Bungee tow hook

[Phill Tadman]

I'm hoping to try a bungee assisted take off for my motorised 6.5kg ASW20.

Any tips regarding tow hook type, placement or nose reinforcement?

Many thanks

Phill

[eric friend]

Hi Phil,

Well done for having a go at the black art of bungee launching large scale gliders. A lot of people don't go much on the idea but if the procedure is well thought out, I don't think there is a problem.

I am initially going for bungee launching my 4 metre ASH 26 off the slope as a precursor to trying larger models as the number of fellow gliderists able to launch large scale gliders is limited and those that we do have are getting older by the day. Those of us who have large heavy sailplanes really appreciate their services but we must look after their health!
Take a look here to see what we put them through! - http://www.goodwindsoaring.blogspot.com

Back to the task in hand. On the ASH 26 I have positioned the towhook halfway between the c of g and the nose as a start point and I think that location should be OK as I have seen another successful slope side launch of a large scale glider with the hook in that location. I also have a 1/3rd scale MDM-1 Fox which weighs 17kg and my ultimate intention is to bungee launch that off the slope as well. I have heard of some people attempting bungee launching using the aerotow release with disastrous results - I would suggest steering well clear of that approach but have a hook that will release the bungee automatically without requiring any input from the pilot.

Regarding bungee assist launch of power assisted gliders, there are a number of YouTube videos of people doing that quite successfully to help prevent that initial nose-down attitude when powered is applied. However I would only use that method on a model that I knew well and as a last resort if the thrust available from the installed power train was insufficient to get the model off the ground. I have a 6.9 metre ASH 25 with an up and go power train which will be maidened in the next few weeks, most probably by aerotow at the Baldock Glider meeting and although I have carried out the Ecalc assessment of its power train, we have yet to see if it will get off the ground under its own steam or whether a bungee assist will be required. Watch this space!

Best of luck with your endeavours and keep us posted with your progress.

Eric

[Phill Tadman]

Hi Eric

Thanks for your advice!

I might be able to get the tow hook through the gear mounting plate to gain some reinforcement.

This launch looks very sedate https://youtu.be/GKyfJ7ao2nU

Bungee and bits and bobs on order and hope to try next week.

Phill

[roo Hawkins]

Hi I have been using a bungee for a while now has I often fly on my own or there is no one experienced to launch. I use a tube at a angle need to the nose about 4in away. I use a pin on the bungee that fits in . I use a double bungee cord with dog steaks to fix it in to the ground. Have a look on the web page of this forum for info. If you use the tube pin you can not see it. ROO :DD http://www.scalesoaring.co.uk/VINTAGE/H ... apult.html

[terry white]

Hi Roo,
I have been thinking about making a bungy on this pattern for some time now.
Any pitfalls to look out for? Any mods you would make?
Like you I do tend to fly the larger, heaver gliders. Do you think the one on the forum is man enough?
Terry.

[roo Hawkins]

Hi Terry I have used this setup and I would not change a thing a part from using 80 lb fishing trace wire from the tow pin to the bungee. I used to use power kite line but it keeps snapping. ROO

[Paul_Williams]

This system looks very neat - can I ask about the relative merits of surgical tubing compared to standard bunjey ?
I the amount of 'zap' the same, length for length and which has the best life expectancy ?

Has anyone trued bunjeying off a scale bunjey hook ?

Paul

[Phill Tadman]

I purchased the L63/20BK from here:

http://www.megaflex.co.uk/tubing/latex-tube

as this was the only site that published kg force at various extensions.

Phill

[roo Hawkins]

I would NOT use the nose hook . I know someone who used it and it did not release. Not mentioning name.

[Phill Tadman]

So I tried my bungee system without success today.

The model rose about 1/2 a metre before cartwheeling in (can't see any major damage yet).

I measured the bungee tension as 13kg - twice the model weight.

This didn't seem anywhere near enough to get the glider up to launch speed.

Does anyone have any suggestions for a bungee tension / model weight ratio!

Thanks,

Phill