Strength of G10 Bulkplates - pullthrough on AV Bay?

[llickteig1]

Here is an image. The temporary wingnuts are attached to 1/4-20 threaded rod. When I fly this, I use regular nuts and lockwashers. (no need to point out that the wingnut overhangs the diameter of the AV-Bay).

The 1/4-20 forged eyebolt is attached with a fender washer, lockwasher (or locknut), nut and a dab of epoxy. Each bulkplate is actually two plates epoxied together.

This design came with my vindicator, hellfire, frenzyXL and competitor 4 so I assume the design is fine. However, I was asked by someone to consider the forces on these plates so that got me thinking about the strength of the plates as the force is residing on the plate and being spread to the fender washer on the eyebolt, then the washer/nut (x2) and then plate again.

Yours is a very common design and the problem is that the force transfer is a bit below optimal. I have used this design on a few AvBays and most likely you won't have a problem unless you get a vigorous ejection, say if the main pops during thrust or something really bad like that. Even than, you probably wouldn't get a complete failure. You could beef-up the connection similar to Windeavor's design if you're worried, but two G-10 plates will take a lot of stress.

--Lance.

[english_1969]

Thank Lance.

I liked his suggestion and will probably do that. The Frenzy XL is probably going to be my L3 rocket so that's what I'll use his tweak on.

W

[dixontj93060]

Another option besides adding a slab of steel is to use a Kevlar cloth laminate to reinforce the hardware attach section of each bulkhead.

[Rocketjunkie]

I use the center rod through the altbay with 4" or over airframes, 2 offset ones on smaller bays . Most of my rockets are cardboard, Blue Tube, etc and the bulkheads are single plywood, fitting into the coupler against a slit coupler as a shoulder. The rods are all 1/2" to fit the lug on my sleds (all interchangeable) aluminum in the larger bays, wood in the under 4" rockets. In fiberglass airframe rockets, the bulkplates would be G10. The eyebolts screw into the rods both ends, all loads go through the rods rather than having the bulkplate taking the load. Never had a bulkplate fail but I have had a plywood CR fail where the eyebolt and fender washer were attached (not during a successful flight, it was a cato). Once I had the eyebolt unscrew from the altbay due to a spinning booster but making sure it's not loose prevents this. (I remove the booster end eyebolt to access the altimeter.)

[AlphaHybrids]

I use the centered rod with eyenuts on either side like Jim. I use 1/4" plywood for my bulkheads because they are not bearing any load, just sitting there. I've never had an eyenut unscrew from a flight. It is hard to imagine how your parachute could be generating enough torque to overcome a lockwasher when the rocket end is free to rotate and not providing resistance.

Edward

[cwbullet]

Another option besides adding a slab of steel is to use a Kevlar cloth laminate to reinforce the hardware attach section of each bulkhead.

I have never seen that done. There a lot of ways to get to the same finish line.