Gassaway 2 Minute Egg

[JAL3]

The 2 Minute Egg is a rocket designed by George Gassaway for egglofting competitions. It is posted as a free download at the NAR site and I found it by posing a general question on TRF and following the many helpful links provided in response.

I chose this particular design because I like the look of the conical shroud, I had an idea for a modification (more on that later) and because it looked easy. The competition for which I build it is not a formal affair; its just some guys who get together for fun. Winning, while desirable, it not really my first goal. I just want to participate and, hopefully, learn something along the way.

The 2 Minute Egg can be made with a piece of cardstock, some 3/32" balsa, a 4" piece of BT20, a centering ring and an egg capsule. Additionally, you will need a parachute and shock cord. The plans can be downloaded here: https://www.nar.org/competition/plans/eggloft.html

Construction of the 2 Minute Egg began with the simple expedient of printing out the PDF file. I used 110# cardstock and a laser printer. Then it was a matter of cutting out the desired shroud. The second page of the plan provides 2 different options. One is for 1.75" diameter capsules and the other is for 1.9-2" diameter. I chose the smaller because of an idea for a modification, alos gotten from TRF.

After cutting out the shroud, I did some pre-rolling by dragging around the corner of a desk and then rolling it into a tube and setting inside my stock of BT20 while I attended to the fins.

 

[JAL3]

The plans have a cut out template for the 3 fins and instructions to use 3/32" balsa. I checked my stocks and found none of that thickness. I did have 1/16" and I planned to laminate the fins so I went with that. I cut out the template and traced the pattern onto the balsa, making sure to align the grain properly. The fins were then cut out with an X-acto guided by a steel ruler.

It doesn't usually get too cold in Texas but it was cold when I was doing this. It was just enough to make the fingers a little less sensitive and more clumsy. I drew the blade across the tip of my left index finger and managed to slice a chunk out. It was mostly skin but got a bit of meat as well. It did not hurt or bleed at first but then the blood started to dribble out and would not stop. I held a paper towel against it to staunch the flow for about a half hour and stopped work on the rocket because I had different plans on the coloring. I mixed some epoxy to fix a piece of trim platic garage cabinet and dribbled some on my desk. I clean such spill from a gallon container of ethanol I keep under my desk. Without thinking, I poked my left index finger into the grain alcohol and the pain nerves chose that moment to wake up.

When i finished knocking over furntiture and generally making an @$$ out of myself, I started sanding the fins. I can't really say I put an airfoil in them but I did round the leading edge and tapered, somewhat, the trailing edge. Each fin was then pressed down on a sheet of self adhesive label paper and the X-acto was used to trim away the excess. The fins were then flipped and the label stock applied to the other side in the same manner.

 

[JAL3]

The rocket needs a 4" length of BT20. I did not have any 4" pieces so I marked off the distance on a full length piece and then used tape to mark the circumference. The razor knife was then used to slowly score around the tube and cut it. The end was sanded down and then an Estes marking guide was used to put the 3FNC lines in place.

 

[sandman]

John, you are a rocket building machine!!

 

[JAL3]

John, you are a rocket building machine!!

Its how I relieve stress...and I have plenty to relieve.

I didn't getto work on any for about a month around Christmas and I could really tell.

Now I've got some built and I need to get them up in the air!

 

[JAL3]

I had some trouble rolling the shroud. This was due mainly to my own clumsiness and lack of facility with the origami arts. I placed a thin layer of white glue along the tab and then tried to press the sides together and get the lines aligned. I met with very little success and had to give up for the day. The following day, I placed another small amount of glue on the tab and started again from the wide end. This time, the glue set a bit faster because I had a double joint. I used a long piece of BT20 in the central cavity to press the seam together and it (mostly) lined up fine.

 

[JAL3]

The plan calls for a BT20 to BT50 centering ring to help steady the shroud on the tube. I didn't have one so I stole one from a Fliskits motor mount kit. Whe glue was used to attach it to the 4" piece of BT20. The ring was filleted and, after drying, a length of Kevlar was tied to the tube just abaft of the centering ring and anchored down with more glue.

 

[JAL3]

When the glue on the centering ring had dried, I tested fitted the BT in the shroud. It looked fairly straight so I took it out, swabbed some glue and re-installed the motor/body tube.

 

[zog139]

John

I am not sure about the newer ASP kits but the older ones from Apogee
( Lacroix ) had you use 3m double sided cellophane tape on the shroud and seal the edge with thin ca.

