An "R"-powered rocket build

[Ez2cDave]

It won’t come to a dead stop.

Hence, my use of the phrase "theoretical dead stop" . . .

Dave F.

 

[Ez2cDave]

If the drogue is sized correctly , descent rate under drogue should be more like 50 fps....something like 16' diameter...

A rate of 50 ft/sec is going to take about 13.5 minutes ( 800 seconds ) to descend from 42,000 ft AGL to Main Deploy altitude ( using 2,000 ft AGL for illustration ). Winds aloft could make for a very long drift downrange.

As an example, "pulling numbers out of a hat" . . . In a constant 20 mph wind ( a VERY conservative number ), descending at 50 ft/sec, from 42,000 ft AGL, taking 13.5 minutes ( 800 seconds ) to reach 2,000 ft AGL, would result in a downrange drift of 4.545 miles ( 24,000 ft ), before Main Deployment.

As we all know, winds aloft can be significantly higher than winds at ground level, making downrange drift much greater. The faster the Descent Rate from Apogee to Main Deploy, the less the Downrange Drift.

Dave F.

 

[Paulb06]

Thanks for the info I didn't realize Rocketman would do a custom build.

That is great news as I've had nothing but success with their chutes.

Chuck C.

I love Rocketman chutes...soft reliable opening....

 

[Ez2cDave]

Chuck,

A possible concern, regarding your GPS / Tracking system . . .

Assume "zero contact" from just after Launch to Apogee ( or later ) . . . Make sure your unit is capable of reliably re-establishing "cold" contact, over 8 miles ( 42,000f ft ) away . . . Possibly further !

Dave F.

 

[Rail Dawg]

Chuck,

A possible concern, regarding your GPS / Tracking system . . .

Assume "zero contact" from just after Launch to Apogee ( or later ) . . . Make sure your unit is capable of reliably re-establishing "cold" contact, over 8 miles ( 42,000f ft ) away . . . Possibly further !

Dave F.

Yep good point.

The BigRedBee apparently has a good track record for this kind of flight.

Chuck C.

 

[Ez2cDave]

Chuck,

This is something you might be interested in . . .

https://www.space-rockets.com/soft.html

Dave F.

 

[Rail Dawg]

Anyone here ever cut G-12 tubes?

I've always made due no problem with what came from the manufacturer.

Any secrets on making straight cuts (like in half) I'm listening.

Chuck C.

 

[Paulb06]

It's fairly easy to protect the recovery system from black powder burns....my favorite way is to sew nomex sleeves that slide over the webbing for the amount of the webbing that will be exposed to heat , I put a short nylon leader on the drogue and build a bag that looks like a tadpole....IOW a bag with a shock strap sleeve sewn to one side of it with a couple grommets at the end of the tail....your shock strap will be fed thru the sleeve and attached to the motor and the grommets secured to the same clevis.....place your shock strap in the bag,...leave a length of shock strap the length of your chute lines out for now.....then pack the chute in the bag ( chute first then the chute lines) and then the remainder of the shock strap...... fold the top of the bag over with the shock strap and leader for the drogue coming out of the top.....make a nomex sleeve for any exposed shock strap ....during deployment what will happen is the drogue leader and the shock cord will extend, then the chute lines will extend and the chute will clear, inflate and finally the rest of the shock strap will come out of the bag.....the bag will stay just inside the booster tube

Something I was thinking about is that if you are using bulkheads fastened together with explosive bolts instead of tube couplers, it may be trickier to obtain much separation velocity between the payload and the booster...the 2 parts may simply fall apart....you'd need to have the drogue and gear packed loose enough to easily come out of the tube...

 

[RocketFeller]

Anyone here ever cut G-12 tubes?

I've always made due no problem with what came from the manufacturer.

Any secrets on making straight cuts (like in half) I'm listening.

Chuck C.

Wrap it with a large sheet of paper to get a square cut.

I love my Dremel Sawmax - for cutting composite material the carbide grit coated blade is unbeatable.

