Laserarts Majestic Modifications??

[TJTucson]

I just sealed the deal on a almost completed Majestic. "Got an offer I could'nt refuse" :D I've been searching for modifications that should be done on the kit before completion. I could not find a build thread nor much information on structural modifications. My intention is to use hi-start and winch launch with this bird. So can you guys make recommendations?!! :o

Here's what I know so far. I need to complete the spoilers. Apparently he had no intentions for spoilers and simply "blocked" in everything needed here. So I will be cutting in spoilers and the mechanical links to make them operate properly.

Need to cover the wings, so all I have now is a skeleton to work with. I'm assuming I need to add carbon or something to strenthen the wing for winch launching.

Once I actually get my hot little hands on it, I'll post some pictures. I would just like to start thinking about how to complete this project.

Oh and the last thing. :eek: I've never built nor taken over building a kit like this one. My building has been with EPP, fiberglass, sheeted wings and other foam methods. So this should be FUN!!

Please any and all comments / suggestions / help / pictures / thoughts (coherent or otherwise) / ideas / drinking suggestions ... ooppps ... well you get the picture .... ARE WELCOME!! :D

Tracy

[fly1milehi]

Tracey I would start with emailing the guys at laser arts. (http://www.laserartco.com/) Since I have not built a majestic or even seen the plans I couldnt say how to make your changes. Photos of the plans and the plane will shed a lot of light so Ill look for them on here.

Im sure it will be possible to add the spoilers back into the wings. You might have to use an individual servo on each side though depending on how its built already.

Covering should be easy enough with any of the iron on heat shrinking materials like Monokote, or Ultrakote. If the fuselage is composite plan on painting, if its built up you can cover it with the monokote as well or prime and sand and paint it.

Sounds fun I know the Majestics are good flying airplanes! Have fun
Greg

[shaneyee]

Join the Allegro Lite group at Yahoo Groups. In the files section there is a list of modifications suggested by Dr Mark Drela.

Shane

Oh... might as well get it for you....here it is.



Recommended Modifications to Laser-Arts Majestic

All mods are roughly independent, so only a partial
mod list can be selected from the list below.

Mark Drela 14 Aug 01 (last modified 2 Nov 01)



================================
Wing layout modifications

Original wing layout
# span chord alpha z
0. 10.0 0.0 0.0
24.75 10.0 0.0 0.0
42.0 8.5 0.0 2.0
54.0 6.0 0.0 6.7

Modified wing layout
# span chord alpha z
0. 10.0 0.0 0.0
24.75 10.0 0.0 0.0
42.0 8.5 -1.0 3.0
54.0 6.0 -1.0 7.5 | suggested 1-bay extension with
56.0 4.5 -1.0 8.25 | curved LE a'la Allegro-Lite

where z is the height of the dihedralled-wing sections above the table

Mid panel now has 1 degree washout twist (TE at 8.5" chord raised by 0.15"),
while center and tip panels are still flat.
- improves tip stall margin (stock Majestic is prone to tip stall during slow circling)
- reduces CDi by 2% at low speeds
- little adverse impact on penetration capability

Effective dihedral has been increased from 8.3 to 10.2 degrees.
- improves roll response
- reduces the sideslip needed to hold a steady turn (and hence reduces drag)

More dihedral burden is now carried by mid panels.
- improves tip panel stall margin when in steady sideslip in turn

Tip panels extended by 2" or more, with curved (swept back) leading edge
like that on the Allegro-Lite.
- reduces CDi by additional 8% on top of washout's reduction
- cleans up tip flow during steady sideslip in turn


In slow, tight thermal flying, the modified wing is expected to be
more maneuverable, more docile, and give a 5-7% sink rate reduction.

If the wingtip extension is deemed to be too much trouble, then just
round off the last rib bay LE like on the Allegro-Lite. The stock
end rib is not used in this case.

--------------------------
Note (29 Sep 01):
John Hayes has recently added the 1 deg washout to his otherwise
stock Majestic, using a heat gun. He reports a major improvement
in tight circling behavior -- the glider no longer tends to fall off
onto the inside wing.
--------------------------

=================================
Tail layout modifications

Original tail layout
# span chord alpha z
0.0 7.5 0.0 0.0
13.0 4.5 0.0 8.3

Modified tail layout
# span chord alpha z
0.0 7.5 0.0 0.0
17.0 4.5 0.0 12.0


A 4" extension is added to the tip of each V-tail half,
and the tail V-dihedral has been increased from 40 to 45 degrees.

- Effective horizontal tail volume is increased from 0.40 to 0.44
+ CG location can be moved back slightly from recommended position

- Effective vertical tail volume is increased from 0.018 to 0.028
+ Yaw damping rate will increase by about 60%
+ Rudder roll power will increase by about 90%
(60% more rudder yaw power together with 22% more dihedral)

A simple way to implement this is to increase the rib spacing
to 2.4", and extend the spanwise wood via splices or just replace it.

