Glider front MOTOR eject feasible?

[Rktman]

Working on an idea for a concept BG glider that needs to eject its motor to dump weight, but the problem is that it would be risky to rear-eject it. Doing so could shear off the tail section (it's a triangular "hoop"-type glider). It's a tractor-motor type setup, so the 3 pylons are 1.9" tall to center them between its "wings".

So the question is whether something like the sketch below would work? The thought is that the ejection charge would sever the anchor thread and expel the nose cone, and the shock cord would pull the motor tube and motor out the front. Feasible? Would the ejection charge & sudden deceleration snap the pylons (two of which are 1/16" balsa, the third 1/8")?

I know it would put it at risk of a Red Baron, but better that than destroying the tail section.

 

[kjohnson]

I don't think you'd have enough momentum from the node ejecting to pull out the motor mount. Maybe adding a CR glued to the back of the tube, and moving the aft CR forward a bit and adding a spring to the motor mount might shoot the mount forward and out of the way of your hoop wings.

 

[Rktman]

I don't think you'd have enough momentum from the node ejecting to pull out the motor mount. Maybe adding a CR glued to the back of the tube, and moving the aft CR forward a bit and adding a spring to the motor mount might shoot the mount forward and out of the way of your hoop wings.

I like the idea of the spring as added insurance. I'd also sand the CRs for a loose fit to ensure it slides easily.

 

[BABAR]

Okay, following is probably Bat-crap crazy, but we'll run it up the flag.

My understanding is you want to drop as much nose weight as possible. Your current configuration is NON-minimum diameter which seems a bit inefficient.

Here's my play:

Minimum diameter tube, longer than yours to accommodate a streamer IN FRONT OF rather than around the motor.

There is a "cut" in the tube, the rear section is mounted to the pylon, the front section is completely loose (we'll get to the attachment in a moment.)

The motor is friction fitted into the front tube, with a significant portion sticking out the back which will slide into the FRONT of the rear tube.

The rear tube has a posterior motor block, although I doubt the motor would kick out. This can easily be made with a 1/8" cut tube, with a segment out. Will recess the motor less than 1/2 diameter to keep away from Uncle Krushnic.

There are two holes in the forward tube which will be just in FRONT of the motor. Using a #8 2.25mm Crochet Hook (doesn't have to be exact, but I find it fits well through a "hole punch" hole and grabs rubber bands well, a rubber band will cross this area to hold both motor in place and hold tube onto back tube.

Not pictured is a forward motor block on the forward tube to perfectly position the motor so just enough sticks out that the rear of the motor will slide into the rear tube exactly to the depth of the rear motor block, so the forward and rear tubes come into contact.

Okay, load up.

Friction fit the motor into the forward tube. If you are insecure about "securing" the motor with friction fit, you can probably add an extra external tape and still be able to slide the rear of the motor in place.

Load the wadding and chute and nose cone into the pod.

Okay, slide the motor into the rear tube.

Now, us the crochet hook to pull a number 16 rubber band through the holes, run both loops around the rear tube. I have attached a video of how I do it for my helis and air brakers.

Now, activation.

Launch rocket.

Ejection fires, it burns the rubber band. The front tube is now loose.

In addition, the nose and chute or streamer are ejected.

Between either the kinetic energy of the nose cone ejection Or the streamer or chute drag, the tube is going to be pulled off the glider.

So there you have it. Minimum diameter, a little longer but likely similar or less weight than planned non-min diameter, and you nearly completely dump not only the nose cone and motor (mount) but most of the tube.

https://www.rocketryforum.com/threads/“tubeless”-video-how-to-motor-mount-rubber-band-helicopter-and-airbrake-recover-method.160118/#post-2014334





https://www.rocketryforum.com/threads/%E2%80%9Ctubeless%E2%80%9D-video-how-to-motor-mount-rubber-band-helicopter-and-airbrake-recover-method.160118/#post-2014334

 

[Rktman]

Okay, following is probably Bat-crap crazy, but we'll run it up the flag.

My understanding is you want to drop as much nose weight as possible. Your current configuration is NON-minimum diameter which seems a bit inefficient.

Here's my play:

Minimum diameter tube, longer than yours to accommodate a streamer IN FRONT OF rather than around the motor.

