Warbirds Replicas P51 Mustang

[Jonathan S]

I have been working my way through the fuselage and I have a general question. 

When I am skinning the curved deck how do people ensure the two sheets fit I.e. same length and will join nicely.  Mine don't but together we'll and one is usually the wrong size needs a  mm or 2 off then is wonky.  Any basic wood work advise welcome.  

[Andy Gates]

I generally fit one sheet from the lower edge upwards but don't glue the top edge (ie the last 5mm or so) and leave to dry.

I then fit the other side lower edge, curve it round into place, hold it with clamps / pegs / pins, then make a cut down the centre of the upper spine through both of the sheet sides usually using a steel rule for straightness. A brief tidy up with a sanding block along the joining edges and glue into place.

For the front or back edges I leave them over long and trim to suit with a scalpel or sanding block. Sounds more than it really is in practice.

[Jonathan S]

Andy, thanks for that, yours is a simple but elegant solution.

I will give it a go this week when I get some more clamps delivered and get the side skins on. 

 

Jon

[Trevor]

After a bit of a technical hitch, I’ve now managed to upload the May diary entry for my P51D build:

http://www.bartonhewsons.uk/home/modelflying/scale/mustangprojectda.html#May

 

One more month ought to do it, but we’ll see.

 

Trevor

[Gordon McConnell]

Nice work Trevor. Enjoying your build diary. Colour scheme looks good as does the Oracover.  Will be very striking and authentic when finished. 

[Jonathan S]

On 06/09/2020 at 15:03, Paul Johnson 4 said:

Motors...

If you intend to use the FMS four bladed props don't go much above the FMS 580 KV motor as they have been known to fail if their driven to hard. (speed freaks always break something)

If you are going to use a two bladed prop then just match it to the motor. There is usually plenty of info online.

Add some small magnets to your shopping list for the hatch retaining too. Ebay is your best bet. I use 8mm disc ones.

Talking of which...

With the hatch cover in place mark the location you want to put them and drill through both the cover and the frame underneath, drop of medium super glue, don't forget to de-grease them before gluing. Or epoxy.

 

That style of drill leave a nice round hole..

/sites/3/images/member_albums/156134/875422.jpg

I had a small errand to run today so this has held up the build............

 

 

Paul what glue did you use on the magnets I am thinking super glue?

[Gordon McConnell]

I used epoxy after roughening up the edge of the magnets with sand paper. I suppose if the fit in the hole is good, cyano would work as well but more difficult to get off the fingers! 

[Andy Gates]

I use Gorilla Glue brush and nozzle, plenty strong enough for magnets

Edited June 4, 2021 by Andy Gates
My spelling is rubbish!

[Paul Johnson 4]

A tight fitting hole, medium super glue and brown paper over the top.

But really anything of the above will do it. Just make sure you get their poles the right way round or you'll have a good cover ejection system ? 

 

[Jonathan S]

Hi,

Another question about the best way to do things.  

I am wondering the best way to sheet the front of the cockpit and attach the dashboard rib.  

I have wet and shaped the two half's of sheet and I am going to join them using the method shared by Andy.  But still unsure how to get that Nice curve around the dash and do you attach the dash rib first. 

 

Thanks for all your help 

[Andy Gates]

Jonathan,

 

I assume the cockpit upper sides attached with blue tape have been fixed on already?

 

If not, take them off, attach the half sheets then once dry sand down to meet the dashboard former. Then attach the cockpit upper sides, you can slightly recess them by removing a small portion of the half sheets using the sides as patterns for the cut.

 

If they are stuck on already, then it is going to be a process of cutting the half sheets slightly oversize at the rear then sanding carefully down to fit, little by little. The section above the cockpit sides will be easier as you can see how much you are sanding down.

 

Sorry I can't be much more help, the Spitfire has the sides / half sheets as one piece per side.

[Jonathan S]

Andy, 

Thanks for the help. They are not stuck on yet just held with tape to see how everything aligns.  

I think I will attach the cockpit former then the half  sheets and cut / sand to fit as you recommended. Thanks for the help

Jon

[Jonathan S]

On 12/09/2020 at 14:00, Paul Johnson 4 said:

You will find some 5mm Square stock listed as fuselage stringer is next fitted you will to soak the stringer has it has some nice curves to fit.... got your clamps handy?

/sites/3/images/member_albums/156134/875829.jpg

 

 

.

 

Paul,

Not sure where the 5mm goes to and from can you elaborate looked at the plans and cannot seem to see it.  

