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highflyer1968

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I'm Getting ready to build the Astrobee d rocket and will be putting rail buttons on it. Is there anything I should do for the slots where the launch lugs would go? I'm thinking that the two areas should be strengthened a little. How can I do that? Also I noticed that the rocket comes with two chutes. One is 22 inches and the other is 30 inches. Without having looked at the instructions yet I'm guessing 22 for the top half and 30 for the bottom half of the rocket. Could I attach one chute(30 inch) and have the rocket come down as one? Or Can I put the two shock cords together and attach both chutes and have it come down as one piece with two chutes instead of two separate pieces?

I think that's it for nowIMG_20200331_102339.jpg
 
Soak the groves with thin CA glue (water thin superglue), and keep doing it until grooves are full, then sand flush.
 
I have never been happy with the 2 chute config of the AT Astrobee D. For me, they almost always tangled together which would cause the 2 air-frame sections to hit into each other. I would use a single longer shock cord and a single parachute that was attached 2/3rd of the way between them. That would eliminate the tangles and the banging together.
 
Last edited:
heada said:
I have never been happy with the 2 chute config of the AT Astrobee D. For me, they almost always tangled together which would cause the 2 air-frame sections to hit into each other. I would use a single longer shock cord and a single parachute that was attached 2/3rd of the way between them. That would eliminate the tangles and the banging together.
Click to expand...
I never thought about the banging and the chutes getting tangled. Do you think the 30 inch chute would be big enough for the whole rocket? Not sure yet what I am going to do but am thinking I will connect the two shock cords together and the one chute or I may just order one long one. Kevlar or tubular nylon? I've been reading shock cord should be about 3 times the length of the rocket. Does that sound about right? That would mean that I should buy 18ft of shock cord and that seems really long for an Aerotech rocket. Also if I want to put a 5 grain motor from CTI do I need to strengthen the rocket or would it be ok as is? I may not put large motors in but wanting to build for them just in case. I have a 6 grain case but it will not fit that size of motor as I am installing the baffle so I can attach the shock cord easily otherwise I have to figure out where else I can attach without the baffle.
 
The shock cords that ship with the rocket are cloth and elastic and so have a lot of give in them. If you were to switch to nylon or kevlar, you need the extra length to absorb the same energy and thus why they're so much longer. Nylon does stretch some but kevlar doesn't. Personally, I'd go with the 18ft section of 9/16ths tubular nylon. It'll be more than enough and is still fairly cheap. Only reason to go with kevlar is for the flame resistance and tubular nylon will be good for dozens of flights at least. I've had PML kits with over 30 flights and the tubular nylon was scorched but still viable.

If you're going to modify the motor mount to accept motors longer than the standard AT 29/40-120, then you should make sure to use epoxy to attach the fins. Plastic fins wouldn't accept fiberglass well so doing a tip-to-tip wouldn't be advisable. That would also mean you'd have to do something else besides the baffle system that AT uses in that kit. If you're going to go through all that, I would drop the baffle and motor hook and use an Aeropack retainer with the separate baffle further up the body. LOC and Apogee both make good baffles that should fit that tube and provide decent shock cord mount points but you could scratch build one just as good if you wanted.

What I would do:

- swap the elastic cord for 18ft or so of 9/16th tubular nylon
- swap the 2 parachutes (but keep them!! they're really good and lightweight) for a single 48" with a spill hole. I have tons from LOC and PML kits over the years that I move between rockets.
- swap the motor hook for an Aeropack to accept large H motors or baby I motors
- swap the baffle for either a nomex blanket or 3rd party baffle. If you go with nomex, you'll have to figure out a shock cord attachment. Epoxying the shock cord directly to the MMT through the forward ring is my normal way.
- use epoxy to build the fin can. It'll be plenty strong as long as you don't land fast on a hard surface. If that is a worry, upgrade to a slightly larger parachute. I keep stock from 18in to 96in just for these kinds of reasons.
- secondary option - add an electronics bay and go dual deploy and ignore the motor ejection. A 2.6" body tube isn't where I'd want to learn dual deploy but I add it to any rocket 3" and up so its not that hard to put on a 2.6" With dual deploy, I'd use the supplied parachutes and swap to 10' and 15' sections of tubular nylon for the shock cords.
 
