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Author Topic: Kitbashing Chinese  (Read 1437 times)
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Iskandar Taib
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« on: February 18, 2018, 02:17:55 AM »

I've always enjoyed simple stick models such as the old North Pacific Star Flyer and Sleek Streek. I've scratch-built many over the years, mainly using 1/32" sheet balsa for wings and getting prop assemblies from SIG and Peck Polymers. Lately I've been modifying Chinese ones I've been buying off AliExpress. The ones in the photos here have sheet foam wings, come in plastic bags, have a projected wingspan of about 15 inches, come with a 5 inch plastic prop, and easily fly two minutes indoors on a loop of 1/16" Tan Super Sport. Built stock, they go together with pieces of double sided tape and a rubber band, and weigh about 11 grams. Modified, I get them down to about 6 1/2 grams, after discarding the plastic bits and substituting a balsa motor stick.

I've been ordering them here:

https://www.aliexpress.com/item/5Pcs-Flying-Glider-Planes-Model-Toys-Rubber-Band-Childrens-Kids-Gift-Toy-Airplane-Birthday-Christmas-Gift/32832980970.html

At $3.67 for five pieces, they come to 73.4 cents each - shipping included! (They do take about 3 weeks to arrive, though the latest shipment came in nine days, an AliExpress record.) Aside from the very satisfying performance, the other reason for building these things is that you don't care when they get hung up or are otherwise lost, since they cost little and take about 30 minutes to assemble. (Where we fly, we've got a very nice 65 foot ceiling, but there are ledges around the sides that have claimed models in the past.) I've built maybe half a dozen, they're very easy to trim, and very importantly, keep their trim from weekend to weekend. Just attach the wing, wind, and fly. (For all that, I've only only lost one so far, a couple nights ago.) I record long flights on the wings with a marker pen.

Will post more about these in the coming days.

Iskandar
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« Reply #1 on: February 18, 2018, 06:19:44 AM »

They sound like they're good flyers,Iskander.Good price too.

Scott
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Iskandar Taib
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« Reply #2 on: February 19, 2018, 01:38:30 AM »

If you're going to buy stick models from AliExpress, stay away from these:

https://www.aliexpress.com/item/Rubber-Band-Aircraft-Children-Adult-Educational-Toy-Creative-DIY-Assembly-Model-Aircraft-Model-Fun-Toys/32828859087.html

https://ae01.alicdn.com/kf/HTB1AaNQSVXXXXbZXpXXq6xXFXXXl/Creative-DIY-Assembly-Model-Building-Kit-Children-Adult-Educational-Funny-Toy-Rubber-Band-Aircraft-1-Pcs.jpg

They're bigger (7 inch prop, perhaps 20 inch wingspan) but they have a pretty big flaw - the prop pitch is close to zero - or might even be negative - at the tips. You could probably fix them by trimming the last 1/2" off the prop tips, or repitching the tips (I tried hot water, didn't work very well).

The good ones are these:

https://ae01.alicdn.com/kf/HTB1TMuKi6uhSKJjSspmq6AQDpXai/5Pcs-Flying-Glider-Planes-Model-Toys-Rubber-Band-Childrens-Kids-Gift-Toy-Airplane-Birthday-Christmas-Gift.jpg

If you've never looked at AliExpress, it's very much like Amazon or Ebay - lots and lots of independent sellers using the platform. You'll find dozens of vendors selling these same airplanes. Prices for the "good" ones vary from 73 cents to over two dollars each. Some charge shipping, some don't, so caveat emptor. The packages have tracking numbers so they usually arrive just fine, but it takes a while. That link I posted on the first post is known to be reliable, I've ordered from them 3-4 times. Don't order more than five models at a time - order more and the software tacks on extra shipping. If you need more just make multiple orders of five. Aside from what we use them for they'd also make great party favors or a basis for a make-and-take event (you can easily get 45 seconds out of one built stock, with some hand-winding). Kind of reminds me of the time in the early 80s when I came across a dozen old Star Flyer kits on a peg in a K-Mart store on clearance, for 50 cents each. I bought all of them, of course. Can't have too many of these, either.