 

[Rail Dawg]

Wrap it with a large sheet of paper to get a square cut.

I love my Dremel Sawmax - for cutting composite material the carbide grit coated blade is unbeatable.

I've got a big ol' miter saw I use for cutting lumber.

Would this cut G-12 ok or would it shred?

Chuck C.

 

[Paulb06]

A rate of 50 ft/sec is going to take about 13.5 minutes ( 800 seconds ) to descend from 42,000 ft AGL to Main Deploy altitude ( using 2,000 ft AGL for illustration ). Winds aloft could make for a very long drift downrange.

As an example, "pulling numbers out of a hat" . . . In a constant 20 mph wind ( a VERY conservative number ), descending at 50 ft/sec, from 42,000 ft AGL, taking 13.5 minutes ( 800 seconds ) to reach 2,000 ft AGL, would result in a downrange drift of 4.545 miles ( 24,000 ft ), before Main Deployment.

As we all know, winds aloft can be significantly higher than winds at ground level, making downrange drift much greater. The faster the Descent Rate from Apogee to Main Deploy, the less the Downrange Drift.

Dave F.

Rockets don't usually go straight up and backslide....generally they gradually track upwind somewhat and nose over so apogee deploy will likely be some distance up range....the air is somewhat thinner at 40,000' so initially it will drop faster....those factors will reduce the distance downrange but...any descent speed a chute will survive could very well end up putting the rocket a little ways downwind....assuming the winds aloft are the same direction as surface winds....they arent always

 

[Rail Dawg]

Something I was thinking about is that if you are using bulkheads fastened together with explosive bolts instead of tube couplers, it may be trickier to obtain much separation velocity between the payload and the booster...the 2 parts may simply fall apart....you'd need to have the drogue and gear packed loose enough to easily come out of the tube...

Due to the altitude we are going to use "BP cannons" and nylon shear pins.

Will use twice as many cannons as needed.

Chuck C.

 

[RocketFeller]

I've got a big ol' miter saw I use for cutting lumber.

Would this cut G-12 ok or would it shred?

Chuck C.

I use a miter saw with a carbide finish blade to cut 4” fiberglass tubes. To get a really square cut you can use a stop and then rotate the tube into the blade.

 

[Rail Dawg]

I use a miter saw with a carbide finish blade to cut 4” fiberglass tubes. To get a really square cut you can use a stop and then rotate the tube into the blade.

Very good.

Thanks.

Chuck C.

 

[Rail Dawg]

Just ordered 10' of 12" G-12 and some couplers. Will order the next 10' of airframe a little later.

Decided to not do the MMT but use several 3/4" Birch plywood centering rings that will fit the motor perfectly.

Between each CR in the fin can section will be x-length couplers spaced x inches apart. These couplers will give each CR an extra amount of strength plus using couplers insures each CR is perfectly aligned.

Can't remember who here gave me the coupler idea but it's a good one.

The Binder Design fin can will be screwed into the CR's.

Rock solid man!

Chuck C.

 

[Ez2cDave]

Rock solid man!

Chuck C.

Chuck,

Did you get your "saddle" yet ?

LOL !

Dave F.

 

[Paulb06]

Just ordered 10' of 12" G-12 and some couplers. Will order the next 10' of airframe a little later.

Decided to not do the MMT but use several 3/4" Birch plywood centering rings that will fit the motor perfectly.

Between each CR in the fin can section will be x-length couplers spaced x inches apart. These couplers will give each CR an extra amount of strength plus using couplers insures each CR is perfectly aligned.

Can't remember who here gave me the coupler idea but it's a good one.

The Binder Design fin can will be screwed into the CR's.

Rock solid man!

Chuck C.

