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Member postings for Peter Jenkins

Here is a list of all the postings Peter Jenkins has made in our forums. Click on a thread name to jump to the thread.

Thread: Warbirds Replicas P51 Mustang
16/01/2021 14:16:32
Posted by RICHARD WILLS on 16/01/2021 13:47:55:

Hi Geoff , For a fully functional , retractable and steerable unit .the FMS 109 and perhaps their P51 both have plug in units . I believe they are around £20 .

I used the Robart one on my Top Flite Mustang 60 build:

mustang 127.jpg

As you can see, I also fitted doors using a spreader bar and elastic bands to open and close them. Couldn't get it to work so used a 9g micro servo to operate the doors with a mix and delay to the retracr servo. Worked a treat on the bench but still have to try it in the air!

mustang 130.jpg

The reason for the long bent wire retainer is to allow the doors to be unhooked and the servo removed and replaced should it fail. The servo mounting plate is retained by the 2 servo screws you can see.

Hope that helps anyone wanting to install a retracting tailwheel and operating doors if you are so inclined.

15/01/2021 14:14:51

Retract or fixed tail wheel? Fixed is quite easy but retracts are a little more complex.

14/01/2021 12:14:48
Posted by Paul Johnson 4 on 14/01/2021 07:29:17:


I have been using various servos in the past and have found a great many variations available. For anyone looking to choose a "suitable" one to fit the model, the decision is a minefield of technical jargon that dumbfounds most. Even the stated Kg rating is given by Kg per cm. This being the force the servo can exert per cm from the centre of the actual output arm. So the further towards the last hole on the arm the less there is torque available.


Sorry to be picky Paul, torque is expressed in force x distance from the pivot hence NOT kg per cm. Otherwise, the further out from the pivot the greater the force exerted. is the max torque the servo generates and so as cm increases then the force exerted decreases for servo.

Edited By Peter Jenkins on 14/01/2021 12:15:22

Thread: It is flying related Flight
13/01/2021 23:58:10
Posted by MattyB on 13/01/2021 15:36:28:

Give it 10 mins and the conversation will circle back to this old chestnut...

(Before expressing a view I suggest you click the link above and read the article, it's a very good explanation)

Edited By MattyB on 13/01/2021 15:41:54

Don't think it did Matty! Still at least the issue of ground speed and air speed got an airing.

The OP posed a simple sum, albeit not seen like that by everyone. Best not go looking at the issue of working out how bounday layers work! That gave me a headache many years ago!

Thread: Watts/lb misleading?
13/01/2021 23:47:57

In general, I wouldn't expect an electric model to be heavier than a similar IC model. Remember you need to weigh them when the IC model is full of fuel. An electric motor is much lighter than an equivalent power IC motor. If you include fuel load in the equation with battery/ESC weight then I wouldn't think there would be much difference between them.

It all depends on what performance you want from your model. As I fly 2 mtr F3A models (competition aerobatics) I am limited to a max AUW of 5 Kg with the flight pack fitted. My motors produce around 2,800 watts (254 watts/lb). With that power they have unlimited vertical performance. That's 3.75 HP.

My Wot 4 with an Irvine 53 weighs in at 4.5 lb and the Irvine produces about 1 HP or about 750 w. That gives it 166 watts/lb but that is insufficient for unlimited vertical. With a throttle pipe on it I that requires a much coarser prop to keep the WOT revs the same so say 1.2 HP or 894 watts making 198 watts/lb. That is unlimited vertical.

I have no light weight floater type aircraft so I don't know what a viable minimum watts/lb figure would be.

Thread: Warbirds Replicas P51 Mustang
12/01/2021 09:22:34

Hi Trevor, as someone who flies mostly electric (of the 10S variety) my comment was a bit tongue in cheek wink.

However, some bright spark (!) might come up with a solution. Indeed, by putting LEDs in the stacks you might be able to simulate the exhaust flames like the jet boys simulate reheat.

