Coming back after 50 years: bit lost

[Kim Taylor]

Posted by 911hillclimber on 06/01/2018 16:27:21:

The plans have no dowls, just a step of about 1/4" for the wing to come up to by virtue of the bands. This is not enough, the wing LE rides over it very easily.

I think you just need more bands - at least 6 - 8 and the right length - needs to be a firm pull to stretch them over the wing.

O/T I assume from your user name that you were involved in speed hillclimb?

I only ask as until recently I marshalled at Gurston Down and our paths may have crossed?

If not, please ignore!!

Kim

[Cuban8]

Very little that I can add to the sage advice proffered so far, except that I have seen several vintage designs built as trainers in my clubs and they invariably wind up with a much more powerful engine or electric installation and are flown harder under R/C and in far windier conditions than they might have been used to years ago. The result has been wing failures when the models were yanked round into wind, or after excessive airspeed has built up following pilot error/disorientation.

I watched a particularly nice Junior 60 'clap wings' in a tight turn a few months ago and asked the builder whether he'd replaced the standard balsa main spars with hard wood, he hadn't, but I understand that the new model will have spuce spars and a tad more in the way of spar webbing.

Just a thought.

[911hillclimber]

Kim, been to Gurston several times but to watch, Wife won't let me run there. I've hillclimbed for 27 years starting in my old 911, hence my forum name!

I'm very involved with Loton Park hill climb.

Cuban;

This Stol has run a PAW diesel in its past as RC 3 channel, but I take your point, failures of the structure are a risk.

I think the plane's biggest risk is me trying to fly it...

Dennis: the UC is held in place by bands with a good 'spring' wire in the design to allow 'spread' on hard landings.

Edited By 911hillclimber on 06/01/2018 23:13:48

[Kim Taylor]

Posted by 911hillclimber on 06/01/2018 23:12:05:

Kim, been to Gurston several times but to watch, Wife won't let me run there. I've hillclimbed for 27 years starting in my old 911, hence my forum name!

I'm very involved with Loton Park hill climb.

Ah, you must be Lolat492 from Uphill Racers, I've followed your trials and tribulations with the Lola with interest.

I'm kimducati on there, although I don't post much - small world, 'aint it?

Kim

[David Davis]

Re vintage models and wings clapping.

Most vintage models were originally free flight models and the stress on the wing was far less in that mode than with the additional weight of radio and an elevator able to force the model to descend or to penetrate a wind. However, some vintage models were built for radio control from the outset or were strengthened versions of an existing design.

The Radio Queen is obviously one example and there are two versions of the Junior 60. Ben Buckle's Junior 60 is based on the original 1946 free flight design while the Flair Junior 60, which regrettably no longer seems to be available, was based on the 1950s re-design with a wider fuselage to take the bulky radios of the day, a larger rudder and a stronger wing made up of three 1/4" balsa spars and spar webbing, as opposed to the original which had a rectangular mainspar. You would have to be very brutal with the later type Junior 60 to cause the wing to fail.

Much though I love the flying characteristics of the Junior 60, if you find youself having to build a model from the Ben Buckle range Hillclimber I would recommend the Super 60 rather than the Junior 60. The Super 60 is a superior radio trainer being better at flying in a wind and easier to build to boot.

Your STOL was designed as a radio controlled model from the outset so you should not have any problems with wing strength.

Finally, I have just started renovating my fuel-soaked Junior 60 and I plan to convert it to electric power. I'll post a thread detailing my progress when I get around to it.

[Piers Bowlan]

I agree Cuban8, I saw a Junior 60 clap hands on Epson Downs when I was a teenager, sadly, about 45 years ago! The wing spar joiner never was very strong (queue, howls of protest!!). I wonder how many Junior 60 wings have failed over the years because 'that was the way the designer designed it' and 'the design has been like that for the last 60 years, so why change it?'. Controversial, Me?  

PS. I wasn't aware of the Flair Junior 60 changes, shame the Ben Buckle kit wasn't updated.

Edited By Piers Bowlan on 07/01/2018 06:40:37

[cymaz]

Posted by Piers Bowlan on 07/01/2018 06:30:08:

I agree Cuban8, I saw a Junior 60 clap hands on Epson Downs when I was a teenager, sadly, about 45 years ago! The wing spar joiner never was very strong (queue, howls of protest!!). I wonder how many Junior 60 wings have failed over the years because 'that was the way the designer designed it' and 'the design has been like that for the last 60 years, so why change it?'. Controversial, Me?

