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Author Topic: Hasegawa 1:48th scale kit fuselage modifications.  (Read 13955 times)
jenshb
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« on: March 21, 2009, 09:15:12 PM »

The Hasegawa Spitfire Mk.IX has got a lot of flak for dimensional and proportional errors on the fuselage, and an overly large spinner to compensate.  To use the clicheof anti-rivetcounters; “it looks like a Spitfire", but for those who want a more correct model, there are correction kits on the market.  I have the Aeroclub injection correction fuselage, but the quality of the moulding and surface finish is a far cry from the crispness of Hasegawa.  I therefore decided to take a closer look at the fuselage and see what could be done to correct it.  The drawings used are scans from Paul Montforton's book, and were printed out to 1:48th scale.  This was verified by using the dimension from the panel line between the fueltank and upper cowling and the rear of the tailfin (the fixed part – not the rudder).  This is 130 mms in 1:48th ( give or take a decimal).  The panel lines were highlighted with ink to make them more visible on photos.

First, I aligned the fuselage to the trailing edge og the tailfin as well as the top contour of the fueltank panel in front of the cockpit.



We see that the fuselage lacks a little depth – about half a millimitre in total.  The location of the panel lines actually fit quite well to the drawings, but there is a gap of about one mm between the kit and the drawing in the location of the aft cockpit glazing.  The triangular panel that ends the wing fillet is correct, but the panel line forwards is again a mm short.



Moving forwards to the cockpit (still aligned on the rear of the fin), the kit door is also a mm too far aft,, but the panel line denoting the location of the instrument panel (forward of the door) is too far aft again.  This means the entire cockpit – and specifically the windshield – is too short.  Detail sets made to fit this kit will correspondingly be too short, and this discrepancy must be taken up by a part that is 10 mms long – the windshield itself.  Note too that the location of the panel line between the cowling and the fuel tank is too far aft – the pencil line shows the location on the drawing.



Still aligned to the tailfin...the 4 mm discrepancy in fuselage length is quite noticeable. 

Next alignment was to the rear of the cockpit at the aft edge of the rear glazing.



The lack of depth of the fuselage is more apparent here, and the panel lines on the rear fuselage have obviously shifted.  The trailing edge of the tailfin has moved forwards about one mm.  The panel line at the front of the triangular wing fillet is correcly located relative to the cockpit, and this looks promising with respect to the wing's location on the fuselage.



I've used a set square here to highlight the fact that the trailing edge of the wing matches the drawing when the kit is aligned to the rear cockpit glazing.  The leading edge of the wing also matches well.  Comparing the kit wing to the drawing gives an almost perfect match.  The aft edge of the door is correctly located, though it is overall a little short.  The panel line forward of the door (denoting the location of the instrument panel) is too far aft. 



The nose is still significantly short – by about 3 mms.



When aligning to the nose, this actually mathces fairly well – the thrust line is correct and the cowling is just about one mm too short.  There were both “flat” and “bulged” Spitfire cowlings, so the Hasegawa kit isn't wrong in this respect.   The panel line for the instrument panel is now too far forward. - as well as the rest of the fuselage... 

Should one correct all errors, there will be a lot of cutting and joining, and I suspect some of these operations – like the fuselage depth – will not be worth the effort.  My proposed solution (which I intend to try out) is therefore as follows:



Cut the nose 1 mm aft of the panel line between fuel tank and upper cowling, though leave the wing root fairing as is.  Blend the contours of the upper cowling to it's new trailing edge with filler.  Add 3 mms to the fueltank and rejoin the nose.  Use an Ultracast spinner and prop.  Rescribe the panel line for instrument panel 1 mm further forward of the existing pane line.  As the kit windshield will be too short, replace it with a vacuum formed part from Squadron or Falcon or perhaps a modified Tamiya part.  The rear glazing can be used from the Hasegawa kit to ensure proper fit.  Extend the door by scribing slightly further forward, or adapt your chosen detail set to match (Ultracast have doors too).
After identifying the major cause of the problems and deciding how far I want to go, I could take the matter into my own hands - though they also had to handle the camera:)



Note the use of masking tape to mark the cut and guide the saw for the first cut.

