Note that for NARAM-50, the Egg
Lofting Altitude event for D engine class.
Egg Lofting Altitude combines the challenge of flying a model containing
a Grade A Large egg (and recovering it intact), with trying to reach the
highest altitude possible.
Egg Lofting Altitude models can be staged.
If the egg is not returned or is damaged (cracked, broken, etc.), the flight
is disqualified.
You can NOT catch the egg lofter, it must be allowed to land naturally.
For
the full rules for this event, please see the Egg Lofting Altitude Rules
on the NAR web page.
Scoring - For Egg Lofting Altitude, the scoring is best
SINGLE qualified flight’s altitude (egg returned intact), of the two flights
allowed.
Design considerations - To balance the ability to fly a model containing
an egg as high as possible with the need to return it safely. Compromises of
low drag and low model weight, protecting the egg (capsule and cushioning),
and deploying a chute that is not big enough for a gentle landing versus too
big a chute which can jam inside the tube or let the model drift away
unrecovered.
There are many engine choices available for
this event. The best-flying will tend to be 18mm composite engines, such as
the D10 and D21. There is also the D13 reload, though that adds a bit of
extra mass and the cost of the reload casing will hurt if you lose the model.
Also, the higher the thrust of the engine, the stronger the model will need
to be to not shred its fins off. A model flying on a D21 needs to be a lot
stronger than one flying on a D10.
The classic old reliable way to go is to
use a D12 engine.
This event was held at the very same site
at NARAM-46 in 2004. Some of the better-flying models drifted off into the
wood. It was not very windy, simply it was an issue of models flying so high
up, and needing to land slowly enough not to break the egg, that it took them
so long to land that some of the best models drifted into the woods. So, this
may be an issue for 2008 as well.
A list of plans and kits
is included further down on this page.
General Tips for Egg Lofting Altitude
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An egg lofter with a long tapered conical shroud is OK for egg loft
altitude. The Two Minute Egg
plan is such a model, and both ASP
and QCR have similar contest
oriented kits.
A straight body-tube model with capsule on top also is competitive. Such
as an all-18mm body, or all 24mm body. QCR has kits of this type. Custom
Rockets' Elite Egg
Lofter kit is a reasonable C egg loft altitude model.
Some competitors feel the straight body type flies higher, while some
prefer shrouded bodies. Straight bodies have simplicity going for them,
while shrouded bodies have reliability in their favor due to the recovery
system storage space and room for tracking powder.
A straight body tube with a larger diameter, such as 1.3" to
1.65" diameter (BT-55, 35mm, BT-60) can be used. The model will be
draggier and usually heavier, of course, and therefore at a competitive
disadvantage. The Quest "Courier" egg lofter kit can be
used with 18mm composite D engines or on a D12 if built with a 24mm engine
mount. Some regular models you might already have can be adapted to fly as
an egg loft altitude model by replacing the nose cone with a capsule. But
they cannot be too heavy or they just will not fly safely enough with the
added weight of an egg.
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Straight tube
(Prangroc)
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Conical Shroud
(2 Minute Egg)
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Build well - A key to any altitude event is building the model
to fly straight and true. Work towards attaching all of the fins so they are
straight and parallel to the body. This should translate to a straight boost,
with minimal wobbling that would hurt the altitude.
And the faster the model boosts, the more
strongly it needs to be built, to avoid shredding the fins at high speed.
Egg Capsule - Pratt
Hobbies makes an excellent vacuformed egg capsule (the old CMR capsule).
Some companies like ASP and QCR carry that capsule. Apogee also has their own vacuformed
egg capsule.
Another capsule sometimes used is a plastic
Easter Egg, of a size that is just a little bigger than an egg. Such capsules
use two "long halves" from two 1.75" diameter Easter eggs,
rather than one plastic egg due to the short half with a flange sticking out,
as the flange limits the inside diameter too much. Easter Egg capsules that
small can be hard for the eggs to fit in and be safely cushioned, however.
"Grade A Large" eggs tend to vary significantly in diameters, so
Easter Egg capsules are somewhat risky. It's best not to risk using a
too-cramped capsule.
Padding - Use foam or some other flexible material to try
to cushion the egg so it will not get cracked. My favorite basic cushioning
is to get hold of a foam egg carton and cut out the four corner
"cups" as they fit the egg pretty well. I add other thin foam
padding as well. The egg needs to be padded enough that it can't rattle, but
don't pack it so tight that it's under pressure when loaded in the capsule.
If you are using a plastic capsule, don't bother with putting the egg inside
of a plastic bag....if the egg breaks you can just clean the capsule with
water, without any damage.
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Parachute - In Egg Lofting Altitude, the trick is to balance
using a chute size that will not land so hard that the egg might crack,
versus using a bigger chute that may let the model drift too far off to recover.
A ballpark suggestion for decently padded eggs in a light model is to use a
12" to 14" parachute. For Egg Lofting Altitude, using a
commercial type chute canopy is usually OK, you don't want to use a canopy
so thin that it rips easily.
- Andy Jackson of ASP (Aerospace Specialty Products) has
written a great
article on considering what size or type of parachutes to use in
egg lofting competition, whether for duration or altitude. It also has
tips on chute packing.
Shroud lines can be "button and carpet thread", which is what
most manufacturers use.
