Guillow's PBY-5 Catalina Conversion - RC Groups
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Sep 05, 2006, 11:01 AM
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Smokin' Beaver's Avatar

Guillow's PBY-5 Catalina Conversion

A few years back when I knew a lot less, I bought this kit with the intention of running it on DC brushed motors, NiCd cells and flying it off water.

Anyway, thankfully I took stock of my knowledge, put her aside and decided to learn to fly first.
I'm glad now that I had that sudden fit of rational thinking.
This old girl has since sat around in the living room/shed/garage/studio collecting dust, patiently waiting her turn in the queue and has been the subject of many a conversation over a beer or three with friends.

Finally, it is her turn & this is her story...

Knowing then what I thought was sufficient to make her fly, I'd framed it up quite strong
I used all the Guillow's wood as it certainly looked hard and to be sure, I added a dirty great mainspar (1/2" x 3/16") made of Pine from tip to tip.
Added to that, what I wanted was good access to the battery bay so the centre sections needed to be ply for longevity.
Oh and I felt all the flying load forces would be at the very centre of the wing so that had to be double ply!
The mechanics of the tail section were theoretically simple - a bellcrank & conrods.
I had some old bellcranks from an old .40 size kit - "they'll do nicely" I thought get the gist of it, I had a fair re-work job on my hands when I called her up to the plate!

At the re-commencement of proceedings, I had nutted out my plan.
I couldn't afford to kit this plane out with top-shelf gear so I went with some cheap but proven equipment.

Span - 45"
Wing area - 306 sq in
AUFW ~ 29oz max. (26oz optimum) edit: Nov 2006 AUFW = 32oz = very good flying weight
Wing loading - 15.5 oz/sqft
Flying Controls - A/R/E/T
Ground/water controls - retractable tip floats, water rudder (future)
Total servo count = 5 x 9 gram micro's (GWS,TP & Waypoint)
Battery 3s 2200ma/hr 8C Lipo
ESC - Single Tower Pro 30 amp - happily runs 2 BP2408 motors in parrallel
Motors - 2 x BP2408-21 (rewound to 2408-8Y = 8 turns,1 wind of 0.63mm dia) = 2200 to 2500 rpm/volt
Props - Cox 5x3 3 blade. Each motor spins these @ 16k rpm for 12 amps, 10.8V @ WOT and 12oz static thrust.
Post maiden flight - these are great props for this kit but make sure you balance them.
The initial weigh in came to ~12 oz totally empty. Ouch - that was a fat cat in the making.
So out with the dremel (for 2 weeks) and I hogged out 3.5 ounces from the wing and another 1.8 from the fuselage.
Pics below show a few of the "before the diet" status.
I've finally learnt how to optimize pics before uploading so I don't have to wait all night (still on the dial up dinosaur line)
Last edited by Smokin' Beaver; Nov 17, 2006 at 08:00 AM. Reason: motor rewind data added & AUFW spec
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Sep 05, 2006, 11:59 AM
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Pilot44's Avatar
Looks good, always wondered how they would fly, I built this one before the Lipo thing. So, its flying now as much as it ever will.

Keep us posted on this one.

Sep 05, 2006, 01:25 PM
Lori, hey, you're home early
CarreraGTSCS's Avatar
Mike-- Are you using one or two ESC's? Very nice looking project.
Sep 05, 2006, 05:02 PM
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Nice Pilot44. This one's ready, if I had the nerve. See you started a thread now Smokin Beaver. Keep 'er going.

Sep 05, 2006, 05:20 PM
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Pilot44's Avatar
Originally Posted by scratchandbash
Nice Pilot44. This one's ready, if I had the nerve. See you started a thread now Smokin Beaver. Keep 'er going.

Whoa, awesome. good luck mate.

She is a beauty...

Jim G
Sep 05, 2006, 07:00 PM
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Cheers guys, they are both museum jobs!
I hoped this thread would bring some out of the woodwork.
The only one I've heard of that has actually flown is by St Martin.
Steve had a twin gas powered one that flew. (diesleized cox motors).
Bill, I wouldn't blame you mate if you left it grounded. So much work is hard to throw into the air to simply answer a "what if?" question.
My mindset has always been to see it fly. If it fails - ah well, I'll still have the plans and I can build a new one with all my newfound knowledge, share it here and see others enjoy building & flying a Catalina.
imo it is a worthy subject. If the 1:1 plane was so good, why can't a model be half as well behaved?

Sep 05, 2006, 07:43 PM
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Rekitter's Avatar
Thanks for starting a thread on this Phil. Your PBY looks great. Seems like it ought to fly with your specs. Keep posting your progress. Alex
Sep 05, 2006, 09:15 PM
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Originally Posted by CarreraGTSCS
Mike-- Are you using one or two ESC's? Very nice looking project.
Hi Mike,
I'm using a single 30 amp Tower pro ESC. I've actually bench tested it on the two motors and it worked very well.

Originally Posted by Rekitter
Thanks for starting a thread on this Phil. Your PBY looks great. Seems like it ought to fly with your specs. Keep posting your progress. Alex
Cheers Alex, I've got plenty more pics to upload.
At present I have the wing 85% finished - just the cowlings to sort out and final L/E , T/E & aileron sanding.
The washout is done & I'm really happy with that part.
It just looks 'right' if you know what I mean?
My biggest concern is water landing as that is where we slow down the most & stalling is possible so I've given that highest consideration.
Having enough power to pull it out of the water by it's whiskers is all well & good but worth nothing if it is unstable at landing speed.