There is a "cut" in the tube, the rear section is mounted to the pylon, the front section is completely loose (we'll get to the attachment in a moment.)

The motor is friction fitted into the front tube, with a significant portion sticking out the back which will slide into the FRONT of the rear tube.

The rear tube has a posterior motor block, although I doubt the motor would kick out. This can easily be made with a 1/8" cut tube, with a segment out. Will recess the motor less than 1/2 diameter to keep away from Uncle Krushnic.

There are two holes in the forward tube which will be just in FRONT of the motor. Using a #8 2.25mm Crochet Hook (doesn't have to be exact, but I find it fits well through a "hole punch" hole and grabs rubber bands well, a rubber band will cross this area to hold both motor in place and hold tube onto back tube.

Not pictured is a forward motor block on the forward tube to perfectly position the motor so just enough sticks out that the rear of the motor will slide into the rear tube exactly to the depth of the rear motor block, so the forward and rear tubes come into contact.

Okay, load up.

Friction fit the motor into the forward tube. If you are insecure about "securing" the motor with friction fit, you can probably add an extra external tape and still be able to slide the rear of the motor in place.

Load the wadding and chute and nose cone into the pod.

Okay, slide the motor into the rear tube.

Now, us the crochet hook to pull a number 16 rubber band through the holes, run both loops around the rear tube. I have attached a video of how I do it for my helis and air brakers.

Now, activation.

Launch rocket.

Ejection fires, it burns the rubber band. The front tube is now loose.

In addition, the nose and chute or streamer are ejected.

Between either the kinetic energy of the nose cone ejection Or the streamer or chute drag, the tube is going to be pulled off the glider.

So there you have it. Minimum diameter, a little longer put likely similar or less weight than planned non-min diameter, and you nearly completely dump not only the nose cone and motor (mount) but most of the tube.

https://www.rocketryforum.com/threads/“tubeless”-video-how-to-motor-mount-rubber-band-helicopter-and-airbrake-recover-method.160118/#post-2014334


View attachment 598400


https://wView attachment 598400ww.rocketryforum.com/threads/%E2%80%9Ctubeless%E2%80%9D-video-how-to-motor-mount-rubber-band-helicopter-and-airbrake-recover-method.160118/#post-2014334

I like how your mind works. This much simpler and quite elegant solution totally hadn't occurred to me. Seems I was overthinking/over-engineering the design. I am absolutely going to go with this!

 

[BABAR]

Clarification to above.

While the rubber band WOULD function as a motor block, without support it likely would “dig” into the body tube.

In this case , a real BT-5 motor block or a sturdy scratch built one may be advisable.

This will go in appropriate position to leave enough motor out the back to fit perfectly into the rear tube, seated against the rear tube’s REAR end motor block (which can be wimpy single layer body tube.)

The HOLES in the forward tube will be just IN FRONT of (and in fact, maybe should just slightly overlap) the front edge of the front tube motor block. This should still give you plenty of room for your crochet hook, but will have the band pulling in the MOTOR BLOCK, less likely to dig into the outer body tube.

 

[Rktman]

Clarification to above.

While the rubber band WOULD function as a motor block, without support it likely would “dig” into the body tube.

In this case , a real BT-5 motor block or a sturdy scratch built one may be advisable.

This will go in appropriate position to leave enough motor out the back to fit perfectly into the rear tube, seated against the rear tube’s REAR end motor block (which can be wimpy single layer body tube.)

The HOLES in the forward tube will be just IN FRONT of (and in fact, maybe should just slightly overlap) the front edge of the front tube motor block. This should still give you plenty of room for your crochet hook, but will have the band pulling in the MOTOR BLOCK, less likely to dig into the outer body tube.

The only speed bump I've come across (and it's a minor one) is that the hole punch can't slide far enough into the tube to put the hole where I want it. A small drill bit in a pin vise or my dremel should do the trick.

 

[BABAR]

The only speed bump I've come across (and it's a minor one) is that the hole punch can't slide far enough into the tube to put the hole where I want it. A small drill bit in a pin vise or my dremel should do the trick.

