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Old Jul 15, 2012, 07:34 AM
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Build Log
Peter Rake's 43' LWS Cato Butterfly

The first time I saw Paul Matts Drawing of the LWS Cato Butterfly I fell in love with the design. I like planes with unusual proportions, when certain dimensions and details seem somewhat off and nevertheless everything comes naturally together, giving it a lot of character. That is certainly the case with the Butterfly; the wing has an incredible cord, with ailerons sticking out even further, and the stubbiness of the wings is in strong contrast to the elegant streamlined fuselage. Not only that wings and fuselage seem so different in character, they are also merely stuck together, without any fairing or mediating element which would confirm that they actually belong together. Then there are these huge wheels, and the motor with cylinders just sticking out into the open...

I have not found much information about the Butterfly. Apparently it was a one-off built in 1920 as a sporting plane (great time, the Twenties) derived from a similar parasol plane. It was designed by J.F. Cato, including the engine. The plywood monocoque fuselage must have been state of the art of the time. It is an equivalent of today’s Ultralight planes. There are a couple of photos floating around the web, that is about all I could find.

In terms of models there is a drawing for a rubber powered peanut model from Samsmodels. It seems the Cato has rarely been modeled (which also makes it more enticing) and so I was really glad that Peter Rake agreed to draw up a plan for it. Once he was done Manzano prepared a laser kit for me, which I found at my return from our annual Europe vacation; ready to go...
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Old Jul 16, 2012, 08:44 PM
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Usually I start a model with the fuselage, however for the Butterfly my immediate instinct was to go for the wings; they seem quite simple while the fuselage is more complex. Going through Manzano’s parts, I realize I would not want to undertake this build without the laser cut parts. There are many plywood parts with numerous holes and Peter seems to base his designs more and more on the precision of the laser cutter. My Eastbourne was still easy to do without parts, the Rumpler Taube would have been hell and it is the same for the Butterfly.

Anyway, I started with the left wing, which was quickly assembled. I left out the ailerons, as they did not fit anymore on my building board…I never before build a wing with such a long chord!

I am glad Peter made the wings removable on this design. Not that I will take it apart for the way to the field, but I realized the hard way (with my Eastbourne and Nieuport) that one-piece models are hard to repair after a crash.
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Old Jul 17, 2012, 04:39 AM
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Ulrich,
I was just wondering what happened to this one and then saw your first post.
The best way around the one-piece model problem is, of course, not to crash them.

That's the thing with CAD, it is so precise that you are inclined to get carried away with intricately fitting parts. However, since publishers always list laser cut parts these days, it isn't such a huge issue. If someone desperately wanted to cut their own parts, there's nothing that can't be cut, given the correct tools.

Pete
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Old Jul 19, 2012, 07:42 AM
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Old Jul 21, 2012, 03:00 AM
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The fuselage is under way, starting with the crutches, than formers and longerons, all nicely laser cut already. The cutouts in the formers for the central 'spine' seem a bit loose. The former F7B is 5mm too high, which I realised only after gluing it in. So just cut out 5mm strips in the two paralles verical sections and stuck it on again, after that everything fits. The BT plywood plate was badly warped. I clamped with opposite warp for some time and than again flat. First it stayed flat after releasing, but after gluing everything together I noticed a very slight tendancy to warp the crutch frame. I hope I won't end up building in warp in the fuselage..

When adding the formers F3 and F5 one has to be careful to put them in in correct orientation, tubes for gear and wing attachment on correct side according to sideview. In particular since the tubes are on the front side fo the former for the bottom half, and on the rear of the formers for the top half. Otherwise the wings might not mount when finished.

It's great that there are already cutouts for servos and cooling holes in the battery compartment. However I wonder whether I should cut a hole in the bulkhead to stick in the ESC from the front, rather than putting it behind the battery. Considering the short nose, probably everything should go as far forward as possible CG-wise. I should be clear about the installation before sheeting, as access isn't that easy after that anymore.

After completing the two half frames, I wonder, should I glue them together as they are or sheet (partially?) first in order to make them more rigid?
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Old Jul 21, 2012, 04:43 AM
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nice job mate, very intersting looking plane! Pete, these shell types fuselages will develop into a habit at the rate you are designing them

Cheers
Craig
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Old Jul 21, 2012, 04:50 PM
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Craig,
Not If I can help it mate.

Ulrich,
What were you going to cut a hole in for the ESC. That and the receiver can be mounted above the battery plate if you like, installed before the shells are joined.
My idea with these types is to do as much sheeting as possible while the keel assemblies are still pinned to the board. That way you don't warp anything during the sheeting process and it may even help to solve your warped battery tray problem.
Once the shells are sheeted, you can do as much of the installation as you like before joining them. Plenty of access that way. Yes, it will mean certain items are in there for the life of the model, but as long as you use reliable equipment and don't overload anything that shouldn't be a problem.

