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Eggloft Altitude
Note that for NARAM-46, the Eggloft Altitude event for A Division is C
engine class, while for B, C, and Team divisions it is D engine class.
Eggloft 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.
Eggloft 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 egglofter, it must be allowed to land naturally.
For
the full rules for this event, please see the Eggloft Altitude Rules
on the NAR web page.
Scoring -
For Eggloft Altitude, the scoring is best SINGLE qualified flight altitude,
returned, of two flights allowed.
Design considerations - &endash; 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.
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An egglofter with a long tapered conical shroud is
OK for eggloft altitude. The Two
Minute Egg plan is such a model, and both ASP and QCR have similar contest
oriented kits. A straight body-tubed model with capsule on top also
is competitive. Such as an all-18mm body for C Eggloft, or all 24mm body for
D Eggloft. QCR
has kits of this type. Custom Rockets' Elite Egglofter kit
is a reasonable C eggloft 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" egglofter kit
can be used for C Eggloft, also for "D" eggloft if built with a 24mm
engine mount. Some regular models you might already have can be adapted to
fly as an eggloft 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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A list of plans and kits is
included further down on this page.
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.
Egg Capsule
- Pratt Hobbies makes an excellent
vac-formed egg capsule (the old CMR capsule). Some companies like ASP and QCR carry that capsule. Apogee also has their own
vac-formed 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 Eggloft 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 eggloft Altitude, using a commercial type chute canopy is
usually OK, you don't want to use a canopy so thin that it rips easily.
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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Shock Cords
- It is useful to use a shock cord that can actually absorb the shock of
deployment , given the weight involved with egglofters. 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, are 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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Engine
recommendations for C Eggloft Altitude (A Division): |
C6-3 (somewhat
heavy or draggy models) |
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or |
C6-5 (low drag
light model) |
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or |
C6-7 (high
performance low drag light model, if not too windy) |
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Engine recommendations
for D Eggloft Altitude (B/C/T Div's): |
D12-5 (low drag
lightweight model) |
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or |
D12-7 (high
performance low drag lightweight model if not too windy) |
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or |
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 Eggloft Altitude, not really recommended. |
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Model Plans & Kits |
Designer |
Notes |
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ASP
Rocketry - Egglofter Kits (various) & Pratt Egg Capsules |
ASP
Rocketry, Andy Jackson |
Good competitive kits |
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QCR
- "Easter Egg" & "Pratt " capsule Kits for
18mm & 24mm engines. |
QCR
- Qualified Competition Rockets, Ken Brown |
Good competitive kits |
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C
& D Egglofter Plans - straight tube type |
Plans by George Gassaway |
Competitive plans for C and D power, minimal details |
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Prangroc
plan straight tube type (NAR website) |
Plan by Mike Burzynski |
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 Egglofter plan straight tube type (NAR website) |
Plan by Glenn Feveryear |
The basic 24mm body of this dual eggloft plan can be
used with any practical egg capsule for D single Eggloft altitude. |
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2-Minute
Egg Plans shroud type (NAR website) |
Plan by George Gassaway |
Good competitive plan for C power (shroud) |
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Elite
Egglofter kit by Custom Rockets |
A reasonable model for C Eggloft Altitude |
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Shecter
Rockets Egglofter kits (PDF list) |
Fred Shecter |
Straight tube (18mm) egglofter kit with Easter Egg
type capsule. Fins shown seem much bigger than necessary. |
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QUEST - "Courier" sport egglofter
kit |
QUEST - Model
Aerospace Company |
Not too competitive, but flyable on a C6-3.
Available from various Quest dealers, including Apogee |
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by Andy Jackson, on the ASP Rocketry website |
Great article on considering what size or type of
parachutes to use in egglofting competition, whether for duration or
altitude. Also tips on chute packing. |
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Last
Updated 4/18/2004