having a canard. Sorry about that...
 
Last edited:
Back
Top