1/18 P51C Mustang "Lopes Hope the 3rd"

[JayW]

Sorry Peter - I have to make a correction.  Further inspection of drawing 73-33102 (LG strut assembly) show that under full compression, there is 1 29/32 inch of exposed compression strut oleo (not slammed down as I previously said).  If you want to see this dimension, see zone A4.  

 

"... I think in length they are ok - the compression strut showing is 5.89mm and 0.2 inches os 5.09mm so its ballpark."  you say.

 

So if "static" extension is 1.5 inches from fully compressed, then static extension has 1.5 + 1.906 = 3.406 inches exposed oleo.  Or in 1/18 scale - .189 inch.  That equates to .189/.039 = 4.85 mm.  That puts your 5.89 mm much closer to static.  

 

 

[JayW]

I might be hurting rather than helping.  I closely studied drawing 91-33106 Support Assembly - Landing Gear Pivot.  That drawing puts the gear pivot point (intersection of gear pivot axis and centerline of gear oleo) at Wing Sta 69.346, dist above wing ref plane 0.9325 inch, dist forward of wing 1/4 chord 13.3125 inch.  That drawing also shows local wing contour ordinates where I was able to determine (with the above ordinates) that the lower wing loft at the point where the gear strut protrudes is about 4.25 inches below the gear pivot point.   Account for the 11 deg rake angle and you get 4.25 / (cos 11 deg) = 4.33 inches.  From here, I can take drawing dimensions of the gear strut to arrive at the proper gear strut protrusion from the lower wing skin:

 

 

Miss Velma has 1.07 inch protrusion of the upper strut to the lower wing skin (very close).  Peter - I suggest you check Lopes Hope for gear upper strut protrusion relative to the lower wing skin.  Should be 1.08 inch per above.  If it is close, and if your gear door is an exact scale-down from the drawing (73-33302), then you can be assured the relationship between the gear strut and the door will be right.  If not, then you will need to make some adjustment to the gear door length or strut length.  

 

Also note the 2.625 inch dimension above (from upper strut lower edge to door lug centerline).  Scaled down to 1/18 and that is .146 inch.  Check your door lug locations to that dimension.  That way, assuming you have an accurate gear door,  you can assure the orientation of the door links is right.  So many Mustang efforts get this wrong. 

 

I will shut up now.   

Edited November 5, 2019 by JayW

[DonH]

7 hours ago, JayW said:

assuming you have an accurate gear door,

 

Peter has an accurate gear door. If there is any discrepancy, it will be the full size version that is wrong.

 

Stunning stuff and I am enjoying all the details being swapped between experts.

 

[dodgem37]

Stellar.

 

Don't forget the lug nuts.  I would hate for the wheels to fall off.

 

Sincerely,

Mark

[airscale]

thanks folks & Jay, thanks so much for all the research

 

I have 1 & 1/16 inch from skin to lug and the door seems to sit right - at least it does on dry runs, I will have to fettle it when I put it all together

 

So Telford was great, really enjoyed it and we did very well on our stand - thanks to those who dropped by

 

Since being back, I have managed a few bits & bobs - first the outer gear doors..

 

I made blanks of the doors in rigid nickel silver and fashioned the internal pressing shape from 3mm plastic card - it is profiled in many different directions and is actually quite a complex shape...

 

 

..these were then fitted and litho annealed and formed around them...

 

 

..and completed with the mounts for the lugs that fit to the leg, and the sealing strip along the bottom edge..

 

 

 

..then it was on to some wing bits & bobs.. the guns were fitted..

 

 

 

..they are just dry fitted for now, so some fettling to do..

 

then onto the wing nav lights - these were shaped & polished from perspex samples - the blue is a bit dark, but it's all I have... also added the wing stiffeners near the ailerons on the upper wing, though some of the alclad came off with the tape I used to mount them so they need respraying..

 

upper side..

 

 

lower side...

 

 

 

 

..have also finished the spinner & prepped & painted the prop blades so hope to have the prop done next..

 

TTFN

 

Peter

 

 

[Out2gtcha]

Lovely work as always!

[Anthony in NZ]

Spectacular, and inspiring!

[JayW]

Upon my word!  (how's my British?)  Your latest details are just stunning shrink ray stuff.

 

  "I have 1 & 1/16 inch from skin to lug and the door seems to sit right - at least it does on dry runs, I will have to fettle it when I put it all together..."

 

Let me get this straight - 1.06 inch from lower skin to the door lugs?   Or the torque link lugs?  And, to the lug holes?

 

 

If the 1.06 dimension is to the door lug holes, then your upper strut is too long.  By a good bit (about .13 inch).  And I am sounding the alarm.  Per the above sketch, of which I am certain of its accuracy,  the measurement from wing lower skin to door lug should be 1.08 - .146 = .934 inch.  +/_ .02 inch would be fine.  Please check my numbers if you feel unsure.

 

Did I misunderstand?  If by "lug" you mean the torque link lugs, then that will probably be OK but still a tad long.  Can the upper end of the struts be cut back if necessary?  It appears to me they can without much if any impact.       

 

Another way to check is to approximate the orientation of the door links (dry fit the gear and door and inspect the link attach points).  The link should be very nearly level (horizontal).  Actually, the door side attachment of the link should be a smidge LOWER than the gear side attachment, giving a slightly downhill orientation (down outboard, up inboard).  Check pics of Mustangs and this will be very evident.  I suspect if you do this, you will get the opposite - the links will tilt up outboard.  And that will be noticeably incorrect. 

