By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

Ben Buckle Junior 60 build

questions

All Topics | Latest Posts

Search for:  in Thread Title in  
Andy Hat29/05/2019 09:28:42
avatar
64 forum posts
42 photos

I'm building a Ben Buckle Junior 60 and I'm not clear on the wing joining.

When it comes to joining the two wing halves, there's no plan (other than the instructions and drawings to build a two part wing). Looking at the roughly cut dihedral brace and/or doubling up the width of the half-joiners, implies that the width of the flat centre section is -greater- than the width of the fuselage. i.e. the two outer ribs are further out than the edges of the fuse. This feels wrong since I'd normally assume that the pressures of the wing bands would go through the ribs, down directly on the top edges of the fuse. I've looked at many pictures online but can't quite determine what's correct.

Also, any ideas on where I can get some nice 4-inch small-hubbed vintage balloon wheels like the Flair Smooth Hub Wheels shown on **LINK** ?

Mike Etheridge 129/05/2019 09:46:25
1535 forum posts
429 photos

I am probably repeating myself here but I do have a Ben Buckle Junior 60 fuselage (1946 version) I acquired at the Nationals plus a Keil Kraft 'New Junior 60' (1955) I built in 1962 / 3. They both share the Keil Kraft wing but as the Ben Buckle plane's fuselage is not as wide as the Keil Kraft fuselage (Same as the Flair Junior 60) there is a slight overlap of the centre section which seems to make little difference. I do not have the Ben Buckle plan but I have got the Flair plan which matches the 1955 Keil Kraft plan plus a centre section detail from Keil Kraft. I hope you can make sense of the above ?

001 jr60.jpg

1946 JNR 60 and original Keil Kraft 1955 New JNR 60 Built 1962/3

Cuban829/05/2019 10:01:11
2771 forum posts
13 photos

A word or warning based on what I've seen others suffer. If you keep the original wing structure and then fit an engine or electric motor that's more powerful than what was fitted in the original, you really do risk total wing failure, especially if the model is flown in a manner that is anything more than R/C assist.

I've lost count of the times I've seen these and similar retro designs 'auger in' when over-powered and then looped or flown in windy conditions that would have grounded the originals.

Lovely models, just need to be operated appropriately with modern tech.

Mike Etheridge 129/05/2019 17:43:08
1535 forum posts
429 photos

I have to agree with Cuban 8, the wings do need beefing up at the joints. I am sure my wings have ply reinforcements on the joints which are not shown in the detail above. Additional reinforcements would also be advisable. I did feature the electrification of a Mercury Matador on this website a few years ago. The plane which belonged to my nephew Nigel got caught in a thermal at Croydon airport. My nephew put the plane into a spin to escape the thermal but the wings folded and the plane was scrapped and finished up in a dustbin from where I recovered it. I re-built the wings with spruce strip reinforcements on the wing spars.

To date my Junior 60 wings have survived but have only looped the loop twice once with the Ben Buckle fuselage attached and once with a Super 60 fuselage attached.

028.jpg

Colin Leighfield29/05/2019 17:59:08
avatar
5962 forum posts
2492 photos

Interesting to read some of the experiences here. When flying my Ben Buckle Mercury Matador (PAW 149 diesel), I got carried away and looped it. The wing folded! I keep kidding myself that it is repairable and I will get around to it. Story of my life!

Andy Hat29/05/2019 18:19:07
avatar
64 forum posts
42 photos

Thanks. I think I'll make the centre section as wide as the fuselage (so the outer ribs sit on the longerons) and build in a new 1/8 ply dihedral brace.

PatMc29/05/2019 21:55:43
avatar
4223 forum posts
521 photos

Andy, Keil Kraft made 2 versions of the Junior 60.
The original appeared in 1949 and was intended purely for free flight.
The second version came out in 1955 it was also intended for F/F but with the option of single channel RC. A number of design changes were made to the new version, main ones being a wider fuselage in order to fit the receivers & batteries required at the time also the wing design had to a better spar arrangement.
The wing centre section of both versions were the same width as the respective fuselage. If yours has a wider centre section it could be the later design on an old version fuselage.

You can identify which version you have by downloading pdf files of each plan from Outerzone, open the files in Acrobat Reader & comparing them. Here's a link to the 1949 version & here's the 1955 one.

I have a Flair kit Jnr 60 that was based on the 1955 version, I built it around 1986 then refurbed & converted it to electric about 6 years ago.
The wings were never strengthened in any way but if you take a look at the refurb link you'll see they are retained by peg & screw instead of rubber bands. This model has has regularly been looped, rolled, spun down from altitude & flown inverted without any problem, it's also been flown as a floatplane.
In short, it's not the wing and it's joiner strength (at least not the 1955 design wing) that's the problem, it's the method of fixing. The position of the wing band dowels was fine for free flight but allows too much flexibility of the wing position during RC controlled manoeuvres, particularly the leading edge being able to rise off it's seat.

Andy Hat31/05/2019 18:38:44
avatar
64 forum posts
42 photos

The Flair and KK designs of the wing joiner/centre looks stronger than the Ben Buckle version. I've now joined the wing with a 1/8 ply brace. It was too late to change the wing fixing method but I don't intend to fly it in anything other than a vintage way. I think I might double up the uprights under the wing though.

Does anyone have an estimate of how much Solartex is needed to cover a Junior 60?

Edited By Andy Hat on 31/05/2019 18:39:11

Dwain Dibley.31/05/2019 22:21:26
avatar
1270 forum posts
1265 photos

I think I used about five metres on mine.

Have you got some squirrelled away, cos it's Oratex otherwise Andy.

D.D.

