Blast tube recommendations?

[tpwpny]

Decided to install a blast tube into my first model. I've heard that aquarium tubing works but my local pet shop didn't have anything wide enough. Any other recommendations? I imagine it has to be a super light material... maybe something I can find in Home Depot?

[Bill Gaylord]

If you have a large sheet of clear acetate like these models use for the windshield, you could roll your own, using a dowel rod as a mandrel, and glue the seam. A good hobby shop should have it. I would use a thin gauge, to keep the weight light. I've made various EDF ducting tubes from clear sheet, using thick CA with activator on the seam.

[tom arnold]

You said "install... one INTO your model". Is that a misprint? You take the blast tube into and out of your model each time you wind.
Possible tubes are carbon fiber helicopter booms, arrow shipping containers, aluminum tubes (the best), cardboard rocket bodies, or a roll-your-own as noted.

[Steve Blanchard]

Tom is correct. A blast tube is slid into the model around the rubber motor while winding. When you are finished winding you remove the tube before flying (Unless you are Al Lawton who in the heat of a mass launch battle forgot to remove the blast tube one round. He still won!). Anyway, if you are getting into using blast tubes then you will need more than just the tube. You will need a wire for winding and removing the tube. Do a search on you tube for using blast tubes on Rubber models. I'm sure you will find something.

Steve

[tpwpny]

You said "install... one INTO your model". Is that a misprint? You take the blast tube into and out of your model each time you wind.
Possible tubes are carbon fiber helicopter booms, arrow shipping containers, aluminum tubes (the best), cardboard rocket bodies, or a roll-your-own as noted.

Go figure - that's how new I am to this... I thought the blast tube stays IN to protect the fuselage from a break during flight!

I'm sure everyone will get a chuckle from that one! Sorry!

Given that, I guess some of the tubing I already have around can work. Heavier is okay then... if you're pulling it out of the plane before flying!

[Bill Gaylord]

Comet models used heavy cardboard tubes inside the model, encasing the rubber band. Wouldn't be bad, with a really light grade of acetate sheet. I built of few of those models, but for r/c and not rubber. I doubt they would have been very good rubber flyers.

[andywhitam]

I have a friend that has flown free flight for many years and was in a hurry one day and left his blast tube in by accident. It did not protect the fuselage during flight.

[tom arnold]

Why was that? Did the motor blow in the air?if so, that is VERY unusual.

[tpwpny]

My question in using a blast tube is, why a wire to go from winder to rubber? I understand the need for a blast tube. I understand the need to stretch and wind, but why not just attach a crocket hook from rubber directly to winder? A wire seems redundant if you are already stretching the rubber out the blast tube.

[tom arnold]

This is one of those events in life that become absolutely instantly apparent after you try it. I guarantee that the heavens will split open, a beam of sunlight will fall on your head and you will hear the hallelujah chorus the second you finish winding your motor. Because you now have a blast tube in the fuselage, a fully wound motor with the winder attached to it snugged up to the nose, and the question becomes "How do I get the blast tube out?" Here's where the wire with a hook at one end and a handle at the other comes in. You transfer the wound motor from the winder to the hook on the wire and drop your winder gently. Holding the handle, you slide the winding tube outside the model. Taking the prop you have been holding in your mouth, you transfer it to the rubber motor and gently drop the winding tube and wire. Settle the nose block in place and now finally remove the back wire from the stooge and take the model out for flight. Turn to go out into the field for flight and gently step on the winder and blast tube in the grass (no, don't really!).

There is more to using a blast tube than the above, though. A blast tube needs a couple of slots at the back end to slide back around the motor peg. Not only that but those slots also need a equally wide 90 degree dogleg at the end of the slots. This is such that you slip the blast tube in and over the motor peg and then turn it 90 degrees and "lock" it in place such that you cannot pull it out. Now when you wind and the motor blows, the tight angry knot will fly back to the motor peg, stop and jam up inside the blast tube---trapped. Here is the most important move to make----take the model out of the stooge and TAKE THE MOTOR PEG OUT OF THE MODEL. Do NOT remove the blast tube until you do!!!!! The peg will be jammed in there but work it out as all the pressure is being exerted against the blast tube internally. When the peg is worked out, that energy-filled, angry knot that wants to unwind explosively is still trapped in the blast tube. Now remove the blast tube from the undamaged model, poke out the knot and watch it jump and whirl like a mad animal on the grass and imagine what that would have done to your model on the stooge.

[Chris A.]

Tom A. That is the best description I've read of "how to use a blast tube". Nicely stated, thanks. I recall seeing a picture online of the exact instant a rubber motor broke inside a fuselage. Not pretty.

[kittyfritters]

If you are flying giant scale rubber models with really big rubber motors a fully wound motor breaking can release as much energy as a quarter stick of dynamite. Now, that's equivalent energy, not explosive force, still, if you've got your hands anywhere near that motor when it comes through the side of the model you are going to feel it, (Don't hand stooge a large model for someone who isn't using a blast tube!), not to mention the destruction of the model! Even a motor made of 1/16" flat breaking will severely damage a light model like a peanut or dime scale. So, blast tubes are a good idea, even though I will admit that I don't always use one,

An interesting approach to this is to use a light weight Tyvek tube inside the model. A tube made of Tyvek is practically indestructible. It also has the advantage of keeping the rubber from flopping around in the fuselage, almost self lubricating to the rubber, allowing you to use a much longer motor than otherwise. Motors five times the hook to peg length can be handled with a Tyvek tube. A good source used to be non-tearing mail envelopes. Roll it around a dowel and glue with C/A. If a motor breaks inside a permanently installed Tyvek tube you grab it with your Oh Oh Stick (You do have a long wire hook in your field box to pull loose motors out of your models, don't you?), pull out the motor peg and drag the squirming motor out the front. The tube in the picture added only one gram to the model,

[Bill Gaylord]

Tyvek is very slippery stuff. I could see that working well.

[tpwpny]

Great tips, all. Until now, my only experience with rubber motors has been, "Step 1: Wind with finger. Step 2: Fly."

[elkhart]

Great post, I also thought the blast tube stayed in the aircraft.