I’ve done some with the tip of an exacto knife, then hardened with CA, but not pretty.

you can also flatten the tube here, just pressing both sides together, and come in from side OUTSIDE, punching both holes at same time. It puts a crease in the body tube, but putting a REAL motor block (or for a BT-20 a real BT-20 to BT-5 centering ring) will restore the shape. Again, not pretty but most of my creations are for my own amusement, so I don’t really care if they look pretty nor do I care If they go that high, I just like solving engineering challenges.

 

[Rktman]

I’ve done some with the tip of an exacto knife, then hardened with CA, but not pretty.

you can also flatten the tube here, just pressing both sides together, and come in from side OUTSIDE, punching both holes at same time. It puts a crease in the body tube, but putting a REAL motor block (or for a BT-20 a real BT-20 to BT-5 centering ring) will restore the shape. Again, not pretty but most of my creations are for my own amusement, so I don’t really care if they look pretty nor do I care If they go that high, I just like solving engineering challenges.

This one isn't going to win any beauty contests either. Long story short, I originally retained the motor cause it needed nose weight, but misjudged how much moving the motor pod forward for stability would affect the CG location (like how extending one side of a seesaw suddenly makes that side "heavier"). Had to do some surgery so the remaining section of motor pod is pretty battered.

Anyway, realized after the fact that if I had attached the rear of the motor pod so that it overhung the pylon by 1/4" or even 1/8", it would've made an ideal location to loop the rubber band over it to anchor it. Ah hindsight, you're such a wonderful thing. Too bad you're always tardy.

 

[Rktman]

I’ve done some with the tip of an exacto knife, then hardened with CA, but not pretty.
I just like solving engineering challenges.

BTW, any suggestions on how to anchor the shock cord? I'm leaning toward Estes-style teabag.

 

[BABAR]

BTW, any suggestions on how to anchor the shock cord? I'm leaning toward Estes-style teabag.

Although not a fan of teabag for most rockets (I theorize it causes some bumpiness that may prevent a tight chute from coming out) if you have space for wadding and streamer (which in this case you should) it’s a good solution.

It does have advantage of keeping shock cord away from forward end of motor. I’ve burned through many Kevlar cords that were attached to motor mount (@BEC swears by the old rubber cords). So if space is not too big an issue T-Bag is great. You only NEED a small streamer to recover this. If you make a thin long SHINY streamer it may make it easier to FIND this piece , both tracking descent and fluttering on the ground.

 

[Rktman]

Although not a fan of teabag for most rockets (I theorize it causes some bumpiness that may prevent a tight chute from coming out) if you have space for wadding and streamer (which in this case you should) it’s a good solution.

It does have advantage of keeping shock cord away from forward end of motor. I’ve burned through many Kevlar cords that were attached to motor mount (@BEC swears by the old rubber cords). So if space is not too big an issue T-Bag is great. You only NEED a small streamer to recover this. If you make a thin long SHINY streamer it may make it easier to FIND this piece , both tracking descent and fluttering on the ground.

I like the shiny metallic mylar streamers from Apogee. They unroll easily and quickly and their highly reflective nature makes them easy to track as they flutter down. Teabag it is.

 

[Rktman]

Although not a fan of teabag for most rockets (I theorize it causes some bumpiness that may prevent a tight chute from coming out) if you have space for wadding and streamer (which in this case you should) it’s a good solution.

Holes punched. Pretty chuffed that I finally found a use for these 0.25" grommets that I've had for decades (from my design school days when one of my classes involved bookmaking). Sometimes being a packrat has its advantages. It finishes off and strengthens the ragged holes drilled for the motor anchor elastic perfectly.

 

[BEC]

Although not a fan of teabag for most rockets (I theorize it causes some bumpiness that may prevent a tight chute from coming out) if you have space for wadding and streamer (which in this case you should) it’s a good solution.

It does have advantage of keeping shock cord away from forward end of motor. I’ve burned through many Kevlar cords that were attached to motor mount (@BEC swears by the old rubber cords). So if space is not too big an issue T-Bag is great. You only NEED a small streamer to recover this. If you make a thin long SHINY streamer it may make it easier to FIND this piece , both tracking descent and fluttering on the ground.

