4x OT R/C Glider Ignition

I finally got the R/C ignition to work on the glider of the 4x Orbital Transport (Upscale). The booster had a CTI J285 relying on the motor time delay, which is a little bit too long. It looks like the glider was inverted or upside down initially at separation. The motor in the glider is an Apogee F10, which is an AP composite end-burner and can be difficult to ignite. There have been at least 2 previous attempts that did not work. Since there was probably some soot on the propellant I gingerly cleaned this off with a small screw driver several weeks ago. Yesterday, I put about 0.5" length of thermalite through the nozzle prior to putting in an Aerotech First Fire Jr.



There was a key chain camera on the booster looking forward. The link for the video is here. The lift-off is about 1 and 1/2 minutes into the video. A few seconds after the glider separation upon booster parachute ejection, you can hear the motor on the glider ignite. The booster parachute is large so it takes awhile to land. The booster actually landed upright, but then fell over. This can be seen on the video.

[video=youtube_share;BKi9AsStSdM]https://youtu.be/BKi9AsStSdM[/video]

There was also a key chain camera on the glider (orbiter) looking aft. The motor can be seen firing on the glider, but it is not very pronounced. I had hoped that the motor would give some air speed to glider, so that the glider would fly better, but alas the glider is just too heavy and still landed in pancake mode. There was no damage to either the booster or glider.

[video=youtube_share;6apRWL92JxI]https://youtu.be/6apRWL92JxI[/video]

Very cool! I take it you didn't get any shots of this in flight looking from the ground.

Ari.

iter said:

Very cool! I take it you didn't get any shots of this in flight looking from the ground.

Ari.

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Alex (aksrockets) told me at the UROC launch that he has a video that he took from the flight-line and will post here it here sometime this week.

Some more pictures of this model would be cool too.


Richard

I just got the video from Alex. I think the video shows that the glider is difficult to glide, probably because of the weight.

[video=youtube;C5VvLWcogeM]https://www.youtube.com/watch?v=C5VvLWcogeM[/video]

Real sorry I got lazy with the video, Bob! Hope you can get that glider working!

Alex

What is your weight of the glider and the wing area?

Some more pictures of this model would be cool too

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Richard, I've got some more pictures here at that launch.



There is some documentation on Rocket Reviews.

https://www.rocketreviews.com/scratch-4x-orbital-transport-by-bob-morstadt.html

Real sorry I got lazy with the video, Bob! Hope you can get that glider working!

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Thanks, Alex, your videos are always great. I hope I can get the glider to work, too.

What is your weight of the glider and the wing area?

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Frank, the glider is heavy weighing 2 lb 10 oz. If I count all the wing surface area, even though it is a dihedral, I get about 308 sq.in. not counting the elevons and counting the wing that is under the fuselage. I calculate 7.33 sq.in./oz. This is not counting the F-10 motor, which weighs almost 4 oz fully loaded.

I went back and checked my Double Shuttle gliders. They are about 11 oz each and the BP E-motor case is about 1 oz. I count the wings as 205 sq. in. not counting the half shell fuselage ahead of the wing. This gives 17.08 sq.in./oz. The Double Shuttle gliders glide much better than the OT orbiter.

I looked at the RocSim9 simulation for the OT to find a maximum velocity of 265 fps. The Double Shuttle maximum velocity is 194 fps.

Hi, I think your calculation is off, normally for the rc world we work on ounces per sq foot....where below 10 is a good point for gliders, most of my depron gliders are more in the 4-7 oz/sq foot range and are floaters.

Your orbital at 300 sq inches and 42 ounces gives 20 ounces per sq foot, which is pretty heavy for my preference, especially with a flat plate airfoil which it looks like it has...then add the weight of the motor. In the video it looked like what I could see, the motor burn gave it just enough speed to barely keep the nose up, and as soon as it stopped it just stalled and dropped the nose....

Your double shuttles would have a wing loading of about 8 ounces/sq foot which is pretty good.

I use stall speed at about 5*square-root of the wing loading in ounces/sq foot, so stall speed for the shuttles is 13mph and the orbital at 22mph, so you need at least 30mph to have a reasonable glide with some margin before stall.....

I think it needs a significant weight reduction....also, I'm not sure of your CG location pre and post burn, you might be really nose heavy requiring lots of up trim to keep the nose up.....I'm not sure what sort of materials it's built out of....I'm sure you could build one with other materials/components at under a pound easily.....and could get by with an E motor if you wanted to do a boost....

