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Nov 29, 2016, 02:02 AM
Old gasbag glider guy...
Stan Hinman's Avatar
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Micro Bird Of Time


While working on other projects, sometimes a distraction is needed to keep the mind fresh. Crank a few hours on the important stuff, then relax 15 minutes or so on the distraction. This project is just such a distraction. Though I have no idea when I'll have time to build it, I could not resist the attraction of a Micro-sized BOT, one of my all time favorite RC Soaring machines.

Over the past few months the idea of using micro radio gear salvaged from piled-in Horizon ultra-micro foamies for scratch building projects has been getting a lot of traction. My first exposure to it was when my friend Bill Watson started teaching a building class at his local club, and designed a 36" span, very Zaic-esque all balsa glider called the Scout that was ideal for that radio gear. I built a couple of those, and then last February blvduzzard here on RCG came up with the idea of a half scale (36") Wanderer. I modelled that up, but before I could build it, Alien_Tech introduced his Micro Wanderer (30" span) to thunderous acclaim, and suddenly there was a lot of longing for Micro versions of classic RC Glider designs.

I campaigned for many years ('72 to '78) with a Windfree, and thought I could quickly knock out one of those, but Red (Alien_Tech) beat me to that as well. The only other design I was really interested in was the Bird Of Time, which was my follow-on contest ship to the Windfree. I still fly that poor, beat-up, and well used 38 year old BOT, because it flies so dog-gone good, even after being completely rebuilt 3 times.

This Micro BOT was sized to contain the smallest UM brick I know of; the mini Vapor brick (PKZU1252). This brick is also capable of running the UM P-51 motor, which hopefully will be enough to drag it into the air; we'll see...

I love the lines of the BOT so much that I did not want to alter the scaled fuse shape length/width ratios to accomodate this brick, therefore the fuse was scaled until it could just swallow the brick, yielding a 16.5" long fuse, and a wingspan of about 40", which isn't that much bigger than the 36" I was shooting for. I expect the larger size will also help the performance of the wing as well.

It will not be built with the same ease as Red's Wanderer, still it should not be too much of a challenge either. Construction is similar to the original, with spars and shear webs, but with obvious efforts to save weight, e.g. no lower surface sheeting on the wing. (Had to have upper sheeting to maintain the "look".)

The tail surfaces, which are all 1/32" sheetwood (ala Watson's Scout) could probably use some lightning holes, but I'll wait to add them until there's no option.

As I said, I have no idea when I'll have one built; I have many other more pressing projects I've committed to that need to be completed. I recently discovered that there is a laser cutter at work that I have access to, but I'm sure there's a learning curve to climb. And I know how long it takes to develop cutting files, so that's probably a ways out as well. It'll take as long as it takes. In the meantime, I've got a pretty 3D model to look at and keep me excited about the project. Hopefully after the New Year I'll have some time.
Last edited by Stan Hinman; Nov 29, 2016 at 02:39 AM. Reason: Sp
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Nov 29, 2016, 02:09 AM
No serious dane bramage
brokenspar's Avatar
Looks like a fun project. Good luck!
Nov 29, 2016, 08:42 AM
Registered User
nice!
Nov 29, 2016, 07:13 PM
Registered User
Looks great. I would love to see performance. Just got a used BOT and electrified it. Gonna be my winter soarer.
Dec 01, 2016, 01:33 AM
Old gasbag glider guy...
Stan Hinman's Avatar
Thread OP
If you mean the Sunbird, yes! Very cool little glider. Never had a chance to fly one though. By '79 most of my modeling activities had been curbed by school. I did have the Bird wth me, but not much time to fly it. One of those rare occasions when I did happened to be the first time I ever thermaled the Bird out from a hand launch; something I never thought would happen with a 118" glider, and something I hope to repeat with this micro version.

I'm getting some parts cut, but still don't expect any major progress till the new year.
Dec 02, 2016, 10:42 AM
Registered User
Stan

you said in an earlier post you are having some pieces cut. Do you have your design made into a cut file already?
Dec 02, 2016, 12:22 PM
Registered User
Cool project. Needs a longer tail. It will turn so much better. Here's my very modified BOT. Only thing original is the wings. After a crash I ditched the old fuselage and built a carbon fiber one with a bubble dancer boom and a geared motor up front. Lighter and flies great.

Brian
Dec 02, 2016, 07:53 PM
Old gasbag glider guy...
Stan Hinman's Avatar
Thread OP
Quote:
Originally Posted by Newman12
Stan

you said in an earlier post you are having some pieces cut. Do you have your design made into a cut file already?
No, not yet. While I do intend to create laser cutting files for this Bird, for the time being I'm doing it the old fashioned way, and just cutting things out by hand. This won't take nearly as long to do as the Graupner Cirrus wing rib set I cut for replacement Cirrus wings I built from scratch for my Dad.

It makes sense to me to get one flying and work out any kinks first.

Quote:
Originally Posted by bennetbr
Cool project. Needs a longer tail. It will turn so much better. Here's my very modified BOT. Only thing original is the wings. After a crash I ditched the old fuselage and built a carbon fiber one with a bubble dancer boom and a geared motor up front. Lighter and flies great.

Brian
We'll see about the tail moment; my calcs indicate the tail volume is adequate. My main concern for now mirrors one of yours: keeping it light enough. If the prototype lacks directional or pitch stability, it's easy enough to make a new longer fuse. I'll be making a second one anyway to try out a powered version with the UM P-51 motor.

Thanks to all for the encouragement.

