Oz/In when glassing tubes.

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Handeman

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I'm putting together plans for my next scatch built. The BT will be 4 LOC tubing which I plan to glass.

I know the weights per sqr inch of the plywood I'll use for fins and CRs, the weight per inch of the tubing, the nose cone, ect.

What I don't know and am having a difficult time estimating is the additional weight when glassing the tubes.

The 4" Loc tubes weight 0.4 oz per inch. If I put two layers of glass on it, what type of increase will I get. I don't see much weight difference from the fiberglass cloth. The whole tube area is about 1/3 yard so the difference between 6 oz and 2 oz cloth would be 1 1/3 oz for the whole tube, or 0.04 oz per inch.

The resin that makes up most of the weight when glassing the tubes. Can anyone tell me how much weight per inch or per sq inch I will add when glassing? I would suppect there is a difference when just glassing and when vacuum bagging. How big of difference in weight is there?

Does these same weights apply when doing TTT on the fins too? Would it be slight higher because of the resin soaking into the ply fins and BT?

I can get all the weights after I build and glass, but I need a pretty accurate CG estimate beforehand to determine what fin size to use and thus CP placement.

Thanks....
 
If you are going to fiberglass the whole rocket. I would think you'd be adding more weight to the top of the rocket. If the size of the fins are really going to be that close to making it unstable just add nose weight. The weight of the resin depends on how thick you apply it thicker cloth more resin to absorb.If you can vacuum bag or use a roller to squeeze out excess resin much better. Sorry I dont have weights theres going to be a lot of variables and how much resin you squeeze out.
 
The added weight depends on how "happy' you get with the resin.
For your comparison I glassed a 4in thor with 2 wraps 6oz and added a total of only 3/4 lbs to the weight of total rocket.

Used just enough resin for the glass to show clear. No excess dripping off or running. These are loc tubes I believe.

On 7.5 in tubes 48 in long, 2 wraps and resin added 1 and 1/2 lbs.

The weight is evenly dispersed and does not require adding any NC weight.

The size of your fillets can add just as much or more weight, than glassing the rocket if you go overboard like many do. They definitely add to the rear end weight.

Build light and strong = fly high on smaller motors !
 
The added weight depends on how "happy' you get with the resin.
For your comparison I glassed a 4in thor with 2 wraps 6oz and added a total of only 3/4 lbs to the weight of total rocket.

Used just enough resin for the glass to show clear. No excess dripping off or running. These are loc tubes I believe.

On 7.5 in tubes 48 in long, 2 wraps and resin added 1 and 1/2 lbs.

The weight is evenly dispersed and does not require adding any NC weight.

The size of your fillets can add just as much or more weight, than glassing the rocket if you go overboard like many do. They definitely add to the rear end weight.

Build light and strong = fly high on smaller motors !


This sounds like what I'm looking for. How long was the 4" glassing on the Thor? I tried looking on the BSD site for specs. but it's down because of an accident with a saw.

The 1 1/2 lbs on the 7.5" x 48" works out to .021 oz per sq in. which would mean about 9 oz on my 4" by 34" Loc tubes or .265 oz per inch. That's pretty good considering the tubing itself weighs in at .400 oz per inch. I would have thought the glassing would equal or surpass the weight of the tubing.

This works very well because I have 6 oz glass on hand.

I would like to keep the rocket about 6lbs empty, 8 lbs at the most. It'll have a 54mm MMT at 22" long which will hold the largest 54mm casing and a K1275R load. I want to make test flights with 38/360 or 480 I motors. Most should handle 6 to 8 lbs. For an L2 cert, I might use the K1275R or a K700W. Either would be a really cool cert flight, over a mile high and pushing mach.
 
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