FlyFly Nimbus 4 - RC Groups
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May 19, 2013, 01:59 PM
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FlyFly Nimbus 4


Hi all

FlyFly Hobby in China has in recent years steadily been expanding their range of RC gliders. Although the standard of the kits are not great in general and certainly not comparable to high-end gliders from Europe, I still consider them good value for money. I think their planes should not be though off as ARFís since there are always some areas to improve. I personally donít mind this and consider it a part of the hobby. I had my eye on their four meter Nimbus 4 with spoilers since it became available from their distributor Hobby88 in December 2012. A kit with a retractable main wheel was added to the range from March of this year. The kit is available as a pure glider or as an electric glider with provision for a nose mountable motor. I like the design of the Nimbus 4 with its long slender wings but it was a bit difficult to convince myself to spend double the amount of money on it compared to Hobby88ís DG808 which also is a four meter glider. I could find very little information on the glider on the internet except for what is available on the FlyFly Hobby website. I was also a bit sceptical about the specs that state a flying weight of 2100g which is light for a four meter scale glider. None the less I was brave and clicked on the pay button for the pure glider version (http://www.hobby88.com/shop/product_info.php?cPath=66&products_id=542). The kit finally arrived after 21 days at my local post office. It came double boxed with some colourful pictures on the inner box. All the major parts were wrapped in foam sheeting and sealed in plastic bags. Fortunately there was no damage to any part of the kit during its long travel to South Africa. So what did I get for my $278 plus $70 shipping?

Wings

The wings come in four sections and are made up of foam cores covered with balsa and covering film. In my kit they are straight with no warpage and very little wrinkling in the covering was evident. The inboard and outboard wing sections are joined by means of 10 mm carbon fibre rods with lengths of 200 mm. A 520 mm carbon fibre rod of the same diameter is also used to join the wings to the fuselage. The inboard wing sections have flaps over their entire lengths and have servo operated metal spoilers pre-installed. The spoilers operate smoothly once the film is cut away that cover them and rise to a maximum of 20 mm above the surfaces of the wings. Upon removing the foam inside the servo pockets, I found a layer of fibreglass between the foam and balsa wood. Considering the rigidity of this section of the wing, I think it is safe to assume that the entire core of this section was first covered in fibreglass before the balsa wood was laid on. I could not find any fibreglass in the outboard sections but this should not be big concern since most of the stresses are applied to the inboard sections during flying. The ailerons are installed in the outer sections of wings and cover almost their entire lengths. The covering film serves as hinging material for both the flaps and ailerons and is hinged from the top surface of the wings. Movement of the control surfaces are restricted by this setup especially the flaps. There are only servo covers provided for the flaps with none for the ailerons and spoilers. The pockets for the aileron servos are close to the leading edge of the wings where there is a pronounced curvature to the underside of the wing. Standard flat servo covers will need to be modified to work in this position. Two hollow fibreglass wing-tips are supplied with the kit which are beautifully made and follow the profile of the wings very nicely.

Fuselage

The fibreglass fuselage was gel coated in the mould and no additional paint was applied afterwards. All plywood support frames for the servos etc. are pre-installed in the fuselage. The canopy and its support tray are of good quality but have to be trimmed to fit the fuselage properly. By the length of the canopy, I would say the kit represents the D version of the Nimbus 4 which is a two seater version of the glider. The horizontal stabilizer is fabricated in fibreglass with a foam core and is very sturdy although a bit heavy. The elevator is moulded as part of the stabilizer and is hinged by partially cutting through the fibreglass. The hinge produced such is a bit stiff and movement is limited. The rudder is film covered balsa.

Retract

As mentioned, the kit is supplied with a retract unit for the main wheel which is operated by a servo. The frame of the unit is 2 mm aluminium and the rubber wheel has a diameter of 75 mm with a plastic hub. Operation is very smooth with positive up and down lock. A minor problem with installing the unit is that it does not fit properly in-between the pre-installed plywood frames inside the glider. The hole cut into the belly of the glider also does not correspond well with the position of the retract unit. There are no doors supplied to close the opening once the wheel is retracted.

The weights of the different components in the kit are as follow:

Fuselage: 392 g
Canopy: 74 g
Wings:Left inboard section: 302 g
Right inboard section: 313 g
Left outboard section: 100 g
Right outboard section: 114 g
Left wingtip: 14 g
Right wingtip: 16 g
Horizontal stabilizer: 56 g
Rudder: 20 g
Retract: 72 g
Bag with miscellaneous items: 59 g
CF rods: 520 mm: 61 g
200 mm: 23 g / 24 g

Total weight of all components as received: 1640 g

In general I am impressed with the quality of the kit and consider it good value for money. The few issues mentioned with the kit should be fixable without too much effort. This is however not a kit you quickly pop your RC gear into and go fly, some work is required on it. The flying weight stated by FlyFly Hobby should be achievable if one sticks to components of reasonable weight. This will be a long term project for me since my time to work on it is unfortunately limited. I also have a Geronimo 3m glider from FlyFly Hobby that I would like to finish before I start working on the Nimbus. I would really be interested to learn of any of you guys that have flown the Nimbus 4 before.

