Thin-walled tube of soft metal when you try to bend often creased. To avoid this, they are usually pre-stuffed with sand.
With the same purpose, you can use another method: navit on the future site of bend copper or aluminum wire – turns will not allow the tube to wrinkle at the bend.
The same result can be achieved using a suitable inner diameter of the spring.
Recommend to read
THERMOSTAT FOR VEGETABLES
Read the article A. Christmas "Cellar, on the balcony" ("M-K" No. 2, 1984) and not all agreed with the author. He applied heater power of 500 watts. This implies that the air circulating...
AMATEUR SPRAYER
I made it for the treatment of plants with pest garden. Gathered from local funds, mostly from the motor from the sewing machine, and gear-type oil pump of the motorcycle "Ural"....