The only thing about not using a motor mount tube is all the thrust and landing forces are transferred through the thrust plate and rear centering ring to the outer body tube, whereas with a mmt the load is shared between the outer airframe and every centering ring instead of just the last one....not saying it won't work...just something to think about

 

[blackjack2564]

I used this 1950's Craftsman to cut 12 in. G-12 tubes. Framing square to true both fences & carbide blade. Tube in background.
You will have no problem with saw you have. Lower blade...set tube on table and raise blade just enough to be about and inch into tube, rotate slowly...very slowly. Will cut perfectly clean ...no shattering of edges. Tube in background. This was for a 3/4 scale Nike Smoke...weighed 325. 8inch motor mount.



To keep BP charge to a minimum and tube integrity I designed a 5in. long "doughnut av-bay". Slid into position so no excess room in tube to pressurize, keeping charge size at 8gram for 28ft man rated chute. Loaded up and slid bay into position.
Used [8] 1/4 in bolts to hold bay in place.Used work light to see where placement of bay was internally to mark for bolt holes.



Drilled through and placed bolts into position on bay, then JB Weld glued nuts to interior of bay.



2 U-bolts and Y-harness on each end for recovery....4 5/16 rods and nits holding bay together for recovery stresses.
Custom charge holders with 15 gram capacity.
This design allows for placing av-bay exactly where it's needed and keep pressurized space [from bp charge] to a minimum.
BP then dog barf on top....3 layers of aluminum duct tape covering charge. E-matchs always on TOP of BP..not bottom of well This keeps concussion from one charge setting off the other, which IS a concern with large rockets as you probably know .



Edit: staggered rows of bolt holes 4 each row. total 8

 

[Rail Dawg]

I used this 1950's Craftsman to cut 12 in. G-12 tubes. Framing square to true both fences & carbide blade. Tube in background.
You will have no problem with saw you have. Lower blade...set tube on table and raise blade just enough to be about and inch into tube, rotate slowly...very slowly. Will cut perfectly clean ...no shattering of edges. Tube in background. This was for a 3/4 scale Nike Smoke...weighed 325. 8inch motor mount.

View attachment 370774

To keep BP charge to a minimum and tube integrity I designed a 5in. long "doughnut av-bay". Slid into position so no excess room in tube to pressurize, keeping charge size at 8gram for 28ft man rated chute. Loaded up and slid bay into position.
Used [8] 1/4 in bolts to hold bay in place.Used work light to see where placement of bay was internally to mark for bolt holes.

View attachment 370775

Drilled through and placed bolts into position on bay, then JB Weld glued nuts to interior of bay.

View attachment 370776 View attachment 370778

2 U-bolts and Y-harness on each end for recovery....4 5/16 rods and nits holding bay together for recovery stresses.
Custom charge holders with 15 gram capacity.
This design allows for placing av-bay exactly where it's needed and keep pressurized space [from bp charge] to a minimum.
BP then dog barf on top....3 layers of aluminum duct tape covering charge. E-matchs always on TOP of BP..not bottom of well This keeps concussion from one charge setting off the other, which IS a concern with large rockets as you probably know .

View attachment 370777

Great info. Awesome pics!

Thanks for this.

Looking for a good table saw. Maybe Craigslist. My mighty miter saw ain’t got the clearance needed.

Chuck C.

 

[0011001100]

Anyone here ever cut G-12 tubes?

I've always made due no problem with what came from the manufacturer.

Any secrets on making straight cuts (like in half) I'm listening.

Chuck C.

I've got a big ol' miter saw I use for cutting lumber.

Would this cut G-12 ok or would it shred?

Chuck C.

I use a diamond coated tile blade. Makes cuts so clean you can rub your finger over them without sanding just take it slow when cutting.

Just ordered 10' of 12" G-12 and some couplers. Will order the next 10' of airframe a little later.

Decided to not do the MMT but use several 3/4" Birch plywood centering rings that will fit the motor perfectly.

Between each CR in the fin can section will be x-length couplers spaced x inches apart. These couplers will give each CR an extra amount of strength plus using couplers insures each CR is perfectly aligned.

Can't remember who here gave me the coupler idea but it's a good one.

The Binder Design fin can will be screwed into the CR's.

Rock solid man!

Chuck C.

