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Feb 21, 2016, 06:44 PM
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Build Log

57" PBY-5a Catalina - Dollar Tree Foam Flying Boat - Giant Scale Version Pg 6


ETA: Maiden of Prototype Up

PBY Catalina Maiden 4/3/16 (6 min 50 sec)



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I've had this in mind ever since I saw that Flitetest may be coming out with waterproof foamboard. If that actually happens, it'l be great, however, in the meantime I think this can be easily done with dollar tree foam with some simple waterproofing methods. The scale floats I designed for a 42" A6M Zero have done an excellent job of keeping the water out.

Since I'm still watching paint dry on some of my other builds I started on this.









The wingspan is 57 inches. Smallest you can go and have 6" props not fighting each other and make the power pod setup work.. It will be powered by 2 250 quad size motors. Something like a 25 gram 2204 2300 kv brushless.

If all goes as planned, this won't be a difficult build, you'll just need to take your time on the parts that need to be sealed. Flight characteristics should be very gentle. With anticipated wing loading, this should fly like a high wing trainer, which will be great for learning how to land and take off from water.

This plane should be able to take off and land from water, grass, snow, then with the addition of wheels, dirt and pavement. Truly all terrain. I'm also hoping it will be able to carry significant payload, which will be great for simulated bombing runs / candy drops etc...

I'm still playing with fuselage designs, and haven't yet decided if I want the wing to be easily removable or not. Here's a preview of where I'm at:



Lower half of Hull, this will be completely sealed:





Tail section will glue to the top/back of this, and there will be formers and such for the top half of the fuse. I plan on making the printable clear canopies and weapon blisters like usual.



Messing with tail designs. Think I'm going to use the one from WWII with the split elevator.



Wing prototype (Final will have cutouts for the power pods and cowls):





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Most Recent Beta Plans:


Mighty Mini PBY Catalina Beta v.2 - Tiled

Mighty Mini PBY Catalina Beta v.2 - Full
Last edited by localfiend; Sep 09, 2016 at 11:59 AM.
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Feb 21, 2016, 09:18 PM
Free Sarcasm!
Nice! I was thinking about doing this for my next plane, not sure how to do the fuselage but it looks like you have it all figured out. The PBY is a great plane.
Feb 21, 2016, 10:00 PM
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Quote:
Originally Posted by Decroxx
Nice! I was thinking about doing this for my next plane, not sure how to do the fuselage but it looks like you have it all figured out. The PBY is a great plane.
Yeah, the fuselage has a lot of weird lines. I'm still working out the details but I think It's going pretty well so far. It's hard to balance ease of assembly with looks.




Been keeping a build log as I test fit parts. Hopefully what I've done so far won't change too much, so I'm uploading pics of the build.

Everything I'm showing here is without packing tape as I plan to try and seal the lower hull using only water based Min Wax Polycrylic. Polycrylic is great, and hot glue still sticks to it.

If you don't want to use minwax, then the packing tape method can be used (worked great on my A6M Zero Floats). It's easiest to cover one side of a piece of foamboard entirely with a layer of tape. When your foamboard is taped, you can then cut out your parts. Doing it this way makes the build very clean looking, and does an excellent job of keeping out the water if you seal all edges well with hot glue.

Ok...

Remove all the paper as called for on the plans, make your bevel cuts, then glue in the bottom former:




Pre-bend the bottom plates on the lower hull:



The foam should compress nicely:



This is a pretty standard B fold like you would do on most fuselages, it's just not 90 degrees. Add glue and fold the sides up against the former angle one side at a time.



Use tape to hold the side plates in place:





A little bit at a time is easiest.





Do both sides, then go ahead and attach the little rear pieces with some tape as well.



Now start joining the bottom pieces of the hull the same way you did the sides:



When you're done this is what it will look like from the back. There will be a gap.



The next bottom piece will fit into that gap (the finalized piece won't have quite so much extra paper around the edges....

You might not be able to see it, but I went of the edge that fits into the gap with a marker to flatten it a bit.



Stuck in the slot:



View from the bottom:



Glued in place and excess paper trimmed off:



Side View:



Weight check:



Not too bad. That's as far as I've gotten. Gonna go test fit the next bottom pieces and get to work on the tail.
Feb 22, 2016, 08:00 AM
Allways the hard way!
georgy's Avatar
Watching with interest.. any-one that builds this bird and gets even half those funky compound curves right has my admiration!!
Feb 22, 2016, 11:41 AM
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Feb 22, 2016, 10:11 PM
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Quote:
Originally Posted by georgy
Watching with interest.. any-one that builds this bird and gets even half those funky compound curves right has my admiration!!
Yeah, the compound curves have been a bit of a pain. Certainly more complicated to design than anything else I've attempted so far.

These last few parts have been a pain. Got lucky up until this point, most of my first drawings for the fuse just worked. Think I've got them figured out now though and the lower hull section shouldn't be too hard to put together. I took a bunch of time making sure stuff was repeatable and will go together well even if your cuts aren't perfect.