Thread: SKY Rc switch
11/01/2021 23:42:44

I usually use Powerbox digi switches that rectify a 2S LiPo to 5.9 v. As with all LiPos I always remove the battery at the end of the flying session or when it drops to below 50% capacity so don't worry about the very small drain during the flying session. I've just bought a magnetic switch for a scale model but as I intend to use 2S LiPo for that then again I will be removing the Rx pack at the end of the flying session. A friend uses a magnetic switch and has not had a problem.

OTOH, on a petrol model I have 2 LiFe packs, one for Ignition and the other for the radio, switched by mechanical switches. They are heavy duty ones from Als Hobbies with a tell tale for when they are on. They have not given any problem in the 3 years that I've flown that model. Touch wood!

Thread: Panic! Damaged prop shaft threads - can't fully unscrew retaining nut. Help please!
11/01/2021 23:35:45

I would recommend buying a die and "rearranging" the thread rather than using a second nut as the die will win and the nut might not! Just tighten the prop nut and use the prop to hold the shaft steady as you run the die up the shaft.

Thread: Warbirds Replicas P51 Mustang
11/01/2021 23:30:17

+1 for those stacks!

Now, have you worked out how to get a puff of smoke out of them on start up? A small amount of flash powder linked to a switch on the TX? That would be fantastic!

Thread: Flying with Spectacles
10/01/2021 00:26:36

I've worn specs for short sight since I was 12. When I reached the age that I needed stronger lenses for reading than for distance I went the Varifocal route. As others have said, they are a bit strange at first as there is a lot of distortion off centre. However, the brain is quite remarkable and everything was fine after a week or two.

Interestingly, I have a pair of glasses with just the distance correction lenses in for night driving as I found that I could not glance down and read the sat nav or radio selection buttons at night as that fell into the reading range! So, for driving I prefer the single prescription for distance.

For flying, they are just the ticket. I use over glasses for sun protection even though my prescription includes the auto darkening feature. The main reason is to cut out the problem of eye watering on a cold and windy day! I have 3 pairs of overglasses. A yellow set for flying in low light, a normal pair for normal sun and a very dark polaroid set for if I have to fly with the Sun shining into my field of view.

The only problem with varifocals is that they need to be the other way up when I'm building stuff - a bit like that snooker player used to use. I usually have to take my specs off to do detail work that needs you to look upwards into a small opening! I have thought of getting a pair for close work only that would overcome that problem but it's cheaper to just take my specs off to deal with those few occasions when I get that problem.

Thread: Warbirds Replicas P51 Mustang
28/12/2020 23:09:37

Paul, I don't know if it's the angle of the photo of the wing tip in plan view above, but it seems the wrong shape to me. The wing tip on a P51 looks more like a tear drop shape rather than the double curve it looks like in the photo. At least, that's what all the photos I have of Mustangs plus the kit I'm building are showing.

Thread: Good Grief
20/12/2020 23:04:07

It's a bit like when you fill in the form for entry to the US and they ask you if you have ever committed a criminal offence. What a silly question I thought as people will lie. Aha, said the man in the bowler hst (stetson I suppose) if we find you have lied we can deprt you immediately as you have entered the country illegally.

So, since ignorance of the law is no defence, if you go doing naughty things with your camera equipped <250 gm model, the authorities can charge you with breaking the law. Simples!

20/12/2020 20:57:22

Martin, you may have missed the driving force for the unmanned aviation industry which is to provide the European Union (of which we were a member state at the time) with a new industry to provide employment and generate revenue.

At the size of vehicle we are talking the potentisl exists for a wide range of activity that will require use of the airspace we occupy. A small example of the roles these unmanned aircraft can fulfill:

  • Agriculture - e.g. checking for crop health
  • Powerline inspection
  • Search and rescue
  • Emergency services
  • Transport of critical medical supplies
  • Environmental inspection

There will be many more and I haven't mentioned Amszon delivery - yet.