heada said:
The shock cords that ship with the rocket are cloth and elastic and so have a lot of give in them. If you were to switch to nylon or kevlar, you need the extra length to absorb the same energy and thus why they're so much longer. Nylon does stretch some but kevlar doesn't. Personally, I'd go with the 18ft section of 9/16ths tubular nylon. It'll be more than enough and is still fairly cheap. Only reason to go with kevlar is for the flame resistance and tubular nylon will be good for dozens of flights at least. I've had PML kits with over 30 flights and the tubular nylon was scorched but still viable.

If you're going to modify the motor mount to accept motors longer than the standard AT 29/40-120, then you should make sure to use epoxy to attach the fins. Plastic fins wouldn't accept fiberglass well so doing a tip-to-tip wouldn't be advisable. That would also mean you'd have to do something else besides the baffle system that AT uses in that kit. If you're going to go through all that, I would drop the baffle and motor hook and use an Aeropack retainer with the separate baffle further up the body. LOC and Apogee both make good baffles that should fit that tube and provide decent shock cord mount points but you could scratch build one just as good if you wanted.

What I would do:

- swap the elastic cord for 18ft or so of 9/16th tubular nylon
- swap the 2 parachutes (but keep them!! they're really good and lightweight) for a single 48" with a spill hole. I have tons from LOC and PML kits over the years that I move between rockets.
- swap the motor hook for an Aeropack to accept large H motors or baby I motors
- swap the baffle for either a nomex blanket or 3rd party baffle. If you go with nomex, you'll have to figure out a shock cord attachment. Epoxying the shock cord directly to the MMT through the forward ring is my normal way.
- use epoxy to build the fin can. It'll be plenty strong as long as you don't land fast on a hard surface. If that is a worry, upgrade to a slightly larger parachute. I keep stock from 18in to 96in just for these kinds of reasons.
- secondary option - add an electronics bay and go dual deploy and ignore the motor ejection. A 2.6" body tube isn't where I'd want to learn dual deploy but I add it to any rocket 3" and up so its not that hard to put on a 2.6" With dual deploy, I'd use the supplied parachutes and swap to 10' and 15' sections of tubular nylon for the shock cords.
Click to expand...
Ok to start I will go with tubular nylon. The place I buy my rocketry stuff has 5/8 tubular nylon and I will check the parachutes as well. Why a spill hole? Aerotech kits now come with a 29 mm retainers so no engine hook. I have a Nomex blanket as well. Now about the baffle that comes with the kit a will probably use and I will still be able to use up to 5 grain motors. I have gfrorce rocket and with the baffle I can still use AT I205 in it. People say building it stock can take I205 with out epoxy and I'm guessing that's because its a big rocket(sims to 3200 ft)and have more drag. I'm not a fan of losing rockets and the astrobee d sims to 3800 on an I. I think though I will use epoxy a little on this one. Should I do epoxy fillets or just the fin can? Dual deploy hmmmm something to think about as well. I do have the stratalogger cf Altimeter.
 
highflyer1968 said:
Ok to start I will go with tubular nylon. The place I buy my rocketry stuff has 5/8 tubular nylon and I will check the parachutes as well. Why a spill hole? Aerotech kits now come with a 29 mm retainers so no engine hook. I have a Nomex blanket as well. Now about the baffle that comes with the kit a will probably use and I will still be able to use up to 5 grain motors. I have gfrorce rocket and with the baffle I can still use AT I205 in it. People say building it stock can take I205 with out epoxy and I'm guessing that's because its a big rocket(sims to 3200 ft)and have more drag. I'm not a fan of losing rockets and the astrobee d sims to 3800 on an I. I think though I will use epoxy a little on this one. Should I do epoxy fillets or just the fin can? Dual deploy hmmmm something to think about as well. I do have the stratalogger cf Altimeter.
Click to expand...
The spill hole gives a more controlled descent. Normal parachutes have to spill captured air out of the sides of the parachute and thus induce a side to side rocking. This can become fairly strong and I've had many rockets pop fins off when they swing to a side just before landing. There are a few options to combat the rocking such as parachute shape (sky angle doesn't rock but it twists) or a spill hole. Its been probably close to 10 years since I've built one of these kits so I didn't know they switched to a screw on retainer. That's good! Sounds like they also changed the MMT to be longer. In the past, it was only long enough for a 2/3 grain case before the baffle started. No reason to not keep the baffle if there's room for it and your longer case. I'd only epoxy the fin can. The fins are molded to scale shape and you could epoxy the fin to body tube connection but a fillet would ruin the scale fin appearance and probably is not needed. I've built one with nothing more than CA once and it was good for a few flights before a fin popped loose.
 
