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Old Mar 15, 2014, 08:41 PM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
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Build Log
Bird of Time Laser cut scratch build: Modified!

I loved my BOT but last summer I got into some weird turbulence and I ended up folding up the wings at about 2,000 feet. Part of the problem was the altitude and trouble seeing the plane's attitude but never the less it came down like a lawn dart. Was very disappointing. Built my first BOT (BOT I) in the late 70's from the original Mark's Models kit and used to high start it.

BOT II (2010):



At the time I really wanted to build a version without polyhedral and with ailerons added and maybe flaps. However, I hesitated to buy a new kit because the balsa was really heavy and hard in my last kit. So, I wanted to make my own kit and modify some annoying things and add the features I wanted while taking out quite a bit of structural weight (traded off for the addition of several more servos).

So here it is: Rudder, elevator, flaps and ailerons. I will be using a 400-500 wat 3s power system with a folding prop.

I hope it flies well with ailerons and no polyhedral.

Initial wing build with my own CAD produced parts:








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Old Mar 17, 2014, 08:26 AM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
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initial weigh in: 32 ounces without covering. This includes a 2200 mah 3s battery.

I have no idea what the Ultracote and fuselage paint will add but I think the canopy & horizontal stab will be less than 2 ounces.

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Old Mar 17, 2014, 12:23 PM
Registered User
USA, MN, Blaine
Joined Feb 2011
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It really looks sweet!

I hope she flys great
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Old Mar 18, 2014, 01:10 PM
Ochroma Lagopus Tekton
Fly Wheel's Avatar
Blackstock, South Carolina
Joined Sep 2007
1,831 Posts
It should fly fine. Since a flat wing lacks the self correcting tendency of di/polyhedral craft it will not self level as well and therefor require a little more attention to the sticks, but those should be the only differences.

Nice work on the rebuild. I had to chuckle at all the lightening holes though, last time I saw anything as extensivly drilled out as that was on a 1970's racing bicycle!
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Old Mar 18, 2014, 02:46 PM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
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Quote:
Originally Posted by Fly Wheel View Post
It should fly fine. Since a flat wing lacks the self correcting tendency of di/polyhedral craft it will not self level as well and therefor require a little more attention to the sticks, but those should be the only differences.

Nice work on the rebuild. I had to chuckle at all the lightening holes though, last time I saw anything as extensivly drilled out as that was on a 1970's racing bicycle!
Well, I thought as long as I had access to a laser, I might as well take some weight out to make up for having ll additional servos. The last BOT I made was just rudder, elevator and spoilers. This one has 4 more servos, a slightly larger motor and will likely weigh in 7 ounces less. I weighed everything out and calculated he weight o the covering and it should be 40 ounces AUW. The two things I changed up for the weight were using a competition grade of balsa and adding a lot of lightening holes. The wood that came with the Dynaflight kit was very hard and heavy.

I have many years of sailplane experience but only with super simple 3-4 channel planes. Now that I am building this full house glider (with flaps) and have a computer radio I can do some interesting things. So, one question I have is with flaps and ailerons is there any reason to have spoilers? If I can "crow" the plane is the need for spoilers gone or are they used for a different purpose like dumping out of a strong thermal. I would imagine the amount of drag from the "crow" configuration would be more than enough for spot landings.

Anyway, before I button up the wings I am interested in hearing opinions on the spoiler option.

Dave
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Old Mar 18, 2014, 09:06 PM
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Canada, ON, Newmarket
Joined Jul 2013
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Subscribed.

I just bought Dynaflite balsa kit of the BOT at a local swap meet so I'm all eyes. The previous owner also included the RCM plans and several generations of kit instructions.

No opinion on dropping the spoilers as I'm not sufficiently knowledgeable.

All the holes in the trailing edge and wings tips will make for quite a distinctive overhead appearance.

An all up weight in the low 40 ounces with 400/500 watt motor is very very good.

What material are you using for doublers in the front fuse and any carbon tape reinforcement in the rear fuse? Any reinforcement of the wing spars beyond kit instructions.

Please keep posting pictures and narrative of your build.

thanks

Michael
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Old Mar 18, 2014, 09:26 PM
Balsa&Tissue
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United States, OR, Beaverton
Joined Jan 2011
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Quote:
Originally Posted by 2michaely View Post
Subscribed.

I just bought Dynaflite balsa kit of the BOT at a local swap meet so I'm all eyes. The previous owner also included the RCM plans and several generations of kit instructions.

No opinion on dropping the spoilers as I'm not sufficiently knowledgeable.

All the holes in the trailing edge and wings tips will make for quite a distinctive overhead appearance.

An all up weight in the low 40 ounces with 400/500 watt motor is very very good.

What material are you using for doublers in the front fuse and any carbon tape reinforcement in the rear fuse? Any reinforcement of the wing spars beyond kit instructions.

Please keep posting pictures and narrative of your build.

thanks

Michael
MIchael,

I put 1/8" aircraft ply between the firewall and the first former on the left and right sides. The firewall (1/4" birch aircraft ply) as well as the doublers are epoxied in place. Also, Hardwood tri stock behind the firewall. I mounted the motor so the back of the prop/spinner would be slightly ahead of where the fuse would have normal ended minus the nose block.

My first BOT shed its motor at about 1500 feet and was lost for almost 1 day. I finally glassed the nose. I may glass the fuse on this one but I would rather just seal and paint it. with all the ply and tri stock I don't think I will need the glass but I have not decided yet.