Well...not old rubber cords exactly. The white rubber that Estes has been using for a long time is OK for longer than I expected, but when it dries out, it's done. What I am currently doing in most of my models (exception: I just put the supplied 1/4 white rubber cord in the So Long I'm about to start painting, figuring it's not going to get dozens of flights on it) is use FAI Tan Sport rubber from FAI Model Supply. This is as close as I can currently get to the Sig Contest rubber that Estes used way back in the sixties. I do have one model with an original shock cord from that period that is perfectly flyable at about age 55.

And in tubes BT-50 and up, I'm fine with the tri-fold. In smaller models it can be exactly what you suggest — an impediment to getting the 'chute out. This was one factor in the unfortunate two no-deploy flights of my wife's K-31 Star Blazer flown in Classic Model at NARAM-64. But it was not the only issue with that model. It will be fine and get a 'chute out when flown at Sod Blaster V in a little less than two weeks, I am sure.

One thing I've also started doing is going down a size on the rubber when I'm using FAI Tan. In small/light models I'm using 3/32 inch wide stuff instead of 1/8. There was 1/16th inch wide stuff in most of my contest models at NARAM with no separations. This makes the tri-fold, which is a very effective way to attach the shock cord well away from the ejection charge, a little less of a problem in smaller diameter tubes.

Now back to the actual discussion in this thread, which is quite interesting.

 

[Rktman]

@BABAR Gah! Just realized that I made the hole for the elastic far too big.
The pressure drop through what are now essential vent holes will very likely not be able to push off the forward section of motor tube. I'll just have to redo another tube section but this time dropping the hole size down to 1/16" or 3/32" diameter.

 

[BABAR]

@BABAR Gah! Just realized that I made the hole for the elastic far too big.
The pressure drop through what are now essential vent holes will very likely not be able to push off the forward section of motor tube. I'll just have to redo another tube section but this time dropping the hole size down to 1/16" or 3/32" diameter.

Yeah, I thought the grommets were right purty but definite overkill.

I think a diameter hole just a bit larger than the crochet hook, #8 2.5 mm (just what works for me) should give you enough room for accessing the retention band without overly diverting/decompressing the nose cone, chute, shock cord and wadding ejection. You can harden the hole post cutting or drilling with CA.

As said previously, an internal engine block should provide a strong internal support to keep the band from “cutting” or “zippering “ the body tube. On my helis and airbrakers I can put something OUTSIDE, but in these the tube is NOT the outer airframe (the blades are) so I don’t have to worry about drag with my supports.

Whatever size you choose for holes, you will lose a little ejection force. So best to pack the nose and laundry on the loose side.

 

[Rktman]

@BABAR
Let me borrow your keen analytical eye: As a fail-safe, what do you think of this setup? Nose cone is sealed to BT, so that remaining ejection pressure will more likely expel the forward tube section, exposing the streamer which is stored in the forward part of the tube but tethered to the center of the shock cord so it's pulled out and exposed to the airflow when tube sections are pulled apart. As before, motor casing is pulled out and goes along for the ride.

 

[BABAR]

@BABAR
Let me borrow your keen analytical eye: As a fail-safe, what do you think of this setup? Nose cone is sealed to BT, so that remaining ejection pressure will more likely expel the forward tube section, exposing the streamer which is stored in the forward part of the tube but tethered to the center of the shock cord so it's pulled out and exposed to the airflow when tube sections are pulled apart. As before, motor casing is pulled out and goes along for the ride.

View attachment 599579

It maaay work. You probably didn’t draw to scale, but you need a much longer cord between the streamer attachment and the nose to make sure the forward tube goes forward enough that streamer clears (specifically must be longer than streamer and short streamer inverted “T” cord segment.

Also need a longer segment between streamer and motor to give it a chance to build up some kinetic energy before “yanking” the streamer out.

Biggest concern is that initially the ejection blast will ram the wadding and streamer up against nose cone, which may pack it so tight it doesn’t easily come out, Again, a very loose streamer fit is your friend.

Also more nose weight makes chance of success higher, but you may pay a price in performance.

You may want to use the pencil loop wrap technique or crochet daisy chain for shock cord packing. Gonna be a good bit of cord to pack.

 

[Rktman]

It maaay work. You probably didn’t draw to scale, but you need a much longer cord between the streamer attachment and the nose to make sure the forward tube goes forward enough that streamer clears (specifically must be longer than streamer and short streamer inverted “T” cord segment.