heada said:
The spill hole gives a more controlled descent. Normal parachutes have to spill captured air out of the sides of the parachute and thus induce a side to side rocking. This can become fairly strong and I've had many rockets pop fins off when they swing to a side just before landing. There are a few options to combat the rocking such as parachute shape (sky angle doesn't rock but it twists) or a spill hole. Its been probably close to 10 years since I've built one of these kits so I didn't know they switched to a screw on retainer. That's good! Sounds like they also changed the MMT to be longer. In the past, it was only long enough for a 2/3 grain case before the baffle started. No reason to not keep the baffle if there's room for it and your longer case. I'd only epoxy the fin can. The fins are molded to scale shape and you could epoxy the fin to body tube connection but a fillet would ruin the scale fin appearance and probably is not needed. I've built one with nothing more than CA once and it was good for a few flights before a fin popped loose.
Click to expand...
At allrockets website he has this https://www.allrockets.ca/Build/Parachutes/Nylon-48?cPath=19_213& Is that a good one? I think there is another site for chutes but I cant remember it? Aerotech changed to 29mm retainer a few years ago and yeah I can get up to a 5 grain motor in the motor mount with the baffle in. I've got the cheetah and the strong arm and built them with just CA and yeah they both pop fins off once and awhile.
 
highflyer1968 said:
At allrockets website he has this https://www.allrockets.ca/Build/Parachutes/Nylon-48?cPath=19_213& Is that a good one? I think there is another site for chutes but I cant remember it? Aerotech changed to 29mm retainer a few years ago and yeah I can get up to a 5 grain motor in the motor mount with the baffle in. I've got the cheetah and the strong arm and built them with just CA and yeah they both pop fins off once and awhile.
Click to expand...
That's a PML parachute. I have several and they're good. The nylon is thicker than some others like the AT parachutes that come with the kit but it being thicker material and heavier stitching should allow it to better survive a fast deployment. With it being a bigger parachute and thicker/heavier materials, you'll need more space to pack it. Might want to eliminate the bulk-plate that is used in the forward half of the airframe and attach the forward end of the shock cord much higher up. That'll give you almost twice the space for the parachute and it'll help move weight forward too.
 
heada said:
That's a PML parachute. I have several and they're good. The nylon is thicker than some others like the AT parachutes that come with the kit but it being thicker material and heavier stitching should allow it to better survive a fast deployment. With it being a bigger parachute and thicker/heavier materials, you'll need more space to pack it. Might want to eliminate the bulk-plate that is used in the forward half of the airframe and attach the forward end of the shock cord much higher up. That'll give you almost twice the space for the parachute and it'll help move weight forward too.
Click to expand...
Ok now any ideas on how to attach the forward end of the shock cord higher up? Well I'm off to work so I will check back tonight.
 
You could glue the coupler to both sections of airframe and blow everything out the forward end and attach to the nosecone. You could use the bulk-plate but rather than glue it to the top of the coupler, attach it near to the bottom on the nosecone. If it were me, I think I'd cut about an inch off the coupler and use that and the bulk-plate near the nosecone so mostly like the instructions, just much further forward. It'd still allow the airframe to split in the middle which helps alot with transport but gives you nearly the entire length of the airframe for recovery space.
 
