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Here are some of my collected thoughts on building plane.
General Thoughts on Construction
General thoughts on fuel. You'll note that below all of my A
list planes are 6 cylinder 250hp plus rockets. The B list
planes are <200hp 4 cylinder powered. It's all about cost - of
course we want the sexiest speed daemon to fly to the Bahamas for the
weekend but that jump in speed and power translates to 10s of
thousands of $$ in construction costs. The A list is pretty
much what I get if my pot of IPO gold still gets found - otherwise
I'm looking at reality and the B list. It is also worth noting
that these thoughts on fuel and milage apply to production aircraft
as well - the tradeoffs- are the same. Whether certified or kit
built the same rules of physics and cost apply to both. The
main difference is that you won't find many production planes at the
higher end of this performance scale due to the certification
requirements of Part 21/23 on single engine piston aircraft.
The biggest limitation is the stall speed requirement. This
forces certain limitations to wing loading and aerodynamics that
makes it hard to be as fast on the top end.
The B list planes are cheaper to fly per hour but true mileage is
largely a wash. At a simplistic level you can figure about 5gph
per pair of cylinders, a little more at the higher end of the HP
curve, a little less at the low end. So for common 4-cylinder
engines - a Lycoming O-320 at 160 hp burns 7-8gph cruise, an O-360
burns 8-9gph at cruise. For 6-cyl, a 260HP IO-520 might burn
13-16gph and a Lycoming 300HP IO-540 or a Continental 310hp IO-550
might burn 15-18gph. But your cruise speed and climb rate goes up so
your basic MPG figure stays surprisingly constant.
Only thing is for this to hold true for the larger aircraft you need
longer average trips to get to climb to higher altitudes for better
TAS cruise speeds. However - all of these planes - especially the A
list - are spectacular climbers. The Canards will always out climb
and out cruise the traditional planes due to their higher efficiency
since they don't have to counter the negative lift of the rear
stabilizer. The A list planes both climb at 1500fpm or better
initially and both have time to climb to 10k of less than 10
minutes. You also need to plan ahead so you can do a power descent
at higher speed and make back part of the energy invested in your
climb. For the Canards which are incredibly efficient gliders this
can mean having to budget 3 miles or more of descent for every 1000ft
of altitude.
On construction - "Moldless composite" construction has become very
popular. This is where you build up a composite skin around a foam
core without needing custom molds. The Velocity and the Cozy are
moldless construction. The Express is "molded" construction where
composite layers are set in one operation against an exterior mold.
But the molding is done as part of the kit fab so the user doesn't
need mold. (The "fast build" Velocity wings are actually molded
construction too). Molded construction is generally done with
vacuum
bagging which helps squeeze excess resin out of the parts and yields
lighter aircraft - but is higher tech and the bagging materials cost
some $$. Vacuum bagging isn't commonly done with moldless
construction although it can be. Some people building Velocity have
had good success doing vacuum bagging on the key structural (read big
and heavy) layups especially for the wing spars and have trimmed
20-50 pounds off their empty weight. Every pound you save in
construction is a pound in payload because regardless of design your
actual aircraft usable load is the _design_ gross weight minus the
_actual_ empty weight. Sloppy construction with excess epoxy
actually weakens parts and can add 50 pounds or more to the aircraft.
The down side of composite construction is it requires essentially
indoor building conditions. The fabrics and epoxies generally need
a working temp of 75F or better and the actual cure should be done at
85F plus for maximum strength. Also - things must be very clean -
both the air and the working surfaces. It can be done in a garage
that is clean with the doors closed and proper heat (or summer) but
it really can't be done in a barn or unheated storage area or
hanger. This can be especially challenging as the sanding finishing
required of composites produces large amounts of very fine dust.
Metal construction is a nice option. Metal planes can be built at
any temperature above about 10F (it's not good to do the sheet metal
working with the aluminum alloys used in aircraft below this although
the finished planes are fine). Metal parts don't care if they get
dirt or dust on them as long as you keep the joints clean and
minimize
dirt on the interior. The plane can be washed for painting (actually
it has to be to get the sealants off the metal) at the end - it can
get pretty dusty in the interim without pain. The most popular kits
(several thousand flying) are the Vans RV series - the ability to
build them anywhere is part of their success.
Overview of Homebuilt Process
To be written.
Sportair Workshops
In August Candy and
I are going to a SportAir workshop on "Aircraft Composite
Construction". These are sponsored by the EAA. These are a great resource -
information is available at
www.sportair.com. The Intro
course is a great survey course that covers all major construction
techniques and includes a small hands on work for metal and composite.
If you are too broke - the What's Involved Course is an evening lecture
only intro to building including regulations, etc. It's only $30. The
2-day workshops have a discount if you're an EAA member that is cost of
the EAA annual dues plus you get the other EAA benefits (their monthly
magazine is beautiful). It's buried on the website but if you register
your "spouse" for the same workshop they knock another $40-$50 off the
fee above and beyond the EAA member discount.
Favorite Kits
This has been moved to is own page on My
Kit Favorites.
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