Cheers and happy flying.
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May 19, 2013, 10:53 PM
Registered User
I've been waiting for someone to get one of their new epoxy glider models. Thanks for the write up.
May 20, 2013, 04:12 AM
Registered User
Excellent write up with lots of information on this glider. Will be monitoring this very closely to see the progress of your build.
May 20, 2013, 04:12 AM
Registered User
Damian Couzoff's Avatar
It looks like flyfly have chosen foam cores, instead of using built up wood wings on this model.Because of the narrow wings,that are only sheeted in balsa,and not obechi veneer,it might be worthwhile stripping off the covering,and glassing them in 3/4 ounce cloth,prime then finishcoat.The fueslage is made using woven cloth ,but vinylester(polyester) resin is used,not epoxy.The fuses are then painted,not gelcoated,and alot of paint is used,and it also cracks easily.I have x2 flyfly DG808S,with three sets of wings,one set has foam cores,with flaps and bigger aileronns,and weighs 4.5 kg,and flys very fast off the slope,wingloading is high.The other two sets of wings are the built up wings,one set has 370mm graupner spoilers installed,and the other is the standard set with flaps -ninety degrees deflection.I fly both models off the slope,and have never aerotowed them,so any extra weight is not really a hindrance.I have also glassed the cockpit with epoxy resin and woven cloth on both fueslages.I dont use the 12mm carbon wing rod,but 12mm aluminum T6 bar instead.
Last edited by Damian Couzoff; May 20, 2013 at 04:36 AM.
May 20, 2013, 03:13 PM
Registered User
Quote:
Originally Posted by Damian Couzoff
It looks like flyfly have chosen foam cores, instead of using built up wood wings on this model.Because of the narrow wings,that are only sheeted in balsa,and not obechi veneer,it might be worthwhile stripping off the covering,and glassing them in 3/4 ounce cloth,prime then finishcoat.The fueslage is made using woven cloth ,but vinylester(polyester) resin is used,not epoxy.The fuses are then painted,not gelcoated,and alot of paint is used,and it also cracks easily.I have x2 flyfly DG808S,with three sets of wings,one set has foam cores,with flaps and bigger aileronns,and weighs 4.5 kg,and flys very fast off the slope,wingloading is high.The other two sets of wings are the built up wings,one set has 370mm graupner spoilers installed,and the other is the standard set with flaps -ninety degrees deflection.I fly both models off the slope,and have never aerotowed them,so any extra weight is not really a hindrance.I have also glassed the cockpit with epoxy resin and woven cloth on both fueslages.I dont use the 12mm carbon wing rod,but 12mm aluminum T6 bar instead.
This is an epoxy gelcoat model. It's new.
May 21, 2013, 07:17 AM
Registered User
Damian Couzoff's Avatar
Quote:
Originally Posted by jwrendenver
This is an epoxy gelcoat model. It's new.
One of the members on rc groups (steve wenban) has visited the flyfly factory in china,and he has witnessed the manafacturing process from start to finish on their production line.It is NOT an epoxy fueslage as advertised on their website.It is woven fibreglass cloth,coated in vinylester resin,then removed from the mould ,then PAINTED white,no gelcoat is ever applied.I own the flyfly asw 28,Condor and DG808S and they are all the same as your nimbus.They are still okay,but remember you get what you pay for,these are NOT european made gliders with genuine epoxy fuses and genuine gelcoat finish.
May 21, 2013, 08:29 AM
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Woodstock 1's Avatar
I wouldn't have a clue about this, but is there any chance Fly-Fly may have seen the light, and are dragging themselves into the 20th century with more modern production methods / materials (subsequent to Steve's visit)?

Chris
May 21, 2013, 08:19 PM
Registered User
It's an epoxy fuse. Foam core wings. It's new. They now offer a few epoxy gliders.
May 23, 2013, 02:25 PM
Registered User
RUSS CONRADT's Avatar

Fly Fly Nimbus


Hi Sungazer,
Nice username you have, I cant help wondering if you have ever been to the annual event at Volksrust?
I have a friend who is flying a FlyFly Fox, and it is a very nice performer on the slope.
A point about the finish, as far as being painted in the mould, gelcoat, etc whatever, if you can see a join line along the top or bottom of the fuselage, then it is painted or gelcoated in the mould.
The CMPro Discus was a shocker for finish quality on the fuz, earlier the Chinese shops hadn't perfected the spray in the mould technique, so they patched and painted every fuz after pulling it from the mould. And that was as thick as an army tanks paint job!
Looking forward to seeing the final result of your Nimbus, and more so, seeing it fly at a Sungazer event
Regards
Russ
May 23, 2013, 10:50 PM
Registered User
Nice one Sungazer .
Subbed in.
I bring a small batch of FlyFly models in once a year and have been hanging off till next summer hoping somebody would be the guinea pig on the Nimbus.
Will follow your report with much interest.
Our group has ASW 28, ASK21, Condor and Fox, Brilliant value.
They do an electric version of the Nimbus as well and that is my thing.
Cheers
Tony
May 24, 2013, 01:03 PM
Registered User
Quote:
Originally Posted by RUSS CONRADT
Hi Sungazer,
Nice username you have, I cant help wondering if you have ever been to the annual event at Volksrust?
I have a friend who is flying a FlyFly Fox, and it is a very nice performer on the slope.
A point about the finish, as far as being painted in the mould, gelcoat, etc whatever, if you can see a join line along the top or bottom of the fuselage, then it is painted or gelcoated in the mould.
The CMPro Discus was a shocker for finish quality on the fuz, earlier the Chinese shops hadn't perfected the spray in the mould technique, so they patched and painted every fuz after pulling it from the mould. And that was as thick as an army tanks paint job!
Looking forward to seeing the final result of your Nimbus, and more so, seeing it fly at a Sungazer event
Regards
Russ
Hi Russ

