F4F-4 Wildcat length

[warhawk]

On 4/19/2017 at 10:25 PM, dragonlanceHR said:

To the subject of drawings by Jun Temma, I had some correspondence with him regarding the Yak and LaGG technical manuals and original drawings, and he uses the original manufacturers data, esp. the ordinate tables, whenever possible.

As to his research, he is very observant and meticulous. He even re-discovered the different F8F windshields 🙂

 

I agree with You Vedran.

His research pointed out first (to me at least) that Spitfires Mk.I and early Mk.Vs had different main canopy covers.

I do not want to disprove his research from my (amateur history buff) point of view, but if he is correct, then this statement made by Bruce Archer is not.

 

On 4/14/2017 at 4:56 AM, Bruce Archer said:

I  found the Martlet/Wildcat was the same length, regardless of engine. The Cyclone cowls are shorter, but the length between the wing leading edge and the rear of the cowl is longer, and conversely aircraft with the longer P&W cowl have a shorter length between the wing leading edge and the rear of the cowl. The reason was the Cyclone needed to be mounted further out due to CG issues.

Bruce

 

Please don't get me wrong, there are two contrasting pieces of information given by two equally respectable sources, but they can't both be right.

Either FM-2 and F4F-4 had the same total length (as B. Archer claims), or they had the the same firewall location, and different cowling lengths (as J Temma claims). 

Temma shows the firewall at nearly the same place for both, with a difference in length.

 

 

 

And the point of my question was to determine this length.

 

Regards,

Aleksandar

Edited July 14, 2018 by warhawk

[Garry c]

The overall length as given to the U.S. Navy (from Grumman I assume)

 

F4F-3    28 feet, 10 and 5/8 inches

F4F-4    28 feet,   9 and 3/8 inches

FM-2     28 feet,   7 and 7/32 inches

 

This is from the tip of the propeller to the end of the rudder. Unfortunately the length of the propeller hub/nosecone will affect overall length measurement.

 

The F4F and the FM-2 are the same from the landing gear bulkhead back (except for the height of the rudder)

 

This bulkhead is also the mounting point for the wing spar.

 

The firewall is sandwiched between the engine and the engine mount and is quite different for each engine.

 

F4F

 

FM-2

 

Note that the cowling of the FM-2 overlaps the firewall by several inches.

 

I do not have the measurements you are requesting, but I hope this helps explain the firewall confusion although I probably just added to it.

 

Garry c

[Work In Progress]

Good point by Garry. Can we be careful about terminology please? Temma's lines as indicated by Warhawk's second green line from the left are not denoting the position of the firewall, they are simply the rear edge of the cowl.

Coming to the substance of the question of the nose structure I would note that Temma's lines may to you be  "nearly in the same place", but what that means is "in a different place".

 

The photographs in Gwart's post on the previous page --

-- clearly showed the difference in the fuselage structure ahead of the leading edge for the single-row and two-row engine variants.

Edited April 25, 2017 by Work In Progress

[MDriskill]

Garry C, a superb post, thanks for the great photos and comments.

 

You are correct that the factory overall dimension typically INCLUDES the spinner hub...so is of limited value when analyzing fuselage geometry. A very important point.

 

But speaking of terminology...have I been using the word "firewall" incorrectly all these years? I would call the solid bulkhead to which the wing, gear, and engine mounts are attached the Wildcat's firewall, but you use the term for the enclosure at the immediate rear of the engine. Is there a consensus on this?

[Graham Boak]

Strictly speaking it is only a firewall if it is fireproof.  Many of these heavy-duty frames used for mounting the engine were not fireproof, but through casual use the term firewall has become commonly understood as this major forward structure.  Does this help or not?

[Garry c]

   I agree that the bulkhead is the actual firewall. What I called the firewall is no more than a cooling shroud to help control cylinder temperatures and attach the front panels.

The F3F and F4F/FM-2 are the only aircraft that I can think of that have the landing gear ahead of the firewall which leads to confusion.

The dimension drawings have this all-important bulkhead marked as "Fuselage Station #2" which leads to more confusion.

 

On a side note,I think the FM-2 would have been longer had Grumman not moved the oil coolers from under the wing to ahead of the wheels.