Where are you running your CG, for a delta wing,

Here's a pretty close approx of your wing with similar area, and a max rearward cg of 33% of mac, which for deltas is pretty close, typically around 50% of the root chord....with that heavy of a motor the cg shift is probably pretty far for that short of a model....in my dyna-soar which is a similar size, slightly bigger, with an E motor, which burns 21 grams of propellent, the cg shift is about 3/4"...yours is burning 40 grams, so your shift is probably twice as far..

https://wingcgcalc.bruder.com.br/en...p5=0&angle5=0&panelspan6=0&chord6=0&sweep6=0&

Frank

aerostadt said:

Thanks, Alex, your videos are always great. I hope I can get the glider to work, too.



Frank, the glider is heavy weighing 2 lb 10 oz. If I count all the wing surface area, even though it is a dihedral, I get about 308 sq.in. not counting the elevons and counting the wing that is under the fuselage. I calculate 7.33 sq.in./oz. This is not counting the F-10 motor, which weighs almost 4 oz fully loaded.

I went back and checked my Double Shuttle gliders. They are about 11 oz each and the BP E-motor case is about 1 oz. I count the wings as 205 sq. in. not counting the half shell fuselage ahead of the wing. This gives 17.08 sq.in./oz. The Double Shuttle gliders glide much better than the OT orbiter.

I looked at the RocSim9 simulation for the OT to find a maximum velocity of 265 fps. The Double Shuttle maximum velocity is 194 fps.

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aerostadt Thanks for the photos.

I agree with Frank's accessment. The first thing I thought when viewing Alex' vid was CG too far forward but am trying to figure out how it could pancake the landing in that configuration. Did you hand toss test the shuttle?

Cool on board vids BTW.


Richard

I just got the video from Alex. I think the video shows that the glider is difficult to glide, probably because of the weight.

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I built one of these a few years ago and haven't flown it yet. My glider weighs about the same as yours @ 2lbs. 5oz. We tried a test glide with my son and it was pretty steep. Probably 1 to 1 or less. That's with him running about fifty MPH when he released. I have aircraft that are over 20oz. wing loadings and fly very well but none are flat airfoils nor are they gliders.

I haven't flown mine because I am thinking about replacing the plywood wing with a balsa sheeted foam core to save weight. There really isn't any other place to shave weight off. R/C system, and other necessaries are fixed. I am determined to fly mine this winter come snow or high water.

I'm going to slow down the controls and crank up the Exponential. Looks pretty touchy.

I put a 32mm motor mount in the glider but have not gone any further as far as adding power. Just like to get it to glide first.

What is leading to this heavy of a weight, have you broken it down by parts?

Reasonable components: Receiver 5-9 grams, BEC, 5-9 grams, servos, 10 grams each, battery 30 grams, so rc component weight should be approx 2.5 ounces and that is conservative.
It's basically a hollow tube and cone and wing after that, and some mechanism to attach to the booster. Light tube should be about 2-3 ounces.....cone another 3-4 maybe....Even flat 3/16" balsa should be around 3 oz for a 4" by 36" sheet and your wing area is about 2 of those sheets....You should be able to easily come it at less than a pound..without doing even a non plate wing structure....

1/8" Ply should be around 5-7 oz/sq foot, so if used would account for about 12-16 ounces of weight....

Frank

At one time the glider was as light as 1.68 lbs with 1/64" ply epoxied on only one side and no electronics for in-flight ignition. (My original figures give the same as Frank's, which are 19.6 oz/sq.ft. for the latest OT glider and 8.4 oz/sq.ft. for the Double Shuttle glider). The 1.68 lb glider gives a loading 12.6 oz/sq.ft. I remember the lighter glider on some flights would have a better ability to glide, however, the wings had a bad tendency to fail on ascent (remember 265 fps or 180 mph). When I went to epoxied wings with 1/64" ply on both sides (1/2" foam core in-between) and the inflight ignition system the weight grew to about 2 lb 10 oz, which is too heavy. However, there was no longer any failed wings. (There is also the possibility of the wings failing during arc over or perhaps separation.) There is no camber (essentially flat plate) on either the OT or DS glider. I did build a second OT glider with 1/4" balsa sandwiched between 1/64" ply, but the final glider weight came in as the same as before.

I have thought of putting a 29 mm G80 in the OT glider, but I don't think that is a very good idea, because I do not have good control of the glider prior to inflight ignition. Another option is building a new glider similar to the DS glider, which works well. It does survive the ascent, but at a lower velocity (194 fps vs OT 265fps). It looks like the DS has 1/8" balsa sandwiched between 20 pound stationery paper with white glue. Another thing about the DS is that it is a half a shell. It has occurred to me that I could maybe buy a shaped foam core wing. I would need to decide how to cover the wings. I remember that the Estes AstroBlaster covered shaped foam wings with thin balsa sheet using spray adhesive.