heada said:
You could glue the coupler to both sections of airframe and blow everything out the forward end and attach to the nosecone. You could use the bulk-plate but rather than glue it to the top of the coupler, attach it near to the bottom on the nosecone. If it were me, I think I'd cut about an inch off the coupler and use that and the bulk-plate near the nosecone so mostly like the instructions, just much further forward. It'd still allow the airframe to split in the middle which helps alot with transport but gives you nearly the entire length of the airframe for recovery space.
Click to expand...
Ok that gives me something to think about. Going to order the chute and tubular nylon shock cord shortly
 
heada said:
That's a PML parachute. I have several and they're good. The nylon is thicker than some others like the AT parachutes that come with the kit but it being thicker material and heavier stitching should allow it to better survive a fast deployment. With it being a bigger parachute and thicker/heavier materials, you'll need more space to pack it. Might want to eliminate the bulk-plate that is used in the forward half of the airframe and attach the forward end of the shock cord much higher up. That'll give you almost twice the space for the parachute and it'll help move weight forward too.
Click to expand...
Ok now the question is why 48 inch and not a 36 inch chute? Do you need a little bigger with the spill hole because the rocket will come down faster? I am just wondering as I don't really want the rocket coming down so slow that it drifts away. Now I have not flown the Gforce rocket yet but it has a 40 inch chute and weighs about 8 oz more. just looking for your thoughts as I have never changed the stock chute and any rocket.
 
Normally it's 2x 30 inch parachutes without spill holes. Replace both those with a single 48 inch with a spill hole.

Honestly, I didn't do a Sim or anything, it's just the seat of my pants kinda sizing. Could go down to a 36 if you're coming down into a plowed farm field or go up to a 56 if coming down on rock/concrete.
 
Have you added the areas of the two chutes that are stock for this rocket and then figured out how large a diameter a single chute would need to be to have the same area as the two chutes. The sum of the 22" and 30" chutes areas are a bit over 1086 sq inches, so a single 37" chute will have the same area as the two smaller chutes, so I would use a single 36" chute, if I were going to use a single chute. I would also use a Jolly Logic Chute Release if drifting were a serious issue for your field.
 
I built this rocket years ago, it's a great looking design, and flies well. Medium CA is plenty strong for the fin can, it'll provide a stronger bond than epoxy between the fins and fin-lock rings. Build without the baffle. While I've built a number of AT kits with the baffle, I like to fly AT RMS-Plus motors, with the large red ejection cap - this is incompatible with a baffle. I mostly flew mine on 3 and 4 grain H motors. Definitely tie the two halves together with a long nylon shock cord, I used about 15'. IIRC, I used a 36" chute. To provide more room for the chute, I made the separation point higher than the kit design, by cutting off part of the payload and attaching to the bottom section with an extra coupler. The AT coupler was really tight, I needed to peel a layer, then used thin ca on the exposed portion, and sanded smooth. For motor retention, I used home-made Kaplow clips, though if you have the latest version of the kit, it comes with a nice aluminum retainer.

Lastly, I used springs from the HW store rather than the aluminum tubes for the antennae. They're much more durable. I was able to find tightly-wound springs the same diameter and length, and glue them right on to the plastic base.
 
rharshberger said:
Have you added the areas of the two chutes that are stock for this rocket and then figured out how large a diameter a single chute would need to be to have the same area as the two chutes. The sum of the 22" and 30" chutes areas are a bit over 1086 sq inches, so a single 37" chute will have the same area as the two smaller chutes, so I would use a single 36" chute, if I were going to use a single chute. I would also use a Jolly Logic Chute Release if drifting were a serious issue for your field.
Click to expand...
Now each section comes down separately with its own chute. Does the area of the two chutes still apply as the main part of the rocket comes down with a 30 inch chute?
 
highflyer1968 said:
Now each section comes down separately with its own chute. Does the area of the two chutes still apply as the main part of the rocket comes down with a 30 inch chute?
Click to expand...
The single 36" is if you decide not to use dual chutes, descent rate is partly based on weight, other factors also apply but weight is the most common easy to use factor.
 
Okay so I ordered to chute and the 18 ft of nylon tubular shock cord and it's here now. The shock cord seems like overkill for this rocket. It's much much heavier and with the shoot it adds approximately 5.45 Oz of weight. The new Sims with the added weight come to about 500 ft less altitude. What is everybody's thoughts on this large shock cord. Maybe if I was building the g-force rocket that would be a good choice.
 

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