Also need a longer segment between streamer and motor to give it a chance to build up some kinetic energy before “yanking” the streamer out.

Biggest concern is that initially the ejection blast will ram the wadding and streamer up against nose cone, which may pack it so tight it doesn’t easily come out, Again, a very loose streamer fit is your friend.

Also more nose weight makes chance of success higher, but you may pay a price in performance.

You may want to use the pencil loop wrap technique or crochet daisy chain for shock cord packing. Gonna be a good bit of cord to pack.

Yup, not to scale. Streamer will be attached via a cord to the main shock cord such that at full extension, it'll clear both tubes. The streamer "leash" will be long enough to allow it to be stowed toward the top of the forward tube, hopefully out of harm's way from the majority of the heat and force from the ejection charge. Since I'll try to use only the bare minimum of dog barf, I'm thinking of wrapping the streamer in the old Estes-style 'chute protector (remember those?) as extra insurance.

 

[BABAR]

I wish I could find the source for attribution.

Someone came up with a way for streamer recovery for motors in minimum recovery rear ejects.

The motor contents HAD to leave enough room inside the forward end of the casing, so couldn’t use a C or a D12 or A10-3T.

You cut off the rear end of a safety pin, cutting both “legs” a bit forward of the spring loop. You make the cuts at an angle so the points are sharp.

You bend one leg outward, so the space between the tips is a bit larger than the inner diameter of the casing.

Attack shock cord to look, may want to use a short wire length, as it’s gonna get blasted.

You insert the pin, loop side first (so pointy ends facing noseward, AWAY from the nozzle) into the space in the rear end of the motor. The spring allows a slight flex to allow the legs to get into the casing. These act as “grappling hooks”, WITHOUT modifying the motor (so motor isn’t DQ’d for NAR sport purposes. Yeah, @Daddyisabar , Pad Fuhrer will look at you funny, but he or she ALWAYS looks at you funny.)

The streamer and wadding are packed into the tube. I guess a forward bulkhead is required, and likely no motor block, need external tape wrap to keep motor from shooting into tube on ignition/boost.

Ejection charge kicks motor out (also unfortunately rams cord, wadding, and streamer IN/forward up against bulkhead. Need enough cord (definitely NOT elastic, BTW) to allow the motor to get a “running start” to generate enough kinetic energy to hopefully disengage the wadded up recovery system from the tube.

I can’t say I’ve tried it, I’ve yet to fly fields where freely ejected motors were verboten.

I could see this being useful on such a field with a cluster of 2 or more B6-0 motors around a central 24 or 29 mm motor, would make for a visually entertaining flight near simultaneously ejecting multiple motors which deploy streamers.

Not as exciting as SOBs (sorry @kjhambrick , I mean Strap On Boosters ) but would still be fun to watch.

 

[Rktman]

I wish I could find the source for attribution.

Someone came up with a way for streamer recovery for motors in minimum recovery rear ejects.

The motor contents HAD to leave enough room inside the forward end of the casing, so couldn’t use a C or a D12 or A10-3T.

You cut off the rear end of a safety pin, cutting both “legs” a bit forward of the spring loop. You make the cuts at an angle so the points are sharp.

You bend one leg outward, so the space between the tips is a bit larger than the inner diameter of the casing.

Attack shock cord to look, may want to use a short wire length, as it’s gonna get blasted.

You insert the pin, loop side first (so pointy ends facing noseward, AWAY from the nozzle) into the space in the rear end of the motor. The spring allows a slight flex to allow the legs to get into the casing. These act as “grappling hooks”, WITHOUT modifying the motor (so motor isn’t DQ’d for NAR sport purposes. Yeah, @Daddyisabar , Pad Fuhrer will look at you funny, but he or she ALWAYS looks at you funny.)

The streamer and wadding are packed into the tube. I guess a forward bulkhead is required, and likely no motor block, need external tape wrap to keep motor from shooting into tube on ignition/boost.

Ejection charge kicks motor out (also unfortunately rams cord, wadding, and streamer IN/forward up against bulkhead. Need enough cord (definitely NOT elastic, BTW) to allow the motor to get a “running start” to generate enough kinetic energy to hopefully disengage the wadded up recovery system from the tube.