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Iskandar Taib
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« Reply #3 on: February 19, 2018, 07:10:00 AM »

This latest spate of building started when I came across the Paper Plate Challenge on endlesslift.com:

http://www.endlesslift.com/the-second-foam-plate-rubber-band-powered-airplane-contest-2017-2018/

and the Snowflake:

http://www.endlesslift.com/make-your-own-snowflake-a-rubber-band-powered-foam-plate-airplane/

Yes, I'm building and testing some models for this, more on that in a month or so.

But I've borrowed some of the techniques used on the Snowflake for this kitbash. I think 8-10 creases on the wing is a bit of overkill, for my 3 inch chord wing I've used only three creases, and since I'm reusing some of the templates and jigs I've got only two creases on these 2 inch chord wings.

http://geology.um.edu.my/ntaibpublic/Xiaomi%202017%20jan-1/IMG_20180103_171828.jpg

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Iskandar Taib
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« Reply #4 on: February 19, 2018, 11:05:23 PM »

http://geology.um.edu.my/ntaibpublic/Xiaomi%202017%20jan-1/Processed/IMG_20180103_171845_small.jpg

The five inch props that come with these kits is attached to the usual North Pacific style plastic prop hanger/nosepiece. The Chinese prop hangers differ quite a bit from the American ones that you get these days from SIG and Midwest. The American ones are made of nylon, which makes them easy to bend to adjust in sidethrust. I used sidethrust a lot when trimming stick models, especially Delta Darts. A tendency to climb too steeply under power is easily trimmed out by tweaking the front bearing before launch. The Chinese ones seem to be made of ABS (like the props). Twist them too much and a stress line appears, twist even more and they'd likely break off (haven't had this happen yet). They do stay bent when you bend them, but it's probably best to avoid doing so in the first place. With the current models, I trim the climb by setting the turning circle (left) using the rudder, then adjusting the wing fore/aft.

American prop hangers are made to fit 1/8"x3/8" motor sticks. When building the last batch of Delta Darts, I was using 1/8"x1/4" motor sticks with a small piece of 1/8"x1/8" slung underneath. Chinese motor sticks are 4mmx6mm (and seem to be some sort of pine - heavier than balsa, in any case). For these models I strip 1/8"x1/4" sticks out of medium hard sheet, about 11-12 inches long (might try longer in the future), and then use a piece of 1/32" (or 1mm) balsa glued to the side. After saturating with a couple drops of CA (this keeps the wood in the nose from deforming, and keeps the prop hanger tight week after week), some light sanding will get it to the right dimensions for a tight slip fit into the prop hanger. Probably best not to glue the two together, especially if you forget to install the dental bands for the wing saddle first. Use a knife to remove the flashing from the prop hanger before installing.

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« Reply #5 on: February 20, 2018, 12:19:15 AM »

Thanks Iskandar!  A lot of valuable information.  Thanks for taking the time to put it out here.

Marlin
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Iskandar Taib
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« Reply #6 on: February 22, 2018, 04:21:02 AM »

The glue I use for foam-foam and foam-balsa joints comes from Daiso. If you have a Daiso store nearby, they're a source of all sorts of potential modeling items - everything from tools to pieces of Paulownia wood (which is very much like basswood - nice for carving props) to glues, paper clips... The glue you want is this one:

http://geology.um.edu.my/ntaibpublic/Xiaomi%202017%20jan-1/Processed/IMG_20171231_145443_small.jpg

There's more than one packaging, you want the one that will glue PET bottles. It's very similar to the glue GWS provides with their kits. HobbyKing also sells a similar glue:

https://hobbyking.com/en_us/clear-foam-glue-medium-cure-large-100ml.html

 Apply to one of the surfaces to be joined, hold the two parts together for about 10 seconds, and they'll stay together. After about a couple minutes the joint is hard enough that you can handle the assembly without it coming apart. After 3-4 hours it's pretty solid, though very slightly flexible. I join the horizontal and vertical stabilizers with this simple butt joint:

http://geology.um.edu.my/ntaibpublic/Xiaomi%202017%20jan-1/Processed/IMG_20180105_110953_small.jpg

It's strong enough that I haven't had any come apart.