It didn't take long, and here the fuselages have been stretched using 3.2 mm Evergreen strip with the lower cut has been built up from strips of 0.25 mm plastic - no need to be too neat at this stage.  The upper (port) fuselage has been joined using the drawings as a guide to make sure the centre of the propeller comes in the right place.  When dry, the starboard side will be joined.  As the cowling will be 1 mm longer, filler has been applied to build up the rear to fair it in.



The lower cowling with the air intake looks pretty good when aligned to the front of the cowling.  Two things stand out the intake is a little short and lacks depth - both easily fixed. 



As the lower cowling fits well to the front, it must be stretched at the rear.  The two triangular pieces either side of the air intake must be cut off and glued to the wing. 



The resulting gaps are now easy to sort out with Milliput...



One of the problems of the Hasegawa kit is the spinner as previously mentioned.



The diameter of the backplate matches well, but the spinner is too long so the overall effect is that it is too big.

The ICM spinner...



...is a tad short and too pointed, making it look overall too small. .

Ultracast have a goodlooking spinner in resin, and this was delivered less than a week after ordering.  Their usual quick turnaround from Canada to the UK.



It's a little round towards the tip, but well detailed.  Included are also four wonderfully thin propeller blades in resin. 

The great surprise of this lineup came when I checked the spinner from an Otaki kit, later issued by Arii and also Airfix before they released their awful Mk.IX a few years before they were taken over by Hornby.



Somewhat lacking in detail, but in shape and proportions it's virtually bang on.  Just make the flat spot on the tip a little bigger, and it's as perfect as you can get it in plastic.  I guess most modellers on this site will have an Otaki kit in the stash - or several.   With so many overall better Mk.IX kits out there, this is bet left for spares.  If you get a set of blades from Griffon Models, then this spinner will be an excellent candidate for them.

Here are all four lined up...  Looking at the numbers, the differences may net seem like much, but compared they are easily seen.



Now I just have to build the thing:) Feel free to add comments or further helpful suggestions.

Jens
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Miroslav
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« Reply #1 on: March 21, 2009, 10:26:04 PM »

Excellent work! Bravo!
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John Adams
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« Reply #2 on: March 27, 2009, 06:50:54 PM »

This was all done before on Hyperscale over two years ago.  The front modification is partly covered by primer.

 



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Spitbuilder
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« Reply #3 on: March 27, 2009, 10:16:54 PM »

Hi Jens

I was just catching up with your Hasegawa Mk.IX correction article. I thought the way you went about identifying the Hasegawa kit's shortness was a bit odd. When identifying where the fuselage shortness exists you need to start from the canopy and work forward and aft from that position (relative to the wing position). I did a correction exercise of the Hasegawa Spitfire Mk.IX years ago when the kit was first released. In short, the kit was short by 1mm in the forward cowling length, 1mm short in the fuel tank length, 0.5mm short in the cockpit door area and 1.5mm short in the rear fuselage (4mm in total).

Adding approx 0.5mm to the cockpit mid-section is problematic because you destroy the internal detail of the cockpit sides so most people would not bother correcting this area. When building the Hasegawa kit with canopy open you need to add .5mm of plasticard to the kit fuselage where the rear transparency is attached. This will bring the rear transparency forward level with the cockpit door and there is also a small notch to fill in the area where the rear transparency sill meets the cockpit door line.

I have taken measurements of several Spitfire airframes to ensure that the drawings that I was working from are correct. I don't have the Paul Monforton book yet to comment on the accuracy of his drawings but be aware that many published drawing of Spitfires have errors and that those errors are from time to time copied by people who reproduce new drawings.

Keep up the good work with your build...it looks good.

Regards
Steve



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gingerbob
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« Reply #4 on: March 28, 2009, 12:41:10 PM »

When identifying where the fuselage shortness exists you need to start from the canopy and work forward and aft from that position (relative to the wing position).

Why?  Do you mean so that you're using the wing position as the baseline?  That certainly is important, and is addressed in Jens' analysis.  That is, the wing needs to be in the right place relative to the fuselage.  I suppose you should properly start at Frame 5, the firewall/ wing spar attach, since that is the datum point.  But starting from other points is a good double-check. 

