supersonic LOC cardboard

How fast have people been pushing LOC tubes? One of mine went about 1300mph once, at least according to an Eggtimer, without serious problems though it came back with some odd blistering near its seams. Not on the seams, but nearby, and at the same angles. I suppose it could have been caused by a rough landing, but that seems unlikely given the location and nature of the damages. Placing heavy weight on it down its length gave no sign of weakened strength, though.

You have to watch out for column buckling. Eliminated if you use a full length coupler inside the airframe.

Bob

I'm happy to hear that, 'cause I have one I'm planning to push similarly some time in the near future. As for the damage, that seems weird. I wonder it the blisters are directly over the seams in the second layer spiral? How high did that flight get? Conceivably the blistering could be from air trapped in the second layer expanding as the ambient air pressure dropped. Maybe? Possibly?

watermelonman said:

though it came back with some odd blistering near its seams. Not on the seams, but nearby, and at the same angles. I suppose it could have been caused by a rough landing, but that seems unlikely given the location and nature of the damages. Placing heavy weight on it down its length gave no sign of weakened strength, though.

Click to expand...

More likely that you blistered the glassine where it was over the seams of the tube. The seams we fill are actually the seams of the glassine wrap. The tube seams are about halfway between, but covered by the wrap.

38mm tube I presume? Kurt

Weird, my damage was only a few millimeters from the filled seam, not far enough to be halfway. I still suppose it could have been impact damage, but my naive eye still thinks it flight pressure damage. I wish I had taken better pictures before I started fiberglassing.

This was a 54mm airframe with a big 38mm motor, about 1300mph to 8000 feet. Like I said, though, it is getting fiberglass now, and I will push it to various increasing speeds up until a little past the speed I think originally damaged it.

Any loc type tube with the glassine layer should have the glassine layer removed before lamination in my opinion.

I am in the process of glassing a section of LOC 3" tube. I removed the glassine and found that the layer below has a waxy feel to it. Still gonna glass it but I am slightly worried about bonding. That said the surface mounted fins seem like they are on for good.

markkoelsch said:

Any loc type tube with the glassine layer should have the glassine layer removed before lamination in my opinion.

Click to expand...

I am probably going to get a lot of grief from a lot of you here but . . .

I used a Soller Composites glass sleeve on my 5.5 inch Loc Big Nuke. Five flights later the glass showed no sign of separation. The last flight was on a single use Aerotech L1000 that cato'd. Even then when the tail end blew apart, there was no evidence of layer separation. I did not remove the glassine layer before laying on the FG sleeve.

I also did not remove the glassine layer from the 54 mm MMT in that rocket. I only rough sanded the areas where the centering rings were. Again, the two forward centering rings I put in it were very much intact without evidence of epoxy separation. The aft ring was blown out by the cato so I cannot comment on that one.

I've had no problems with leaving the glassine layer on Loc tubes, even for motor mount attachment sites.

I would not give you grief- it is working for you. I know somebody who did a loosely laminated tube, and who hammered it pretty hard- the entire lamination broke loose in a cylinder. Only saw it once though...