LOC "Park Flyer" Sandhawk Motor Retention

[techrat]

Hello everyone! Currently on the build pile is a LOC Sandhawk -- the 1.6" diameter "Park Flyer". Comes with a 29mm motor mount and with an adapter, can fly on D through H motors, which makes it one of the more "flexible" kits I've seen in terms of the total impulse that it'll accept, and how you can fly it depending upon conditions. Interesting to note that LOC 1.6" tubes are considerably thicker than the Estes 1.6" (BT-60) tubes, so you can't swap bits between them easily.

So, here's the Question: Anybody else build this particular kit? I notice there's no motor retainer included, and the Estes plastic 29mm retainer would stick out too much, and potentially unbalance the rocket (although not likely given the length of the body tubes and the weight of the nosecone). But it might also get in the way of the fins, so I'm not using it. So what's the motor retention solution? Tape for a friction fit, plus a little on the edge of the MM tube to wrap around the plastic nozzle of the F motor?

Or is there a better retainer I should consider?

 

[heada]

I used the Estes plastic retainer and added a small bit of wood (popsicle stick) under the launch lug to clear the retainer. As for that added mass aft throwing off the CG/CP balance, the weight is so small, it almost doesn't move the CG at all.

 

[sl98]

I used the Estes plastic retainer and added a small bit of wood (popsicle stick) under the launch lug to clear the retainer.

You can also sand the ribs off of the Estes 29mm retainer and it will fit flush with the 38mm body tube. I used this method on a LOC EZE park flyer as well as numerous other 38mm/BT-60 based rockets. The thread below has a few pictures.

LPR / MPR Motor Retention Comparison

There has been a fair amount of discussion regarding the various LPR/MPR retainers. I've taken some pictures and weights of Estes, Rocketarium and Aerotech retainers. Hopefully this will help you choose what is best for your build. First the 18mm and 24mm retainers: The Rocketarium 18mm...

www.rocketryforum.com

LPR / MPR Motor Retention Comparison

There has been a fair amount of discussion regarding the various LPR/MPR retainers. I've taken some pictures and weights of Estes, Rocketarium and Aerotech retainers. Hopefully this will help you choose what is best for your build. First the 18mm and 24mm retainers: The Rocketarium 18mm...

www.rocketryforum.com

 

[DragonRocketry]

Aero Pack retainer and you do not have to modify anything.

 

[techrat]

Sanding the ribs off the Estes retainer seems like an acceptable solution and makes it look much better. I may give that a try once my extra parts arrive...

 

[samb]

Tape is always my first choice for these kinds of applications. I would move the aft centering ring forward a half inch. Then some quarter inch tape around the motor and tube and I’m good to go.

 

[Off Grid Gecko]

Aero Pack retainer and you do not have to modify anything.

I second this. I have a 38mm rocket with a 29mm MMT and the aeropack tucks in nicely at the back of the rocket. I've been having some trouble with mine being super tight on Aerotech single-use motors. Pretty much have to peel the sticker off to get them in there.
With smaller estes motors I wrap some pinstripe tape around the motor for a stop end and slide it in, works fine.

 

[techrat]

Well, I'm not planning to use Estes black powder F motors. Those seem to incurr HAZMAT fees when shipping, but some composite F motors do not, so I've been partial to those, and the Aerotech motors at least, have the rib to prevent them from sliding forward under thrust. When using D or E black powder Estes, the plastic Adapter Estes sells also has the rib, so I'm good there as well. I guess if I'm lucky enough to tumble over some Estes F at a hobby store, I'll give 'em a whirl, but never used those guys yet.

I'll look at the Aeropack retainer, but I've already got some Estes on the way from eRockets... but we'll see...

 

[jmasterj]

Giant Leap slimline will fit nicely without modification as well.

 

[heada]

The Estes retainers aren't perfect but you can't beat the cost for what you get.

2 Estes retainers for $7 from ACSupply ($3.50 each!)
1 Aeropack from CSRocketry for $23
1 Slimline from Giant Leap for $24

The only option cheaper is friction/tape. It works but I don't care for it when I have another option available. Also, since the Estes retainer is plastic, it can be easily modified like sanding the ribs down. You can't easily modify the Aeropack or the Slimline but there isn't really a need to either.

 

[techrat]

2 Estes retainers for $7 from ACSupply ($3.50 each!)
1 Aeropack from CSRocketry for $23
1 Slimline from Giant Leap for $24

I'm going to assume the non-Estes options are Aluminum? That might make them worth the extra $$.

