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Author Topic: Consolidated PT-3 for Indoor Rubber  (Read 16234 times)
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Pete Fardell
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« on: July 10, 2018, 09:19:35 AM »

I'm nearly ready to start my next effort for open rubber. I want this next one to be:
1. A properly documented model
2. A biplane which hasn't been modelled too often, and
3. To have sensible proportions and characteristics that will result in a lightly loaded model with a good chance of flying well.

I had intended to do a Sikorsky S-16, but reluctantly have now decided there are just not enough non-clipped photos available for a competition model of that one.
So, PLan B...

Consolidated PT-3
I've liked this one for a long time, and have a couple of good three views, plus there is a big RC plan which might be useful. All these are to be found in the Plans Gallery here.
It's a fairly simple aircraft, apart from the spoked wheels and radial engine, but I shall enjoy making those. A few hundred PT-3s were built, so you'd have thought there'd be plenty of potential subject aircraft photos to base a model on. Early on I ruled out doing the sole existing PT-3 because although there are tons of pictures of it, it is not really a very authentic example. As far as I can gather it's built from the remains of a PT-1 but with a radial engine to make it more like a PT-3. It has a tail wheel instead of a skid and although it's a lovely thing it doesn't quite do it for me.
There was one other example, a blue and yellow one in the original San Diego Air and Space Museum, but it was destroyed by the fire there about 40 years ago. I have now got some pictures of it though (I emailed the very helpful archivist at SDASM and their archive is on Flickr too). This plane is a possibility, except I have no good side, end or plan view photo of it for my docs. At least one of those three photos is meant to be of your chosen subject under the BMFA rules.

So that still leaves all the original black and white photos of PT-3s that I can find online or in books. The problem has been finding one which I can use as a basis for markings and colours, which can also be part of my photo evidence and which is also the right variant to match my 3-view drawings. The drawings are both of a standard Consolidated PT-3 but there are several variants of this plane, such as the NY-1, PT-3A or the O-17 Courier. As ever on the internet, not all photos are correctly labelled. I discovered I could even watch watch the 1935 film, "West Point of the Air" online, which features these aircraft heavily. Good for getting underside views for markings etc, but stills from it are not very sharp.

Anyway, I think I'm homing in on the example in the first of these pics. It actually says PT-3 on the fuselage, which is good (although it was labelled as an O-17 on the website where I found it). I suspect the fuslage is silver/aluminium and the wings are certainly yellow. It is described as a Signal Corp aircraft and dated 1928, which according to a book I have is when the US Army phased out olive drab fuselages on their training aircraft, and did them aluminium instead (later replaced by blue). The other two pics I've added here show similarly marked aircraft suggesting a plain yellow top wing and words U.S. ARMY underneath. No stars anywhere which was not unusual for those days I understand.
Hopefully, together these pics and will do for colour and marking evidence. I have other photos taken of PT-3s from end and underside elevations which will do nicely for my outline documentation as these don't have to show the subject example (so long as at least my side view does).

All thoughts and advice very welcome. Span will probably be 28 inches-ish.
Attached files Thumbnail(s):
Consolidated PT-3 for Indoor Rubber
Consolidated PT-3 for Indoor Rubber
Consolidated PT-3 for Indoor Rubber
« Last Edit: July 10, 2018, 10:15:43 AM by Pete Fardell » Logged
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« Reply #1 on: July 10, 2018, 02:28:32 PM »

Looks like a nice project Pete with some complicated bits to tackle too with the spoked wheels and radial engine. I look forward to seeing progress  Smiley
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DavidJP
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« Reply #2 on: July 11, 2018, 06:06:59 PM »

Has your name on it Pete - it looks quite nicely proportioned - a bit of dihedral - a nice progression from the Eindecker. 
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Tim Horne
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« Reply #3 on: July 11, 2018, 06:49:36 PM »

Sounds like a good plan Pete! I will enjoy watching this one come together.

I presume it's a little late to be aiming at Nijmegen this year, or are you going into speed building mode?