PS. I wasn't aware of the Flair Junior 60 changes, shame the Ben Buckle kit wasn't updated.

Edited By Piers Bowlan on 07/01/2018 06:40:37

Piers, mine clapped its wings. IIRC the spar joiner is a piece of the thinnest ply. Powered by SC 30fs.

[Cuban8]

Just remembered.................back in the early summer (!) I watched another vintage model that had been converted to electric, (enlarged Tomboy IIRC) commit aeronautical hara-kiri due to violent wing flutter that tore the wing off completely and left the fuz to describe a beautiful ballistic trajectory into the deck from a hundred feet or so - thankfully, no collateral damage, except to the pilot's pride.

[911hillclimber]

Got some good time on the Stol today. Having built cars, restored cars etc M3 screws and flyweight parts are very different to work with than a 1000Kg of car where M6 is the smallest fastener!

 

Takes a bit of getting used to, but progress today. For the pro modellers watching me thump my way through this, please do not cry when you see my efforts.

 

Thought I would try the M3 long stainless 'posts' to hang the little motor off, what a BAD idea this was.

After a pause for thought decided on a much more robust idea that still gives me some means of adjustment if required and looks like it might survive my first landings.

I elected to cut and shut the IC motor mount figuring I could always buy another if I need to go to IC.

The dimensions sort of fell into place, but I had to lower the shaft centre line 4mm. I'm hoping this is tolerable.

No doubt you will advise.

 

After some delicate drilling, tapping and screwing the result is loosed together as above as a 'dry' build.

First shot, studs are crooked as they are loose, remember, NO crying!

Edited By 911hillclimber on 07/01/2018 16:58:04

Edited By 911hillclimber on 07/01/2018 17:01:14

Edited By 911hillclimber on 07/01/2018 17:03:00

Edited By 911hillclimber on 07/01/2018 17:04:01

[Ron Gray]

Others may disagree but standoffs that long are not ideal. Why not make up a plywood mounting box similar to this (a photo Bob posted on his Easy Street 2 thread)

**LINK**

 

Edited By Ron Gray on 07/01/2018 17:11:58

[911hillclimber]

I saw a similar mod to a Jn60 the other day, I think on this forum where a ply box had been made.

I am trying to keep the model as the original design which may be a folley I know.

With the materials I could do the very same and bolt it to the original bulk head.

Food for thought!

If there is an outcry this is a bad attempt, I'll do as you suggest.

[Tim Ballinger]

911

Not exactly crying but I think I would suggest you tried something designed for the job. There are others about I think but I have just used these shown below.

They are relatively cheap and are designed to spread the loads evenly. Mine were from 4 Max. You just need to check the hole centres on the crucifix if if you go for the full cage. By implication you can just buy the standoff’s but a full cage is the most rigid. If you measure your hole centres and give George at 4max a ring he should be able to sort you out. Others may know of other cages you can buy. Or you make up something like Ron suggested .

Tim

Edited By Tim Ballinger on 07/01/2018 18:49:25

[Ron Gray]

I think that the ‘limit’ for the alloy cage would be about 60-70mm in length.

[Tim Ballinger]

Lost track of what diameter motor you ended up with and desirable stand-off would vary with diameter. I think you were in the 28 to 30 mm area so Ron’s number of 60mm would be close to the mark.

Tim

[911hillclimber]

Ok, I give in to a ply box bolted onto the existing captive nuts in the bulk head!

On impact at least the back spider on the motor will be supported by a sheet of ply. 1/8 ply should do it.

[Piers Bowlan]

The motor is 28mm dia and the distance between centres of the cruciform mounting holes is 33mm. Hill climber, you note the holes drilled in the bulkhead to allow cooling air to ventilate the fuselage. The ESC can be located in the fuselage with the battery, if that is easier than trying to squeeze it inside the cowl where it might foul the spinning motor. Don't forget to make a vent further aft to permit cooling air to escape. Cooling is not critical with this low power set up but worth taking into account in more powerful model builds.

Incidentally, I am sure you are an expert at soldering but I thought it worth mentioning that if your LiPo battery has an XT60 connector on it then clearly you will need to solder the corresponding (male) XT60 connector onto the ESC you purchased (they don't normally come with plugs). What may not be so obvious is that it is best to connect a female plug to the male when you solder the male to the ESC. Even when soldering swiftly with a large hot iron the heat can melt the plastic in the connector ruining it. With the male and female plunged together this does not happen-usually.

just my 2p worth.

