Fibreglass needed?

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Well-Known Member
Jul 23, 2009
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Hi everyone,

Havent been here for a while... I am about to build a PML Bull Puppy for my Level 1 cert, and have a question regarding the use of fibreglass. I plan to fly it on mainly H's and a few I's. It it worth the time and money to fibreglass the inside of the piston and engine mount (baring in mind I haven't fibreglassed anything before, so would need to buy laminating epoxy and everything), and if it is, where is a cheap place to buy laminating epoxy and fibreglass cloth in the UK??

Thanks in advance,

Depending on the "I" motors you intent to fly, you don't need reinforcements.

See here:

If you glass a rocket, you may glass the body tube and maybe even the fins (tip to tip). This should only be done with the phenolic kits, as Quantum Tube is unsuitable for glassing.
The engine mount is rarely glassed and the size of the motor doesn't matter for the piston. I don't remember seeing a piston glassed.

Forget the fiberglass, buy yourself a motor retainer instead!! A decent way to retain the motor is the biggest issue with this kit. I used an Aeropack on mine.

I used fin fillets: MMT, internal and external body tube, nothing more. Rough up the areas were epoxy is to be applied with 60 grit paper and clean with rubbing alcohol. Mine is holding together just fine.

Bullpup -retainer.jpg
Simple answer: no..Expanded: No, you will just be adding unneeded weight in an area non condusive to a stable flight..You CAN use the epoxy to 'ablate' or coat, the bulkhead in the piston that faces the motor to protect it from the ejection gases. I recommend installing the piston like it was a cup so the open end is toward the nose of the rocket and 'scoops' your parachute out at ejection.