 

Garry c

[BD1944]

Greetings ... Bri Derbyshire here, author of "9 Lives" back in 1990. Google and I obviously differ over what constitutes a relevant search term, because I've been looking in vain for stuff like this for a year or more. I too bought the AZ G-36 (for a Martlet I) - it's SO like the Sword FM-2, and also needs a completely new noisy end. (Thanks, Airfix, for your old SBD.)

 

I couldn't find this site, or anything similar, ao I did other stuff like searching for nice side-on photos that I could measure. Ideally I wanted shots taken from the plane of the cowl inlet, but in all cases I plotted, on an extended plan view drawing, bits of airframe that lined up. (For instance, the MI on Archer P. 1 is photographed from somewhere on a line with the rear of the hood and the aft corner of the wingtip.) Two or more lines like this will give an approximation of the camera's POV. Lines from this to prop tip, cowl LE, cowl TE and wing LE will intersect the aircraft CL and the cowl etc. flanks at measurable angles ....  well, anyway, this enables an estimation of the "angle off" and "range" of any dimension measured raw on the photo. Correct these according to angle and relative range, feed in known dimensions like Bruce's 14-5/8" & 22" and/or the prop-tip-to-LE numbers off our GAs and it's all sorted, yes?

Well, no. Even with the biggest and best photos I could find, and averaging where I had enough examples, the scatter was high and the results for Martlet I/IV, Martlet II (bullet hub) F4F-4 (stepped hub) and FM-2 (both hubs) were mutually incompatible. Overall length from wing LE to cowl lip came out at around 50", but + as much as 3". My estimates of prop hub length (from cowl lip) were simply not believable. Several weeks down the drain ...

 

So I'd love to be able to accept Bruce's (or JT's) measurements ... but how big, exactly, is "the same length?"  What's being measured, from where? I know it's all over a couple of inches, and my model (once I've rebuilt the canopy, see the MI strand) is going to have errors like the cowl diameter being 2" or so under and the prop hub tapered instead of parallel: but if my write-up is going to tell fellow modellers how it ought to be, then it ought to be right, and from primary sources if possible. Please, primary sources with tape measures out there, will you clarify, before I go even madder?

 

Further gripe: the -3 and FM-2 GAs out there, and copied on this site, are illegible on my kit. I have to read the thumbnail copies printed in SAM, using a jeweller's loupe,and all the fractions have filled-in numbers on them. Advice and/or assistance welcome. (I date from the days of pencils and Letratone.)

 

Bruce - I love GW in FAA, but I can add bits to it. (I'm not all gimmegimme.) I failed to track you down when I first found it, last year. Please PM me or whatever - I'll learn how to drive this sort of thing eventually but I'm still a tyro at forums.

 

Cheers all, and thanks for all the input - Bri.

[dragonlanceHR]

BD1944,

 

send an e-mail to Jun Temma, he uses both data from manufacturers and his own photogeometry analysis.

 

Below is the link for the English version of his equisite 1/72 FM-2 build.

 

http://www.geocities.jp/yoyuso/fm2/fm2e-1.html

 

Vedran

[BD1944]

Thanks, Vedran - I already have this site bookmarked, and am duly impressed. The snag is I can't read the drawings - too faint, numbers too small. Dunno how to manipulate the screen, or to copy bits other than as a GIF which is even worse. Bring back the slide rule, and maybe I'll be able to cope!

 

BD

[tempestfan]

1 hour ago, BD1944 said:

 Dunno how to manipulate the screen, or to copy bits other than as a GIF which is even worse. Bring back the slide rule, and maybe I'll be able to cope!

 

BD

There's a small "full size drawing" clickyfield beneath each drawing. When clicked, you get a magnifyer Symbol in the pop-up window. If even I am able to read the measurements then, you should be too...

Edited June 13, 2017 by tempestfan

[BD1944]

May your Sabre never seize! I never thought it meant anything other, because aircraft drawings are traditionally always done at a scale of 1:1 - they are all "Full size drawings!" (so are mine - with CadCam your board is always big enough.) I shal away, one click, and try it. Thanks ...

BD

PS Bingo!  Thanks again - BD

 

Edited June 13, 2017 by BD1944
Update

[BD1944]

There are certain advantages in being retired, like being able to pursue one's bonnet bees NOW.

