Scratch Swarm

Scratch - Swarm {Scratch}

Contributed by Chris Taylor Jr.

Manufacturer: Scratch
Style: Saucer
theswarm.gif (7296 bytes)
Welcome to the SWARM !!!

The Swarm Consists of a small fleet of different scale Flying Saucers (4 Total) This Entry is just for the High Powered Specimen :-)

Mega saucer

This is the Ultimate saucer !

2 Foot in diameter and made to be lofted on H55 engines and if built carefully on an H128.
It has a Monster Smoke vacuum effect (See pictures) and can be flown on engines as small as F20 and F50 (Although under CAREFUL conditions)

Dia1=38* Dia2=150
Length=110

Dia1=150 Dia2=300
Length=110

BT=250/29

Plate=300/38*

*Standard 29mm MMT has Outside diameter of 38mm Adjust this if yours is different

Above is the VCP Vital Stats. All Dim Specs are in mm Plate Dia= Diameter of the Bottom Plate/Diameter of MMT Hole, BT= length and diameter of body tube (XXmm/XXmm) Dia1, Dia2, Length = VCP data to enter for printing the shrouds which you would assemble and past to appropriate sized poster board Except 18mm saucer and NSS in which case you can use the printed and assembled paper shrouds if you wanted to save weight. The Mega Saucer MUSTuse thin Poster board.

CA is advised for all models Except Mega Saucer where 20 minute or better epoxy is suggested.

Mega Saucer:

This may be my Level 1 Cert rocket if I do not finish my Special project in time for Naram :-)

Assembly is a little more involved than a normal saucer but still easy and straightforward. Print out/Cut Out/Glue together the sections that VCP prints using the data above. Transfer this to Thin Poster board. One large sheet and one regular sheet. To make the same saucer the Large sheet is Silver and the Normal Sheet is Gold (dim's later But basically the biggest one they have (I figure at least 4x3 feet) ) Cut out and assemble.

Use this to make the Six Ribs for the inside of the saucer
mega1.gif (4394 bytes)
The Ribs are made of paper Backed Foam board. Use CA to tack in place Radially (3 fins like then the other 3 between those 3 for six total) then get the joints good with the 20 minute or better epoxy. Now this next step is very important

Very Important Step Follows !!!!

The Six Ribs must be evenly spaced to privet erratic flights. Although at the minimum safe distance for an H flight even it were to veer towage the crowd it would be unlikely to reach them On smaller distances flying with F or G engines it could reach the spectators. if the distance between each rib is not the same when the skin flexes from the boost speed it will not flex evenly causing differing amounts if drag or even vectoring on the uneven side. It is not so critical that if you are off by half and inch it will crash and burn But if you have a good eye and it looks ok then that is fine. Only gross errors will cause problems.

If you want you can add braces in-between each brace abut 75% out from the center Just make sure it comes in contact with the outer shroud or it will have no effect. But Personally I like the aerodynamic deformation it undergoes at speed. It looks cool and is actually more stable like that (increases the shroud angle)

Next Attach the Upper shroud and epoxy good from inside. Be sure to leave an Open hole large enough to fit a 1/4" launch lug! For the larger lower shroud CA on one side of each rib OR white glue is more than sufficient since Aerodynamics Hold this together not the glue. Once Dry make another upper shroud except let it extend a little farther past the edge of the printout for the outside diameter (make it neat and even!!!) epoxy the area just above the upper shroud and BT and epoxy the inside outer diameter edge of the second upper shroud and slide this onto the Saucer so that is overlap the original joint and mates smoothly with the silver shroud (mostly for neatness and show but it makes a big difference in looks!

Now cut off the excess Body tube to make it 1/4 past the top of the second shroud.

The Bottom Plate is next. Before you glue this into place install a Full length 1/4" launch lug. and make sure there is a hole for it in the bottom plate. What I did was to take another piece of paper back foam board and using a string and pin make a 2 foot diameter circle. Cut out the motor mount and then proceed to remove the paper backing from both sides (saves a tremendous amount of weight) Epoxy this into place (Ca will now eat it without the paper backing. I then covered this in Thin golf foil wrapping paper type stuff (Golf foil car stock is again heavy and strength in this component is not relevant since the foam takes care of that.

Note the flights below are without a bottom plate or internal cross ribs just to show how strong and stable the design is!

Recommended Engines: F20, F50, H55 (anything else in-between will likely work But I have only flown it on the 2 F's and designed it for the H. usually Longer Burn is better for altitude, Sound and Smoke effects etc.. Letter's in the 50 range are best (F50 - G40 - H55 would likely produce some cool flights. The F20 was a little tiny underpowered but the entire flight smoke effects are incredible (see pics) I friction fit the motor in place with tape block on nozzle end. retention is not important since there is nothing to eject. BUT the thrust ring IS important!! I do not need ejection so I dump out the BP and use it for my ejection charge challenged D12's :-)

Notice I have not spoken about a recovery system. That is because there is none. The saucer flips over and descends featherweight like any other saucer. It comes down so soft that YES I would not mind standing under it and having it land on my head :-) I flew it in front of my entire club and the slow decent rate was scarily eerie :-) The decent rate is about half that (Eyeballing) of most of the successful cert flights I have seen. On one of the flights this Saturday the saucer landed less than 3 feet from the pad :-) (see pics below for entire flight sequence.) The delay was over 6 seconds which was very cool for it had the cool smoke effects all the way to the ground (No Ejections charge so no danger :-)

Some have worried that the rocket has SOooo much drag that the motor and mount might fly through the rocket. Although this is NOT possible (ask anyone who has held this and they will tell you) to belay these fears I will permanently install a small 9" nylon chute attached to the MMT with 4 separate lines of Kevlar® so that IF the MMT flies free of the saucer it will take the chute with it and this will allow the chute to open keeping the errant MMT with burning motor in check. Nice show no danger. The Chute will not deploy under normal conditions. I still feel this is not needed but it makes others feel better and does not effect performance or fun so why not I say :-)

Built properly this rocket has strength that far exceeds its apparent mass. Remember that those ribs are Epoxied to the MMT full length !! that is a Joint 18 times stronger than most any cert rocket. 3 times for each rid and 6 ribs. IT is not going anywhere. (I tend to overbuild :-)

Also to note what I meant by vectoring. Note the first launch picture. See that flattened panel that is slightly more flattened than the rest of the panels?? Well you guessed it that is the direction it arched. (there was NO wind this day as apparent with the landing location :-) can we say spot landing champ :-)

After Thoughts:

I Later flew this on an F20 in much higher winds and it was NOT pretty It veered horizontal almost immediately and although it landed FAR from anyone (right back on top of the pad, literally) the RSO was justifiably not impressed. Again the design is harmless even when all goes wrong since it can never REACH people. Max Altitude on the even the F50 was about 60 feet.

If you plan to fly on lighter motors Make sure there is NO wind. As an after thought I may gut the 29mm mount for a 38mm mount and fly on an H73 which I think would be a PERFECT mix of slow enough burn to get some altitude BUT enough of a kick to make sure weather cocking is not a problem.

This flight above was simply too cool ! Not only did it Light up that shroud BUT the shroud left open (which it may remain just for the effect) acted as a megaphone amplifying the throaty roar of that Econojet!

Expansion effect of the wide base was just too cool as well. This is just a plane waste of a motor but SUCH a FUN waste of a motor :-)

Adding some batteries and LED's and a strobe would make for a very neat night time flyer.

If you build this saucer please let me know and send some pics! I love to see other people enjoying my designs. It makes me feel good, and useful :-) megasaucer@nerys.com

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