I've altered that former on both plan and cut file. Havent a clue how it happened, but it's fixed now.
I don't really know why the top and bottom keels should be loose, there can only be around 0.001 - 0.002" of play, depending on cutting losses. It isn't an issue anyway since they are really only there to assist with getting the formers upright. On my files the slots are 0.121" and the ply keels should (and I emphasise SHOULD) be 0.12".

Pete
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Old Jul 24, 2012, 01:05 AM
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Thank you Pete,

so I will get going on the sheeting, agree that will give me more confidence that the two halves are strong enough not to get warped during their mating.
This means I will have to decide whether to use 1/16 thickness sheet material or 3/32 and sand it down, since these two options are mentioned in the plan. I think I prefer the thinner material. If I use the thicker balsa and sand it I will have no reference of how thin I sand down to and might get weak spots. If I use the thinner material I will have to avoid sending much into the wood and use putty to get a smooth surface. I have done so on my (still incomplete) Lockheed Vega, and it helped also to fill the balsa grain before painting.

For the Cato I am still not decided how I finish it. To reduce labor, it would be good to use iron-on foil. However glossy silver Monokote could look a bit synthetic for this plane, and I have some trouble ironing on spherical fuselages. Or should I paint the fuselage and use iron on for the wings? In this case the color won’t match unless I use transparent foil and paint it as well? Finishes are not my forte.

Yes, I will insert the gear before closing the fuselage. I might have to go to the hobby shop to get a trustworthy ESC (25A), rather than putting in one of the Hong Kong components I have already. One of these ESCs abandoned me during takeoff of my Nieuport, which led to a 3 months intermission of flying it.

Concerning the keel, the plywood I got is 0.11”, so that explains the free play. I used thick Elmers, which fills the gaps.
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Old Jul 24, 2012, 01:18 AM
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You could use polyspan on the fuselage, it is nice and light, locks down well on planked and sheeted surfaces after shrinking and doping, adds a lot of strength, and takes paint very well. it worked really nicely on my Pfalz fuse which is similar in construction. The wings could be done with the same, or litespan which requires less finishing, and also paints well.

Craig
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Old Jul 30, 2012, 05:37 AM
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Thank you, Craig. I checked out your Pfalz, beautiful! I just wonder where I can get polyspan and litespan. If you have any good mailorder sources, please let me know. I have used Ecolite from Graupner on my Nieuport 11 and Taube, that worked well. I wonder whether it is the same than Litespan; it came also with a gluepot similar to Balsaloc. I still have some cream colour left, perhaps I can use that and paint over, or I wait until my next trip to Germany to get a roll of silver.

For the fuse, I was wondering whether I could do away with any covering and just seal the wood with epoxy or polyester, and apply the primer and putty over that. When I did my Lockheed Vega the main problem was that the balsa kept soaking up the primer, until I got a smooth surface after many layers. However the sheeting appears strong enough without cover (haven't flown this project so far though, I don't know how it will resist real operations). So with that experience I was wondering about a sealing layer before finishing the wood without cover.

The weekend brought more progress to the fuselage, with parts of the sheeting done and the assembly of upper and lower half.
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Old Jul 30, 2012, 09:59 AM
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I would be tempted to be "old school" and dope on some tissue or silkspan to prep the surface for whatever painting you'd want to do. While I've used Litespan/Coverlite on more than one model, I'd be uncomfortable using it on such a fuselage as this...

James
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Old Jul 30, 2012, 10:27 AM
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looking great bud. if you do decide to go the polyspan route the best place i have found for both it, and litespan is

http://www.a2zcorp.us/store/category.asp?Cguid={FD3F1D5A-2F40-41A2-B176-4547219B3607}&Category=BuildingMaterials:Covering

as to leaving it uncovered and just sealing and painting, i couldn't say mate, never tried it.

Cheers
Craig
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Old Aug 01, 2012, 11:39 PM
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Thank you, Craig, that is very helpful, I will order there and give polyspan a try. With that I will have to worry less about sanding too deep. Do you putty up the shape before applying the polyspan or do you apply it directly to the wood?

I found a mention in Flight about the Cato Butterfly, seems it was exhibited in 1920 at a show in New York. There should be photos of that? Does anybody have other pictures of this plane?
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Old Aug 02, 2012, 12:24 AM
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Mate I used automotive spray putty on the bare fuse and then sanded 90% of it out, then covered it. Just remember the better the finish of the fuse the better it will look after covering, polyspan hides nothing

Craig
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