[911hillclimber]

I've decided to build a ply box, embarrassed by my make-do today. Waiting on the battery to arrive, note the cooling.

Soldering should be ok, if it's rough I won't picture it...

Thanks as ever!

[Ron Gray]

No need to feel embarrassed, you haven’t seen some of the ‘make do’s’ that I’ve tried in the past!

[911hillclimber]

I didn't think it through enough a few days ago before I braved the model shop.

The ply box is the best way structurally as on impact my 'design' would render the 'X' mounted very bent as it has no support across the back of the motor base.

Doubt the motor would come out of a thump too well either. Hard to believe such a small thing will pull this plane off the ground!

Shop is closed tomorrow, but hope to have a finished box done by next weekend.

[Piers Bowlan]

The front face of the box could be 1/4in ply which might give self tappers a bit more to bite into? The extra weight will be where it is needed - up front. Self tappers are fine for small motors, with larger ones T-nuts can be pushed into the back of the ply mount (with a vice, not hammered) but use thread lock on the screws.

While I think of it, it is generally a good idea to balance props for turbine smooth operation .

[Tim Ballinger]

911,

Echo Ron’s comment above. We have all made howlers often in a desire to bodge something quickly and get flying. Sometimes it works but most often it bites. Showing pictures is a great way of getting folks to give you best practice.

Did I see you go to Penn models ? I was a young teenager flying with Kinver Aeronauts Radio Contol Society (KARCS) when Pete Littley first set up the shop . He used to bring his van laden with goodies to the old airfield at Perton where we flew. Sadly airfield, KARCS & Peter have all passed on. I think his son runs the shop now. I moved away as well and was shocked how few model shops still exist when I started flying again . I survive ,like most, on mail order so in that respect you are very lucky.

Tim

[911hillclimber]

Yes, I have Penn Models about 3 miles away so that is good even if the shop is not the most welcoming of places, maybe better week days.

I'll be bolting it all to the bulkhead using the existing engine bearer bolts as they are captive. Plan is to build a simple cube, about 50mm each side length and double up the 1/8 ply on the motor and bulkhead faces where bolts are passing through. I'll add some holes to allow finger/plier access to the slippery M3 bolts for the motor mount. and clear dope the ply box for weather protection.

Due to lead lengths, the ESC and the battery will need to be in the cabin with the battery under the CofG range.

I hope to mount the ESC sort of suspended so air can get around all surfaces.

As to venting the cabin...I think this might be tricky to decide, perhaps cut a hole in the underside fuselage sheeting where I think the air pressure is light, but that is certainly a guess!

[Ron Gray]

Use T nuts for the engine mounting bolts, attach them to the ply motor mount plate before you stick your box together, that way you don't have to worry about finger access!

Venting - if air is getting in then a hole in the underside will allow it to escape, the position isn't critical as long as it is behind the potentially 'hot' components.

Here is a better photo of an engine box (courtesy of Ripmax)

And here are a couple of shots of typical venting holes

[911hillclimber]

Thank you for these details.

The box is what I had in mind, but not so many tongues and slots! My skill set is more MIG welding than fret saws...but the principles will be the same, just simpler.

Got all the stuff today from Penn Models.

The vents are as I imagined. The Stol has a good length of sheet underside extending a good 1/3 of the way back from the nose, I'll open a slot in that and seal the edges with the clear dope I've just bought, and add a slot in the bottom of the front bulkhead.

I've bought enough 1/8 ply to make the box twice....

[911hillclimber]

It has taken a long time, but the motor box is all made and trial fitted.

It bolts to the original bulkhead using the IC mount thread inserts. The electric motor screws to the front using captive M3 nuts and screws.

The motor spindle looks to be on the centre-line of the original IC engine, the lower cowl half fits and I've put a good hole in the lower section to get cool air into the cabin. I've cut also a hole 125% larger in the lower fuselage sheet as an escape.

Next step will be to clear dope the box and route the motor wire correctly now I have the ESC and the battery and then modify or re-make the top cowl.

 

Radio after that!

 

Edited By 911hillclimber on 10/01/2018 17:59:18

Edited By 911hillclimber on 10/01/2018 18:02:23