The rear fuse is quite stiff as designed especially with the ply brace the plans call for.
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Old Mar 19, 2014, 08:06 PM
Mesa AZ, it's a dry heat!
USA, AZ, Mesa
Joined Oct 2004
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I think you will find the spoilers are redundant as the flaps with or without 'crow' ailerons should be more than sufficient for accurate landing and dethermalizing.

The power is EXCESSIVE. you are in the 200W/lb range which is great for hotliners, but you will be in danger of surface flutter with the speed that much power can produce.
Try one less cell on the battery and a larger prop diameter and less pitch. That should slow it down a little.

It sure looks like a beautiful airframe with all the lightening holes.

I built my first BoT from plans in 1979. ( If memory serves the plans were published first in RCM in January of 1979.).

I have owned 4 or 5 over the years, the last on an ARF converted to e-Power.

Iain
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Old Mar 19, 2014, 08:56 PM
Balsa&Tissue
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United States, OR, Beaverton
Joined Jan 2011
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Quote:
Originally Posted by rev.iain View Post
I think you will find the spoilers are redundant as the flaps with or without 'crow' ailerons should be more than sufficient for accurate landing and dethermalizing.

The power is EXCESSIVE. you are in the 200W/lb range which is great for hotliners, but you will be in danger of surface flutter with the speed that much power can produce.
Try one less cell on the battery and a larger prop diameter and less pitch. That should slow it down a little.

It sure looks like a beautiful airframe with all the lightening holes.

I built my first BoT from plans in 1979. ( If memory serves the plans were published first in RCM in January of 1979.).

I have owned 4 or 5 over the years, the last on an ARF converted to e-Power.

Iain
Lain,

My first e powered BOT had a similar power issue and I tried both a .10 and .15 motor in it. I agree, it is overpowered but with a smaller motor and/or smaller battery it still ends up needing nose weight. If I remember right from my last build a 3S battery and .10 or .15 motor balanced the plane perfectly. I basically never went full throttle. My original ecalc and instincts told me a good 480 size motor would be just fine but then I just end up adding lead to the nose and finding room for the lead was a problem.

I have several motors in my parts box such as a 400, 480 and the .15. Also the folding props I have only seem to come in an 8 pitch once the prop diameter is over about 9".

The way the firewall is made I can slap almost any rear mount motor in place

As always, I am open to further suggestions and ideas.....

Dave
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Old Mar 20, 2014, 11:00 AM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
Joined Jan 2011
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Air-frame is complete and all servos and electronics installed. The AUW is right at 39 ounces.

Will be checking the CG with the plane temporarily assembled. If it balances with a 480 motor I may consider trimming the power back. With a 480 I could use a smaller battery as well.

Covering will start this evening and I suppose once it is on the plane may finish out at 45 ounces. I decided to skip the spoilers.

Dave
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Old Mar 20, 2014, 11:35 AM
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Cant wait to see it all covered!

You haven't said I don't think but what's the wingspan and is it a 2 piece wing? If its a 2 piece how are you joining the wing and what's your plan for attaching it to the fuse?

About how long did it take you to build?
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Old Mar 20, 2014, 12:25 PM
Balsa&Tissue
payne9999's Avatar
United States, OR, Beaverton
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Quote:
Originally Posted by Newman12 View Post
Cant wait to see it all covered!

You haven't said I don't think but what's the wingspan and is it a 2 piece wing? If its a 2 piece how are you joining the wing and what's your plan for attaching it to the fuse?

About how long did it take you to build?

For me it looks like the build will be 2 weeks. This is working a couple hours in the morning and 4-5 hours evenings. Probably about 40 hours work.

It has a 2 piece wing joined with the typical .250" steel rod and .250" ID brass. The fit of the brass si super snug which is wnat I wanted. Any slop will allow forces to use that space to break the glue joints. I used a lolt of epoxy and cut the balsa filler so it had a half round cut in it to perfectly nest the bras tube.

The wingspan is the original design of 118" and I am using the designed rubber band method for holding on the wings.
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Old Mar 20, 2014, 04:35 PM
Ochroma Lagopus Tekton
Fly Wheel's Avatar
Blackstock, South Carolina
Joined Sep 2007
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Spoilers break up the airflow over part of the wing to reduce lift. Crow is basically an airbrake (ailerons both up, flaps down). Both are good for competition spot landings, neither is really needed to get out of a thermal, add some down elevator and point the plane towards the ground.
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Old Mar 20, 2014, 04:51 PM
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Northumberland, England
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Quote:
Originally Posted by Fly Wheel View Post
Spoilers break up the airflow over part of the wing to reduce lift. Crow is basically an airbrake (ailerons both up, flaps down). Both are good for competition spot landings, neither is really needed to get out of a thermal, add some down elevator and point the plane towards the ground.
The trouble with that method is that the fuselage usualy meets the ground whilst the wings are still descending, independently, some distance downwind.
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Old Mar 21, 2014, 02:01 AM
Balsa&Tissue
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United States, OR, Beaverton
Joined Jan 2011
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Got some covering done tonight. Only have one wing to go. The fuse is sealed with traditional dope with talcum powder added (balsa filler) and then primed and painted to match the Ultracote.

I liked the color scheme of my last BOT so I did the same this time.



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