Revell PV-1 Ventura

[KSL]

1"/48=.02"=.5mm dia. not 1mm

Write R-2600 diameter 1397mm/48=29.104mm

The problem is that a R-2800 in 1:48 scale should be 1.11" 28.1mm

29.1mm-28.1mm=1mm

Sergey.

[Otto]

Write R-2600 diameter 1397mm/48=29.104mm

29.1mm-28.1mm=1mm

Sergey.

I am comparing the available diameters that we have been given to work with on the model. Unless you want to do an entire new nacelle for the kit. To do new nacelles in resin would be twice as expensive as the kit itself (from Vector maybe even three or four times as expensive, I paid $22 for my complete kit). I am concentrating on correcting the cowl SHAPE nothing more. I don't know what argument you are trying to start with your comment. If you want to do a new cowl than do so. The 2600 is 54-1/8" with baffle mounting brackets. But that is still besides the point. If you have a point than make it. I don't know what you are trying to teach me about these engines, I have been working on them now for over 20 years.

Edited January 18, 2012 by Otto

[Otto]

Just out of curiosity what is the correct EXTERIOR diameter of the Ventura cowling and is the kit cowling the correct exterior diameter? I would have expected that the kit designer would have been centered on getting the exterior dimensions correct and then reduce the interior components the apropriate amount to allow for the thickness of the plastic. Would this not account for the reason the engine may be smaller than the published actual size?

Dave

I doubt that ANY of these large companies EVER verify any dimensions. They go by what ever drawing someone tells them to use.

[Otto]

Here is a "Nye" drawing of the PV-2. Nye has been respected of one of the best for decades. I like the cowling shape in this drawing.

This is the critter I want to do.

Edited January 18, 2012 by Otto

[Otto]

Here is a nice picture for those of you interested in detail.

Edited January 18, 2012 by Otto

[Tracy White]

Otto, I think you ruffled his feathers by pissing on his work, so he is obviously going to ride you hard on yours now.

[HistnScale]

Lockheed-Martin is very kindly sending a set of factory spec drawings showing the cowl cross-sections and dimensions. I'll post them to this thread when they arrive.

Cheers,

Dave

[Tracy White]

+1

[David Rapasi]

For a different perspective I superimposed the Revell kit wing onto the Don Greer drawing in Squadron Signal #1048 PV 1 Ventura. A pretty close match all the way around.

A photo of the Revell kit wing and cowl was superimposed onto a photo of a PV 1.

I made the kit cowling photo slightly smaller so the outline of the aircraft can be seen. This also looks pretty close.

The diameter I have for a P&W 2800 is 52.8 inches which scales to 1.1 inch. The O.D. of the kit cowl tapers from 1.185 to 1.095 inches

Dave

Edited January 22, 2012 by David Rapasi

[Otto]

Otto, I think you ruffled his feathers by pissing on his work, so he is obviously going to ride you hard on yours now.

I stated that he has very nice stuff and that I would like to have some of it but just can't afford the price. He has beautiful stuff just very costly.

In the photos I provided in the previous posts take a look how close the engine was cowld. The cowling sits about 1/2" from both the front and rear rocker covers. I am just saying that the cowling is the wrong profile. So either enlarge the front or shrink the back to change the shape. Shrinking the back is going to be massively more difficult. All we have determined here is that the front needs to be a bit larger and the back a bit more smaller. I do not plan on making the front of the nacelles smaller, to do that entire mod would be very prohibitive. I just want the cowlings to have the right shape. This means that I am going to adapt everything to the simplest dimension to work with which is the cowl flap diameter.

Now take a look at the drawing in the Squadron book. Measure the speedring diameter in the top view and than in the profile view and tell me what is wrong since the base of the speedring is supposed to be round. Squadron Publications are a JOKE in MOST situations.

If you want to see factory drawings than look at Ginter Books #86 PV-1 Ventura PV-2 Harpoon it has the cowling factory drawings in it. Here are some relevant pictures. i refuse to brake the spine of the book so I will not scan it but just took snap shots.

Edited January 18, 2012 by Otto

[Otto]

The diameter I have for a P&W 2800 is 52.8 inches which scales to 1.1 inch. The O.D. of the kit cowl tapers from 1.185 to 1.095 inches

Dave

Mine measure 1.075

[Brad-M]

More nice work David! For me, the kit cowls work. Appreciate you posting all this stuff.

Cheers

Brad

[Falcon50EX]

1) First off, hats off to those who have managed to finish the model, or at least post photographs of their progress.

I think David Rapasi's treatment of the cowlings is very nice. FWIW, Revell got the distinct curve of the nacelles aft of the cowl flaps better than Academy did (which is a 1987-88 vintage kit). Dave did a fine job of closing the metaphorical gap. Or in the case of the cowl flaps, opening it. His narratives are well photographed, His research is sound and free of rivet counting rhetoric like "Silly", "Wacky", etc.

