Curtiss America

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Re: Curtiss America

Postby BillG » Mon Aug 30, 2010 2:01 am

Hello Roy,
The props are heavily poly coated, which should help, although I'm not sure how well it will fully waterproof. I strip/reshape the Zingers a bit, and then recoat with poly, which is also used in the balancing process. Some of these props are horrifically out of balance, off the shelf. Of the various design types, I'm optimistic that this plane will not have spray issues, as it is always a concern. I've watched a number of videos of seaplanes that do not perform well in scale, due to that problem.
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Re: Curtiss America

Postby BillG » Sat Sep 04, 2010 3:25 am

Started assembling this plane, which will be more work than some entire builds that I've done. I had the tail control cables separated to exit the fuse without twisting over one another, but that did not last for long. After making the cable exit block which mounts on the rear fuse, I had the exiting task of separating all the cables, such that none were twisted, and then routing them through the block.

The Curtiss graphic was screen copied from a photo of the tail, rescaled, and printed. The paper was then smeared with gold paint, which applied thin enough to still be able to see the perimeter of the script letters. The paper decals were then laminated with 3M clear tape, and carefully cut out with an exacto knife. 3M contact spray was used to heavily coat the rear of the decals, for application to the tail.

Added stringers routing from the double laminated engine mount wing former to the inner former, so that the covering does not warp the inner former, when shrunk. This corrects a minor previous oversight.
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Hand cut clear laminated printed paper decals.
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Working on setting up the pull-pull linkages, where the rudder is now functional and working well. I abandoned the idea of adjustable front horizontal stabilizer struts, but they could easily be changed to adjust the incidence, if needed.
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Window glass installed. First a well fitting paper template was made, which was then clear taped to clear sheet plastic, and then cut out with an exacto knife.
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Cable guides on elevator installed to resemble the full scale plane. All tail controls are working well now, if not the best of any tail pull-pull I've done as of yet.
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Routed the servo extensions between the extended floor board and the cabin wall, and then under the front servo framer. This was not a particularly fun time, but they are well routed away from the linkages.
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Magnetic cabin floor access door covers the receiver bay. Grab the strut attached to the cover with your fingers to lift it out.
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The daily hangup:
The engine output shaft extensions were not 100% scale, which really didn't concern me. When I realized that the engines would not mount as intended, and allow the props clear the top wing cutout, then it did concern me. This called for shaft extensions. I took the prop bullet nuts that were included with the motors, and drilled through them, with a drill bit that just fit inside the threads, and then ran a thread tap completely through the bullets. Shaft extensions were then added to the bullets, using threadlock. The entire process was actually quite easy to do. I'll likely build up the outside of the bullets with plastic tubing, to resemble the drum like output shafts on the real engines.
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Re: Curtiss America

Postby BillG » Sun Sep 05, 2010 10:33 pm

Finally got to complete the less than ideal harness assembly procedure, which I had discussed before. :shock: With the servo extension connectors, sheer number of wires, and thin wings, it would have been difficult to snake the harness through the wings, after assembly. This created the lovely task of routing the harnessing through the bottom wing, with the top wing and motors hanging from the bottom wing, and then covering/painting the inner portion of the wing. With that now complete, I can move on to assembling the struts, motors, top wing, and flying wires.

It's always a good thing to test your gear, before closing up an area. I had a little scare when testing the motors, when one would stutter and not start. The motor had ran just fine the other day. The problem came from using an older battery which has been retired to test duty, and was at the low end of it's acceptable minimum cell voltage, due to not being charged in a good while. This was causing one of the ESCs to go into LVC. Along the lines of ESCs, I'll likely use a switching UBEC inside the fuse. I have never had issues with 4 low draw sub-micro servos overloading a well cooled linear BEC, but I started thinking about another issue: If the ESC gets wet and the BEC quits, then you still have a controllable glider, with a working UBEC. As for the servos, there is a reason I am a fan of GWS, Hitec, and Dymond sub micro servos, versus the nearly free Hobby King servos:
http://homepages.paradise.net.nz/bhabbott/Servo.html

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The small "line" across the nose that looks like a crease, is actually a reflection from the window glass. I had to run downstairs and make sure that it hadn't been from damage. :lol:
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Last edited by BillG on Wed Sep 08, 2010 3:07 am, edited 1 time in total.
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Re: Curtiss America

Postby TASSE » Mon Sep 06, 2010 12:58 am

Hi Will, thanks for the link, i always use Hitec so the link makes me feel comfortable.

Roy.
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Re: Curtiss America

Postby BillG » Wed Sep 08, 2010 3:04 am

TASSE wrote:Hi Will, thanks for the link, i always use Hitec so the link makes me feel comfortable.

Roy.
That's what I should always use, if it wasn't for the cost, but that's no excuse. The HS55 seems to be the only sub-micro with a geartrain so smooth, that it can be easily turned from the servo horn (although not recommended). You don't hear about them failing often, if ever at all. I have Picos on everything but the elevator on this plane, where the elevator is an HS55, as it will likely be the most heavily loaded surface. For whatever reason, I once tried 3 of the cheap Hobby King Hextronix servos that folks say are the "same thing" :D as an HS55. With one out of 3 not passing my test of 10 cycles, I don't believe they are the same thing. I've also read about brown outs with 5 sub micro servos, where I'm convinced that the additional draw of the cheaper HXT or other high draw servos may have been what pushed the linear BEC over the edge. The only linear BEC I've ever shut down was with a poorly cooled ESC installed in the fuse of an EDF, with a combination of 5 sub micro Pico and HS55 servos. On this plane, I still installed a Dimension Engineering Park switching UBEC, just to be safe.