I can’t say I’ve tried it, I’ve yet to fly fields where freely ejected motors were verboten.

I could see this being useful on such a field with a cluster of 2 or more B6-0 motors around a central 24 or 29 mm motor, would make for a visually entertaining flight near simultaneously ejecting multiple motors which deploy streamers.

Not as exciting as SOBs (sorry @kjhambrick , I mean Strap On Boosters ) but would still be fun to watch.

At the expense of being wishy-washy, I expended a few calories on thinking about the pros and cons and realized that I'm adding back more complexity, and therefore more chance of possible failure. So after prolonged re- reconsideration I'm opting to go with your original suggestion.

 

[Aeronerd]

@BABAR
Let me borrow your keen analytical eye: As a fail-safe, what do you think of this setup? Nose cone is sealed to BT, so that remaining ejection pressure will more likely expel the forward tube section, exposing the streamer which is stored in the forward part of the tube but tethered to the center of the shock cord so it's pulled out and exposed to the airflow when tube sections are pulled apart. As before, motor casing is pulled out and goes along for the ride.

View attachment 599579

I think the original method would probably work better because it was simpler. with this way it is more complicated so more chance of failure.

 

[Aeronerd]

At the expense of being wishy-washy, I expended a few calories on thinking about the pros and cons and realized that I'm adding back more complexity, and therefore more chance of possible failure. So after prolonged re- reconsideration I'm opting to go with your original suggestion.

Oh.didnt see your post. Guess we crossed posts I think you made the right choice.

 

[Buzzard]

https://www.nar.org/wp-content/uploads/2014/05/FlyBaby-B-BG-Russell.pdf
Why not just use a pop-pod? You stated that you were designing a RG which is a rocket glider and by defination must retain the motor. A pop-pod removes the motor to change the glide CG.

Chas

 

[Rktman]

https://www.nar.org/wp-content/uploads/2014/05/FlyBaby-B-BG-Russell.pdf
Why not just use a pop-pod? You stated that you were designing a RG which is a rocket glider and by defination must retain the motor. A pop-pod removes the motor to change the glide CG.

Chas

You're correct, my bad. I've since corrected it and changed it to "BG". I really should start a build thread. When I built a cardboard prototype, it actually needed nose weight so I retained the spent motor. Since building out a larger version of balsa and carbon tubing, the opposite is now true and I need to dump weight from the front end. Can't do it with a traditional pop pod that ejects backward and up. You'll see why when I start that build thread. Been kind of tied up with other concerns but I'll do it as soon as I can and post the spinoff link here.

 

[BABAR]

. Since building out a larger version of balsa and carbon tubing, the opposite is now true and I need to dump weight from the front end. Can't do it with a traditional pop pod that ejects backward and up. .

ERROR! ERROR!

Internal rear eject pop pod CAN be done and CAN dump nose weight. Been dere, done dat, no T-Shirt.

Remove plastic nose cone bulkhead so internal lumen of cone is open to body tube. Coat inside of cone with JB weld or something to protect it from direct blast.

Extend motor mount via a down sized tube (say BT-20 to BT-5) so forward tip of tube extends as far into the nose as possible. This will also substantially increase your space for pod streamer or chute. Put a single layer rolled aluminum can about 4” long inside the downsized tube just forward of the motor to prevent burn through, which from experience WILL happen due to concentration of flame if you don’t. Seen it happen without such internal protection. it’s the rule, not the exception

Also, because this skinny tube connects two heavy ends, motor casing on one end and nose weight on other, and because it IS, skinny, doesn’t hurt to reinforce with a carbon fiber rod or strip.

Attach your nose weight to the forward end of the motor mount tube INSIDE the nose cone. Won’t be quite in the tip, but still pretty far forward.

Now, when pod ejects, you are dumping motor, extended mount, AND the nose weight.

This works great for SR-71 shaped gliders. See Apogee SR-72 or search on this forum for SR-73 Raven.

Usually this activate an elevator with elastic when internal pod deploys.

Agree with @Buzzard , most efficient is your classic pop pod like MPC Flat Cat, but you are trying something different.

 

[Rktman]

ERROR! ERROR!

Internal rear eject pop pod CAN be done and CAN dump nose weight. Been dere, done dat, no T-Shirt.