Tim
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Pete Fardell
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« Reply #4 on: July 11, 2018, 07:02:30 PM »

Thanks for the encouraging words, chaps.
Tim, it's probably a bit late to be built in time for Nijmegen, but we'll see how I go...
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Pete Fardell
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« Reply #5 on: August 15, 2018, 08:42:04 AM »

Nearly ready to begin with this. The plan is to keep it light and go easy on the detail. One big inspiration for this project is Lars Tolkstam's lovely Rumpler. This flies beutifully, and looks great but does not have scale rib spacings. It's light and slow and very convincing in flight. Here it is at Nijmegen: https://www.youtube.com/watch?v=AxFOtTp9w2c

I'm further encouraged by Graham Banham's plans for his forthcoming new Fike, which will also have quite minimal structure. I intend to put in only every other rib (or even every third) for this one and keep the weight right down. I'll rely on a simplified radial engine and a pair of spoked wheels to make it still look the part.

First job is to blow up the 3 view to the right scale. I'm going for 1/14 which gives a 27.6 inch span. My reason is that it will mainly be an indoor model and  27.6" is quite okay in a hall like Walsall but still big enough to fly outdoors too when conditions allow.
Unlike many previous projects I seem to have got two properly drawn three views to choose from. Quite a luxury. They both look okay to me at first glance. I'm inclining towards the second of these (which is from a 1963 Air Progress magazine) simply because it is much less cluttered than the very detailed Nieto drawing (nonreduced version is the plans gallery here) but I suppose I should compare both drawings carefully with my photos before I decide which to use.
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Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
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Mark Braunlich
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« Reply #6 on: August 15, 2018, 06:09:53 PM »

Pete,
The U.S. Navy's NY-1 has a bigger vertical tail.  Not sure if that would help or be a detriment for indoor flying.

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Re: Consolidated PT-3 for Indoor Rubber
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Mark
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« Reply #7 on: August 16, 2018, 11:03:13 AM »

Nearly ready to begin with this. The plan is to keep it light and go easy on the detail. One big inspiration for this project is Lars Tolkstam's lovely Rumpler. This flies beutifully, and looks great but does not have scale rib spacings. It's light and slow and very convincing in flight. Here it is at Nijmegen: https://www.youtube.com/watch?v=AxFOtTp9w2c

I'm further encouraged by Graham Banham's plans for his forthcoming new Fike, which will also have quite minimal structure. I intend to put in only every other rib (or even every third) for this one and keep the weight right down. I'll rely on a simplified radial engine and a pair of spoked wheels to make it still look the part.

First job is to blow up the 3 view to the right scale. I'm going for 1/14 which gives a 27.6 inch span. My reason is that it will mainly be an indoor model and  27.6" is quite okay in a hall like Walsall but still big enough to fly outdoors too when conditions allow.
Unlike many previous projects I seem to have got two properly drawn three views to choose from. Quite a luxury. They both look okay to me at first glance. I'm inclining towards the second of these (which is from a 1963 Air Progress magazine) simply because it is much less cluttered than the very detailed Nieto drawing (nonreduced version is the plans gallery here) but I suppose I should compare both drawings carefully with my photos before I decide which to use.

Very nice choice Pete. I have fancied doing one of these Consolidated Bipes too for a while. The PT-1 is also nice and there is a restored one hanging up in a museum somewhere. I like the second 3v as you mentioned, it has less detail, which I think is always a good thing, better not to show the judges too much detail, you'll feel you have to put it all on! One thing that works well with ribs if you want to have less wood, is to make every third rib (for instance) a full rib, then the ones in between can be 'sliced' top ribs. its easy to to, and importantly you get the effect of scale rib spacing on the curved top surface. Maybe a slight dihedral angle tweak up, to ensure she circles reliably? Oh but then you may need a little area tweak too to the rudder! As mentioned elsewhere, the Navy version did actually have a larger fin, as did the PT-1 from memory.
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Re: Consolidated PT-3 for Indoor Rubber
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« Reply #8 on: August 16, 2018, 02:06:51 PM »