 

[heada]

I'm going to assume the non-Estes options are Aluminum? That might make them worth the extra $$.

Yes, exactly. 6061-T6 I believe. Nearly the same weight as the plastic Estes but vastly stronger. I've had a rocket land aft first on concrete and while the Aeropack was dinged and scuffed up bad, it was still usable. If the same happened with an Estes retainer, it would shatter and become a mess.

 

[tsmith1315]

Those Giant Leap and Aeropacks are very nice, but cost half as much as the kit. To fly D and E motors? I can't play at that table.

 

[Funkworks]

I'm going to assume the non-Estes options are Aluminum? That might make them worth the extra $$.

I built the Park Flyer Hawk, and sanding the Estes retainer worked beautifully, especially with the real Hawk having a long tail cone.

Looking at a real Sandhawk, it seems to have a thin black tail piece, so if scale accuracy was a concern and cost of aluminum wasn't an issue, I'd go with an Aeropack.

 

[techrat]

Those Giant Leap and Aeropacks are very nice, but cost half as much as the kit. To fly D and E motors? I can't play at that table.

Come on man... It's only money! It's not like you're not already turning money into smoke and flame. Consider this. Between the cost of a motor plus shipping, it's $20 per flight on a composite "F", so what's the problem when you're flying a $40 kit with a $20 motor?

 

[Back_at_it]

I've done two methods. I have built the LOC Hawk and Magnum in 1.6". Both are great kits but the Hawk needed a lot of nose weight to be stable. On the Hawk I used a stock 29mm motor mount and simply friction fit the motor when using 29mm motors. When I run 24mm motor I use the Estes plastic adapter and friction this that as well. Both work well but you'd be surprised how tight it needs to be not to push the motor out. I can tell you that an F44 has one heck of an ejection charge and I have spit the motor out once and partial out a second time.

For the Magnum I quickly realized I wasn't going to fly it on a 29mm motor. Mine was only a touch over 8oz when completed so it was over kill. I made my own 24mm motor mount and permanently attached it inside the 29mm tube. The new mount extended past the rear of the rocket far enough to attach a 24mm Estes motor retainer. I painted it black so it looks like a engine nozzle sticking out. Have flown a number of times with no issues.

I personally think Estes retainers are the way to go. I can replace the Estes retainer 6 times before I get to the price of one Aeropack. I have yet to need to replace an Estes retainer on anything.

 

[tsmith1315]

Come on man... It's only money! It's not like you're not already turning money into smoke and flame. Consider this. Between the cost of a motor plus shipping, it's $20 per flight on a composite "F", so what's the problem when you're flying a $40 kit with a $20 motor?

Oh, I understand that perspective! And I understand there are a lot of folks here who can build the way they want and cost isn't much of an issue. More power to those who can do it just like they want!

My annual budget wouldn't build the average J-K rocket I see here, much less fill it with AP. So, I build everything with economy as a priority. In that light, $20 is significant, as is increasing the price of a kit 50%. It has to be evaluated as opportunity cost around here.

 

[techrat]

My annual budget wouldn't build the average J-K rocket I see here, much less fill it with AP. So, I build everything with economy as a priority. In that light, $20 is significant, as is increasing the price of a kit 50%. It has to be evaluated as opportunity cost around here.

I get it. In another thread, I was trying to calculate the cost of a cluster of 4 C6 motors versus a Single E12 motor, because I was changing a Quest "Quad Runner" from a clustered rocket to a single 24mm motor'ed rocket -- I really wasn't interested in the cluster because it's often problematic and I think it burns up a lot more money per flight (assuming it even launches properly). So I was going to build the kit as a 24mm single. However, the current idea is to build it with swappable motormounts so I have the option of flying both ways.

 

[tsmith1315]

However, the current idea is to build it with swappable motormounts so I have the option of flying both ways.

Cool. I'm doing that with a Big Der Red Max and a 4 x18mm mount that was given to me, mainly because I have it and have never flown a cluster. Will be swappable with 24 and 29's.

I hope it works well for you!

 

[jmasterj]

I get it. In another thread, I was trying to calculate the cost of a cluster of 4 C6 motors versus a Single E12 motor, because I was changing a Quest "Quad Runner" from a clustered rocket to a single 24mm motor'ed rocket -- I really wasn't interested in the cluster because it's often problematic and I think it burns up a lot more money per flight (assuming it even launches properly).