The tail hook is made from a small paper clip (from Daiso). I make a hole in the motor stick using a micro screwdriver (also from Daiso).

http://geology.um.edu.my/ntaibpublic/Xiaomi%202017%20jan-1/Processed/IMG_20180222_155741_small.jpg

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« Reply #7 on: February 22, 2018, 05:47:48 PM »

Thanks for posting that info,Iskander.

Scott
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Iskandar Taib
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« Reply #8 on: February 22, 2018, 11:22:55 PM »

You guys are very welcome. If you build some yourself post photos.

Tail details: Not really quite sure why I started doing the tails this way, but it seems to work OK, haven't had any snap off yet. Maybe it's because I have a bunch of 1/16x1/8 strips that I made for Delta Darts and they were at hand. I use them for attaching the wing as well. The T-join formed by the horizontal and vertical stabs makes for a very strong and stiff structure, so there's no worries about the tail snapping off behind the motor stick. The balsa-balsa join is done with a drop of superglue. The foam overlaps the back of the motor stick by maybe 1/4", so it's not going to snap off there, either. I've flown models with short motor sticks and a long, fragile tail boom before - it works in flight, but if the tail brushes against the ceiling or hits some other obstruction the tail boom sometimes snaps off, with spectacular results. My Ikara Bulldog kept doing this - coming down in pieces from hitting something.

Iskandar
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« Last Edit: June 03, 2018, 10:02:00 AM by Ratz » Logged
Iskandar Taib
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« Reply #9 on: February 23, 2018, 01:01:18 PM »

A couple of problems I ran into. Some weeks ago, as an experiment, I built one with much flatter dihedral. At half power it flew around in the circle OK but would NOT climb at full power. Set the wing forward and it would start stalling in the cruise, set it to cruise and at full power it would fly in a fast, flat circle. Obviously the side area wasn't enough to keep the nose up at high speed. I fixed it by putting in a couple of polyhedral breaks, and after that it climbed to the ceiling, as it should. The proper amount of dihedral seems to be about 3 to 3 1/2 inches under one wingtip with the other wing flat on the table. I usually just eyeball it in.

The second problem happened tonight. Under full power, the model would nose over and dive after climbing 5-7 feet. Yet at half power it would cruise just fine. If you tweaked the tail for it to climb it would start stalling 20 feet up. Turned out to be "EZB Syndrome" - a too-soft motor stick. It was bowing downwards under full winds. You do need fairly stiff balsa for the motor stick, though a deeper motor stick might work with softer wood.

Another interesting thing tonight was that the model I lost up in the ceiling ledges last week came back. One of the workers at the "mamak" restaurant at the shopping mall had it - apparently someone actually climbed up there with a ladder and brought it down, maybe one of the maintenance workers. (Too bad they didn't also bring down the other half dozen hung-up models - there's a couple Delta Darts, and maybe three or so foam plate models up there.) The motor stick was broken, and the tail had been broken off. Someone tried to fix the fuselage with cellophane tape and what looked like a piece of wood veneer peeled off some old furniture. We repaired it and I'll give it back to the restaurant guy next week along with a short loop of 1/8" rubber - he can have some fun with it using hand-winds.

Iskandar
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Iskandar Taib
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« Reply #10 on: March 19, 2018, 10:33:44 PM »

Interesting discovery. All this while I thought the foam parts were expanded polystyrene. Apparently they are not - CA does not dissolve them! I'll try putting one together using CA except for the wing saddle (that's a scrap piece of styrofoam picnic plate).

Iskandar
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Iskandar Taib
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« Reply #11 on: June 03, 2018, 03:34:38 AM »

https://www.youtube.com/watch?v=GvOwSFy95bo

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« Reply #12 on: June 03, 2018, 09:27:18 AM »

That was a very nice flight.  Quite different from the combat you used to fly when you were in the states.
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Iskandar Taib
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« Reply #13 on: June 03, 2018, 12:40:26 PM »

Yeah, this is sort of a CL combat flier's approach to free flight rubber. The models are cheap, I can build one in 30 minutes, I show up with a box containing a half dozen and I don't care if they get hung up or lost. Strangely, so far I've only lost three, two of them last week. I could have retrieved them easily if I had a long stick but they were ones that had problems so I couldn't be bothered!


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