Protect Your Aft

[Joe V]

My club flies at an airfield, some of us were having a discussion this past Saturday at the launch; if your airframe extends below the fins, when it impacts a hard surface, the airframe, motor retainer, and/or motor case take a hit. I am thinking I will add a piece of PVC with a diameter smaller than the airframe and larger than the motor mount. This piece would extend just slightly longer than the motor mount or airframe so it would take the hit and protect the other parts. One of our other members adds a short piece of blue tube coupler to the end of the airframe to achieve the same protection.

Does anyone else have the same issue with hard surface impacts? Looking to see what other solutions are out there.

 

[G_T]

I'm not sure what size motors you are flying, and it might make a difference. But, were you to attempt the extended tube with a larger motor, it would melt and burn away the tube. The tube would be in close proximity to a major source of heat!

If there is a big concern with landing on hard objects, perhaps a larger main chute to slow the descent rate might be in order.

Gerald

 

[Joe V]

Mostly talking high power, G and above, the extended tube would only extend just a hair past the motor retainer and it would be a larger diameter than the motor mount, so I'm fairly sure it would not burn.

 

[Coop]

Eh.... I'd have to see it before I decide, but I don't really dig the idea of putting extra stuff at the aft end. I'd be more likely to have the MMT recessed a bit into the airframe or rethink my recovery approach...


Later!

--Coop

 

[jimzcatz]

Ahhhh, Fentress Airfield. I know it well!! I grew up in Va Beach.

 

[PhlAsh]

Joe, I think it was JoeZ's Formula98 - he did that with a piece of BlueTube. So it landed on the grass...

 

[patelldp]

Vern Knowles did something very similar on his Dynacom Scorpion:

If you haven't yet, give his site a look!

 

[Joe V]

Dan, thanks for the Vern Knowles reference, that is exactly the issue I am trying to find a resolution to. I wonder if that rubber burns up any? I'm thinking, in my case, the rubber ring would have to be removed to load/unload the motor, a pain. He's got some detailed info on his rocket builds, really cool website!

Phill, yea I was talking to JoeZ and he showed me his Blue Tube solution. I think I'll try the Blue Tube if I can get my hands on a small piece, if not I'll try PVC. I have a 3.9" dia rocket that I may be able to get some BT for, I also have a 3" dia so we will see if I can get BT for that.

Jim. yes good old Fentress, lots of concrete and asphault. The good news is that they are cutting down lots of trees around the runway and our (treeless) field is getting much bigger. I think when they are done it will have doubled or tripled in size.

 

[patelldp]

If you look at some of the pictures, the bumper he has in place does some funky things to the motor exhaust...



It appears to mess with the 54mm Medusa nozzle motors. The AMW's he's flow it on are unaffected.

 

[G_T]

It appears to be acting as a nozzle extension, and the result is an over-expanded nozzle. That degrades motor performance. This is a risk with having anything near the exhaust path. It can potentially alter the flow.

Gerald