I think Sungazer is actually a pretty descriptive name for us RC glider pilots in general because of all the time we sit/stand in the sun staring up into the sky. (A Sungazer by the way is a lizard that lives in South Africa that spends a lot of its time doing exactly that.) No I havenít been to the Volksrust slope soaring event yet but definitely plan to next year. I hope the organizers of the event donít mind me using their name too muchÖ. I am really glad to learn that everyone appreciates my write up. As far as paint on the fuselage is concerned; no their definitely is none on the Nimbus. I am no expert on fiberglass technology but the joint line between the mould halves is very clear (see 3rd last picture in my write-up). It may be that FlyFly has moved away from painted fuselages. My Geronimo 3m, which is also a newly released glider, also has no paint on the fuselage except for the little piece between the wings that is painted red.

Cheers
May 27, 2013, 03:50 AM
Registered User
Damian Couzoff's Avatar
Icarerc have a Nimbus 4d-4 meter as well.This model however has moulded wings instead,and is virtually identical in specs-the fueslage is two inches longer,and it has a very small increase in wing area,being 45 dm sq.It has a HQ 3015 airfoil,which l think the flyfly hobby nimbus 4 has as well,identical to the flyfly asw 28 airfoil.Root chord for the moulded wings is 150mm.Anyway,l did a bit of researching on the moulded wings model,and found a webpage of the exact model in question.The guy who owned it,found the model pitched down severley when a gust of wind caught it whilst flying,also it was very hard to turn.Initially,he thought it was the stab size being to small,but after trying a bigger stab,there was no improvement.He then used a wind tunnel at university,to test the wing.By placing a zig-zag turbulator strip along the entire leading edge was the best result to increase the wings efficency.He then flew the model,and it now turns easily,does not pitch down,and the only difference being in reflex(flaps)the model gains speed but sinks.Because the wing has a high aspect ratio,he commented that the airfoil is to thick for the aspect ratio of the model.I have ordered a flyfly nimbus,and the first thing l will be doing before its maiden,will be to add this zig zag turbulator strip......and have 3 to 1 aileron differential.Also to cut the flaps off,and flip them upside down,and swap them,right to left wing and vice versa,and then bottom hinge with tape.I will be using 6 channels-ailerons,spoilers,rudder.elevator ,flaps,tow-release,and installing a fixed front and rear wheel,instead of a retract.I will also have a spare 10mm carbon wing rod,the same length,for the nimbus in case l break it,from my flyfly condor,l use a aluminium wing rod for that instead.The outer panels will be epoxied to the inner panels,and the tips will be epoxied as well,once l have all my wing servo wiring sorted...
Last edited by Damian Couzoff; May 27, 2013 at 07:52 AM.
May 27, 2013, 03:42 PM
Registered User
Hi Damian

The research on the turbulator strips on the Icarerc Nimbus is very interesting, thanks for posting this. According to the plans that came with my kit the airfoil is Eppler 205. I traced the airfoil at the root of the left wing (see below) and it looks very much the same as the HQ 3015 you have shown. The root chord measures 153 mm. I agree swapping and flipping the flaps will solve the limited deflection problem. You will also have to make a plan with the ailerons for their down deflection is only about 6mm. (The plans suggest 20mm). It is great to learn that you have also ordered a Nimbus, I donít think you will be disappointed

Cheers
May 27, 2013, 05:20 PM
Registered User
simonslim's Avatar
Don't know if it will be worth-while doing the flap mod as you have spoilers which can be mixed to deploy with crow/butterfly and will be very effective. Plus you will have an ugly gap on the top surface of the wing which could disrupt the airflow over the flap rendering it less effective. It would probably be easier to increase the angle on the leading edge of the flap to get the desired flap angle. I have the Flyfly Fox with the "limited" flap travel which is still more than adequate when using crow/butterfly.
The turbulators work well on these smaller scale gliders, I fitted them to my 3 meter all glass ASH26 and it made a marked improvement in it's handling. I made mine from white electricians tape cut with pinking shears that I bought from a dress makers for £5.
May 27, 2013, 07:21 PM
Person of interest
KiwiKid's Avatar
Interesting stuff. Did you fit them as in the pic above with the flat side on the leading edge and the "pinked" edge to the rear?


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