 

Another good check is to look at the gear and door from the side.  The lower edge of the door should be just barely above the axle cap of the wheel, hiding nearly half the wheel spokes.  I recognize that this relationship depends on how much gear oleo extension you have, but we have already gone over that and yours is within a realistic range for an aircraft resting on the ground.   I suspect you will find your door edge is well above the axle cap, and exposes much more of the wheel.  If so that's going to be wrong, and it will look wrong.   Again, Mustang pictures abound which showing the proper relationship. 

 

The reason I dwell on this is that this is sooooo easy to get wrong, especially if using the drawings like we do.  Your use of a simple reinforced hole on the inside of the wing upper half for attachment of the gear strut, while a perfectly acceptable way to attach (a way most mass produced models are), it is entirely different from how the gear is attached in real life (of course), and therefore entirely different from the gear strut drawing.  So this leaves it to the modeler to do alot of painstaking research into just how long the gear strut must be.  I am not sure how you arrived at a strut length, but unless you did some equivalent of what I did above, the strut length has a high probability of being errant.   I have the benefit of travelling this road already, so for me it is straight forward.

 

Aw hell - I'll include some pics.  This picture adequately shows how "long" the door is relative to the gear on a typical aircraft on the ground.  Note the lower edge is just above the axle cap.

 

 

And this picture shows the proper orientation of the door links (doesn't matter if it is a D model - it's the same for either).  Note the slight downhill-outboard orientation of the links:

 

 

You posted this pic back when you first put her on her legs: 

 

 

 

If the gear length in that pic is the same as now, and if the door length shown is the same as the beautiful doors you have just fabricated, then I am pretty sure your struts are too  long (or less likely the doors are too short).    Indulge me, and recheck Lopes Hope 1/18.  This model of yours is absolutely magnificent - never seen anything like it.  But do not screw this up!    And with that, I will bow out, and wait for your continued acts of wizardry.

 

 

Edited November 16, 2019 by JayW

[airscale]

Hi Jay

 

thanks for all the help as I know this is crucial to the sit and 'feel' of the aeroplane

 

i dry fitted where I am at and made a wire link for the link assembly 73-33313 to check the distance & angle of the door (& angle of the link)  - it's all a bit loose & flakey but the gear has been shortened vs that earlier pic

 

the bit I am more bothered about is the rake - there is definately work to do there..

 

 

 

 

 

..its dark here so the pics are crap

 

on another note - I really need help on this DF Loop thing - what bit of kit is it from (so maybe I can look it up) and what particularly is the diameter of the loop?

 

asking anyone out there - not pinning all this on you Jay

 

 

..any ideas?

 

thanks in advance

 

Peter

 

[vespaboy48]

This Isn't model making....This is pure art!!

 

What more can I say apart from like most I'm in awe!!

 

Mark

[JayW]

Peter - Now THAT is what I'm talking about!  Looks about right.  Consider me satisfied.  You say you shortened the gear?  Good.  And the link orientation looks good too!  As far as rake angle is concerned, if you can wring a degree or so out of it, I think it will be fine.

 

The other thing to be careful of is the other aspects of hanging the door.  The front link is straight as you know, and the rear one has a big kink in it, but I believe the links are the same length.   Even so it isn't obvious how the door hangs, either inbd/outbd, or fore/aft, or at what angle (toe in or toe out).  You may have noticed the door kinematics is not parallel with the gear itself so the attach lugs are at an angle to the other features on the gear strut.  That just complicates things further.  Do not use fairing drawing 73-33302 to orient the door to the strut - although it shows the oleo centerline in the field of the drawing, the door is defined in the retracted position, looking down on the wing reference plane (not normal to the outside surface of the door, which BTW is far from flat as you know).   So the as shown door is actually foreshortened a bit.  Far better is to take the various views on the LG installation drawing 102-33001 and just measure the dimensions after determining the approximate scale of your drawing print.  And then much study of various pictures helps of course.  The P-51 aficionado will spot it right away if the door is hung wrong!  So happy hunting.

 

Let me see if I can find something on that antenna.  Later.

[Fencer-1]

18 hours ago, airscale said:

Hi Jay

 

thanks for all the help as I know this is crucial to the sit and 'feel' of the aeroplane

 

i dry fitted where I am at and made a wire link for the link assembly 73-33313 to check the distance & angle of the door (& angle of the link)  - it's all a bit loose & flakey but the gear has been shortened vs that earlier pic

 

the bit I am more bothered about is the rake - there is definately work to do there..

 

 

 

 

 

..its dark here so the pics are crap

 

on another note - I really need help on this DF Loop thing - what bit of kit is it from (so maybe I can look it up) and what particularly is the diameter of the loop?

 

asking anyone out there - not pinning all this on you Jay

 

 

..any ideas?

 

thanks in advance

 

Peter

 

Loop Antenna link The fighter loop antenna has 9 inches diameter. "The loop itself is 9 inches diameter, and the unit is 14 inches high, with the base of 10 inches long, and 5.5 inches wide"

"Generally, a 9-inch rotatable loop, such as the MN-20" from this Manual

[Hacker]

so the question is are you going to have another go at that Firefly?

 

Hacker

[Out2gtcha]

Tigercat is in line first! 

 

 

That does look fabulous my friend! 

[RadBaron]

Mind boggling, mate!