Twas me
Also I think using a motor tube might be better just to distribute the load more evenly

 

[Paulb06]

I use a diamond coated tile blade. Makes cuts so clean you can rub your finger over them without sanding just take it slow when cutting.


Twas me
Also I think using a motor tube might be better just to distribute the load more evenly

I do also, even , say a 4' long one picking up 4 centering rings will unitize the whole booster section and help transfer the approx 5000 lbs of thrust to the body tube through all those centering rings ....otherwise you'll need a thrust plate on the bottom that can support the equivalent of a pickup truck

 

[Rail Dawg]

Thanks guys.

There will be a 1/4" thrust plate on the bottom transferring the thrust to the airframe and aluminum fin can.

Also a thrust plate at the top of the motor.

Should be plenty of support for the power.

Chuck C.

 

[Ez2cDave]

Thanks guys.

There will be a 1/4" thrust plate on the bottom transferring the thrust to the airframe and aluminum fin can.

Also a thrust plate at the top of the motor.

Should be plenty of support for the power.

Chuck C.

Chuck,

If there is no motor tube and the force will be applied to the airframe and the aluminum fin can, via a 1/4" aft thrust plate, what is the force applied to the upper thrust plate going to be transferred to ?

Dave F.

 

[blackjack2564]

Thanks guys.

There will be a 1/4" thrust plate on the bottom transferring the thrust to the airframe and aluminum fin can.

Also a thrust plate at the top of the motor.

Should be plenty of support for the power.

Chuck C.

How it was done on the Smoke.....threaded rod from bottom thrust plate to top plate,"clamped" the motor between the 2 plates...spreading the load.

Many large motors are held in place with no motor tube...not needed.

 

[Rail Dawg]

Chuck,

If there is no motor tube and the force will be applied to the airframe and the aluminum fin can, via a 1/4" aft thrust plate, what is the force applied to the upper thrust plate going to be transferred to ?

Dave F.

The upper motor enclosure will be against the aluminum thrust plate (actually a centering ring) butted up against a coupler.

Chuck C.

 

[Ez2cDave]

The upper motor enclosure will be against the aluminum thrust plate (actually a centering ring) butted up against a coupler.

Chuck C.

Chuck,

And then the two thrust plates will be "tied together", somehow ?

Dave F.

 

[Titan II]

Chuck,

And then the two thrust plates will be "tied together", somehow ?

Dave F.

see post 684

 

[blackjack2564]

I would think much like this:
looking down from top of motor fincan
1ft of 12in diameter coupler..glued and pinned.
Aluminum bulk plate that motor will butt up to [upper thrust plate] coupler.

In this case {Chucks} there will be CR's involved in the stack,rather than a solid aluminum BP.. if I'm getting correct.
Threaded rods go alongside motor,down to lower thrust plate,tying whole shebang together.
This project had recovery eyebolts coupler nutted to ends of threaded rods with double Y-harness exiting from 4 positions.

 

[Ez2cDave]

I would think much like this:
looking down from top of motor fincan
1ft of 12in diameter coupler..glued and pinned.
Aluminum bulk plate that motor will butt up to [upper thrust plate] coupler.

In this case {Chucks} there will be CR's involved in the stack,rather than a solid aluminum BP.. if I'm getting correct.
Threaded rods go alongside motor,down to lower thrust plate,tying whole shebang together.
This project had recovery eyebolts coupler nutted to ends of threaded rods with double Y-harness exiting from 4 positions.

Jim,

I'm hoping that Chuck will give a detailed reply. Similar concepts are interesting and informative, but I would like to have more specifics on Chuck's setup.

Dave F.

 

[Theory]

I find the concept of omitting the mmt interesting, however quite contrary to the “over built at every point” mantra that appeared to be the theme of the project earlier.

Relying on a pair of thrust rings for an ‘R’ may prove detrimental.

A for the saw, the blade and “trueness” of the rig is much more important than the actual machine. Also, as was previously mentioned, limit the degree to which the blade enters the tube. Excessive drag will really mess with the final result