By continuing to use this site, you agree to our use of cookies. Find out more

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
02/06/2020 23:35:37

Jonathan

Plasterboard makes a good building board. Flat and it will take pins quite easily. You can get your supplier to cut the board to size or take a circular saw to it.

I use the SLEC Plan Protector over the plan and that has worked brilliantly.

In addition to your existing tools, a pillar drill is a good long term investment.

Good luck.

Peter

Thread: Who Else Wants a 63" Lavochkin La7 kit?
01/06/2020 16:29:38

Excellent work Ron! Full marks.

Thread: Maps for no fly zones
31/05/2020 21:02:30

Christopher, there are maps showing danger and prohibited areas that you can get hold of. You do need to pay money for them and they are subject to copyright. That's the reason the BMFA doesn't do what you think they should. These maps are for all avaitors - full size and model. There are also publications available from the CAA - again at a charge.

Thread: Top Flite P51 - 65" span
31/05/2020 20:55:48

I managed to finish off fixing the captive nut ply pads to the rear of the firewall and bolted the Dubro Softmount into place.

mustang 112.jpg

I then couldn’t resist plonking the OS 120 onto the bearers. Pleased to say that it drops in smoothly with minimal side to side movement. I have a 4.2 mm drill coming on Monday which I will need to enable a 5 mm thread to be cut in the softmount arms. I’ve never bolted an engine in place using a threaded metal bearer. I have some Nordlock washers that I will use under the bolt head to hold the bolt in place. For those who have not come across Nordlock washers, they have 2 parts that have a some ramps built in so rotation of the bolt or nut has to generate a lot of torque to ride up over the ramp before any rotation can occur.

By eyeballing the space available for the throttle push rod, using a bowden cable will solve all the problems I was considering before.  Thanks Ron.

mustang 113.jpg

Ooh! This is getting exciting!

Having now dealt with the front end engineering, I can now turn back to fixing the tail feathers in place.

Edited By Peter Jenkins on 31/05/2020 20:56:35

Edited By Peter Jenkins on 31/05/2020 20:58:36

31/05/2020 17:10:27

Good point Ron. Have ordered a Bowden inner and outer combo.

Thread: Taurus retro aerobatic build
31/05/2020 16:58:10

Very nice Mike. Can't wait to start on mine.

Thread: Drone delivery service, the shape of things to come?
31/05/2020 16:55:40

Video of Scan Eagle launch and recovery here.

31/05/2020 16:26:34

Interesting. Reminds me of a small UAV called Scan Eagle by a small company in Oregon that Boeing bought. Scan Eagle was originally conceived for use in spotting fish in the Pacific for US fishermen. It was then turned into a reconnaissance device for the US military in Iraq. The RN trialled it and were shaken that the drone could be sending back video of the warship but no one or sensor on the warship could see it as it flew by half a mile away! This was back in 2007.

It looks like a model aeroplane, then with a 10 cc petrol engine and a duration of 28 hours. It was launched by catapult as in the video in the OP. Recovery was to fly it into a rope trailing from a mast using differential GPS for the rope to be contacted on either wing. The rope then slid down the wing to a hook at the end of the wing tip. As soon as the Scan Eagle was captured, the engine was cut and the aircraft hauled in. This was demonstrated at sea with recovery to a moving ship.

In a way, nothing new although a slight change of role and the use of GPS to deliver goods to a specific location. The biggest problem then, and now, was to integrate it into a world of manned aviation. We are still not there in the west with operating regular services as shown although there is no problem with operating such services in the under developed parts of the world as its far easier to allocate a dedicated route and tell manned aviation to stay away. Plus there are not RC flyers there!

Scan Eagles had a pretty good safety record and flew thousands of hours in Iraq and Afghanistan.

Thread: Why sudden dramatic voltage drop in 700mAh 4.8v NiMh pack?
31/05/2020 00:53:21

Sounds like you've got it sorted Jonathan. Good luck with your 2 packs in the future. At least you have a good safety margin built in now.

Thread: Web hosts
31/05/2020 00:49:49

Hi John

The BMFA already hosts a number of Club websites - for free. Take a look at some to see what is possible and how to go about gettting one - LINK.

The man to talk to is Andy Symons who adminsters all the website stuff.

Peter

Thread: Top Flite P51 - 65" span
31/05/2020 00:45:49

I spent another day looking at the engine installation and, in particular, the routing of the throttle pushrod.