The flying wires will be used to set/hold the wings straight, but you still want to start with the IP struts mounted as straight as possible. The basswood strut corners were rounded, then stained oak color, and poly coated. The top wing has enough flex to allow the center struts to be installed at a later time.
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Really starting to see the finished result now.
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Re: Curtiss America

Postby BillG » Sat Sep 11, 2010 12:15 pm

Roy, thanks for the Sea Lion diagram.

On the America, it's all downhill from here, after mostly completing the motor mounting. I also bought more of the thin nylon coated braided steel rigging wire, as the 30 foot roll from the LHS that I have will not be enough, and who knows when they will reorder items such as it. Dubro 2-56 wire is good for robust control wire, but is heavier that what I care to use for rigging. The 2-56 also requires larger crimps, which are a bit unsightly for a model this size. The coated wire I have for rigging is .3 and .4mm and is sold as jewelery beading wire.


The motor mounting assembly would have likely been done 50 different ways, by 50 different people. There's more to it than appears, as I had to think through the assembly procedure to make sure that I wouldn't "paint myself into a corner". The motor's are potentially removable, although I sure hope that I never have to. Some rigging would almost certainly have to be cut away, which will make it practical to clamp off the rigging in sections, which also will be done for more precise setting of the wings.


The outer motor mounts are first installed to the IP struts with screws, and the inner will next be installed using tubing, which will replicate the center bar reinforcers. The tape is used to prevent the black painted wires from scuffing against the IP struts. Not much of a worry though, as a bit will look like weathering and grease from the mechanics.
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Motor mouting interplane strut diagram.
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The center bar sections will be installed over the tubing pins, and the pins (pointer) will be pushed into the center bar, with rigging brackets first in place over the pins. All will be CA'd together.
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Re: Curtiss America

Postby TASSE » Sat Sep 11, 2010 4:26 pm

Hi Will, transfers are easy these days. I go to a company that makes plastic lettering for commercial vehicles. All you need to give them is a coloured copy of what you want and they can scale it and print as many as you want. Quite cheap too.

Roy.
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Re: Curtiss America

Postby BillG » Wed Sep 15, 2010 5:02 am

Hello Roy. I used to do the graphics work for a small power inverter company, and sent prints off to a place like that to have their labels made. It's not near where I live now, but I'm sure there are places around that I could find. I hope that someday soon we will be able to inexpensively buy equipment like that, to use at home. Not far off, considering that a printer/scanner/copier at home would have been a dream, even when I was a kid.

At this point I can pretty much list the specs accurately, which are 32oz AUW, 105W/lb, and 8.7oz/sq-ft wing loading, which is my lightest wing loading to date. About the only change in plans is that I will now use a 3s-1800, instead of a 3s-1345. With the 1800, I will not only have better flight time, but only needed 14gms of nose lead to balance at 25% center chord. I could have come in overall a hair lighter with the 1345, as the heavier 1800 battery is not as efficient at setting CG as adding ballast placed clear in the front, with the lighter battery. On the other hand however, I barely had room for the lead that I added with the 1800, and would have needed a bit more lead with the 1343 to set the CG, so for the slight addition in overall weight I'll go with the higher capacity battery.

Black tank made from rolled thin sheet plastic, with balsa plugs in the ends. Light weight scale hosing is made by pulling wire from the inside of wire lengths, and then using the sheathing.
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The engines now have carburetors with fuel lines attached. The only remaining part to make is the wind driven generator. The rads are temporarily tilted forward, as it makes rigging easier.
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Re: Curtiss America

Postby TASSE » Wed Sep 15, 2010 3:43 pm

Hi Will, you have got so much fine detail into it that one would think that it was twice the size that it is - congrats.

Roy.
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Re: Curtiss America

Postby BillG » Sat Sep 18, 2010 5:02 pm

Thanks for the comment Roy.
It probably is my most detailed model as of yet, although I don't miss not having to fabricate 2 Vickers guns for it. :D

Still plugging away at rigging, but getting closer to completion. There's always yet another rigging bracket to be fabbed, such as the rudder bracing cable brackets which were made last night. Other than a few lower wing-fuse bracing struts, I finally made the last part (or so I think) last night, which is the wind driven generator. I'm not sure if these were used for electrical generation, or to drive a speedometer, which would likely be essentially a calibrated voltmeter. I'll have to look that one up. Either way, the little prop should spin in the wind, as it spins freely.
Attached Thumbnails

Small "wooden" prop made from GWS 3020 prop, painted brown with black rubbed in. I had to add globs of CA to the center hub and sculpt, to make the hub area look correct. Probably easier to just carve/shape from wood.
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...and the real thing from Seawings UK
I got the prop bolt pattern 45 degrees off, but close enough.
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