Andy Hat31/05/2019 22:33:12
avatar
64 forum posts
42 photos

Thanks Dwain. 5m? blimey. I have quite a few rolls of Solartex but probably not 5m of the same colour.

I usually use the Hobbyking film, which is excellent, and cheap. Shame they don't do a "solartex" equivalent since I really want to give this a vintage (non-shiny) material look. Oratex is pricey. Tissue wouldn't survive my handling and I've not had much luck covering in nylon. Covering this thing looks like it could easily cost as much as the kit cost to buy. I may have to work out colour-scheme which uses the Solartex that I have in stock...

Dwain Dibley.31/05/2019 23:03:36
avatar
1270 forum posts
1265 photos

Sorry...............

I'm being silly mate, its more like 3 meters, 2 on the wings and another on the fuz. You should get one wing panel out of a meter of 26 " wide solartex. I have just been trying to find a photo for you but failed.

D.D.

Edited By Dwain Dibley. on 31/05/2019 23:04:53

Andy Hat16/06/2019 15:16:49
avatar
64 forum posts
42 photos

It's nearly finished. Just a few more things to do, primarily the decoration. I've ordered some matt black vinyl for that.

I can confirm that less than 3m of Solartex was enough to cover it. Luckily I had this much in cream.

20190616_145937[1].jpg

Edited By Andy Hat on 16/06/2019 15:17:06

Percy Verance16/06/2019 17:58:50
avatar
8108 forum posts
155 photos

DD

Until I saw your second post, I was about to ask where on a Junior 60 have you used 5 metres? I thought you must have been wrapping it round 3 times or something...... wink

Dwain Dibley.16/06/2019 18:12:00
avatar
1270 forum posts
1265 photos

Chortle......................

I did a refurb of a J60 I bought from a swap meet a few years ago, but all the pics have been lost. It was a bare bones buy, built but not covered and it would have helped immensely with the J60 build Q's we have had lately.

D.D.

Andy Hat20/06/2019 20:56:22
avatar
64 forum posts
42 photos

It's finished!

I had to add 220g of lead to the front to get it anywhere near balancing.

Looking forward to flying it soon. Slightly worried about it climbing too fast and needing permanent downtrim. Also worried about the small rudder - will it be enough to control it?

20190620_204337.jpg20190620_204413.jpg

20190620_204434.jpg

20190620_204359.jpg

PatMc20/06/2019 22:30:08
avatar
4223 forum posts
521 photos
Posted by Andy Hat on 20/06/2019 20:56:22:

It's finished!

I had to add 220g of lead to the front to get it anywhere near balancing.

Looking forward to flying it soon. Slightly worried about it climbing too fast and needing permanent downtrim. Also worried about the small rudder - will it be enough to control it?

Looks great, Andy thumbs up

Once you've flown it a few times & are happy with the trim you could try removing the lead incrementally, adjusting the elevator trim as you do. My Junior has the cg 1.3 inches rearwards to that shown on the plan & has been flying without problems since 1986. The rearward cg improves the glide & widens the speed range.

Control the rate of climb with the throttle & the speed with elevator trim. Don't worry if you end up with some permanent down elevator when you've established a comfortable cruise setting, it will have no ill effect. With the tx trim at neutral mine has 1/4" permanent down elevator which gives a nice cruise setting at about 1/4 - 1/3 throttle.

The Junior is quite responsive to rudder & even though the BB version rudder is much smaller than the Flair the rudder control should be more than adequate.

Dwain Dibley.21/06/2019 00:22:04
avatar
1270 forum posts
1265 photos

Very Nice !!!

D.D.

David Davis21/06/2019 06:02:26
avatar
3442 forum posts
613 photos

220 grammes that's nothing!

The Junior 60 was my first successful r/c model and in its first manifestation powered by an Irvine 20 I had to put 680 grammes (1.5 lbs) of lead under the engine to achieve the balance point shown on the plan. It still flew well.

Andy Hat21/06/2019 20:22:21
avatar
64 forum posts
42 photos

It flies!

Well, the first flight was very scary. under power, and without power, it was ballooning/wallowing/dolphin-ing and there was limited control. I managed to get it down intact (those wheels are great at absorbing a heavy landing!).

So, I put two halves of a lolly stick (4mm) under the leading edge of the tail, added two washers to the top of the motor mount, added another 75g of weight to the front and moved the clevises in by two holes on both the elevator and rudder.

The next flight was much better and followed by 3 more batteries-worth of flights. It flies around nice and slowly. Most enjoyable! (I did learn that trying to take a photo whilst flying is probably not a good idea...)

The extra weight may not have been needed so I'll try taking it out as Pat suggests. Both the rudder and elevator now move ~40 degrees. The Flair tail, with larger moving surfaces) looks much better but these are OK for now. Raising the tail LE 4mm meant that it flew well with zero elevator trim.

Any suggestions on how to permanently build-in the raised tail LE? I'm not sure I'd be able to accurately sand a piece of balsa sloping from 4mm to zero, or cut a slope into the existing rear end.

20190621_153659[1].jpg

Edited By Andy Hat on 21/06/2019 20:24:20

cymaz21/06/2019 21:12:26
avatar
8767 forum posts
1190 photos

You could raise the wing TE

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E! 

Latest Forum Posts
Support Our Partners
Gliders Distribution
electricwingman 2017
CML
Wings & Wheels 2019
Slec
Pepe Aircraft
Cambridge Gliding Club
Advertise With Us
Sarik
Latest "For Sale" Ads
Do you use a throttle kill switch?
Q: This refers to electric-powered models but do you use a throttle kill switch?

 Yes
 No
 Sometimes
 Rarely

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us