The entry barrier to building these air vehicles is low unlike the huge barrier to entering the existing man carrying aircraft industry. This represents a huge opportunity to the EU nations and to the UK even outside the EU. Like all aviation matters it's important that laws are agreed internationally so that national boundaries do not present an articicial constraint to an aircraft.

I think that the BMFA's CEO has done a quite outstanding job to get first EASA and then the UK DfT and CAA to recognise the special position that model flying needed to be treated as an exception. The problem as ever is the law of unintended consequences. Hence, the need to make sure that people don't game the system and use the model flying exemption to conduct commercial work. Notwithstanding that I'm sure that there will be some clever dick who will find a way through to bending the rules. The pilot who flew the ill fated Emiliano Sala using an aircraft and pilot qualification that did not allow a hire and reward flight to be undertaken.

I think that's what has upset you, and probably a good many others, as nit picking regulations. The regulations did not stop the footballer Sala's tragic end but the law exists to allow action to be taken against those who hazard the safety of others. Yes, it will make no difference to law breakers but as part of a civilized society we use the rule of law to help us to live harmoniously.

Well, that's my take and I'm just delighted that the F3A aerobstics world can continue to operate by exceeding 400 ft height limit to which non-model flyers are limited.

Thread: Mick Reeves Gangster 63 Lite
20/12/2020 10:23:13

Mark, you asked for advice on which orientation to place your aileron servos. This shows one way of orientating them. For a built up wing all you need to do is to make a ply cover that sits between the ribs and then glue in the 4 corner supports to which to secure the ply cover. Same technique as I used except I had to cut out the veneer and dig out the foam to allow space for the servo. You may also need to reinforce the supporting ribs by gluing in a couple of 1/8 balsa spars to strengthen the structure that will carry the servos weight. Remember that you can cause the aircraft to generate as much as 20 g in a sharp pull out that increases the servo weight by 20, so a standard 50 g servo rises to 1 kg during the pull out so the structure needs to support that weight.

Thread: Pace Makers and Radio Control Query
20/12/2020 00:07:15

I might be wrong, but I believe the higher output from US standard Txs makes them illegal in the UK.

Thread: Mick Reeves Gangster 63 Lite
19/12/2020 23:59:06


On my Gangster 75, I've used 2 aileron servos with the ailerons sunk into the wing as in the photo below. As you can see, the wing is foam with veneered covering. I then made a ply plate to fit the hole, glued in ply triangular corner pieces in the box to allow the servo plate to be held in with servo screws. The servo was mounted on hardwood mounts allowing the servo arm to extend vertically through the servo plate.

Gangster 9.jpg

Thread: Good Grief
18/12/2020 23:50:12

Martin, I think you are doing the BMFA a grave disservice. If it wasn't for their efforts, specifically their CEO, we would be in the same position as the US modellers are in. So, incidentally, would the rest of Europe. So, rather than ranting about the BMFA, and to be fair the other 3 organisations, you should be cheering them to the rafters for essentially arriving at a state where there is almost no difference from where we were before all the drafting of drone laws started. The gobbledegook is EU and UK DfT inspired. There is a simplified set of block diagrams produced by the BMFA that sets out very simply what you can and cannot do.

Enjoy your freedom to keep flying on pretty much the same basis as before. The EU rules have been put into British Law and that comes into force on 31st Dec as the EU rules fade out.

Thread: Article 16 Authorisation is here
17/12/2020 17:24:12

Great outcome. Enormous thanks to Dave Phipps for taking the lead over so many years. I agree with Andy about Dave getting a medal! Maybe an OBE? After all, he has achieved a fantastic outcome for model flying in the UK.

Thread: Covering - how long does it take you?
27/11/2020 23:44:41
Posted by DaveB1 on 27/11/2020 12:16:21:

Lovely looking covering job on that Gangster !

Thanks DaveB1.

27/11/2020 12:13:33
Posted by Eric Robson on 27/11/2020 00:24:10:

When I was asked if I knew how long a piece of string was , I said I am a frayed knot.


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