I built one of these a few years ago and haven't flown it yet. My glider weighs about the same as yours @ 2lbs. 5oz. We tried a test glide with my son and it was pretty steep. Probably 1 to 1 or less. That's with him running about fifty MPH when he released. I have aircraft that are over 20oz. wing loadings and fly very well but none are flat airfoils nor are they gliders.

I haven't flown mine because I am thinking about replacing the plywood wing with a balsa sheeted foam core to save weight. There really isn't any other place to shave weight off. R/C system, and other necessaries are fixed. I am determined to fly mine this winter come snow or high water.

I'm going to slow down the controls and crank up the Exponential. Looks pretty touchy.

I put a 32mm motor mount in the glider but have not gone any further as far as adding power. Just like to get it to glide first.

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Joe, good luck! Let us know how your flight goes.

1/2" thick wings with no profile aren't helping, I'd dump the onboard ignition, and get a good CG location for glide with as much weight shaved as possible, maybe swap tube types, etc....Part of the problem as you say is the speed...Is there any way you could boost on a longer burn motor in the OT and reduce your speed and get by with the lighter constructed wing? Or do some sort of vacuum bagged type of wing with a foam core and light fiberglass or carbon as a skin....and try to keep the weight down around 16 -20 ounces....at that size. What tubing size and type are you using for the orbiter and where is your CG location?

Frank

My CG is at 11" behind the leading edge (front point) which is close to 25%. I have been flying R/C since 1975 and learned a long time ago that a nose heavy airplane lasts longer than a tail heavy one. I planned to start out at 25% and slowly move it back by removing nose weight until I get flight characteristics I can live with and not be too touchy in pitch.

My body tube is a standard Loc Precision 3" tube and nose cone with part of the shoulder cut off.

I also have a little reflex angle in the elevons at neutral. Boost will be at 0 degrees and then reflex added with a switch at separation. At least that's the plan. It works well on the Phoenix glider using slight down elevator on boost and then switching to zero degrees at apogee for the glide.

I think Frank is right in that the weight of the wing is the culprit but not sure how to get that down significantly without spending lots of time and money on a rocket that will spend most of its life on display (I hope).

So, 25-33% of the MAC is what you want, however for a delta, that is normally around 50% of the root chord depending on the shape etc...that's why I was asking, if you are at 25% of the root chord, that's pretty far forward...

If you look back at my example where I'm using 33% of MAC setting which is approx 50% of the root chord. https://wingcgcalc.bruder.com.br/en...p5=0&angle5=0&panelspan6=0&chord6=0&sweep6=0&

Feel free to plug in a modify the parameters at that site and see what you get. If you have access to some foam, make a chuckie glider of the approx same shape and see how it glides with different cg settings to confirm.

Frank

So, 25-33% of the MAC is what you want, however for a delta, that is normally around 50% of the root chord depending on the shape etc...that's why I was asking, if you are at 25% of the root chord, that's pretty far forward...

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No, I have my glider balanced at 25% of the MAC which is around 45% of the root chord. It is eleven inches from the front tip.

I'm still wondering where aerostadt's CG is?


Richard

My fuselage is also standard 3" LOC tubing. The nose cone is hard balsa wood from The Sandman. I have hollowed out the nose cone using a large drill, sanding and cutting.



The weight of the 2 basic components shown in the picture are 1 lb 12 oz for the air frame and 14 oz for the carriage that holds the electronics. Overall, the model is very heavy for gliding. By Frank's 10-to-1 criteria, cutting the original 2 lb 10 oz (without motor) in half would give 1 lb 5oz, which is heaver than current air frame alone.

I think if you built it from lightweight tubing, it would help, I did a quick check, 30" of loc 3" tubing and a basswood cone is 8 oz, if you used bt-80 and a pnc 80 it would be under 2 oz. Especially if you are using a sled, the tube doesn't need much strength. Also, why the sled? Just mount the components to the wing and mount the tube over the top, you can cut it out to clear them....cut a hatch in the tubing to access the battery....dump the motor tube, and onboard ingnition, just go with a glider, I think you can shave 8-10 oz that way....

frank

aerostadt said:

My fuselage is also standard 3" LOC tubing. The nose cone is hard balsa wood from The Sandman. I have hollowed out the nose cone using a large drill, sanding and cutting.



View attachment 247559

The weight of the 2 basic components shown in the picture are 1 lb 12 oz for the air frame and 14 oz for the carriage that holds the electronics. Overall, the model is very heavy for gliding. By Frank's 10-to-1 criteria, cutting the original 2 lb 10 oz (without motor) in half would give 1 lb 5oz, which is heaver than current air frame alone.

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burkefj said:

I think if you built it from lightweight tubing, it would help, I did a quick check, 30" of loc 3" tubing and a basswood cone is 8 oz, if you used bt-80 and a pnc 80 it would be under 2 oz. Especially if you are using a sled, the tube doesn't need much strength. Also, why the sled? Just mount the components to the wing and mount the tube over the top, you can cut it out to clear them....cut a hatch in the tubing to access the battery....dump the motor tube, and onboard ingnition, just go with a glider, I think you can shave 8-10 oz that way....

frank

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I get the same weight for the current 26" x 3" tube (5.6 oz) and nose cone (2.4 oz) giving a total of 8 oz. The BT-80 is a smaller diameter tube at 2.6" diameter. I might be able to shave off about 6 oz that way. I think that there is still the option of cutting the tube and nose cone down the middle as on my double shuttle. It doesn't look as good, but it saves weight. There is also the wings to think about. I went back and looked at the Lady Hawk design, which is powered by 2 D-motors. The leading edge (LE) has a standard rounded 3/8" wood spar followed some distance by some more spars and thin cross ribs. Only the front near the LE has some 1/16" balsa planking. The rest is just monokote and the wing holds up. Maybe a foam core with some 1/16" planking using spray adhesive is an option. The Estes Astroblaster uses this type of construction.

The carriage had several advantages. The components on the sleds can be moved to adjust the c.g. and the tube does not heed hatches.

For a winter project I am building a new Orbiter for the 4x OT based on a design similar to by earlier Double Shuttle. It is slightly larger than the original Double Shuttle, but a little bit smaller than the Orbiter. The wings are made from 1/8" balsa sandwiched between 20 pound stationery paper and bonded with white glue (Elmer's) on both sides. I noticed that a square of this material took about 4 oz of white glue. I tried to be careful on pressing these balsa-stationery sheets to keep them flat and I think the results turned out good.

I made one large square of material and then cut the entire underside surface except the nose cone.

Will be interesting to see how the weight winds up with this method. Are you going to go with lighter body tubing as well, maybe like the kind estes uses in their psII kits?

burkefj said:

Will be interesting to see how the weight winds up with this method. Are you going to go with lighter body tubing as well, maybe like the kind estes uses in their psII kits?

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Frank,
For this Orbiter version I am using the heavy LOC 3" diameter tubing, but it is cut in half lengthwise. Likewise, the nose cone is cut in half, so the final weight will be low.

Oh interesting, you'll probably need to move cg forward a bit due to flat plate of the forward part

Frank

aerostadt said:

Frank,
For this Orbiter version I am using the heavy LOC 3" diameter tubing, but it is cut in half lengthwise. Likewise, the nose cone is cut in half, so the final weight will be low.

View attachment 304985 View attachment 304986 View attachment 304987 View attachment 304988

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I have added the Hitec HS-55 servo's. The current weight is about 13 ounces, so compared to my earlier orbiters it will be light. I put the servo's on top, because the attachment points to the booster will be on the bottom. Also, if I fly at the salt flats, there will definitely be salt on the underside upon landing. Also, I am planning on covering the servo's with nacelles. This adds some weight, but I think it will improve the looks.

I still haven't flown mine. The reason the weight is so high on mine is that I used plywood for the wing.

I keep thinking I will rebuild it with balsa or maybe even foam board with carbon spars but just haven't gotten around to it yet. I really need to do that. New Year's Resolution?

Back around 1996, I started a 4x Orbital Transport. Did not get much past cutting out the booster parts. Still have them around somewhere.

If I were going to complete it today, I would use the lightweight 3" T300 tubing from BMS for the airframe for the glider. Nose cone would be a well hollowed out balsa cone, or a foam cone with lightweight glass on it.

I think the way to go on the wing and tail material would be to build it up out of balsa using a 1/8" sheet balsa built up core with the grain running parallel to the wing LE and sheet it both sides with 1/16 balsa with the grain running perpendicular to the wing root edges.

With the drag built in to the OT design, the glider does not have to be built from heavy LOC style tubing and plywood, as the booster is simply not going to be moving that fast.

Ought to be light enough to glide well with this approach and be more than strong enough.

Might get back to my 4x upscale one of these days, but would likely do a smaller one first, either a 2x or a 2.6x. I would air start the glider with the 18mm D2.3 at this size.