 

After a bit of searching I found the relevant dimensions on JT's drawings to relate his cowling dimensions to the "root chord" mentioned in our favourite GA drawings -  actually the L/E of the root chord, which is itself 97.63". This turns out to be 23.432" forward of the wing ref. line, or 20.59" forward of the "firewall" skin joint. After that, it's arithmetic.

 

Bruce reckoned that cowl-to-L/E for 1830 engines was 14.625". JT makes it 14.412". Good enough, yes? Especially at 1/72 scale.

 

The GA dimension for the FM-2 front end, 73.78", included a domed Curtiss hub. Subtracting the appropriate JT dimensions gives this prop a length of 24.3" from the cowl lip. (My own calculations and measurements from photos made it 25.88", but my sample's small and my photos fuzzy, so I'll take JT's.) Adding this to his F4F-4 cowl-lip-to-L/E figure of 54.3495" we get 78.65". The -3 GA gives 77.187"  for a stepped Curtiss. Difference for dome fairing = 1.46". Personally I'd reckon about 2" or 2-1/2" extra, but again I won't argue.

 

What this means is that, prop for prop, we should expect cowl-lip-to-L/E to be about 4 - 7/8" longer for an F4F than for an FM-2. Sorry, Bruce, that's about 10 times the tape error I'd expect over a couple of yards.

 

If Cowl-to-L/E for the FM-2 is indeed 49.46" (vs. 54.35" for the 1830) then perhaps we should expect the Martlet I to be similar. I had several decent MI photos to go at, and a fair Mk IV, and my best estimate was 29.5" cowl (Vs. Seahawk's 28".) Add Bruce's 22" cowl-T/E-to-L/E and we get 51.5".   But if Seahawk's admittedly hurried 28" is correct - and a tape on the ground is worth many a ruler on a photo - then 50" is near enough to 49.46" for my money.

 

My estimate for the length of the HS prop is about 23.6". That would make the OAL of the Martlet I 343", i.e.28' - 7", damn near identical to the FM-2.

 

Subject to revision by the man in site, of course ....

 

BD

[BD1944]

This isn't strictly relevant to this topic, but the thread is still live ....

 

I'm involved with Wildcat ammo covers, trying to convert somebody else to The Cause - namely that the two inboard guns shared a cover. I've pointed him in vain to the technician putting an ammo box into a space too small for even one row of Dzus fasteners between the boxes (let alone two) and to the "oops" moment aboard USS Copahee, and the retreating FM-2 in "Wings of the Navy."

Please, MDriskill - I know you're another True Believer - could you post (or point us to) some of the photos which you have, in the past, claimed as proof of the point? The earlier the BuNo. the better ....

 

Regards, BD

 

STET! I've just seen  "Even more wildcat stuff"  - Thanks, MD ...

Edited June 28, 2017 by BD1944
Superseded

[warhawk]

New F4F-4 announcement by Arma hobby brought me back to the length conundrum.

I managed to find two photos with nearly the same perspective, and judging by the position of the propeller hub  - there indeed was a small difference in overall length Between F4F and FM-2/Martlets:

 

 

 

 

 

 

 

 

 

[Chuck1945]

Warhawk, neither of those photos are FM-2 Wildcats. The Martlet IV does have a single row Wright engine that results in the the fuselage in front of the cockpit being slightly longer and the cowl shorter than the twin row P&W engined Wildcats but it isn’t a FM-2

[warhawk]

My mistake, I thought FM-2 also had a single-row radial.

[Graham Boak]

It did.  

[gingerbob]

[continuing Graham's statement] ...but the FM-2's cowling/engine installation was not the same as the earlier R-1820 variants.

[Graham Boak]

And there we have the core of the argument.  Did the FM-2 have a long fuselage structure (aft of the cowling) of an earlier Cyclone-engined F4F or the shorter one of the F4F-4/FM-1?  Having said that, did it then have a cowling the same as the previous Cyclone F4F or something new?  The key problem lies in understanding what happens underneath.  Where is the Cyclone?  It has to be mounted so that the CG is in the same place as the longer twin row P&W engine, so (on the earlier variants) the rear of the engine is further forward and the fuselage extended to match.  If the Cyclone is installed without this extended fuselage, then the cg has moved aft fairly drastically and the aircraft is liable to be unstable.  So Temma's drawing of the FM-2 appears odd in that respect.  Yes, the taller tail will help the directional stability but what about the longitudinal?  Does any source suggest that the FM-2 had a larger tailplane/horizontal stabiliser? 

