Hive Ship

[neil_w]

Thanks for the info, first swing test I’ve ever done. It was stable in flight just pointed the wrong direction, which I figured would violate the pointy end up principle.

Well, this rocket doesn't have a pointy end. Maybe it's just confused?

 

[jqavins]

It was stable in flight just pointed the wrong direction, which I figured would violate the pointy end up principle.

Well there's your problem; you've got no pointy end! Which way is up? This poor rocket is confused!

EDIT: Damn, we think alike.

 

[lakeroadster]

Thanks for the info, first swing test I’ve ever done. It was stable in flight just pointed the wrong direction, which I figured would violate the pointy end up principle.

Vern Estes wrote a paper on Rocket Stability, see below. He mentions "if the center of pressure is extremely close to the center of gravity, the rocket will not point itself into the wind unless it is pointing directly forward at the time the circular motion is started".

 

[Daddyisabar]

Have no fear. Power, Nose weight and swing testing are your friends; as is a good launch system and calm weather. Widely spaced motors will fly even though they are hallmarks of poor rocket design. It is mostly an ignition issue.

 

[DrewW]

Rebuilt and repaired my 3D printer over the last few days and its now working better than ever. New tailcone has been printed which is about 20% lighter, and some hexagonal tube fins as well. to help add some more stability. Hoping to have something that swing tests straight by next weekend.

 

[DrewW]

3D printer has been seeing lots of action the last couple days as I've been printing off and testing various nose weight holder prototypes to get enough weight in addition to not ruining the aesthetic I'm going for. Current holder holds 58 steel BBs and is press fit into the main body. This is iteration 5 or 6, and can only really be observed unless you're looking down the pipe.



I have various length hex shaped tube fins printing right now, and ready to attach tomorrow. Only gap at the moment is rail lugs...still not sure if I want to use mini rail buttons or 3/16" lugs.

Hopefully I'll have a stable swing test this weekend and then it's just painting and waiting around for the next club launch.

 

[Hobie1dog]

you sure are creative

 

[DrewW]

Well first some pictures of the build earlier today















So today I finally managed a stable swing test, unfortunately it was without the hive tailcone. I had taken it off earlier while getting hex fins epoxied on. I thought no big deal and slapped it in to test, only to find things unstable.

The rocket CG shifted by 1/8" so that clearly wasn't the issue. I'll have to take a hearty I was told so by @lakeroadster at the outset of this project. Regenerated my tailcone with a 50% increase in grid cell size and printing now. Hopefully that is enough to keep the air flow from choking, and stagnating in the main tube. After that mini rail buttons will make their appearance and we'll be ready for some dressing up.

 

[lakeroadster]

Quite the interesting looking ship. Well done.

 

[DrewW]

Well that was an interesting couple of months, the day after my last post I ended up in the hospital for an appendectomy. Even though I've been feeling mostly normal for several weeks now, the summer heat and humidity has been something else and making it less fun to be in the garage workshop. As weather gets a little more bearable, and with an October launch in my sights I'm back to pushing this forward the last few steps.

I think this is going with launch lugs/buttons so I don't worry as much about rod whip with an asymmetric motor start.

 

[lakeroadster]

Glad you're doing better.. looking forward to the updates. Funny how life gets in the way of hobbies, right?

 

[DrewW]

Planning motors for the launch, looking at lots of initial thrust. OR didn't like the C5 not enough oomph but I locked myself in to 18mm sizing so my options are limited. OR and thrustcurve helped me narrow the choices a bit.




Overall, it looks like the D13W is the winner. High total impulse, very fast rise with a slow decay, and the longest tail...hopefully this accommodates an asymmetric motor start. Unfortunately these appear to be in short supply at the moment but I was able to snag several sets of these and 18/20 cases at BuyRocketMotors.com

Hopefully I've considered the concerns appropriately but this will end up on an away pad regardless.

 

[DrewW]

Mini rail buttons mounted. Added some #2-56 screws to the honeycomb grid so I can replace with a different grid size/configuration based on performance of the maiden flight.

final weight appears to be ~240grams with D13 motors and will be coming in a little fast on two 12 inch chutes.

Probably not going to launch this weekend because the weather is calling for moderately high winds, and this is probably going to take some very low winds to be stable.