Re: [RCSE] High Start tubing, what he said!

[Gord...@aol.com]

Thanks Tim,

I'm pretty sure I've used it all and Hose Monster has clearly been the best. Theraband is defintely at the bottom for our use.

MCmaster is expensive considering the per foot and shipping and joiners and time screwing etc.

 

Glad to hear Mark is still out there.

Gordy

 

In a message dated 10/24/2013 2:35:37 P.M. Central Daylight Time, TSE...@comcast.net writes:

Elongation is a measure of how far the material can be stretched
while producing a proportional force response,  without yielding,
and then returning to it's original relaxed condition (ie, it obeys
Hooke's Law).

Elongation is good for a hi-start, and the more you can get, the
better.

The original commercial surgical rubber high starts (Airtronics /
Dynaflite) had an elongation spec of 300%,  and that's typical of
"extruded" Latex surgical rubber tubing.   "Extruded" means that
continuous long lengths can be produced, so no splices are required.
The McMaster tubing is extruded despite being sold in shorter, 25'
lengths.

"Mandrel dipped" Latex rubber (like Hose Monster) typically has an
elongation of 500%, although Hose Monster force-rates their tubing at
300% stretch in order to be easily compared with the extruded
variety.   Mandrel dipped tubing is limited to the length of the
mandrel used.   A 50' length like Hose Monster is exceptional, and
less expensive mandrel dipped tubing is typically in the 25-30 foot
range.   Splices are required for a 'full-length' hi-start using
mandrel dipped rubber.

Theraband uses a less expensive grade of Latex rubber that typically
has a lower elongation rating of ~250%.   You can't stretch it as far
before it seems to go hard, and stop stretching.   The converse of
low elongation is that you don't get the l-o-n-g, slow pull that is
nice to have in a hi-start.   More elongation means higher launches
for the same line tension... less elongation means a lower launch.

Theraband is less expensive per foot, and may fit a budget more
easily.   However, all else being equal, Theraband only stretches
roughly 50% as far as Hose Monster, or 83% as far as extruded
surgical rubber tubing.   For identical hi-start configs (tube length
+ line length),  a Theraband hi-start will deliver a much shorter
pull and a lower launch height.

In order to get the same amount of stretch distance with Theraband,
you'll need a longer length of it.   And longer will be heavier,
making it more difficult for a smaller sailplane to lift it off the
ground... limiting the launch height produced by the same force over
the same stretch.

'mandrel dipped' Latex rubber,  'extruded' Latex surgical rubber,
and Theraband will all work for a hi-start,  they just don't all
perform equally.   Let your budget and your launch goals be your
guide.

From old data... I've not done this recently:

Extruded Latex Surgical Rubber Tubing
1/8 ..... 1/8 ..... 3/16 ... 1/4 ..... 3/8 ..... ID, inch
3/64 ... 1/16 ... 1/16 ... 3/32 ... 1/8 .... Wall, inch
7/32 ... 1/4 ..... 5/16 ... 7/16 ... 5/8 .... OD, inch
.025 ... .037 ... .049 ... .101 ... .196 ... X-Sect, Sq In
4.43 ... 6.44 ... 8.59 .. 17.17.. 34.36... Lbs at 300%

Mandrel Dipped Latex Rubber Tubing
1/8 ..... 1/8 ..... 1/8 ..... 1/8 ..... ID, inch
1/16 ... 3/32 ... 1/8 ..... 5/32... Wall, inch
1/4 ..... 5/16 ... 3/8 ..... 7/16... OD, inch
.037 ... .064 ... .098 ... .138 ... X-Sec, Sq In
6.44.. 11.27.. 17.18.. 24.16... Lbs at 300%
6.0 ..... 8-10.. 14-18.. 20-24... Lbs Launch Tension
Can typically stretch to 500%, but tension not measured.

Theraband
Yel... Red.. Grn... Blu... Blk ... Slvr... Gold
5.8 ... 7.0 ... 9.6... 13.3.. 17.6.. 25.3.. 40.1 Lbs at 250%

Regards,
Tim Engel



----- Original Message -----
From: Ed Anderson
To: rc...@googlegroups.com
Cc: RC...@googlegroups.com
Sent: Thursday, October 24, 2013 11:08 AM
Subject: [RCSE] Re: Anyone know of a high start tubing source?

5/16 and 3/8 OD are typical for general purpose HS.  But these come
in a variety of wall thicknesses.  If one was going to use these,
what wall thickness would you use.  If we use these as an example,
for 4 25 foot lengths your HS rubber would be $117 to $120 and then
you have to join them.

(Snip)...
Are they  the same as the stuff above?  I don't know. but we know
what the pull strength is of the Theraband.  We don't know the pull
strength of the "surgical tubing".

It would be great if someone had both and could compare.out.

--
You received this message because you are subscribed to the Google Groups "RCSE" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rcse+uns...@googlegroups.com.
To post to this group, send email to rc...@googlegroups.com.
Visit this group at http://groups.google.com/group/rcse.
For more options, visit https://groups.google.com/groups/opt_out.