Remove plastic nose cone bulkhead so internal lumen of cone is open to body tube. Coat inside of cone with JB weld or something to protect it from direct blast.

Extend motor mount via a down sized tube (say BT-20 to BT-5) so forward tip of tube extends as far into the nose as possible. This will also substantially increase your space for pod streamer or chute. Put a single layer rolled aluminum can about 4” long inside the downsized tube just forward of the motor to prevent burn through, which from experience WILL happen due to concentration of flame if you don’t. Seen it happen without such internal protection. it’s the rule, not the exception

Also, because this skinny tube connects two heavy ends, motor casing on one end and nose weight on other, and because it IS, skinny, doesn’t hurt to reinforce with a carbon fiber rod or strip.

Attach your nose weight to the forward end of the motor mount tube INSIDE the nose cone. Won’t be quite in the tip, but still pretty far forward.

Now, when pod ejects, you are dumping motor, extended mount, AND the nose weight.

This works great for SR-71 shaped gliders. See Apogee SR-72 or search on this forum for SR-73 Raven.

Usually this activate an elevator with elastic when internal pod deploys.

Agree with @Buzzard , most efficient is your classic pop pod like MPC Flat Cat, but you are trying something different.

Okay, quick sketch time. Here's why I can't do a traditional pop pod, and why I didn't want to chance just ejecting the spent casing backward: it would stand a good chance of taking out the rear "wing" of this "box kite" type glider. Once that happens, the whole structure falls apart (the "fuselage" is just 3 thin carbon tubes joining the triangular "wings" on the fore and aft end. If any one component gets damaged, it'll re-kit itself pronto.

 

[BABAR]

Okay, quick sketch time. Here's why I can't do a traditional pop pod, and why I didn't want to chance just ejecting the spent casing backward: it would stand a good chance of taking out the rear "wing" of this "box kite" type glider. Once that happens, the whole structure falls apart (the "fuselage" is just 3 thin carbon tubes joining the triangular "wings" on the fore and aft end. If any one component gets damaged, it'll re-kit itself pronto.



View attachment 600291

I like it!

If you can get the Ring Hawk (hows that for a blast from the past?) to fly, this outa be a cinch.

Hmm, a triangle is a Delta, so this could be the Delta Hawk.

I think post 4 here may be your simplest solution.

With your design I am not sure about is if your rocket plume is gonna toast either your forward or rear fin sets. (had this discussion with @Daddyisabar , didn't get a straight answer, probably because the straightest answer is "it depends.")

I HAVE found a simple if inelegant solution for some of tubeless balsa birds, which occasional got toasted (and in at least two cases actually caught fire---- funny, in a bright sunlit day it can be really hard to SEE that the rocket is on fire, all you see is the fin getting smaller and blacker!)

I have found you can take spray adhesive, spray the balsa, and then put a piece of foil on it. Holds pretty well. Not saying you HAVE to use it, you just may not want to fly this is high risk burn ban type conditions until you know it's not gonna be renamed "Phoenix."

 

[Daddyisabar]

Straight answer: Cant your tractor motors up front. Shape you tails with fire during boost. Rear eject both motor mounts. Easy.

 

[Rktman]

I like it!

If you can get the Ring Hawk (hows that for a blast from the past?) to fly, this outa be a cinch.

Hmm, a triangle is a Delta, so this could be the Delta Hawk.

I think post 4 here may be your simplest solution.

With your design I am not sure about is if your rocket plume is gonna toast either your forward or rear fin sets. (had this discussion with @Daddyisabar , didn't get a straight answer, probably because the straightest answer is "it depends.")

I HAVE found a simple if inelegant solution for some of tubeless balsa birds, which occasional got toasted (and in at least two cases actually caught fire---- funny, in a bright sunlit day it can be really hard to SEE that the rocket is on fire, all you see is the fin getting smaller and blacker!)

I have found you can take spray adhesive, spray the balsa, and then put a piece of foil on it. Holds pretty well. Not saying you HAVE to use it, you just may not want to fly this is high risk burn ban type conditions until you know it's not gonna be renamed "Phoenix."

Intend to wrap inside & outside of rear triangle with self-adhesive aluminum tape, and inside of forward triangle with same. Hopefully that does the trick.