To avoid the lines pulling loose from the parachute under stress, the
shroud lines can be attached to run over the top of the chute as shown at
right. Cut-up band-aid pieces can make for very sticky yet flexible shroud
line tabs.
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click on thumbnail
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Shock Cords - It is useful to use a shock cord that can
actually absorb the shock of deployment, given the weight involved with egg
lofters. 1/8" elastic works very well for that purpose, but is not ideal
to attach directly to the body tube. Many competitors prefer to use a length
of 100 pound grade Kevlar cord to attach to the body tube (especially for
mounting inside), then tie the elastic shock cord to the other end of the
Kevlar cord. The 2-Minute Egg plan mentions using wire cable in a similar way
to link elastic to the model. This method was used before Kevlar came into
use for contest models, so 100 pound Kevlar can be used rather than wire
cable for the 2-Minute Egg. Unfortunately, the very hot ejection charge of a
D12 can burn a 100 pound Kevlar shock cord if it is attached within the first
3" or so of the ejection end of the engine, so for D12 models the Kevlar
cord needs to be mounted away from the heat blast or protected from the heat.
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Tracking Powder - It is highly recommended to use tracking powder
in your model. This produces a small "cloud" at ejection which
the tracking crew looks for. Without tracking powder, it is not likely your
model will get tracked.
Dry Tempera paint, or a fine powdered Fluorescent Dye, is often used for
tracking powder. Some contestants used to rely on powdered chalk, but it is
clumpy and does not really produce much of a tracking cloud for the
volume/weight of the powder. Red is a good color choice for tracking
powder, though some like to use black if there is a high overcast or hazy
"white" sky. Fellow competitors are often willing to share
tracking powder.
Here's a good way to install tracking powder. After installing wadding,
pack the parachute and shock cord into the model, and push them down into
the tube to leave room for the tracking powder in the upper part of the
tube. Use a piece of wadding or plain paper to make up a long narrow
"cup" than will easily slide inside the body tube. Press that cup
into the tube, then pour in the tracking powder to fill the cup. About
1" or so depth of powder is a good ballpark. Using tracking powder can
require greater forces to expel everything out of the body, which sometimes
results in the engine kicking out instead (however, the cup method reduces
this problem a bit compared to just dumping powder into the tube). Make
sure the engine is secured in the rocket extra-tight. Some people like to
attach the fins a bit above the bottom of the body tube so they can apply a
"collar" wrap of tape to the bottom of the tube and the engine.
This helps prevent the engine from ejecting.
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click on thumbnail
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Above: Example of a tracking powder
cloud, having ejected from a model that was stuck in its launcher.
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Engine recommendations for D
Egg Lofting Altitude
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D10-7 (light low-drag 18mm
models)
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or
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D21-7 (light low-drag
STRONG 18mm models)
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or
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D13-7 reload (light low
drag strong 18mm models)
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or
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D13-10 reload (light low
drag strong 18mm models )
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or
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D12-3 (heavy and/or draggy
model)
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or
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D12-5 (low drag lightweight
model)
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or
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D12-7 (high performance low
drag lightweight model if not too windy)
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or
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C6-0/C6-7 staged (Low drag
lightweight model if not too windy)*
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* Staging C's is a fairly high risk way to fly D Egg Lofting
Altitude, not really recommended.
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Model Plans & Kits
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Designer
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Notes
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ASP - Egg Lofter Kits (various)
& Pratt Egg Capsules
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ASP (Aerospace Specialty Products),
Andy Jackson
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Good competitive kits
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QCR - "Easter
Egg" & "Pratt” capsule Kits for 18mm & 24mm engines.
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QCR - Qualified
Competition Rockets, Ken Brown
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Good competitive kits
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C & D Egg Lofter Plans
- straight tube type
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Plans by George Gassaway
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Competitive plans for C and D power, minimal details
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Prangroc
plan straight tube type (NAR website)
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Plan by Mike Burzynski
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A very old straight body tube design, showing how plastic Easter Egg
capsules could be used. Modern-day suggestion would be to use BT-20/18mm
body tube and Pratt Egg capsules
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E Dual Egg
Lofter plan straight tube type (NAR website)
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Plan by Glenn Feveryear
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The basic 24mm body of this dual egg loft plan can be used with any
practical egg capsule for D Egg Lofting Altitude.
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2-Minute
Egg Plans shroud type (NAR website)
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Plan by George Gassaway
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Good competitive plan for C power (shroud)
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Elite Egg Lofter kit
by Custom Rockets
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Custom Rockets
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A reasonable model for C Egg Lofting Altitude
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Shecter
Rockets Egg Lofter kits (PDF list)
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Fred Shecter
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Straight tube (18mm) egg lofter kit with Easter Egg type capsule. Fins
shown seem much bigger than necessary.
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QUEST - "Courier" sport egg lofter kit
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QUEST Aerospace
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Not too competitive, but flyable on a C6-3. Available from various Quest
dealers, including Apogee
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TIPS - Selecting
Parachutes for Egg Lofting
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by Andy Jackson, on the ASP (Aerospace Specialty Products) website
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Great article on considering what size or type of parachutes to use in
egg lofting competition, whether for duration or altitude. Also tips on
chute packing.
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Last Updated 12/09/2008