Productive work was limited to drilling all the engine mounting holes, which I'm pleased to report were all spot on - the first time I've achieved that! The increase in stiffness of the 1/8" ply was noticeable once I'd bolted the softmount to the firewall and then clamped the engine in place.

It was immediately apparent that my burblings of yesterday about the carb being correctly setup were wrong. It's amazing how difficult it is to get an inverted engine mounting sorted out when the fuselage is upside down! Anyway, I repositioned the carb for the 3rd time and once the engine was clamped into place it became clear that there was a problem with getting the throttle pushrod to the throttle arm. The tank and softmount arm are in the way of a direct route so after much deliberation it looks like I will have to misuse a servo arm to create a bell crank to route the throttle rod run through 180 deg. I haven't worked out whether to glue a small hardwood block to the softmount arm or drill and tap the arm to take a short bolt to act as the servo arm bearing. I don't like the idea of drilling and tapping into the metal arm so I think a hardwood block will be the way to go.

There is a cavernous space for the tank. I'm using a 12 oz tank as I don't really want much more than 12 min flying time. However, I do need to have the option to increase the tank size so my method of tank positioning is to use some blue foam (from packaging!) to construct a tank size hole that will position the tank in the right place. The trial fit showed that I need to have a piece of string tied around the tank to pull it back against the grip of the foam!

All that was left to do was to glue in the firewall and the third part of former 1 which gives the rounded top for the top cowling and the plywood supports for the T nuts.

mustang 111.jpg

I've left it to dry overnight and will then drill through the rest of the firewall and pull in the T nuts. Since the lower mounting bolts will be pointing straight at the tank, I might cut them to being only just longer than the T nut. That will allow the soft mount to be bolted on and the throttle linkage mocked up.

Thread: Warbirds Replicas P51 Mustang
31/05/2020 00:13:00

OK, following up on my earlier post, the product I had in mind is called FLITE-METAL. This is very thin aluminium sheet. If you click on the "2.4 Spread Spectrum Systems" button you can read about the tests they did. Cutting to the result, they found no difference with the range or function of 2.4 equipment compared with a system sitting in clear air.

It ain't cheap but you can get a 12" x 12" sample for $7 to try out.

30/05/2020 21:07:08

There's a P51D in the RAF Museum that is highly polished. It's fully airworthy but I believe its owner loaned it on the condition that it's never flown! So, a ground exhibit it is. But, it is very shiny!

I have some information on aluminium finish and it shows that even with real aluminium there was no loss of signal strength with the Rx aerials inside the fuselage. I'm aiming to use Oracover Chrome on my TF P51 but will probably do a trial with the Rx in a box wrapped in Oracover Chrome and do a range test. On the basis of what I read though, I'm expecting the test to be OK. We shall see!

Thread: Why sudden dramatic voltage drop in 700mAh 4.8v NiMh pack?
29/05/2020 23:54:01

Jonathan, my first reaction is that a 700 mah pack might be a bit small if you are flying an aerobatic slope soarer. I use a 750 mah LiPo in a 2 mtr electric aerobatic aircraft and that consumes around 80 mah per 7 min flight. Assuming your flights are consuming a similar amount then after 60 mins of flying you could have consumed almost 700 mah. I think you are expecting too much from that pack. I only fly 3, sometimes 4, 7 min flights and change my pack. It is usually just under half full and generally takes about 170 mah to be fully charged.

Do you check how much charge you put back into your pack after flying? It is essential to be able to use an average consumption rate so you can work out a safe level of usage of your pack. While I use a LiPo and you use a NiMh, both are only capable of delivering their capacity.

I would also get a proper delta peak charger as just using voltage as the cut off may not be allowing your pack to reach full charge.

However, I would either invest in a larger pack or take a spare pack with you and swap it over if you have less than 50% capacity remaining. NiMh packs are relatively cheap and running them to their limit of capacity causes problems - as you have found.

Thread: Where are the Watts?
29/05/2020 23:38:53

Simon, you didn't say in the OP what sort of aircraft you wanted to power. You also need to consider what size of prop you wish to use e.g. a fat fuselage might warrant a larger diameter prop. Also, the motor's kv has a bearing here. In rough terms, a lower kv will mean you will want to use a larger prop at a lower rpm. You can play all sorts of tunes with no of cells, kv, amps and prop diameter and pitch.

If you want to power a 2 mtr class aerobatic aircraft, it will have a 10 Cell pack, and if using an outrunner motor it will have a kv of around 280 and swing a 21 x 13 prop. That set up will generate around 2,500 to 2,800 watts for an 11 lb aircraft so around 250 watts / lb. That is a long way from the 100 watts / lb being used as a yardstick above.