Kind regards,

Stan
Last edited by Stan Hinman; Dec 03, 2016 at 01:45 AM. Reason: Sp
Dec 02, 2016, 10:23 PM
Registered User
I ran all the calcs to figure out the tail length and areas to follow Dr. Drela recommendations for EDA and spiral stability. It was interesting because running the calcs on the original design illustrates the need for some refinements, and explains some annoying flying characteristics. Not that the original flew bad, but it could be a real handful when the wind kicks up. The new design handles the wind like most of the other RES ALES ships. When I get time I'm going to build a new wing using Drela airfoils, to get a little better performance. This might also save a few ounces off my 53oz flying weight.

I'm sure your mini BOT will be a blast. I've redesigned mine mainly for ALES, not so much for sport flying. Plus you probably are not going to be flying in 15-20 mph winds with a mini Bird.

Brian



Quote:
Originally Posted by Stan Hinman
No, not yet. While I do intend to create laser cutting files for this Bird, for the time being I'm doing it the old fashioned way, and just cuttings things out by hand. This won't take nearly as long to do as the Graupner Cirrus wing rib set I cut for replacement Cirrus wings I built from scratch for my Dad.

It makes sense to me to get one flying and work out any kinks first.



We'll see about the tail moment; my calcs indicate the tail volume is adequate. My main concern for now mirrors one of yours: keeping it light enough. If the prototype lacks directional or pitch stability, it's easy enough to make a new longer fuse. I'll be making a second one anyway to try out a powered version with the UM P-51 motor.

Thanks to all for the encouragement.

Kind regards,

Stan
Dec 03, 2016, 02:34 AM
Registered User
The BOT is cool in any form of mod/size.
My original balsa BOT is around 53oz too. Having the motor helps a ton in the wind.

Interested to see how the mini BOT works out.
Dec 10, 2016, 11:23 PM
Registered User
Here are a few of my micro builds
https://www.rcgroups.com/forums/show...cro-Sagitta-XC
https://www.rcgroups.com/forums/show...54515-Oly-ii-m
https://www.rcgroups.com/forums/show...72-micro-AV361
I also built a micro wanderer
Your current design looks like you have shrunk the BOT and kept every thing to scale. You can easily remove the leading edge sheeting and half of your ribs 2" spacing on your ribs is sufficient. 1/16" sheet for the fuse (doublers not necessary) and tail works great. I have a micro BOT in the works mine will be built with the cracked rib method. Your models look great by the way.
Dec 11, 2016, 01:35 AM
Old gasbag glider guy...
Stan Hinman's Avatar
Thread OP
Quote:
Originally Posted by saltcitytattoo
Here are a few of my micro builds
https://www.rcgroups.com/forums/show...cro-Sagitta-XC
https://www.rcgroups.com/forums/show...54515-Oly-ii-m
https://www.rcgroups.com/forums/show...72-micro-AV361
I also built a micro wanderer
Your current design looks like you have shrunk the BOT and kept every thing to scale. You can easily remove the leading edge sheeting and half of your ribs 2" spacing on your ribs is sufficient. 1/16" sheet for the fuse (doublers not necessary) and tail works great. I have a micro BOT in the works mine will be built with the cracked rib method. Your models look great by the way.
Hi Salt,
I have been following your builds. They all look great, and the videos I've seen of those that have flown show very nice flying models. I hope my endeavors are as successful. You're right about the scaling. I know I could reduce the number of ribs, but I just like how it looks with the original number. My intent was not necessarily to simplify the construction; just to scale it down, preserve the look and keep it light enough the fly reasonably well. It's much like a glorified peanut scale model; lots of thin balsa sheetwood, small sticks and teeny-tiny ribs.

I've ordered some covering for it as I plan to replicate the color scheme of my very old (1978) BOT. That's it in my avatar. It was built from a kit that Thornburg himself made.

Appreciate the kind words.

Stan
Dec 11, 2016, 12:05 PM
Registered User
Quote:
Originally Posted by Stan Hinman
It's much like a glorified peanut scale model; lots of thin balsa sheetwood, small sticks and teeny-tiny ribs.

I've ordered some covering for it as I plan to replicate the color scheme of my very old (1978) BOT. That's it in my avatar. It was built from a kit that Thornburg himself made.

Appreciate the kind words.

Stan
Are you going to be doing a tissue covering like the peanut scale that would be nice to see done in an rc model. I have always wanted to do a true vintage ff glider to rc built complete like they used to ( I know some still do). Good luck on your build
Dec 11, 2016, 02:56 PM
Old gasbag glider guy...
Stan Hinman's Avatar
Thread OP

Micro BOT covering


Quote:
Originally Posted by saltcitytattoo
Are you going to be doing a tissue covering like the peanut scale that would be nice to see done in an rc model. I have always wanted to do a true vintage ff glider to rc built complete like they used to ( I know some still do). Good luck on your build
I'm getting StevensAero's AeroLITE (SOLITE). Since I'm replicating my original Bird, I've committed to the heat shrink path. Sadly, Stevens is currently out of transparent yellow - which I need to remain true to the scheme - but hopefully they will have some by the time I need to start covering.

I've covered a lot of planes with silkspan (CL mostly), and with Jap tissue (Peanut scale), but the only RC model I covered this way was an old Sterling kit of Don Dewey's Royal Coachman design that I covered with silkspan and dope. It was a fun model that flew well, though a friend insisted on calling it the "Royal Cockroach." He also was the one who steered our group of RC Glider guiders back in the day towards free flight in order to improve our building skills, which it definitely did. My main concerns with doped coverings are a) robustness, and b) applying too much dope and getting it heavy.


Stan


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