Quote
I have taken measurements of several Spitfire airframes to ensure that the drawings that I was working from are correct. I don't have the Paul Monforton book yet to comment on the accuracy of his drawings but be aware that many published drawing of Spitfires have errors and that those errors are from time to time copied by people who reproduce new drawings.

Ahh, but how do we know you measured accurately!?  No, not trying to start a fight...  I don't have the Monforton book either, and one red flag is scaling up (or copying) the drawings, since this can introduce quite a lot of distortion.  Jens said he checked the firewall to rudder post length, but really he ought to check more stations AND the up/down measurements.

My approach was to take data from Supermarine drawings and plot the station positions myself (possibly introducing errors!) but unfortunately I do not have data for the fuselage spine- I do for low back, which obviously gives me the underside line.  Actually if you, Jens, or somebody else with the book, could post the height from datum for each frame I'd be most grateful.

I think Jens has done a great job of illustrating the situation with the Hasegawa fuselage.  Incidentally, I recently taped a Tamiya V fuselage half to the Hase IX, and they line up VERY closely when you compare the panel line locations.  Better, in fact, than the Hase V to IX.  But when you look from the side, you see that the Tamiya is taller than the Hase.  Because of my data shortage, I haven't yet been able to confirm whether one is more correct.  But if the Hasegawa IX is short, then so is the Tamiya V.

OK, I'm veering dangerously off course, so better leave it at that for now...

bob
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Spitbuilder
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« Reply #5 on: March 30, 2009, 09:18:15 AM »

You said:
Why?  Do you mean so that you're using the wing position as the baseline?  That certainly is important, and is addressed in Jens' analysis.  That is, the wing needs to be in the right place relative to the fuselage.  I suppose you should properly start at Frame 5, the firewall/ wing spar attach, since that is the datum point.  But starting from other points is a good double-check.  

Quite simply, yes, the wing position is the base line, set from the leading edge (not the trailing edge of the wing fillet).  From there I' ll check that the canopy is properly located and work forward and aft from there. Jens' eventually gets there but is fairly long-wingded at arriving at his bottom lines. In the end he adds 3mm to the front end whereas in scale the kit is out by 2mm from the fuel tank panel line that covers frame 8 through to Frame FS A. From actual measurements of a Mk.IX, the cowl panel is 1mm short as is the fuel tank panel. He has included the missing 0.5mm in the cockpit area plus another 0.5mm from elsewhere to get to his 3mm front end extension. This is where copying drawings and adjusting them them with copiers can distort things. Of course, you need to make sure the drawings being copied are accurate to begin with too. Then there is a further 1.5mm to add between frames 13 and 19 to correct the rear fuselage length.

You said:
Ahh, but how do we know you measured accurately!? 

I'll put this in the dumb question basket as I find it quite contemptuous and provocative. That is like me asking you a similar question for every statement you make, eg how do we know you have access to Supermarine drawings and whether you have interpreted them properly; how do we know you have Hasegawa Mk.V and Mk.IX kits in your possession etc? How do you know Paul Monforton has measured the Mk.IX correctly or drawn his outlines and panel distances correctly; you don't! At least my measurements are consistent with other persons who have taken similar measurements and at least I have taken actual measurements. Can you say similar?

I'll leave it at that. I don't want to detract from Jens' build because you haven't done similar first-hand research.

Steve


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jenshb
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« Reply #6 on: March 30, 2009, 09:29:05 AM »

Thanks for sharing your expertise gentlemen - I find it informative and highlights shortcomings in my attempt at producing a more accurate (though not completely accurate) Spitfire IX from the much hammered Hasegawa kit.  I would like to point out that the drawings were scanned and then printed on a laser printer, so any distortion should be minimal.

Jens
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gingerbob
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« Reply #7 on: March 30, 2009, 01:27:14 PM »

Steve,

Thank you for clarifying about wing position.  I asked because with all the studies of Spitfire fuselages I've seen on Hyperscale, etc, it didn't seem that enough attention was paid to where the wing fell in relation to the fuselage (fore and aft).  Aside from noting the differences when comparing different fuselage halves, I haven't checked it adequately either.

You said:
Ahh, but how do we know you measured accurately!? 

