Wing Launch - Can it pull your wings off?

On Wed, 18 Aug 2010 13:54:38 +0200, Andreas Maurer wrote:


Generally we found that Dyneema is simply much less fault-tolerant than
a steel cable - small handling errors (like using a little too much
power to pull it out of the wood) often result in a really expensive
damage.

I'm not altogether surprised. I once tried using a light (5-10Kg) woven
Dyneema line the control tailplane release for VIT and d/t on a small
(F1J) power model, which required it to slide round a 3mm alloy tube that
converted the movement from fore and aft through the fuselage to vertical
travel as the tail surface moved. It was a miserable failure -the mere
act of threading the line into the fuselage caused it to fluff into total
unusability. I threw it away and replaced it with woven Dacron. Problem
solved.

Since then the only Dyneema I've used has been 100 lb kite bridle, which
I used as the towline for an F1A competition model glider. This line has
a core of straight Dyneema fibres inside a woven Dacron sheath and is
excellent: no tangles, nice to handle, abrasion resistant. Its very stiff
too. The total stretch is about 150mm in a 50m length under the nominal
5Kg test tension - and even that stretch is mostly pulling the kinks out.

On this showing I'd be wary of any Dyneema rope that lacks a Dacron outer
casing: the ease with which the naked Dyneema line fluffed up was really
a shock.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Some translation from Free Flight Duration Model Airplane speak.

I'm not altogether surprised. I once tried using a light (5-10Kg) woven
Dyneema line the control tailplane release for VIT -- Variable Incedence Tail
....and d/t -- DE-THERMALIZER (brings the plane down quickly after a
set time) on a small
(F1J) (.051 Cubic Inch Displacement) power model, which required it to slide round a 3mm alloy tube that
converted the movement from fore and aft through the fuselage to vertical
travel as the tail surface moved. It was a miserable failure *-the mere
act of threading the line into the fuselage caused it to fluff into total
unusability. I threw it away and replaced it with woven Dacron. Problem
solved.

Since then the only Dyneema I've used has been 100 lb kite bridle, which
I used as the towline for an F1A competition model glider. This line has
a core of straight Dyneema fibres inside a woven Dacron sheath and is
excellent: no tangles, nice to handle, abrasion resistant. Its very stiff
too. The total stretch is about 150mm in a 50m length under the nominal
5Kg test tension - and even that stretch is mostly pulling the kinks out.

On this showing I'd be wary of any Dyneema rope that lacks a Dacron outer
casing: the ease with which the naked Dyneema line fluffed up was really
a shock.

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |