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Nimbus 4D - 7 metre

Let us all watch your new project progress.
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Peter Balcombe
Posts: 1070
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: Nimbus 4D - 7 metre

Post by Peter Balcombe »

Harry,
I saw a link on another forum to a diy retract with a springing option provided by RC car rear shock mount springs.
Whilst these may not cope with a model of this weight, the design concept may be of interest.
The design was done some years ago by a German engineer Ingo Seibert & published in a German magazine at the time.
http://www.rc-network.de/magazin/artike ... QZ0BqT0KYE

John Vella
Posts: 234
Joined: 20 Mar 2017, 22:09
Location: UK

Re: Nimbus 4D - 7 metre

Post by John Vella »

harry curzon wrote:
16 Jan 2020, 21:14
To paraphrase Police Chief Brody in the film Jaws, "I'm going to need a bigger workshop!"

Here's a taster of what is to come, this is Nimbus with the inner wing panels installed, the outer panels are almost the same length again. The fuselage is 2.3 metres long


20200116_134347.jpg
Harry , great work . May I suggest rigging of a big model like the Nimbus is done in the garden to save on "Hangar Rash" if the weather allows. Regards John.

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B Sharp
Posts: 719
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: Nimbus 4D - 7 metre

Post by B Sharp »

Harry, I think you need to invest in a gym membership and get on the weights 3 times a week. You are going to need some muscle to launch that machine off the side of a hill.
Brian :D

harry curzon
Posts: 100
Joined: 21 Jul 2018, 09:32
Location: Gloucestershire

Re: Nimbus 4D - 7 metre

Post by harry curzon »

B Sharp wrote:
17 Jan 2020, 11:07
Harry, I think you need to invest in a gym membership and get on the weights 3 times a week. You are going to need some muscle to launch that machine off the side of a hill.
Brian :D
This model is strictly for aerotow and thermalling, none of the slopes I frequent are suited to launching and landing this beast.

harry curzon
Posts: 100
Joined: 21 Jul 2018, 09:32
Location: Gloucestershire

Re: Nimbus 4D - 7 metre

Post by harry curzon »

B Sharp wrote:
16 Jan 2020, 18:33
Harry, I would get rid of that plastic control arm on the side of the retract if I was you. It will only give you grief in the future. Replace it with a good metal horn.
Brian. :)
I had a hunt through my extensive parts store and found this aluminium arm, I think it was from the tailplane of an F-4 Phantom I had many years ago.

20200117_144216.jpg
20200117_144216.jpg (27.46 KiB) Viewed 594 times

It needed a new hole for the grubscrew to match the location of the flat on the retract drive shaft, so I drilled and tapped it for M3. I prefer to use proper socket head bolts instead of grubscrews as the much larger socket or hex driver is less likely to get rounded if the bolt is tight.
The hole for the shaft was too large so I bushed it with a suitable size of brass tube and now it is a snug fit over the retract drive shaft.

It had some minor issues interfering with other things so I removed the clevis at the retract end of the pushrod and fitted a bolt through ball link which is probably better anyway, an M3 HT bolt being a bit stronger than a clevis's little pin

20200117_153839.jpg
20200117_153839.jpg (43.08 KiB) Viewed 594 times

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Peter Balcombe
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Location: Clevedon, North Somerset, U.K.

Re: Nimbus 4D - 7 metre

Post by Peter Balcombe »

That looks the part Harry :)

SP250
Posts: 140
Joined: 18 Mar 2015, 06:19
Location: North Shropshire

Re: Nimbus 4D - 7 metre

Post by SP250 »

Recycling at its finest for the modern world we now live in !

harry curzon
Posts: 100
Joined: 21 Jul 2018, 09:32
Location: Gloucestershire

Re: Nimbus 4D - 7 metre

Post by harry curzon »

Opinions please -

Problem - I want to fit 2 x batteries of 5200mAh, and also an airspeed pitot tube sensor (I would like to have airspeed compensation for the vario). The best place for the batteries is right up in the nose but the plate that the towhook servo is mounted on leaves room for only one battery. I could fit two if I use the 2600mAh batteries, but the 5200s would be nicer. There is nowhere for the pitot tube, the hole in the nose being occupied by the towhook.

Possible solution - remove the towhook and servo plate, fit the pitot into the hole in the nose and fit 2 x 5200mAh batteries in the nose. For a towhook, do what I have successfully done on my 4 metre ASH 26 and 4 metre K-18, but suitably beefed up for this glider. Run a piano wire in a plastic tube along the bottom of the fuselage. Epoxy the tube down and when cured remove the piano wire and mill a slot from the outside of the fuz right through the tube. Re-insert the piano wire and hook it up to a servo. For this glider I was thinking of 2.5mm to 3mm piano wire, I could reinforce the fuz around the slot with a large patch of light carbon fibre cloth and then a disc of 1mm aluminium, say 2 inch diameter with the tube epoxied to that.

Your thoughts?

Keith
Posts: 66
Joined: 07 Jan 2019, 18:18
Location: Lincolnshire

Re: Nimbus 4D - 7 metre

Post by Keith »

Real gliders have it in the fin.


Keith

SP250
Posts: 140
Joined: 18 Mar 2015, 06:19
Location: North Shropshire

Re: Nimbus 4D - 7 metre

Post by SP250 »

Harry

How about leaving the nose release as is.
Fit the two 2600mAh batteries in the nose wired in series, put another 5200mAh (or 2 more 2600's) battery/s close behind them (it'll still be in front of the CG.
The TEC probe for the vario energy compensation 90% of the way up the fin, where the full size one is?
Bernie Jones does the small bore tubing for connecting to the vario or you could use compressed air U/C retract tubing.

John M

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