Sep 06, 2006, 06:26 AM
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After the carve-up

Last of the 'before' pics shows the tail section before & after.
As I wanted to conceal the rods & linkages, I decided to stick with the symmetrical chord shape of the vertical fin.
Had I added a flat plate horiz stab, it would have looked a touch 'wrong', so I stayed again with the Guillow's form.
To be honest - that design for a static model is crazy to say the least. A hell of a lot of work to build up.
Guillow's could have designed that a dozen other ways that would have been easier, but hey it was already built so press on.
Sure was ugly.
So the best medicine for ugliness? - cosmetics.
I sheeted the lot.
The whole empennage came out at 1.8 oz which was heavy but was aerodynamically more useful than open frame and I got some extra area into the deal.
I can live with that.

The fuze was tricky to sheet but enjoyable. As each plate went on I got more enthusiastic. All tail & fuze sheeting is 0.8mm

Other pics here show the wing/fuze joint - pretty big space to get the battery in and it allows forward placement right up to the nose for CG trials.
The grey nosecone is actually papier mache` about 1/8" thick, it will be filled with spray-in foam to dingproof/waterproof it.

The waterproof method for this opening will be an inner flange & watershed.
Difficult to explain but will work fine for normal water operations.
Pics will help explain that when I get to it.
It won't withstand a >5 second submersion but then again if that were to happen it would probably be the least of my worries.

Sep 06, 2006, 09:49 AM
Lori, hey, you're home early
CarreraGTSCS's Avatar
Phil-- You make Guillows look good! Too bad you'll wind up painting it in the end as it would look great stained and sealed like the old wooden boats. Have you decided on a color scheme yet? Lots of options I would imagine.

As an aside, years ago I read a book called "Black Cats and Dumbos" dealing with the exploits of these lumbering beasts of the air. An easy and very interesting read if you can find it.

Sep 06, 2006, 07:48 PM
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Rekitter's Avatar
Wow Phil, very clever and extensive remodel job you are doing. It is really looking good. I have a grumman mallard seaplane that is a bit bigger, but around this same wingloading and it flies well and is pretty easy to land... though you have to be very level or you will catch a tip. The good thing about landing on water is that the water can be very forgiving to a minor crashes. I found that I really needed to add a water rudder or I was heading out in a canoe to retrive it after every landing. Anyway, keep posting your progress. I am sure this is one of the most challenging guillows conversions!


Sep 06, 2006, 08:01 PM
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Smokin' Beaver that's almost exactly what I did for the elevator. The rudder pushrod exit is high enough I'm not worried about water getting into it.
Color scheme? You're going Aussie like mine, right. That way you can whack off the gun bay post war, for the batt hatch.
The foam is a good idea. I spent a considerable time with those plastic wing tower parts. Darn, this is getting tough typing with a band aid on my index finger tip.
I have a tube that goes across the wheel bay openings, that my plug-in gear goes into. It also serves as a servo tray support. I see that area is still open on yours.

Sep 06, 2006, 09:12 PM
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Cheers guys,
I haven't decided on paint yet. I'll go to the lake & see what colours work for my eyes I think.
I have a feeling a very light colour will work best for me so I can keep orientation.

I just have a love affair with Guillow's kits I guess.
Making a Guillow's kit actually fly is a boyhood dream and I get to fulfill that dream every time I maiden one and then again every time I fly it.

I'll take your advice & plan a water rudder now before I get too far. I'd been toying with the idea of a magnetically coupled device to avoid hull penetrations.
I still have reasonable access to the rear hull.

I was also looking for a solution on the wheels but decided to go a straight PBY5 just to minimize the work.
I want to fly off grass at my park for first shakedown/trimming flights and was thinking of either a dolly or permanently installing a brass tube across the hull & using those horrible GWS 3" parkflyer wheels on a carbon rod axle.
With my access hatch, these could be retro'd later.
Do you have any more pics of that section in yours?
The nose wheel is thought provoking. I still have links to the threads where we discussed the Catalina before so will revist them on this one.

Last edited by Smokin' Beaver; Sep 06, 2006 at 09:20 PM.
Sep 07, 2006, 11:28 PM
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motor/prop setup

Here's a pic of one of the motors.
I took a stock BP2408-21, stripped it out & wound on 8 turns per pole of 0.63mm diameter enamelled wire.
Connected in star.
It really cranks with the Cox prop on and is quiet.
The APC 5x5 I also tried made a hell of a racket at those high rpm and thrust was less too. (not surprising though on a static test).
Balance is just not an issue at 16 000 rpm, they ran very smoothly.
Later I realized that I'd forgotten to put in the shaft retainer circlip on the back of one of the motors. (lucky the rear bearing didn't decide to depart the casing!)
That would be interesting at 16k rpm.
For that reason I always have done & always will wear safety glasses when engine testing.
I have an MS excell graph of the recording I'll post if I can find it again.
Looks to me (athough I'm no expert) around 7 amps @ 10 000 rpm for 10 oz of thrust is optimum.

Sep 08, 2006, 04:06 PM
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Pilot44's Avatar
Yepper, lookin good,


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