Thanks for the great input; much appreciated!  I'd considered the PT-1 (there's quite a nice big one in the plans gallery) and also had a look at the NY-1 but will stick with the PT-3 just because on balance I just like it best of the three, and have already found enough photos to document it.
Trying to decide which drawing to use is proving a bit tricky. On the less cluttered second drawing the fin is clearly wrong and from the cross sections I think the fuselage is perhaps a little too rounded-out with the side stringers. The very detailed Joseph Nieto drawing has the fin and rudder shape much better but doesn't show the side stringers at all. Looking at photos I think PT-3s were indeed almost slab sided, but still with a couple of stringers showing though. I'm now inclined to go with the Nieto drawing and just put the side stringers in anyway. The judges will see them on the side view photo. I can easily get rid of the drawing's copious blurb and numerous surrounding detail sketches before presenting it to the judges. Meanwhile I've just been trying to set out the essential bits that  I'll need to actually build over and have added a red line to mark the lower wing's LE. Compared to the photos I can't yet see any glaring problems with the drawing's  basic outlines but someone please tell me if they do.

Richard, I will probably take on board your advice re sliced top ribs and also up-tweak the dihedral a little. Not yet sure whether to enlarge the rudder. Do you think I can get away with not doing?
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Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
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Bryanair
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« Reply #9 on: August 16, 2018, 04:59:39 PM »

FWIW
This attachment is from the book Air Force Colors vol 1 1926-1942 by Dana Bell.

Bryan
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Pete Fardell
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« Reply #10 on: August 16, 2018, 05:14:01 PM »

Thanks Bryan. I do have that book.
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« Reply #11 on: August 17, 2018, 02:28:45 AM »



Richard, I will probably take on board your advice re sliced top ribs and also up-tweak the dihedral a little. Not yet sure whether to enlarge the rudder. Do you think I can get away with not doing?


You might get away with the rudder Pete. I always think you can get away with quite a lot, the lighter the model is. Why not try a temporary sheet fin at scale size to see if it works at the trimming stage?
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« Reply #12 on: August 17, 2018, 02:41:54 AM »

Pete, Richard, it would never have struck me that the fin/rudder is small. After all, it's on the end of a very long moment. I think keeping the amount of nose ballast down will be a bigger challenge. Fiddling the rudder size will also be glaringly obvious to any judge, with those stripes!
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Pete Fardell
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« Reply #13 on: August 17, 2018, 04:00:49 AM »

Thanks, Richard and Bill- No, it didn't look small to me either, but then I never think about the rudder size much. At any rate, it's got more than an Antoinette!
As to keeping the nose weight down, I hope to keep the whole tail super light by minimising structure and detail at that end (eg. leaving off rudder cables etc. ). At least the skid is nice and simple.

One bit which might be a challenge weightwise are the fat tyred wheels. I'm wondering if I can utilise some kind of foamy stuff.
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« Reply #14 on: August 17, 2018, 09:21:50 AM »

About the wheels, are you thinking something like this?
http://www.jitterbuzz.com/manreal/fleet_biplane_10.jpg
I did some nice wheels by "dremmeling" black styrofoam from meat tray. A bit porous, but "allmost" black and very light
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Pete Fardell
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« Reply #15 on: August 17, 2018, 11:20:32 AM »

Thanks, yagua. No, the wheels won't be as balloon-like as that. Here's a pic of my subject's u/c. Normally I'd just turn balsa tyres but they are quite thick in this case, hence the weight concern. I have got this chunk of black foamy stuff which Gordon Warburton gave me at an indoor meet. Seems light but I'm not quite sure what it is, or how shapable it might be.
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Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
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billdennis747
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« Reply #16 on: August 17, 2018, 11:34:21 AM »

Pete, I think it may have a texture which will be ok for your Dad's - size models but could be too much for this
I'll bring some neoprene foam rod to the Nats for you to peruse. It could be heavy but I use it for all my models. I wonder what stuff Dave Banks uses and how it could be adapted - maybe find a way to squirt it into a rubber tube
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« Reply #17 on: August 17, 2018, 12:52:33 PM »

Pete, I have some of this, which you can buy online - it is PVC tubing and is quite foamy on the snide but smooth on the out.