A couple other things that might have helped you can try next time. Take a fat dowell maybe 3/4 or 1" and roll the shroud around it putting a "curl" into the paper which will make it smooth and not create any folds or wrinkles. Watching somebody do this really helps. Our club use to have build sessions around contest events, but have slowed down recently. The other tip I would offer is to tape your pre-curled shroud down to your work table just above the seam line on both ends. Roll the shroud over and beyond the tab then align it and push down. If you dont use the tape you have to hold it long enough for the glue to grab. Either way once it is attached use your dowell again along the inside of the shoud to bear down on the seam and roll it at the same time to get a good seam the entire length.

Jim

 

[JAL3]

John

I am not sure about the newer ASP kits but the older ones from Apogee
( Lacroix ) had you use 3m double sided cellophane tape on the shroud and seal the edge with thin ca.

A couple other things that might have helped you can try next time. Take a fat dowell maybe 3/4 or 1" and roll the shroud around it putting a "curl" into the paper which will make it smooth and not create any folds or wrinkles. Watching somebody do this really helps. Our club use to have build sessions around contest events, but have slowed down recently. The other tip I would offer is to tape your pre-curled shroud down to your work table just above the seam line on both ends. Roll the shroud over and beyond the tab then align it and push down. If you dont use the tape you have to hold it long enough for the glue to grab. Either way once it is attached use your dowell again along the inside of the shoud to bear down on the seam and roll it at the same time to get a good seam the entire length.

Jim

I very much appreciate the advice. I'm sure it will come in handy.

I was thinking seriously about dousing the shroud in thin CA to strenghten it. Do you think this would be advisable?

 

[georgegassaway]

>>>>>
I was thinking seriously about dousing the shroud in thin CA to strenghten it. Do you think this would be advisable?
<<<<<

Since you said you used #110 cardstock (and not regular paper), no, it is plenty strong.

- George Gassaway

 

[Fred22]

Threads like this are why I love this place
Cheers
Fred

 

[JAL3]

>>>>>
I was thinking seriously about dousing the shroud in thin CA to strenghten it. Do you think this would be advisable?
<<<<<

Since you said you used #110 cardstock (and not regular paper), no, it is plenty strong.

- George Gassaway

Thanks!

That stuff gets me in trouble each and every time.

 

[JAL3]

THe fins were place with a double glue joint of Elmer's yellow. After they had dried, the sides were filleted with white glue.

 

[JAL3]

I figured I was ready to start finishing. I know that many contest rockets remain unpainted to save on weight but I wanted to paint mine. First, because I think it looks better and second because my contests aren't all that serious anyway.

I wanted to keep in the "egg" theme so I chose a yellow that was already open. I began spraying light coats. The printing from the shroud was still showing through but I figured 2 more coats should take take of that. That's when I noticed that I had not installed the launch lug.

 

[JAL3]

After the paint had a day to dry, I took the rocket back to the bench and cut two pieces of 1/8" lug. I used a piece of rod to find a place on one fin where the lug would just clear the upper end of the shroud and then used a razor knife to scrape the paint away from the fin there. The lower lug was then glued in place with white glue.

 

[JAL3]

I looked around for a piece of scrap balsa with the grain running in the right direction, perpendicular to the lug, and found one which I trimmed to the length of the upper lug. I purposely left it to long so that the correct length could be cut when the glue on the lower lug was dry and it could handle a rod for alignment. The upper lug was glued onto the standoff.

 

[powderburner]

I used a long piece of BT20 in the central cavity to press the seam together and it (mostly) lined up fine.

Another way to do this is to use a piece of 5/8 inch wooden dowel, sized to fit through the BT20 end of the finished shroud (try to select one that is actually round, and smooth). If you are rolling a big enough shroud you can also use scrap lengths of metal electrical conduit.
Roll and press on top of a thin (like 1/4 inch thick) layer of stiff foam for better results.

 

[JAL3]

Another way to do this is to use a piece of 5/8 inch wooden dowel, sized to fit through the BT20 end of the finished shroud (try to select one that is actually round, and smooth). If you are rolling a big enough shroud you can also use scrap lengths of metal electrical conduit.
Roll and press on top of a thin (like 1/4 inch thick) layer of stiff foam for better results.

Thanks for the tip.

Not long after doing the above, I went out and got a mess of dowels in various sizes. I had been threatening to do that for a long time and had finally gotten fed up enough to do it.

