ANDRIS GOLTS

Hi all as in previous post im in the process of building a 21 inch air boat for brushless power i would like to build a wire prop cage . Im guessing 1/8 round stock brass or ss or styrene ! What are the procedures for this do i need to make a jig ! In my search i did not find any build threads on this subject. What would be the best way of proceeding with this project ! Regards Andris Golts.
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Tidnab

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I saw one last summer that the kid used a metal cage from a household fan for his prop cage.He made a bracket to hold it onto the boat,which also held the nitro motor he had on it.

Retiredat38

What diameter prop are you looking to use? Make your cage at least 2 inches bigger.

Do not use plastic. The cage is a safety device intended to control a runaway prop. Plastic will simply shatter and add to the pieces flying through the air.

Brass is heavy. If possible I'd go with aluminum tube. Aluminum can work but it would require more fiddling. You can't solder it and welding I suspect is not in your skill set. Otherwise go with a brass rod for the round edge of the cage and use brass tube for all the supports. 1/8 inch should work. Might even get away with 3/32 depending on prop size but no smaller.

A jig can be simple based on the shape of things. You'll have basically two ends to this cage. A smaller hub which attaches in front of (towards the front of the boat) the prop. Usually in front of the motor too. And the larger back end of the cage. Keep it simple and incorporate the front cage mount into the motor mount.

For the larger end I'd make it an inverted 'U' shape. The legs can then mount to the boat hull simply by insertion into some holes and either glue or set screws to hold it. Bend it first and mount to a piece of wood for a jig. Then determine the front piece size and shape (a 'U' shape works here too) and use another piece of wood to hold it in place in front of the big end. Then start sizing and soldering in the supports between the two. A bit time consuming but overall quite simple.

I can see a side view of this where the support tubes have a 90 degree bend in them. Make a bender for this by deciding how sharp a bend it will be (not very sharp). Take a piece of plywood the thickness of the tubes and cut a circle (wheel) out of it with the bend you want. Then put sides on this ply that overhang the edge. Like a pulley. The sides need to be robust (strong) to control the tube. This is your tubing bender.

Sounds like a fun project to me. If I had fewer projects of my own I'd be tempted to do one of these.

Good luck!

ANDRIS GOLTS

Hi Retiredat38 thanks for replying to my post . Prop diameter is 7.5 inch pusher prop as for my skill set would be my luck as i am licensed steamfitter plumber welder for 36 yrs with lots of experience on aluminum and stainless thin wall tubing using tig welding methods and stainless tube bending experience will also come in handy once i make up a jig i will probably start this project next week end . Regards Andris Golts.

Got RPM

Actually, the prop cage is to keep unwanted items out of the prop. I’ve run airboats for many years and have never had a prop shatter, even when hit with a lot of water. NOTE: only plastic props on airboats, no wood! The cage keeps fingers and bystanders out of the prop, so the front and sides need to be covered. The more metal in the cage the less airflow, so use just enough to protect you and others. Screen etc. is a bad idea as it really restricts airflow.



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Retiredat38

Well good luck to you. Don't forget to post some pics. I hope you understood my explanation.

Retiredat38

Actually it does both. As I said, the cage is a safety device. And while you trust plastic props, I have seen them throw a blade or two over the years. One ended up in the leg of a young girl who was watching.

I'll admit for an air boat plastic props are preferred. Especially when running an electric motor. But Wood props can be used. You simply have to take some precautions and seal the wood with something.