Of the several methods available for launching your sailplanes, none offer the convenience and ease of operation of the "Hi-Start." This method can be used by one person without assistance, is lightweight and readily portable, avoids the noise and mess of power assists, and most importantly, is suitable for the beginner.

The "Hi-Start" consists of a length of elastic material (rubber)... that provides the energy to launch the sailplane; a towline to provide additional altitude, a parachute to help release the line at maximum altitude, a stake (tent peg or large screwdriver)... to secure the end of the rubber; plus various rings and snap connectors to link it all together.

In use, the stake is secured firmly into the ground, and the opposite end of the towline is attached to a towhook on the model. The rubber is then stretched by walking away from the stake, then the model is released. The stretched rubber pulls the line and model into the air. It's like flying a kite with a big rubber band replacing the running start used to launch the kite. Properly used, a Hi-Start will launch the model several hundred feet into the air, providing sufficient altitude for good thermal flying. Incidentally, the term "Bungee" (as used by gliding people), means the same as "Hi-Start"...but Bungee rubber isn't surgical tubing!

The heart of any Hi-Start is the rubber used to provide launch energy. For R/C sailplanes, there are three commonly used materials:

Types of rubber in use:

  1. General purpose solid or strip rubber, cut up old inner tubes, etc. (...Unpredictable results)!
  2. Bungee or shock cord, which has a braided cloth jacket over multiple strands of rubber and is available in many sizes. Although very durable, the amount of stretch is limited by the cloth jacket. (...Less than optimum due to the early short burst of thrust - which then quickly fades)!
  3. Surgical tubing manufactured by either the extrusion or mandrel process. The most important advantage that surgical tubing has over the others, is that it provides a smooth controlled release of energy which does not strain the wings of the model. The energy release is fairly constant throughout the launch and provides plenty of pull near maximum altitudes. (...Always provides the best results)
  4. Under the right conditions and using 100 feet of our high stretch rubber, 500 feet of launch height is possible!

 

How Long is a Hi-Start System?

These days there is no longer any clearly defined "length"...A little bit of history first...Originally, (some 20 years ago), there was a "defacto" standard... for competition purposes, 100 feet of rubber was allowed, coupled with an indeterminate length of line; the rule being that the "stretched" overall length was not to exceed typically 800 feet. A popular choice was to use a fishing line length of 400 feet, on the basis that the rubber when stretched from 100 feet to 400 feet, would provide a healthy launch in the "worst" situation of having no wind to assist.

That is history, the formula works well...but so do many others! In reality, unless you're bound by local competition rules, the most likely constraint is... size of flying field, and how high do I need to get? Here are 4 possible set-ups. With so many other "variables" involved... there's no need to be exact when determining lengths. In the table below, lengths given are in metres. As an approximation, 30 metres = 100 feet, 15 metres = 50 feet, and so on...

 
Four Possible Arrangements
Ground Length Required
Typical Situation
Rubber Length (relaxed)
Fishing Line Length
(based on stretching the rubber 3 times MORE than its original "relaxed length", plus an allowance for landing etc.)
30 metres
120 metres
250 metres -
"Very Large Field"
A large expanse of flat cleared land (uncommon in metropolitan area)
20 metres
90 metres
180 metres -
"A Large Field"
Large athletics /general sports area
15 metres
75 metres
150 metres -
"A Medium Field"
Typical Park without trees
10 metres
60 metres
120 metres -
"A Short Field"
School yard or limited area

The more the breeze, the more one may liberalise the so-called rules. The reason for saying this, is that ... the "job" of hoisting up a model is a two-way sharing situation ...between that energy stored in the pre-stretched rubber, and that energy provided by the wind. In fact, with a strong wind, you can take advantage of a "kiting effect" - and use a lot more fishing line than shown in the table.

 

Making up your Hi-Start System

The various components required are:

 

How to choose the size of rubber?

The "Heavy Duty" rubber (8.0mm O.D. x 1.6mm wall thickness), suits gliders in the range 700gm to 1600gm. This includes most trainer models with wing spans from 1.8 to 2.5 metres. (Figures are a guide only)

$65.00 for one piece of 50 foot length
$120.00 for two pieces each of 50 foot length (these can be joined with dowel provided)

The "Extra Heavy Duty" rubber (9.6mm O.D x 2.4mm wall thickness), suits models in the range 1.2Kg to approx.3.2Kg.

$85.00 for one piece of 50 foot length
$160.00 for two pieces each of 50 foot length (these can be joined with dowel provided)

As well as the rubber, the package includes Plug inserts and Screw Eyes to assist in getting started, a piece of 6mm dowel for the option of permanently joining rubber lengths, and of course the Basic Instructions

Other items such as fishing line, reel, and connectors aren't supplied.

Still unsure about which size to use?
 There is quite some overlap in capability. Many so called mid-range 2.5 metre models can be launched with either type of rubber. If you have trouble deciding on the best size, decide on the basis of "wing loading" Heavier, or more "highly loaded" models, need more tension (rubber stretch) than lighter ones.... If for example the 2.5m. model has ailerons, or needs to fly faster or has a loading of above 30 gm/dm2, the "Extra Heavy Duty" rubber is better.


The tubing we offer is made from the highest quality natural latex with additives specially formulated for abrasion and ozone resistance. This surgical tubing provides the highest energy available with a smooth steady pull for safe launches.

This rubber is the BEST you can get, because it

  • Is made by the "Mandrel" dipping process... This means it's smoother and therefore superior to the slightly cheaper "Extruded tubing". Mandrel produced tubing has very few "surface flaws" arising from the manufacturing process.
  • Has a Maximum elongation (stretch) of 600 percent!
  • Has a Tensile strength of 3500 psi