His body of work speaks for itself.

Kudos also to David for re-habilitating the AMT Tigercat propellers into something useful. Reduce, Reuse, Recycle.

2) I don't trust the Nye Drawings; not in this case. For one reason, they are drawings of a PV-2, not a PV-1. For another reason the drawing is too small to really see much detail.

I think the Paul R Matt drawings are better. Not perfect mind you, but better. They are actually of a PV-1.

David

Edited January 18, 2012 by Falcon50EX

[HistnScale]

Just to make it easier on my elderly brain, to summarize, the actual engine is either 52 or 54 inches O.D. Putting a scale on the kit I'm working on, the kit cowl is 58" o.d. at the firewall and 55" o.d. at the cylinders. Now, I guess I will wait on Lockheed to cough up the drawings with the station dimensions on them and see what the cowl measurements were supposed to be.

BTW, nice job on the photo work, David.

Dave

[Robertson]

The problem is that a R-2800 in 1:48 scale should be 1.11" 28.1mm, and the shape of the cowling is completely wrong. I will be using a set of cowlings from an AMT A-20 to fix the problem. They are virtually perfect in size and MUCH closer in shape. I will just cut the scoops and blisters from the Revell cowls and put them on the AMT cowls. I have the Verlinden R-2800s and they are perfect in size but you would have to cut the rockers off to fit them in.

First of all, Vector's prices are incredibly reasonable for the extreme quality and the amount of material you are getting, and even if they were not some of the best, if not THE best, resin pieces I have ever seen (which they are), they would still be a bargain compared to what most other major resin makers offer. Have you tried Sprue Brothers? Prices on Vector items are really reasonable, and if you don't find them acceptable then no resin is acceptable by some margin...

Second, you say: "The nacelle I could live with but the cowling looks silly."

Both the nacelle and the cowling do appear to be too thin, but they could also be too long, which you appear to have discounted:

http://cdn-www.airliners.net/aviation-photos/middle/6/4/3/1177346.jpg

http://www.hyperscale.com/2012/galleries/p7hg_img_1/fullsize/Revell_Ventura_011_fs.jpg

There seems to be little wrong with the taper of the cowl itself.

Finally, I find it odd you use the Verlinden 2600 engine for reference, of all things: It looks nothing like a real 2600 (or any WWII engine I have ever seen), and it is far too large in overall diameter, with a far too small crankcase on top of that... This resin part is hardly even decipherable as to what it is supposed to represent...

The same thing to a lesser degree goes for the problematic AMT A-20 cowlings, which have long been a major problem of this otherwise great kit: This is because of the excessive diameter of the AMT's cowling: On the Quickboost B-25 cowlings, which fit the Accurate Miniatures kit (an excellent-looking part for the same 2600 engine), the diameter is: 29 mm, or 1.14 inches, a tiny amount small for a 29.1 mm 2600 engine, but probably not too far off given how closely cowled these things were.

AMT's A-20 cowling just ahead of the (faint) cowl flaps, not maximum diameter: 30.6 mm, or 1.2 inches, or 2.5 mm wider than the 28.1 mm (1.1 inches) diameter of an 18 cylinder 2800 engine like that on the Ventura: That is five inches wider than the actual Ventura engine, and probably around three inches wider than what is needed for the A-20 itself...

These things had skin 0.5 mm to 1 mm in thickness, and were pretty closely cowled around the cylinder heads...

Given that the Revell Ventura kit cowlings seems quite close to being correct in diameter, maybe it is also the length of the whole nacelle and cowl combined that needs to be looked at... In any case the use of the AMT A-20 cowlings seems not to be a step in the right direction, though I can understand why it would initially appear to be the case.

Robertson

Edited January 18, 2012 by Robertson

[Otto]

Here is My AMT A-20 Cowling sitting atop the existing Revell PV-1 cowl flaps. It fits absolutely perfectly. I don't know where you are getting your 1,2,3mm differences. I couldn't give a hoot how it relates to the A-20 as far as this project is concerned. I just want a proper looking cowl in front of the cowl flaps. What they did was make the cowling come to a point just like they did on the old Monogram P-61 kit. Cowlings might have a slight taper but not like the one on this kit and the old P-61. Take a look at a Monogram/Revell P-61 and take a look at this picture. It is the exact same problem. The major difference being, that the old Monogram P-61 cowl was one molding and it was done to assist mold separation. Here there is no excuse.

There is between .5 and .625" between the rocker covers and the inner wall of the cowling on the real aircraft, to allow room for hardware and prevent vibration chafing. This should make the cowling 1.13" at the base of the speedring. The kit cowl is 1.07" at the OD in that spot. That is 3+" scale too small in front. Considering that the cowling is 1.18" at the cowl flaps, that is about 3+" too large to scale. That is a 6" taper over a length of about 28".