Ok, so here's the other bottom hull piece. Ignore the massive excess paper. I wanted to try something that really didn't work out. The lightening section you cut out of it also doubles as the angle gauge.



Once you have the angle glued it will slide right into here:





You can see how it's kinda ugly on the sides in the back there. I tried using all that excess paper to cover over everything, but it was too crinkly. So I cut most of the excess paper off and just folded over enough to protect the edge of the plate.



Here's the nose plate of the hull. In the future, this will be attached to the fuse rather than a separate piece to cut out. That will be one less seam and should make it easier to assemble. Note the light beveling on the arrowhead looking section. Not really needed but it makes the fit very clean.



Start by gluing down the main back section:



Then go a little at a time until you're done. No need to be sparing with the glue here. You want this to be sealed.



Fold over the excess paper and glue it down. I like to go back over everything with some tape.





I'm starting the drawings for the tail section now.
Feb 23, 2016, 03:12 PM
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This looks too cool, I'll be waiting anxiously for the plans!
Feb 23, 2016, 06:02 PM
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Quote:
Originally Posted by JustFrost
This looks too cool, I'll be waiting anxiously for the plans!
Hopefully it won't take me too long. I'm abandoning the current fuse design for one where the bottom fuse and the tail are combined rather than separate.

Having the tail section separate was going to introduce strength issues, and I have a way of making the tail section simpler if the two are combined. Most of the parts will remain as they are, though I have changed a couple lines to make things a bit more scale looking.

The old lower hull/fuse will be used for waterproofing tests. I've put on a coat of Water Based Minwax Polycrylic. I'll spray paint over the top of that this evening sometime then see how it does sitting in a bathtub overnight.

Feb 23, 2016, 08:46 PM
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Getting started on cutting parts now. Here's what the new lines look like:



Nose shape has been improved. I also reduced the angle of the front center ridge as it was too sharp, and added the extended tail sections. The wing mount drawing is there as well, along with a stronger vertical stab/rudder design.
Feb 24, 2016, 03:21 AM
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Well, I got distracted with work stuff and only had about an hour and a half to work this evening. Got the new fuse design mostly done though. It went together very smoothly and is starting to look like a PBY now.

New Fuse Section:



Tail:






Curve along the front side of the nose looks much better now, and it's just as easy to assemble as it was before. I think I've captured most of main lines of the plane, it's very scale. At least for the bottom.






I think this tail design will be quite strong with the angled bottom plate. I'm considering lengthening the bottom section of the vertical stabilizer up further towards the front of the plane. That will make it act like a spar. Might add a couple doublers to either side of the stab as well. Or maybe do some sort of box spar. If I do that, It will be very tough to hurt the tail.

I don't think weight is going to be an issue. Even with all the hot glue I'm using to seal stuff, that entire assembly pictured above only weighs 61 grams!
Feb 24, 2016, 03:15 PM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
I'll have to keep an eye on this one. I've been wanting to do a boat plane for a while now since there is a river right next to my work, be nice to have something to do during lunch
Feb 24, 2016, 05:24 PM
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Looks great. The more scale the better
Feb 24, 2016, 06:41 PM
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Really excited to see how these plans turn out. PBY has always been on of my favorites.
You seem to have the hull really well nailed down.
Feb 24, 2016, 07:09 PM
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Quote:
Originally Posted by OutcastZeroOne
I'll have to keep an eye on this one. I've been wanting to do a boat plane for a while now since there is a river right next to my work, be nice to have something to do during lunch
Heh. I've got a few "lunch" planes that take turns riding around with me.

Quote:
Originally Posted by JustFrost
Looks great. The more scale the better
I'm going to try and make it as scale as possible with dollar tree foam (or depron, which should work just as well). Just a juggling act of ease of build and looks. If the upper structure isn't too complex I'm estimating total build time for one of these to be 4-5 hours if you're going to paint. Faster if it will be a land beast.

Faster still if you're used to DTF construction. If you're experience build time is probably 3 hours

Quote:
Originally Posted by get_out_and_push
Really excited to see how these plans turn out. PBY has always been on of my favorites.
You seem to have the hull really well nailed down.
Thanks. I'm quite pleased with how things are going so far.




Paint is dried on the old test fuse section:





I don't think there will be any problems. Should be quite waterproof after a coat of polycrylic and a coat of paint.

Any floatplane experts out there?

I'm wondering about a few things. Can a float plane be too light to be stable on water? Any thoughts on wingtip float heights? Are the wingtip floats just supposed to sorta bounce off the surface of the water if your plane tips to either side? I'd imagine the lighter the plane, the easier it is to catch an edge.
Feb 24, 2016, 07:34 PM
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On the Catalina the tip floats are primarily for stability when taxiing and shouldn't touch water when taking off, however they are angled very slightly up so as they wont dig in


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