Actually, the "full context" quote is: "Ahh, but how do we know you measured accurately!?  No, not trying to start a fight... "  (bold added for emphasis}

Quote
I'll put this in the dumb question basket as I find it quite contemptuous and provocative. That is like me asking you a similar question for every statement you make, eg how do we know you have access to Supermarine drawings and whether you have interpreted them properly; how do we know you have Hasegawa Mk.V and Mk.IX kits in your possession etc? How do you know Paul Monforton has measured the Mk.IX correctly or drawn his outlines and panel distances correctly; you don't!

My point exactly.

I'm not questioning that you did measure, but getting an accurate measurement off an airplane in a hangar is no easy task.  You should add, "How do you know that the dimensions given on the Supermarine drawings are correct?"  Draftsmen make errors, too.  I try to check everything against other references.  I have not taken measurements directly off of a Spitfire, because I haven't had the chance, others including yourself HAVE done so, the Supermarine drawings do the job (when I can find applicable ones) and that isn't the purpose of my Spitfire research.  The majority of my time has been spent with primary source material (PRO, Cambridge Library, IWM, RAF Museum, Solent Sky (or whatever they call themselves now), NASM...)  What I've collected about dimensions is more of a selfish tangent because of my interest in modeling, though really it does fit into my overall mission- it just isn't the main objective.

Quote
At least my measurements are consistent with other persons who have taken similar measurements and at least I have taken actual measurements. Can you say similar?

I'll leave it at that. I don't want to detract from Jens' build because you haven't done similar first-hand research.

"Contemptuous and provocative", I think you said?

bob
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jenshb
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« Reply #8 on: March 30, 2009, 03:09:48 PM »

I haven't measured any Spitfires, but as I've made engineering a career, I hope I can provide some input to interpreting drawings before 3D CAD.

A drawing for manufacture is basically worthless without dimensions.  A fundamental rule for draughtsmen, engineers and metalworkers is to never, ever measure anything from a drawing.  All measurements should be taken from dimensions given in the drawing.  The drawing itselt is just a sketch to show the workmen what the part looks like in various views so they can identify where the various measurements go, and the engineer/draughtsman had to provide all the measurements that the manfacturing process required.  /If not, then the drawing should go back to the offices for modification.  General Arrangement drawings are even worse as they are not used for anything at all except providing an overall impression and some basic data like length, width and height.  As long as the data they convey is accurate, the proportions do not matter.  Even in the world of 2D CAD GA drawings could be grossly inaccurate.  In theory all components would be drawn to full size and they could be imported in a file to combine all parts necessary for a complete assembly, but there is no guarantee this would happen. With a set of parts drawin to fit a sheet of paper rather than full size (and then scaled to fit the paper), it's even less likely that the original drawings would be traced.  I am sure the parts would be drawn as accurately as the draughtsman/woman could do, within the limitations of scale and time, but errors might creep in, and changing a dimension is easier than having to erase a long contour or the length of a beam.

The dimensions given on drawings contain tolerances, and this is the design intent.  The nominal dimension must have an allowable deviations as it is impossible to only make perfect parts.  This allowable deviation from the nominal is the tolerance, and often this is symmetric around the nominal value - e.g +/- 1.  Any part that does not have dimensions within tolerances should be reworked or rejected.  Jigs and fixtures were made to reduce the variation in production (and thereby bringing parts closer to the nominal domension), but variations would still occur.  One consequence could be that an access panel from one plant might not fit the fuselage made from another, in spite of both being within tolerance.  The only way to solve this would be to tighten up the tolerances, but tight tolerances cost money and will reduce the output - not what you want when you're churning them out as possible to fight a war.  Some dimensions are important, others are not, so as long as the parts fit, that may be deemed as "good enough".   One particular airframe may be a collection of parts on minimum tolerance, another may be on maximum tolerance - this will both give different results. 

Another thing to consider is repeatability in measuring.  Take a caliper and measure a solid object ten times along the same dimension.  Even though you try your best to be accurate every single time, chances are you won't read the same value twice, but you will get a distribution that will show more readings around a certain number.  The same type of uncertainties will creep into measuring complete aeroplanes - and the more difficult it is to measure, the greater the risk of errors.

