I have an old slingshot 17.5 machine for light days, thinking of inflating the struts with an expanding foam to permanently inflate the struts, kite is worth nothing so not worried about resale just want to save time pumping up, any one done it or have a better idea?

Interesting idea, but your main problem will be the weight. Expanding foam from a can is relatively heavy, and each strut filled with foam will weight about 1-1.5 kgs. Your light wind kite may struggle to fly! Use this calculator to find out your strut volumes and it will give an idea of how much foam will be needed.

www.online-calculators.co.uk/volumetric/cylindervolume.php

2 LB Density Urethane Foam
(U.S. Coast Guard Compliant Marine Foam)
Common Applications: Our 2LB density marine foam is recommended for void filling in nonstructural applications. This product can be poured underneath decks and inside cavities where a lightweight flotation foam is needed to provide buoyancy. This foam has been tested in accordance with U.S. Coast Guard Regulation # 33 CFR 183.114 . This foam is approximately 95-98% closed cell which resists absorbing water, however continuous water submersion can eventually lead to loss of buoyancy over a period of years. We recommend this product strictly for flotation applications. If looking for a liquid foam for sculpting or casting we recommend using at minimum our 3LB or 4LB density. More questions? [Try our Foam FAQ.]

Cat No.
Kit Size(net weight)
Approx. Coverage
Price
FOAM-0204
4 LB Kit
2 Cubic Feet
$22.50
FOAM-0216
16 LB Kit
8 Cubic Feet
$67.00
FOAM-0280
80 LB Kit
40 Cubic Feet
$264.00
5 or more kits of the FOAM-0280
$252.00 / Kit
Drum Pricing (Kit Size 1033 LBS)
Coverage: approx. 500 cubic feet
Call for current price
Product Information:
Free Rise Density: 2.0 lbs per cubic ft.
Expansion Rate: Approx. 25-30x Liquid Volume
Buoyancy (flotation): 60 LBs per Cubic Ft.

*Physical Properties:
Parallel Compressive Strength: 40 psi
Tensile Strength: 30 psi
Shear Strength: 30 psi
Flexural Strength: 50 psi

Lol, buy a battery pump.

Or use an old air/water extinguisher that you can be primed with just air from a compressor.

Or a high volume 12v portable compressor, I have one in my ute for inflating my iSUP.

tried that, the pilbara red dirt f*%ked it after a couple months, might try the extinguisher idea but

All I can say is lazy bastard......

i used beans from a bean bag once cause couldnt get a strutt bladder for my piece o **** Cabrinha, and still cant, They were light as.

Olliefly said...
i used beans from a bean bag once cause couldnt get a strutt bladder for my piece o **** Cabrinha, and still cant, They were light as.

Did it work? Sounds like an almost reasonable idea, possibly lighter than expanding foam anyway?

Just awesome.... Please can you do leading edge with a load of cans of pu foam and post a video of session. Might be an issue with a bigger kite...weight not sure . sounds like bean bag beans are the go for the struts.