Thanks 

Jon

[Paul Johnson 4]

Jonathan,

Look closely at the top of that picture it runs along the edge of the side, on both sides,  to allow you to shape the corners where the side sheet meets the bottom. It prevents you removing all the corner and the bottom sheeting falling off.

Otherwise you end up with a very square corner and not a nice rounded profile.

 

[Jonathan S]

Thanks Paul,  every time I think I have my head around this build and have read and re-read your posts I find another thing I go what the heck does that mean. 

 

I have a few more general questions which have been perplexing me that people a bit more advanced can help with: 

 

1. Looking at the 4S 4000mah batteries what C number are the people who have them in the air already recommending.  My thoughts are between:  
   • Turnigy nano-tech 4000mAh 4S 45~90C Lipo Pack 
   • Turnigy Nano-Tech 4000mAh 4S 30C Lipo Pack 
2. Would it make sense to sort out the tail wheel before I sheet the top deck - is access an issue or can I wait to do that when I do the bottom?
3. Same for the snakes I am thinking it would be easier to do before sheeting
4. What method do people use to fit the wire for the elevator do I need to drill some holes and file a grove or will it push in ?
5. When do you attach the servo horns, do you wait till you have covered it or attach them then cover or attach, then remove for covering.

Thanks for all your help I am trying to plan my next steps

 

[Paul Johnson 4]

Jonathan,

As I do not know what your level of understanding is regarding batteries forgive me if this is covering your knowledge to date,

 The important thing is making sure you don't have a electric setup which demands all the batteries capability of current discharge  C rating is what the battery can theoretically supply current, therefore if you multiply the C rating times the battery capacity it will give you that value, 4000mAh x 30C = 120 amps MAX.

As I said this is the theoretical capacity, in reality its usually less than that. In the electronic world of design, components are normally 'de-rated' to ensure reliability, for passive components this is normally 50% for things like capacitors and resistors. For semiconductors this is usually 30%.

so somewhere in between these numbers usually works fine. If you Motor/prop setup uses a max draw of 50 Amps then the 4000mAh x 30C will be fine and usually cheaper than the higher rated ones.

 

When it comes to working on items that have minimal access then try to get those completed first as with the need to route things like the snakes and tail wheel.

 

the elevator fitting is very important as it needs to be perfectly flat and you  will need to drill a hole into the balsa to glue in the wire linkage, CHECK that there is no twist at all in the linkage on a flat surface. Make sure when you have marked out where you intend to drill those hole that you do so so that they are parallel to the centre line of the elevator centre.

File a groove along the leading edge to allow the   wire to fit snuggly into it it only needs to be from the drilled hole back to the edge of the inside of the elevator.

 

Servo horns I find are best fitted after covering.

 

Edited June 14, 2021 by Paul Johnson 4

[Eric Robson]

Just one thing Jonathan, if I was building another P51 I would make the tail wheel fixed as Paul has done.

[Jonathan S]

Paul, Ron,

Life savers as always.  

It looks so easy when I see all the work on here, still loving it but each step creates more questions.  

Like when bending the tail wheel is there a pattern looked on the plan cannot see one.  

I will definitely be doing a fixed tail wheel. 

 

Thx

Jon

[Eric Robson]

Good to see you are looking at the plan now Jonathan.

[Paul Johnson 4]

Yes... but bend the wire... not the tail wheel ?

[Jonathan S]

4 hours ago, Eric Robson said:

Good to see you are looking at the plan now Jonathan.

 

Ron its pinned on my wall above my build.  I did build the wing over the plan as suggested by Richard. 

 

Thanks to Paul's clarification I will bend the wire not the wheel. but not bent tail wheels before so unsure of what shape should I make.  Looking at some of the pictures I could probably make a guess. but any help would be great. 

 

Thanks

Jon

 

[Eric Robson]

I've been called a lot of things Jonathan but Ron is a new one. Still better to be looking at plans and not headings. 

[Ron Gray]

@Jonathan S I suggest looking at what various companies like SLEC sell as that will show you the pattern to bend to for mounting the wheel. Obviously you will need to decide how you are going to fix it to the fuselage and that will determine the bends need at that end, typically a diamond shape. Some shapes that form a stand tailwheel wire

 

1 3D view

2 side view

3 top view showing fixing diamond

4 rear view showing wheel offset

[Graham Davies 3]

Blimey Ron, your CAD skills are on point!

 

?

[Jonathan S]

1 hour ago, Eric Robson said:

I've been called a lot of things Jonathan but Ron is a new one. Still better to be looking at plans and not headings. 

Eric,

Sorry I was on a work call and trying to multitask between work and non-work.  Clearly failed at both. ?