=================================
Wing airfoil modifications

The SA7038 airfoil is somewhat overcambered for this glider.
It penetrates OK, but not as well as it could with a lower
camber airfoil. One of two modified airfoils is suggested:

SA7038 mod 6
SA7038 mod 7

These differ in the severity of the LE upsweep modification.
Both airfoils have the same TE modification.
Specifically:

a) The bottom LE upsweep is increased slightly (mod 6)
or significantly (mod 7).
b) On both modified airfoils, the slight undercamber of the SA7038
is flattened by removing the rear 5% of the chord, and straightening
the downward-curved bottom surface to regain the sharp TE. This is
simple to do with the Majestic's rib/TE structure. The airfoil is now
flat behind the spar which should simplify construction and covering
somewhat. The aspect ratio has also been increased by about 5%.

Mods a) and b) are cumulative, and only one of these
can be implemented for a partial improvement.


The modified airfoils are quite similar to the MH32, but a bit thicker.
Compared to the stock SA7038, at 50 mph they will increase L/D by
30% or 40% (mod 6 or mod 7), dramatically improving penetration.
Float and winching performance will be only slightly degraded,
but this can be easily more than compensated with a lower flying weight.

A lower weight is highly desirable to take best advantage of the
new airfoils. Consider using light radio gear and a carbon tube boom
to eliminate any nose weight. The elevator is unnecessarily beefy
at the tip. As you go out, use larger lightening holes than those
shown on the plan. Move the elevator hinge to the bottom and
shorten the horns by 1/4".


=================================
Structural modifications

As minimum, beef up the spar. My numbers indicate that to
make it winchproof it wants 0.040" carbon on top, and 0.030"
or 0.020" carbon on the bottom sparcaps at the wing center.
These can taper in thickness outboard. CST's or ACP's
tapered carbon would work well. Wrap this spar near the
end of the joiner rod and at the root rib to prevent it
from bursting apart at these point-load locations. The
shear web wants to be at least 1/4" total thickness of
10 lb balsa in the center, this thickness tapering roughly
linearly outboard. With the specified carbon strips,
the spruce caps are largely superfluous, and could be replaced
by hard balsa. The sparcap carry-though method which is used
on the outer dihedral break of the Allegro-Lite could be used
for both breaks of the Majestic. This is easy to install and
vastly lighter than a ply joiner.

Minimizing yaw inertia should be the #1 priority
for getting the best turn handling possible.
The wing structure looks kinda beefy towards the tips
which doesn't help. I think you can progressively narrow
the TE as you go out (lengthen the capstrips to reach it).
A 3/4" wide TE should be fine at the tip. Narrow the outer
capstrips, maybe down to 1/8" in the tip panels.
Use the lightest sheeting possible for the tips. The extreme
outboard spar can be whittled down. The beefy end rib can be
replaced by the one-bay tip extension with a curved leading edge
as described above, or just installing the curved LE in the last
rib bay. Grams count at the wingtips!

[allanp]

As a former Majestic owner the first thing I'd do is to replace the entire boom. In a moderate to agressive dive there is so much flex in the boom that up elevator will not bring it out. As you add up elevator the boom will flex even more causing more pitch over. To recover you must give it full down and perform an outside loop,quite exciting ! The stock boom on mine was "micarta" painted to look like carbon fiber. Secondly,extending the stabs will force you to add another 2-3 ounces to the nose,mine had most of the "Mods" incorporated and ended up being quite a "lead sled"
Allan Parsons
Orlando Buzzards

[sblckwd]

When you do the spoilers there is no need for the complicated linkage. Simply mount a small servo (I use 55's) so the arm will lift the spoiler panel up. Use a 1/8" rare earth magnet at each aft corner to hold the panel closed (glue a small square of thin metal stock to the spoiler panel corners for the magnet to act on. I use metal feeler guage.) You will have to shim the servo so it sits higher in the wing and put a small balsa shim on the spoiler paner for the servo arm to push against. I hinge the front of the panel with packing tape.
Replacing the tailboom with one from tailboom.com really helps. Don't know if Rick still has any. The majestic boom is kinda wimpy and lets the tail whip around a bit.
On my first wing I did the carbon spar caps but on the second one I just wrapped the spar with Kevlar thread. But I only launch from a (very strong) Hi-Start. Bet if you stayed away from full pedal winch launchs and kept the zooms at the top smooth you'd be ok.
It's a heavy ship once all the lead is in the nose but way fun to fly and stays up quite well.

[TJTucson]

THANKS GUYS!! ;)

This is a big help. Will post some pictures this weekend. Hopefully this will spur some more ideas on mods needed.

:D Tracy