THe foam is a new idea though. Do you think the rubber, self healing hobby mat would be suitable?

 

[powderburner]

I don't know how 'hard' your rubber mat is---sounds like it might not have much give, if it's a cutting mat.

I used a piece of soft foam for a while because it was cheap (free; packing material for a stereo) and it worked OK. When I came across a piece of stiffer foam sheet (higher density, but you can still pinch it easily between your fingers) I traded up.

If you have to work a piece of cardstock into the shape of a conic, hold one end of your roller/dowel in place (at the center of the conic pattern) and slide/roll the other end up and down across the cardstock. The foam backing will gently bend the cardstock to fit against the curve of the roller and usually gets you a better bend, without wrinkles. The thicker the foam and the harder you push down, the faster the cardstock bends (but the more chance you have of getting wrinkles). I like to use a piece of foam about 1/4 or 3/8 inch thick.

But do give your rubber mat a try on a cardstock test-piece, and let us know if that works too?

 

[JAL3]

I don't know how 'hard' your rubber mat is---sounds like it might not have much give, if it's a cutting mat.

I used a piece of soft foam for a while because it was cheap (free; packing material for a stereo) and it worked OK. When I came across a piece of stiffer foam sheet (higher density, but you can still pinch it easily between your fingers) I traded up.

If you have to work a piece of cardstock into the shape of a conic, hold one end of your roller/dowel in place (at the center of the conic pattern) and slide/roll the other end up and down across the cardstock. The foam backing will gently bend the cardstock to fit against the curve of the roller and usually gets you a better bend, without wrinkles. The thicker the foam and the harder you push down, the faster the cardstock bends (but the more chance you have of getting wrinkles). I like to use a piece of foam about 1/4 or 3/8 inch thick.

But do give your rubber mat a try on a cardstock test-piece, and let us know if that works too?

If my wife could read this, she would say you have given me an excellenct excuse for unburrying my mat.

The explanation you gave makes sense and I want to try it.

THanks,

 

[CharlaineC]

I use a corkboard for working with paper models. cant wait to see this finished i just downloaded it so i could build her.

 

[Pat_B]

I've had good luck rolling the dowel on top of the shroud while it sat on my thigh. Sounds funny, but works just fine.

 

[JAL3]

I've had good luck rolling the dowel on top of the shroud while it sat on my thigh. Sounds funny, but works just fine.

It makes sense to me now that I understand what is supposed to be going on. Originally, I was having a hard time picturing it.

 

[JAL3]

The lower lug got to dry overnight and then I used a short length of rod to line up the upper one. I made a mark on the standoff to slice it a bit longer than the right length and then used sandpaper to sand in the contour of the cone. I then marked the shroud for the proper location, scraped off the psint and installed the upper lug with a double glue joint.

 

[Pat_B]

Looking good.

Here's the advanced thigh roller 2000.

 

[JAL3]

Looking good.

Here's the advanced thigh roller 2000.

My thighs would be considerably larger. Probably more cushioning as well.

 

[georgegassaway]

Attached is a GIF for a preview, and four individual PDF's of the Two Minute Egg Shroud.

The shroud was drawn for a relatively large Easter Egg capsule. One version has some extra arcs included, so if you are using a smaller capsule, you can use those to help trim the top of the shroud to fit the capsule.

Two versions have the name “Two Minute Egg” on them.

One is blank.

And one has the NAR logo.

- George Gassaway



View attachment TwoMinuteEggShroud-arcs.pdf

View attachment TwoMinuteEggShroud-NoArcs.pdf

View attachment TwoMinuteEggShroud-NAR.pdf

View attachment TwoMinuteEggShroud-blank.pdf

 

[JAL3]

Attached is a GIF for a preview, and four individual PDF's of the Two Minute Egg Shroud.

The shroud was drawn for a relatively large Easter Egg capsule. One version has some extra arcs included, so if you are using a smaller capsule, you can use those to help trim the top of the shroud to fit the capsule.

Two versions have the name “Two Minute Egg” on them.

One is blank.

And one has the NAR logo.

- George Gassaway

Those look nice!

It almost makes me want to start over.
If I ever do some serious competition, I will start over.

THanks!

 

[JAL3]

After the lugs had an opportunity to dry, they were filleted with white glue and allowed to dry some more. The 2 Minute Egg was then taken back to the booth for a final application of yellow paint. It actually took 2 more light coats to cover the printing.