HPR Build questions

[plugger]

Hello all,

I was hoping I could get some advice from y'all. I've received my PML AMRAAM 2.1 (29mm) and Binder Thug (38mm) and I've got a couple questions regarding the builds. These kits are quite different from my Aerotech Initiator, specifically the lack of a thrust ring and thrust ring flange for the motor mount. My question is should I be fashioning my own, or leave it out. If I don't include one then I don't think I'll be able to fly SU 29mm engines in the AMRAAM. If I do include it I won't be able to use HPR 29mm reload casings longer than 120mm. I haven't received my 29 40/120 RMS yet (it's just left Melb Intl. Customs), but given my 24mm version there seems to be a small lip/ring at the base of the RMS that should keep the motor from shooting straight into the body tube and producing an expensive firework. Are these assumptions correct? Any advice?

Secondly, the Binder came with the nose cone in inverted into the body tube and now the cardboard is a larger diameter than the nose cone to the point where it is quite noticeable. I'm assuming I can just use masking tape to provide a good friction fit for the NC, but I believe I'll have to sand the body tube down quite heavily to provide good aerodynamics. Any advice on this one?

Thanks again for all of your help!

plug

 

[troj]

I haven't received my 29 40/120 RMS yet (it's just left Melb Intl. Customs), but given my 24mm version there seems to be a small lip/ring at the base of the RMS that should keep the motor from shooting straight into the body tube and producing an expensive firework. Are these assumptions correct? Any advice?

Yep, the rear closure has the thrust ring as part of it.

For the SU motors that don't have thrust rings (current revision motors now do), you can use masking tape to build up a thrust ring, to solve that problem, when motors don't come with one.

Secondly, the Binder came with the nose cone in inverted into the body tube and now the cardboard is a larger diameter than the nose cone to the point where it is quite noticeable. I'm assuming I can just use masking tape to provide a good friction fit for the NC, but I believe I'll have to sand the body tube down quite heavily to provide good aerodynamics. Any advice on this one?

Flip the tube around and put the flared end towards the bottom?

I definitely wouldn't sand the outside of the tube down.

-Kevin

 

[Chrisn]

Secondly, the Binder came with the nose cone in inverted into the body tube and now the cardboard is a larger diameter than the nose cone to the point where it is quite noticeable.

You should be entitled to a replacement, although ive never dealt with binder, it should be expected.

 

[Binder Design]

Hello all,

Secondly, the Binder came with the nose cone in inverted into the body tube and now the cardboard is a larger diameter than the nose cone to the point where it is quite noticeable.
plug

The only way to bell that thick airframe material is to jam the cone in so hard that you would have to use a dowel and a hammer to remove it. I'm assuming that you didn't need to do that.

Please test fit the cone in both ends of the tube. You'll find that the fit is the same in either end. Our cones fit loose. Snug it up with tape around the two raised bands on the nosecone shoulder. The OD mismatch after it is finished will be very slight, if any at all.

If one end of the tube is indeed belled out from the nosecone becoming jammed into the tube, we'll replace it.

Thanks,
Mike Fisher
Binder Design

 

[Diosces]

The Thug Body tube is quite sturdy and thick-walled, hard to imagine it would be belled out at one end by nosecone during shipping. A wrap or two of masking should provide a good friction fit.

As for sanding down any slight irregularity in tube od to improve aerodynamics, I suggest dont bother. This model is designed as a classic character in the low and slow league. But it's sturdy enough for the large J's if you went with a 38 mm motor tube.