 

Alternatively, does the FM-2 have the engine mounted the same distance as before but a longer redesigned cowling that is re-shaped (widened) to fit the wider engine?  In which case how does it compare with the original cowlings?  Bear in mind that the propeller is mounted onto the hub fittings at the front of the engine - did this differ between the earlier Cyclone and the version used on the FM-2?

 

 

[Chuck1945]

Graham summed it up nicely. The last time I read any published dimensions, the length of the both the P&W and Wright engined versions were essentially the same with single row Wright engine shifted forward resulting in a shorter cowl and extended forward fuselage. AFAIK it was Temma’s drawings that proposed different lengths.

[dogsbody]

Some drawings from @Geoffrey Sinclair:

 

F4F/FM-1:

 

 

 

FM-2:

 

 

 

 

 

 

Chris

 

[Troy Smith]

6 hours ago, Graham Boak said:

Alternatively, does the FM-2 have the engine mounted the same distance as before but a longer redesigned cowling that is re-shaped (widened) to fit the wider engine?  In which case how does it compare with the original cowlings? 

 

AFAIK Graham,  the FM-2 has a unique cowling.   

from 

http://www.clubhyper.com/reference/wildcatfaaba_1.htm

 

"The Wildcat VI, a FM-2, was an attempt to improve the performance of the Wildcat. A Wright R-1820-56 Cyclone with a single speed, two-stage supercharger was fitted and had an additional 150 horsepower over previous versions. A Curtiss Electric propeller without cuffs was fitted and could have either a domed or a stepped hub. The cowl had a longer chord than the Mk.I and IV, but was shorter than the Pratt & Whitney cowl. There were no external scoops on the cowl; all of the scoops were between the cylinders. The cowl had one cowl flap per side. The exhausts were routed out a cutout on the fuselage (one per side) and out the bottom. The oil coolers were removed from the lower wings and moved into the accessory bay. The wings were folding and had 4 guns with 430 rounds per gun. To counter the added torque of the new engine, the fin and rudder were enlarged. In addition, the windows on the underside of the airframe were deleted. . "

 

 

FM-2

 

 

 

HTH

 

 

 

[warhawk]

Right, let's try the same approach with an FM-2.

I still see a difference:

 

 

 

 

20 hours ago, Graham Boak said:

Alternatively, does the FM-2 have the engine mounted the same distance as before but a longer redesigned cowling that is re-shaped (widened) to fit the wider engine?

 

Certainly seems so. FM-2 cowling looks deeper and a bit more rounded when You look at the gif.

So. I guess they did have to move the single-row engine forward to compensate the CG, but not all the way up so that the new cowling front datum line reaches F4F cowling front datum line.

Edited August 18, 2021 by warhawk

[Chuck1945]

I think it was another Bruce Archer article on Hyperscale where he had actual measurements of cowl length and also the distance from the rear of the cowl back to the wing for both the -4 and FM-2. Since the fuselage length is the same for both versions from the wings back, the sum of the relative wing forward measurements should answer the question. Unfortunately I didn’t save the article… I’ll keep looking

[Graham Boak]

Thanks for the above, but it doesn't answer the questions as to just where the Cyclone is placed.  If on the same place as before, then it is a simple matter of an extension of the cowling to the rear, and the aircraft lengths will be the same.  Give or take different prop hubs and gearbox(?) housings at the front of the engine.  If not, then the overall aircraft will be shorter but the cg will have moved in a normally undesired direction.  Perhaps other changes in the design (lightening the structure?) may have led to this being desirable anyway?

 

I think that by far the most straightforward answer is that the Cyclone is in the same place as before, and the FM-2 is basically the same length as all the others.  The alternative involves engineering problems and resulting actions that surely would have been mentioned in earlier works.  It would be good if Bruce Archer's measurements could be found.