Therefore, studies that use drawings as their primary reference will produce a result that will be closer to design intent than studies that are based on measuring surviving airframes.

Jens
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Spitbuilder
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« Reply #9 on: March 30, 2009, 10:12:15 PM »

Well said Jens, I agree with everything you say here. That's exactly why I never completely trust drawings when measuring a kit against a scaled drawing. This is the motive for measuring Spitfire airframes whenever the opportunity arrives. Measuring panel line length is the best method to find out exactly where a kit like the Hasegawa Mk.IX loses it's fuselage length so appropriate inserts/corrections can be placed.

Hopefully it won't be too long before I have the facility to post photos of kit shortcomings and corrections too. I have plenty to contribute in that area from past research.

Regards
Steve
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gingerbob
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« Reply #10 on: March 31, 2009, 12:03:46 PM »

I agree, Jens and David.  One clarification, though:

Quote
Therefore, studies that use drawings as their primary reference will produce a result that will be closer to design intent than studies that are based on measuring surviving airframes.

I think you mean "factory drawings" or "blueprints".  Accepting any other drawings (or data) as gospel is about like using an artist's profile as proof of the accuracy of your markings.  Actually, blindly accepting blueprints might get you in trouble too- sometimes the measurement on the blueprint isn't correct, which is only one reason for revisions on drawings.  There's certainly nothing wrong with measuring the real thing, and sometimes that's all you've got left to work with (if you're even that lucky), but if you don't do it right (and no, David, I'm not "accusing" you) you're not going to get accurate results.

I would also point out that any variation due to tolerances is going to be invisible in 1/48.  And anyway, that would affect individual skins/ parts, not really the overall dimensions of an airplane.  Components such as wings and fuselages are built in jigs, and the jigs are checked against a 'standard'.  The book "Spitfire Odyssey" describes how a fuselage built in one jig was placed into another jig, and if it didn't fit, the jig was corrected.  True, you might not be able to take a cowling panel off of one Spitfire and fasten it straight onto another Spitfire.  But the tail and wingtip, for example, was made removable specifically so that you could bolt another one on, for ease of serviceability.

Just in case there is any misunderstanding, I think you did a great job of presenting the issue with the Hase kit.  Great photos, understandable frame of reference (the drawing).  And since I've done my own comparisons, I could see that the conclusions were more or less on track.  But I wouldn't start making "corrections" to agree with the drawing without checking numbers.

And I'm still hoping somebody can give me the heights at each frame...

bob
« Last Edit: March 31, 2009, 12:11:43 PM by gingerbob » Logged
jenshb
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« Reply #11 on: March 31, 2009, 12:59:55 PM »

You're right Bob - I was referring to factory drawings rather than "eyecandy" in various modelling publications for example.  I do also agree that tolerances on a scale model would be all but invisible as even half a mm equals an inch in 1:48th scale.  One of my ex colleagues was working for British Aerospace on the Nimrod MR.4, and he said that one of the main problems they had with giving the aircraft new wings was that the wing attachment points could vary by as much as four inches between the various airframes...!

Jens
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« Reply #12 on: April 01, 2009, 01:04:40 PM »

FWIW, I have been comparing Paul Monforton's drawings with my own work on Spit Mk. IX and can witness about the fidelity of his results. According to his book, they are mainly based on factory construction drawings, but he apparently put a lot of (commendable) work into measuring everything and relying on these when creating his 4-views.

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JCote
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« Reply #13 on: April 04, 2009, 01:35:22 PM »

FWIW, I have been comparing Paul Monforton's drawings with my own work on Spit Mk. IX and can witness about the fidelity of his results. According to his book, they are mainly based on factory construction drawings, but he apparently put a lot of (commendable) work into measuring everything and relying on these when creating his 4-views.



Absolutely and unreservedly seconded!  Paul is a en experienced aero engineer, his book provides not only plans but also detailed measurements at every wing and fuselage station.  His work is in a league of its own:  I've got a photo somewhere off the coordinate-measuring jig he used, If I manage to find it again I'll post it.

P.S:  Jens, great mod!
« Last Edit: April 04, 2009, 06:32:32 PM by JCote » Logged
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