I have guessed that you may want either 8mm or 6mm diam but they do many sizes on eaters side of that.

As a guide one metre of the 8mm size weighs 20gm sand 2 feet (forgive the mix) of the 6mm weighs 7gms.  I have used it and it does work.  Some says that a weighty U/C can help stability by lowering the CG!

I think it is PVCtubingonline  or similar.

PS  http://www.pvctubeonline.co.uk/sponge_rubber_cord.htm 
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« Reply #18 on: August 17, 2018, 02:54:48 PM »

Pete-
Again, a wonderful choice of subject. I used to drool over both those drawings as a teenager. I entertained grand visions of a gas FF scale model, at 1/12 scale. I had Nieto drawings from our National Air and Space Museum and the other (I believe attributed to James Triggs)  from very same Air Progress magazine. I got in some trouble in High School, about 1964, age 14. Freshman Science was exceedingly BORING, so regularly perused model mags, instead of the assigned lesson. All under the sophisticated and clever guise of my notebook cover. Teacher eventually caught me and fortunately, I'd not taken a "toy airplane"  mag, that day.  He held up my father's Air Progress , opened to those very PT-3 drawings. He even turned the pages  for whole class to enjoy. Pop wasn't exactly happy when he found out. His magazine would be held till end of term.

Here in US, construction trades use foam "noodles" of various and constant diameters and available in long coils or packaged 36" lengths. It comes in gray and black  and is used in insulation applications and small critter exclusion. Diameters range from 1/8", 1/4", 3/8" 1/2 and so on thru 1".  Very light weight and easily wrapped around a balsa rim to make a tire. Joints are butted and glued. Seam is noticeable, but not objectionable. Works pretty at well making light weight scale like tires. IIRC, Aerodrome kits used these in their range of 1/12 scale WWI aircraft and I may still have one of their separate wheel kit packages, out in the shop.
I have photo somewhere, from my fathers collection, showing rows of parked PT-1's covering a large portion of US Army training base. I don't like the squarish fin and rudder of this variant, but that Hisso front end is classic  and MUCH easier to model  than 9 exposed radial cylinders!  
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Pete Fardell
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« Reply #19 on: August 18, 2018, 02:46:53 PM »

Many thanks for all the tyre info. That's a great story, PP.

I'm curious to know if these foamlike alternatives are significantly lighter than solid painted balsa. If they're not then I'll probably just turn balsa tyres as usual because it means I can make them an integral part of the rim and (if I make the spoked wheels my preferred way) I'll be on altogether more familiar ground. The downside to balsa tyres on indoor models is the 'clatter' on landing, but there are ways round that.
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« Reply #20 on: August 18, 2018, 03:22:30 PM »

I'm sure balsa is lightest, but more work
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« Reply #21 on: August 18, 2018, 03:44:23 PM »

I’ve used that spong rubber cord on A number of non model (work related) designs as seals, for low pressure applications.  It is nice stuff but as has been pointed out pretty heavy relatively speaking, definetly more so than balsa...

Andrew
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« Reply #22 on: August 19, 2018, 08:08:05 AM »

Yes, Balsa is undoubtedly lighter.  But sometimes the extra weight using the “sponge” can be OK and an advantage by the virtue of the spongy  tyres.   My SE5 has spongy tyres but they are small cross section. I think when I weighed them the pair were 1.5gms.
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Pete Fardell
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« Reply #23 on: September 01, 2018, 07:22:44 AM »

Thanks for all the tyre advice. I decided to make the wheels first, and all things considered am going with balsa tyres. The wheel's core is thin ply and I've turned the tyres to shape on a drill. Then I removed the middles and fleshed out the rims with some plasticard rings cut with a circle cutter. I've just fixed each wheel into its own jig as shown, ready to thread the spokes through next.
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Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
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« Reply #24 on: September 02, 2018, 12:46:57 PM »

This is interesting! Smiley Smiley
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