Edited January 18, 2012 by Otto

[Robertson]

You are correct Otto: Your cowl does look much better than the kit part, including the more rounded edge at the front, with less taper overall:

http://www.airport-data.com/images/aircraft/large/258/258059.jpg

Some of the improvement in appearance of your cowl also stems from the shorter appearance of your open cowl flaps. In any case, if the 2800 engine really was 28.1 mm in diameter, then the AMT cowl is still 30.6 mm (1.2 inches), which would leave a 2.5 inch gap all around the engine: I don't know if this was the case (you say half an inch, which is indeed five times less), but 5 inches in total seems extreme, even at the base of the cowl. Since the Revell Ventura kit cowl is quoted as 1.185 inches in this thread, and the AMT A-20 cowl is 1.2 inches, it should be no surprise they fit one another well... Given the correction you have made to Revell's incorrect cowl taper, the potential problem I see looming now is that the prop hub, if correct in size, and the cowl, correct in appearance but five inches too wide, will both combine to make the hub look a bit "lost" in the cowling's cavernous mouth opening...

Robertson

Edited January 18, 2012 by Robertson

[Otto]

I still left some taper on the cowl so. the hub will look just fine. My problem is, because i am used to the real aircraft, it just jumped out at me. I am also working on a second cowl which is a modified kit cowl but expanded in the front. I want to see which will look better. Once I have enough of that finished I will post pictures.

[joncarrfarrelly]

From P&W and Wright documents on the AEHS (Aircraft Engine Historical Society) site.

Douglas A-20A/B/E, P-70, Boeing A-20C: R-2600-11, Diameter 55" (1397 mm). 1.145833" (29.104167 mm) in 1/48th.

Lockheed PV-1, PV-2A/B/C/D, RB-34, RB-34A/B: R-2800-31, Diameter 52.5" (1333.5 mm). 1.09375" (27.78125 mm) in 1/48th.

Lengths are 65" (1651 mm) and 75.72" (1923.288 mm), respectively.

FWIW the R-2600-13 used in the B-37 variant of the Ventura series was 54.26" diameter, 63.1" long.

http://www.enginehistory.org/reference.shtml

BTW those "factory" cowl drawings are assembly drawings, not pattern drawings, thus they aren't necessarily fully "accurate" in outline.

Edited January 18, 2012 by joncarrfarrelly

[Otto]

Here is the second cowl that I am working on which is a modified kit cow. Left to right;

Modified kit cowl, stock cowl, AMT cowl. Ironically the AMT cowl and the modified kit cowl wound up the same shape. There are 14 x .015" inserts along the front of the cowl behind the speedring. the base is left OE.

[Otto]

From P&W and Wright documents on the AEHS (Aircraft Engine Historical Society) site.

Douglas A-20A/B/E, P-70, Boeing A-20C: R-2600-11, Diameter 55" (1397 mm). 1.145833" (29.104167 mm) in 1/48th.

Lockheed PV-1, PV-2A/B/C/D, RB-34, RB-34A/B: R-2800-31, Diameter 52.5" (1333.5 mm). 1.09375" (27.78125 mm) in 1/48th.

Lengths are 65" (1651 mm) and 75.72" (1923.288 mm), respectively.

http://www.enginehistory.org/reference.shtml

BTW those factory cowl drawings are assembly drawings, not pattern drawings, thus they aren't necessarily fully "accurate" in outline.

Who cares about anything about the A-20. I just used the Verlinden kit to demonstrate the taper in the PV-1 cowl, because I did not thave a 2800 handy. We already know that the 2600 is larger in dia, than the 2800. We are talking about re-shaping the PV-1 cowl, nothing more, nothing less. I have the service manuals for about 10 radials, I know what the dimensions are.

Edited January 18, 2012 by Otto

[Otto]

Here you go guys. Kit cowl on left and new cowl on right. This master left today to "Obscureco". The new resin cowls will be available with new props.

Edited January 20, 2012 by Otto

[blunce]

Otto,

Curious about the actual difference between the two, I took your picture, transformed it so they were facing the right way, and put the picture into the following pic to show (somewhat) the difference. Would be better if the shot of your two cowls was more of a straight side view, but I think we can see there is certainly a difference and I think Otto's look much better than Revell, but without same angle picture comparison, it's hard to be 100% sure.

[Otto]

Can't take another picture any more. The master is already on it's way to "Obscureco" It left about 45min ago. I'll keep you guys updated. I sent it Pry-Mail so he should have it Monday, Tuesday at the latest. It is supposed to be 2-3 days.

[Otto]

I forgot that I took some yesterday before I did the scribeing and final shaping. The problem is that i took it with Macro so the image is "fisheyed". I would have to had taken it with a 135mm lens to have it not distorted. In the picture it looks like it is larger in the front than in the back, while in fact it still has some forward taper.

Edited January 20, 2012 by Otto