Another example. I had a 70 size aerobat with a motor of 425 kv for a 6S pack. I wanted to use a 5S pack and because of the reduced rpm through using a 5S pack I needed to run a large diameter and high pitch prop to get the power I needed while staying within the motor's current limitation. I ended up with a 17x10 prop. I fitted a 580 kv motor and had to reduce the prop size to 14 x 10. Both motors produced around 1250 watts but in a very different way.

So, in summary, what sort of power do you want for a given weight (gentle flying (80 watts/lb) or proper aerobatics (250 watts/lb). Is ground clearance a problem - use a high kv motor with smaller prop. Is there a large cowl - low kv motor with large prop. Which sort of pack are you standardising on? Adjust kv to suit appropriate prop.

I hope that helps.

Thread: Top Flite P51 - 65" span
29/05/2020 21:53:03

Not a very productive day today! It began by me tracking down a user manual for the OS 120 FS. It was clear that turning the carb through 180 deg to put the throttle arm in the correct place was relatively easy. So, order of work was to do that first and then sort out the firewall to get the holes for the engine mount drilled.

Having rotated the carb, I found that I had made the classic mistake of forgetting that the fuselage was upside down on the building board and that the carb had been in the right place all along. So, turn the carb back to the original position! While I had tools to hand, I decided it would be a good idea to check valve clearances. That gave the minimum reading for valve clearance so that was fine. Nothing like a bit of unnecessary work!

I then carefully marked up the firewall as per the instructions. There are punch holes for the two centre lines for the firewall and also the displaced centre line so that the spinner comes out in the right place given the side thrust. I'm using a Dubro Softmount for the OS 120 and after carefully examining the mount it looked like I would have to drill and tap the mount for the 5 mm engine retention bolts. That then sent me back to do a Google search for the correct size of drill required for a 5 mm tap. I had the tap but not the 4.2 mm drill. I took a look at the UK Drills website and as my Bosch drill set is now well past the time it needed sharpening, a bit of retail therapy had a boxed set of cobalt drills and a 4.2 mm drill (almost half the cost of the boxed set!) on its way. Hope they'll be here for Monday next so that I can then drill out and tap the engine mounting holes in the Softmount. Never having mounted an engine like this before, I shall have to make very certain that the holes are drilled in exactly the right place!

Back to the shed to drill out the holes for the Dubro mount and forgot they would, being American, be imperial sized. Still a 5 mm drill hole is not too far off the required 3/16" hole required. Having drilled the holes I used the T nuts mounted with the smooth side facing the bolt to bolt the the mount to the firewall. With both mounts "bolted" in place I did feel that the 3/32" firewall was a bit flexible. It will be glued to another 3/32" plywood former that I had previously glued to the fuselage. In the end, I decided that I'd like to make another firewall but out of 1/8" ply as that felt a little bit less prone to flexing. Currently, the combined formers will be 7/32" thick and will be backed up by some 1/8" ply pieces for the T nuts to bite into. I'll see how the glued up formers feel and will decide then whether an additional full width 1/8" ply sheet would be advisable to reinforce the firewall further.

I then used the existing firewall as a template to cut a replacement one out of 1/8" ply taking the opportunity of making it a better fit than the original piece. I drew in the 2 centre lines and the displaced centre line. That allowed me mark out the required width of 46.6 mm for the OS 120 crankcase to be a snug fit between the bearers. I measured up and marked out the position for the four bolts on the firewall and trial fitted the soft mounts. Pleased to say that when looking down each mount hole, the cross marking the bolt hole was centred.

mustang 109.jpg

mustang 110.jpg

As you can see, I have also marked out the centre line on the 2 engine mounts as well as the bolt hole centres on the lower of the 2 arms.

Dubro state that before using the mount, all 4 rubber "grommets" should be removed and washed in glow fuel before being returned and bolted up. I presume that is to provide some form of lubrication to allow them to work more easily. There is no information about the life of these rubber inserts so that might be something to find out about.

Once I've got the engine mounted, I'll return to the manual and install the fin and tailplane.

29/05/2020 12:32:27

Yes EF are good in providing detail. Some F3A kits come without this vital information but I've not found that to be the case with the ones that I have had. As you may know, most F3A models come with wing and tailplane incidence adjusters and you can play tunes on the motor up/down and side thrust as well which is when having an incidence gauge such as Robart's is essential if you want to know your starting and end points.

