Thin wall FW tubing for motor mounts

[boatgeek]

Is there any reason not to use thin wall filament-wound tubing for a 54mm motor mount? The project could fly on a full range of 54mm CTI/Aerotech motors. I'd like to save a little weight if the strength of thick wall isn't needed.

 

[djs]

I can't see why this would be an issue.. the load is more carried by the centering rings/epoxy bonds. I've never heard of an unsuccessful flight where it was the motor mount tube itself that failed.

 

[Bat-mite]

No experience, but if cardboard works as a MMT, then why not TWFG? Of course, you need CRs that accommodate the outside diameter, but you already knew that.

 

[djs]

I've heard of people flying rockets with no motor mount- just centering rings. Not something I'd do, but I guess if that works, then a thin wall fg mmt would work too.

 

[DavidMcCann]

To me, the effort of getting new rings is higher than the tiny weight savings you'd be talking about getting.

But would it work? Sure, I don't see why not.

 

[Bat-mite]

To me, the effort of getting new rings is higher than the tiny weight savings you'd be talking about getting.

But would it work? Sure, I don't see why not.

Yeah, since the inside D of the CRs would have to be smaller, it's not like you can take a std. CR and ream it out. Brand new CRs would need to be made. And if they are FG, you're going to pay for it. And if they are wood, then you aren't really saving any weight, probably.

 

[boatgeek]

Thanks all for validating what was in my head. The CRs for this haven't even been ordered yet, so it's no big deal to make sure they're the right OD. It will also have a retainer, so the forces should be spread out nicely around the MMT tube. I was looking at the two sizes of tubing and trying to figure out why you'd buy heavy wall.

 

[AdAstraPerAspera]

If you are using a tube mount retainer, make sure you can get the right size. I know some kits using thin wall motor mounts needed a special adapter ring. If you are using the bolt on version you are fine.

 

[tim cubbedge]

For what it's worth, all Wildman tubes are now thin wall, MMT included. Probably have been for close to 2 years.