I think people mostly cluster because they think it's cool. With modern motor availability, it doesn't really make sense if you're optimizing performance in hobby rocketry.

 

[techrat]

I think people mostly cluster because they think it's cool.

Yes, exactly. But it really is cool to see lots of flame which is what you get with clustering. But yes, it's like the guys who think it's cool to have straight pipes on the motorcycle and be the loudest guy in the neighborhood. I'm a motorcycle guy, but I like my scooter because it's quiet (and gets fantastic MPG).

 

[jmasterj]

Yes, exactly. But it really is cool to see lots of flame which is what you get with clustering. But yes, it's like the guys who think it's cool to have straight pipes on the motorcycle and be the loudest guy in the neighborhood. I'm a motorcycle guy, but I like my scooter because it's quiet (and gets fantastic MPG).

Not really a good analogy. The purpose of hobby rocketry is primarily the pleasure of the hobbyist. The purpose of a vehicle might be pleasure only, but is often (usually?) primarily getting the passengers or freight from point A to point B. So "because it's cool" is more primary in hobby rocketry than in most vehicle driving.

 

[sl98]

If the same happened with an Estes retainer, it would shatter and become a mess.

Did this really happen or are speculating this would happen?

I regularly use the Estes retainer to fly HP up to and including I200W and H268R. They have not melted nor shattered.

Those Giant Leap and Aeropacks are very nice, but cost half as much as the kit.

True but the other factor to consider is how much weight these add to the aft end of the rocket. I did not have a Giant Leap or Aeropack retainer available when I did my comparison thread but I did have an aluminum Aerotech retainer. The Estes retainer was 1/2 the weight of the Aerotech retainer.

 

[BEC]

I agree… @heada, have you actually seen one shatter?

I have one of the Estes retainers on my LOC “park flyer” IRIS. As with other models that size (notably the Star Orbiter) which use the same OD tubing and the Estes 29mm motor retainer, all you have to do is make sure the retainer is turned so that the launch rod goes up between the flutes. No grinding down required. Regardless of your setup/motor choice surely your can turn the retainer enough one way or another (a few degrees at most) for this.

And with standard rail buttons, it’s not even a concern.

 

[heada]

Coming in from about 2000 feet with a tangled parachute and landing on concrete directly on the plastic retainer. The removable ring broke (not shatter per se) It was the LOC ParkFlyer BBX which is one of their heavier kits on an AT G104T-10. 2 of the aft fins also broke off.

I never said it was likely or even common. Just that the aluminum retainers are much more durable. I would still recommend the Estes retainer over the Aeropack and Slimline in nearly every case.

 

[BEC]

OK - that makes sense. Since the retainers are sold in packs of two sets for $10 MSRP, that’s still a pretty good deal if you have to replace a retainer ring….

I think we actually agree here pretty much .

 

[Back_at_it]

Did this really happen or are speculating this would happen?

I regularly use the Estes retainer to fly HP up to and including I200W and H268R. They have not melted nor shattered.

I've had rocket come down on concrete, rocks, gravel etc. and never shattered or cracked an Estes retainer. I've had large scuffs, and gouges in them but never had one fail. I would think that pretty much anything that comes down without a chute and land on a hard surface will be toast.

 

[techrat]

Update: My plastic retainers came in the mail (hurrah), and I was able to sand those ridges down quite easily. 10 minutes of hand-sanding on 80-grit, and then some 150 grit and those ridges came off easier than I imagined. And yes, once the ridges were sanded down they do not interfere with the fins. Now I just need to come up with an interesting paint scheme.

 

[StreuB1]

Sanding the Estes retainer to round is brilliant! WAY cheaper as well.

Going to grab and handful and prep them up to have on the shelf ready for builds.

Thanks for the tip!!

 

[techrat]

Sanding the Estes retainer to round is brilliant! WAY cheaper as well.

I'd love to take credit for the idea, but it's not mine... Check out this thread:

LPR / MPR Motor Retention Comparison

There has been a fair amount of discussion regarding the various LPR/MPR retainers. I've taken some pictures and weights of Estes, Rocketarium and Aerotech retainers. Hopefully this will help you choose what is best for your build. First the 18mm and 24mm retainers: The Rocketarium 18mm...

www.rocketryforum.com