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Hi start system


Robert Edney
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Great fun. Maybe put a wanted ad on the BARCS forum might get you a 2nd hand one. Sorry our club one isn't for sale.

 

One thing to be aware of is that you must rudder for steering on the tow, so if its a full house glider then make sure your rudder thumb is working.

Edited by Frank Skilbeck
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Just now, Bob Cotsford said:

Especially when the screwdriver (or in the video, metal rod) pulls out and gets launched straight at you.  If you try this please use a corkscrew dog stake as your ground anchor!

Yep, we now use a corkscrew dog stake, we did previously use a long piece of 12mm dia metal rod which we used to hammer in, angled so it wouldn't pull out, problem was getting out at the end of a session ?

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Welcome

Hi-start, bungee launch is a lovely way of flying gliders from a flat field.

I've had 6mm and 9mm silicone rubber in the past and it is very good because it can stretch as the glider goes up the line thus gaining some extra height.

However, over time these deteriorated and ended up having to be knotted back together on a regular basis.

These days I use 8mm cloth-covered luggage-rack bungee. 35m of bungee and 120m of 100lb monofil fishing line. I might not get the same height but, with a "ping" off the top it gives me plenty of altitude and, once a thermal is contacted, then it's away. This is with a "full house" 2.7m Art Hobby Odyssey.

In the past I've used 3m Bird of Time and 3m Algebra. Both fantastic thermal gliders.

In the video I think his climb was too shallow for two reasons. 1. the towhook was too far forward, I put mine 1cm 1/2" in front of the C0fG and 2. he was launching with very little wind. In about 10mph the glider will kite up.

As has been said, use a good size screw-in dog stake to anchor it and an old mig welding reel is ideal for storage.

If there's a Chandlery or Yacht Club/Boating supplier near you then they can supply bungee off the reel.

 

As for flight times, if there's no thermal activity then 2 - 4 mins but on nice thermal days then the only reason I've had to land is because my neck ached too much from watching a specked-out glider for an hour and a half.

 

There's a great sense of achievement from hooking thermal lift and, sometimes, I've been preparing to land at about 10' when I've noticed the wings rock so I've put in an extra circle then, little by little, the glider has soared away in a new thermal. Very satisfying.

PS. I do also have an electric glider so I can just turn the motor on if it loses altitude?

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13 hours ago, Robert Edney said:

Hiya everyone,

I'm having major issues with trying to find a hi start system so I can finally get my glider airborne.

If anyone has one for sale or knows where I can get one that would be great. Thanks again. Robert

 

What is your glider?  If its a modern lightweight, say a 2m F3-RES, then 10m of 6mm bungee and 50m of light fishing-line will suffice.  If it's a bigger heavier beast, you might need 15m of 8mm bungee and a longer thicker line to achieve a decent altitude on launch - but that would require a larger field. 

 

bungee

 

pennant (so you can find the end of the line in long grass!)

 

Spool (or make your own like I did)

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I haven't hi-start launched in a couple of years due to the size of field required to launch from & get a decent height, but I am hoping to do some this summer with a 3m Bird of Time. I have a corkscrew type doggy lead anchor as a screwdriver just isn't secure enough, particularly if the ground is soft. The last thing you want is the screwdriver pulling out under tension and heading towards you at a vast rate of knots ?

 

The video was me launching my 2m Whisper from the flat top of a hill before flying over the slope.

 

https://youtu.be/FiGFStHN5gI

 

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Don't forget the good old tow line for getting huge launches with a glider. The drawback being that one needs an athletic friend or family member to provide the muscle and practice to get the technique correct. Not too bad on small or lightweight gliders though and worth a try for the experience. No bungee rubber to wear out.....only the tow-man!

 

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Hand towing isn't as physically exerting as most people seem to imagine. On most occasions it's a gentle sprint to start followed by a walk, sometimes back towards the launch point. The only time any real running is required is in zero to very light wind conditions, the sort of conditions you're most likely to encounter when you go slope soaring ? and when a bungee is pretty useless. If you want a reliable ground based all round launch system a power winch is the answer, albeit expensive & heavy to lug around.

 

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That is very true about towing, as you say it does depend on wind conditions, type of model etc. Surprising how much stretch you can get in a towline as well to give the model a bit of a start as you make the initial run.

I do remember being lifted a foot or so off the ground when towing a friend's huge glider (carbon fibre everything, so more or less unbreakable on tow) in an open comp on a windy day many years ago. An amazing amount of energy stored in the whole system when you think about it. Easy to rip lighter models to pieces if you overdo it of course.

