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Member postings for Paul Johnson 4

Here is a list of all the postings Paul Johnson 4 has made in our forums. Click on a thread name to jump to the thread.

Thread: Warbirds Replicas P51 Mustang
06/11/2020 17:41:38

Ron, true story once watched a delivery driver carry a large pile of boxes containing aircraft instruments. He couldn't see over the top and struggled to balance them all. Now they were all clearly marked FRAGILE, he dropped the topmost one onto the concrete floor. At this stage he couldn't bend to pick it up so preceeded to kick it all the way to stores....

Wish I had videoed it....

Edited By Paul Johnson 4 on 06/11/2020 17:42:50

05/11/2020 14:58:22

I always as a preflight check move the control surfaces very slowly over their full range looking for any point which my jitter or pause.

It's usually when the feedback potentiometer in the servo which wears that causes an issue.

We can't stop all failures but can reduce them by some easy checks.

05/11/2020 14:46:50
Posted by David Hazell 1 on 05/11/2020 14:41:19:

Fab thanks. I have some Tower Pro MG92B **LINK** which are meant to be about 3.1kg. They're probably fakes mind.

I'll check them for a few hours on a servo tester and make sure they don't fail immediately!

David just check them for for a minute or so. No need to add a couple of hrs running more important is to check them slowly for any dead spots.

05/11/2020 14:25:06

Fms 9g servo at 6v is 1.8kg cm

05/11/2020 14:14:29
Posted by David Hazell 1 on 05/11/2020 12:34:40:

I saw a few pages back that Paul is using some micro size servos that chuck out a whopping 6kg per cm. What spec would be the lower limit assuming we stick with < 20g servos?

David both my Spitfire, Bf109 and Yak all use 3.5kg servos and have been fine. The Yak has, until due to recent illness, had a lot of outings and has been fine.

Most 1400mm fms use servos of a lower kg.

04/11/2020 17:28:13

A few tips to you who have manuals............ and LABELS!

The 1/16" balsa skin is a high quality SOFT material, being a lighter grade it will mark VERY easily with light fingernail pressure etc.

When you cut out the lower skin for the U/C make it your mission to add the balsa sheeting to stiffen the structure up.

Until this is done handle like eggs or you will find bits breaking off.

The soft balsa does contribute to a lighter finished model but until it is completed, covered etc you need to be careful.

04/11/2020 17:11:14

Actually I was quite relieved.... he didn't send the boys..

Well well well so that's what's in the manual..... Well you lot won't need my help any more then!

Now where's the precious.....

04/11/2020 14:24:41


03/11/2020 18:22:17

No wonder I forget where I'm up to with you smutty lot....

03/11/2020 17:35:29

Okay tomorrow will show the niffty little tool for adding the aileron hatch..

03/11/2020 17:32:51

The Nerve racking bit.. cut out aileron and flap...

With the flap cut the top and then the bottom NOT right through from the top!!!!!!

Otherwise you will cut off the ribs.

DONT RUSH Take your time!!!!

aileron and flap cut out.jpg

next sheet the top front of the flap, the curved piece can be formed by wetting and GENTLY forming around a broom handle or similar and allowed to dry overnight as it is a small tight radius for 1/16" sheet.

flap radius sheeted.jpg

Trimmed and mylar hinges fitted and pinned. Make the pins ONLY long enough to go through the 1/16" + mylar + 1/ 8" no longer especially near to where the torsion bar will be glued.

flap trimmed.jpg

The flap was temporarily fitted to show why although fiddly we chose this method.

flap fitted.jpg

flap extension.jpg

03/11/2020 17:15:21

Fast forward..... wing underside sheeted.

wing underside sheeted.jpg

Where's the other foot gone?

Probably searching for labels......

03/11/2020 17:11:16

I hate you Butler.......

03/11/2020 17:10:30

If the eagle eyed amongst you may have spotted, the torsion bar link has been left off. This is to allow you to remove the flap to complete it, cover , fit the hinges, and lastly add that bar. If you do not it will not allow you to remove the flap as it fouls  R2.

flap torsion bar located.jpg

flap torsion bar pivot line.jpg


Edited By Paul Johnson 4 on 03/11/2020 17:12:25


Edited By Paul Johnson 4 on 03/11/2020 17:18:57

03/11/2020 16:57:10


Once you have marked the top sheet, time to sheet the bottom.

1st sheet on underside.jpg

Check that there is not too much weight on the wing that may create a bow on it check the trailing edge with a long ruler to make sure.

At this point also measure the flap spar centres to aid in marking the skin for cutting.

measure bottom flap cut line 1 .jpg

measure bottom flap cut marks 2.jpg

Use YOUR measurements NOT MINE!

03/11/2020 16:49:19


Okay I just checked back on my posts and realised that I had not mentioned that the flap spars should NOT be glued to each other

They are glued to each of their adjoining wing ribs only

Hey but that should be in the manual which you all have and have read BEFORE staring the build eh?


03/11/2020 16:39:08

The next is something you need to take your time and get it as accurate as you can, please do not rush this.

You need to mark the cut lines for the top skin for both the aileron and flap.

Using a pin/needle push through between the aileron spars from the bottom through the top skin.

Do this at both ends of the aileron. With the Pin/Needles through turn the wing over onto a flat surface then using a long ruler as a guide on those pins draw a line on the top of the wing skin.

Next using the same method mark the cut line for the flap. This is as marked in the next picture. Please pay attention to where to mark.

making flap top cut marks.jpg

03/11/2020 16:25:57

Next construct the wing supporting Jigs

wing jigs.jpg

These fit under R1 and R10

wing jigs located.jpg

03/11/2020 16:20:54

Just had Graham and Sweep drop in..... apparently I've been slacking!!

So you balsa sniffers to date the build has gone very quickly, even without a manual, drawing and LABEL.

Wing Sheeting.

This has listed 10 sheets of 1/16 balsa, there is actually 11 in the box.

Even so please be frugal with it because should you damage any you will find it tight to complete the skinning, without trawling the model shops for any stock at the moment.

Laying the wing on it's stand off tabs on a flat surface start with the top and fit the first sheet in line with the main spar centre line. This will help the leading edge sheet when you come to add it.

top sheet 1.jpg

Those damn feet again!

Now you may take the sheet to R1. I did not as I still had to sort out how I was going to utilise the early R1 with it's cut out.

I then worked towards the leading edge. Keep the trimmings!!

top le sheet trimed keep.jpg

and finally the trailing edge. You will need to add a small piece of 1/16 as shown, I have written on it how big.

top te and infill.jpg

Trailing edge trimmed, leave a couple of mm extra to allow a nice tapered trailing edge.

top te trimmed keep.jpg

top te trimmed underside.jpg

03/11/2020 12:40:45

Aww come on David is that all you done so far...

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