I was just surprised at the accuracy of the Mustang's wing incidence. Of course, once the model is finished I shall just have to live with this as changing the incidence, if required, will compromise the scale appearance! F3A models are provided with adjustable wing and tailplane incidences on the whole although some don't necessarily come with the initial set up data! Resorting to the various fora does produce the answers although many will tweak the incidences to eliminate any aileron or elevator trim required to fly level. One can also play tunes on the motor side and vertical thrust lines much more easily.

It will be interesting to see how good the Mustang set up is once it's in flight.

Edited By Peter Jenkins on 29/05/2020 12:33:06

28/05/2020 23:51:01

Didn't get much done today but did manage to finish gluing the wing dowels, plane the lower chin pieces to a 45 deg angle and fitting the T nuts for the 5 mm wing bolts. After that, I decided to measured the wing incidence. I started my making sure the building board on which the fuselage was resting was level.

mustang 105.jpg

mustang 106.jpg

I reckon that's close enough to 0!

On with the wing, bolt it down and then stuck the incidence meter onto the wing.

mustang 107.jpg

The plan states that the wing should be at +1/2 deg incidence. When you look at the incidence reading in the photo below, you will see that Top Flite has done a very good job of die cutting!

mustang 108.jpg

Before someone says that the incidence gauge is showing a negative incidence, do remember that the fuselage is upside down.

I was so astonished at this outcome that I had to go and lie down!

The next task according to the instructions is to fit the tailplane and then the fin. However, I always prefer to deal with fitting the engine before I have a fuselage encumbered with the tailplane and fin while I'm trying to drill holes and fit an engine. So, tomorrow's jobs will be to:

  • rotate the carb on the OS 120 to get the throttle arm on the same side of the fuselage as the throttle servo
  • mark out the firewall and drill the holes for the soft mount, tank feed and throttle rod
  • glue in the firewall and rear supports and complete the fuel proofing of the tank bay with 30 min epoxy.

Till then, tara!

Thread: Who Else Wants a 63" Lavochkin La7 kit?
28/05/2020 00:04:56

Ron, that wing/cowling fairing has come out looking top drawer. Well done. It's always the little bits that take so much time!

Thread: Top Flite P51 - 65" span
27/05/2020 20:47:52

I took the bandages (sorry sticky tape!) off the radiator construction today and it looked a bit chunky! Incidentally, this is the 100th photo in the album!

mustang 100.jpg

It's amazing what 5 mins with a razor plane can do!

mustang 101.jpg

The next task was one that I've been looking forward to for a long time! The first time of mating between the wing and the fuselage. Having slid in the 2 wing mounting dowels and taped some 1/32" ply to the wing over the wing seat position (to emulate the 1/32" ply wing fillet), I was amazed to find that the wing slid into place. It wasn't quite the right place but I was still impressed. Says a lot for the accuracy of the die cutting and the method of construction that you have to follow.

mustang 102.jpg

The next job was to stick some packing into the back end of the fuselage to simulate the fin post, and stick a large pin into the centre of the dummy fin post. Next the piece of string trick to make sure that the distance from the fin post is the same to each wing tip. That required some easing of the wing centre leading edge and then it was a case of taking a deep breath and drilling through the hole in the wing mounted plate into the fuselage mounted plate.

mustang 104.jpg

You can see one wing bolt temporarily persuaded into the drilled hole in the fuselage plate. I'm using 5 mm bolts that will bolt into 5 mm spike nuts. The TF plan calls for the hole in the fuselage ply plate to be tapped so accept the wing bolt but I prefer a spike nut!

The final job for the day was to tack glue the dowels into place.

Tomorrow, before I remove the wing, I'll check the wing incidence since the fuselage is sitting on a flat surface and I can measure the downthrust in degrees as I have a template angle that I can measure with my protractor.   Then, I'll remove the wing and epoxy the dowels into place.

mustang 103.jpg

Edited By Peter Jenkins on 27/05/2020 20:51:46

Latest Forum Posts
Support Our Partners
Slec
CML
electricwingman 2017
Sussex Model Centre
Advertise With Us
Sarik
Latest "For Sale" Ads
Has home isolation prompted you to start trad' building?
Q: The effects of Coronavirus

 Yes - for the first time
 Yes - but Ive bashed balsa before
 No - Ive existing projects on the bench
 No - Im strictly an ARTF person

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us

Magazine Locator

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

Find RCM&E!