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If there's any wind and you have a strong model, it's surprisingly easy to drag your tow person to a standstill with a bit of elevator! Having towed a fair bit, the pull exerted by, say, a 3.5m F3J glider or an F3b glider can be very substantial. Your tow person (or two!) would start running quite a while before you release the model, to get a lot of stretch into the towline. 

Something for the tower to hang onto is a must. 

 

Edited by Matt Carlton
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  • 1 month later...

There is a reference on the RES 2 Metre glider group (F3-RES and F5-RES - UK) on Facebook to Pete Newman, who makes up hi-start/bungee equipment.  That links to this BARCS thread:
BARCS Hi-Start Supplier 

I would echo the comment about needing a very good ground anchor.  A few years ago, someone was killed by their ground anchor pulling out and being launched straight at them.

Ground anchor accident

I'm not sure I would even trust the spiral dog lead anchor if it were into soft sand.

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I used two dog stakes for mine. One for the bungee and a second one joined to the first by about 6ft of bailer twine left a bit slack. Even if the first pulls out, there wouldn't be enough residual energy to pull out the second. 

You can also use a rotten bottom as they do in sea angling, so a short section of lighter mono between the main line and the rubber so that will be the weak point, ensuring that the rubber goes away from the launch in the event of a break. 

You could even double up the length around a turnround pulley so the stake is at your feet. That has the advantage that the glider isn't lifting the weight of the rubber. 

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2 hours ago, Matt Carlton said:

I used two dog stakes for mine. One for the bungee and a second one joined to the first by about 6ft of bailer twine left a bit slack. Even if the first pulls out, there wouldn't be enough residual energy to pull out the second. 

You can also use a rotten bottom as they do in sea angling, so a short section of lighter mono between the main line and the rubber so that will be the weak point, ensuring that the rubber goes away from the launch in the event of a break. 

You could even double up the length around a turnround pulley so the stake is at your feet. That has the advantage that the glider isn't lifting the weight of the rubber. 

Matt, using two stakes is a great idea! 
I've looked up the sea angling 'rotten bottom' to try to understand what you mean in the second part.  Is this between the bungee and the line that goes to the glider, or between the bungee and one or more of the securing stakes?
Having the bungee on the ground would reduce the weight to be lifted but would also lose a fair bit of energy from friction with the ground, plus it may increase wear and tear on the bungee a fair bit.  It would be alright on long grass, but anywhere with stones would be hard on it.

One thing I have noticed is that when launching in a breeze, is that even when you think you have the bungee stretched as far as it can go, after launch it is not unusual for the model to be blown back behind you as it stretches the bungee still further.

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Re stakes, whilst a screwdriver isn't a wise idea, I have complete faith in a corkscrew dog-stake.  Mine is even a miniature version (for lapdogs if you like), but the bungee is only 10m of 6mm diameter tubing (plus 50m of 30 lb strain fishing-line), and I'm only ever securing it into solid earth, not estuary mud or beach sand.

 

The static pull at full extension (I do 3x for a 320g 2m wingspan RES model) is very modest, under 4kg according to the rules (less than holding a very small child in a tug-of-war), the angle of pull before release is effectively wholly perpendicular to the stake thus the maximum force is entirely sheer, and there are no shock-loadings at all.  After release the angle of pull does increase progressively up to about 60 degrees or so, but as it does so the tension progressively decreases.

 

Under these conditions, I've never felt there was anything worry about with my mini-stake:  after several days recently of using this setup for scores of launches each day, removal of the mini-stake at the end was as laborious as it was securing it into the ground in the first place.

 

For an 8 or 10mm diameter bungee the forces will obviously be increased, but the mechanics remain the same and a single regular-sized dog-stake should be more than safe.... unless carelessly secured in loose earth etc!

 

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My bungee was 30m of 10mm rubber tube and 120m of 120lb mono. Full stretch was about 80-90 paces so there was a lot of tension in the system. Never measured it but it certainly needed two hands on the model and a firm grip. I guess somewhere around 30lbs+

On a breezy day, I would regularly hold quite a bit of stretch in the rubber, enough for a reasonable 'ping'. 

 

 

Edited by Matt Carlton
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2 hours ago, Jonathan M said:

Re stakes, whilst a screwdriver isn't a wise idea, I have complete faith in a corkscrew dog-stake......

 

The static pull at full extension (I do 3x for a 320g 2m wingspan RES model) is very modest.......

 

Indeed. My biggest problem with high start is getting the stake in and out of the ground. I need a tommy bar to turn it!

Stake is a large spiral bought from a kite shop. The intended purpose must impose greater loads than my launches of sub 2m gliders.

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