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Old Dec 14, 2014, 07:31 PM
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Joined Dec 2014
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Help!
Does Any Pointers/Advice On This Design?

Just felt I needed to start by saying, I'm very new to this forum and the RC Hobby in general ( So, sorry if I sound novice ) . I've started about a week ago, and about half off that time, I've spent researching.

The reason for all of the research is that I'm planing to build an RC Plane, specifically a Twin Boom Pusher. I figured I'd probably be making this out of depron foam, and as for the electronics, I have very little of an idea yet ( The motor/prop being a place holder ).

The plans I DO have are for it to be a slow flyer, but since I don't actually know the weight, center of gravity, etc... I have no idea where to start when it comes to the power system, to actually allow it to be a slow flyer.

So to return to the question on hand, does anyone have any pointers on any parts of this design I should change, electronics, or just anything in general? I could really use any advice.
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Old Dec 14, 2014, 08:22 PM
Hot glue held together by foam
United States, WA, Vancouver
Joined Aug 2010
2,888 Posts
Quote:
Originally Posted by Suixle View Post
Just felt I needed to start by saying, I'm very new to this forum and the RC Hobby in general ( So, sorry if I sound novice ) . I've started about a week ago, and about half off that time, I've spent researching.

The reason for all of the research is that I'm planing to build an RC Plane, specifically a Twin Boom Pusher. I figured I'd probably be making this out of depron foam, and as for the electronics, I have very little of an idea yet ( The motor/prop being a place holder ).

The plans I DO have are for it to be a slow flyer, but since I don't actually know the weight, center of gravity, etc... I have no idea where to start when it comes to the power system, to actually allow it to be a slow flyer.

So to return to the question on hand, does anyone have any pointers on any parts of this design I should change, electronics, or just anything in general? I could really use any advice.
That looks like a good design ; but for learning how to fly , why not build a PROVEN design beginner RC airplane ? That way when you're learning and you're having difficulties , you'll take away the question of whether or not it's the plane design that's causing the problems . Once you learn how to fly , then build your own design for a second plane .

The scratch-built plane I use to teach first time flyers is the EzFly R3 . It is very stable and can be slow flying if built light weight . There is only one requirement for slow flight ( of ANY plane ) and that is light wing loading . Wing loading is overall weight RELATIVE to wing area . Light wing loading is MAXIMUM wing area with MINIMUM weight .

http://www.rcgroups.com/forums/showthread.php?t=1174874

Here is one of my EzFlys built with an extended wingspan and lightweight electronics for light wing loading . It's so slow and stable , I'm flying with my right hand while filming with my left hand .

Al

Copy of EzFly with under-cambered wing (1 min 57 sec)
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Old Dec 14, 2014, 09:58 PM
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If you reallly want your first plane to be a twin boomer, there are several threads here on the scratchbuilt forum for those type planes. I would search for them (take a look through the 600+ planes sticky thread for the links) and find one that is well documented (templates, motor,prop, gear detailed) and build it. Then go for your own design with the learnings from the other guy's design.

I also agree with BoC, though that a purpose designed trainer is an even better first plane. The idea is to build a simple plane that can be built, crashed, repaired easily, so your learning to fly is not lost in time consuming rebuilds. The first one is essentially a throwaway, fly it til you get the hang of it all, then move the gear to a more advanced design (a twin boom for instance) and keep learning!

Lastly, unless you have access to cheap Depron, I would go to your nearest Dollar Tree store and get some Readiboard foamcore for a buck a 20x30" sheet. Remove the paper and make your first few plane out of it. Depron is a primo material, but it is way expensive for most of us. Plus it's more brittle than Readiboard, so will crack/break when crashed where Readiboard will bend and can be straightened by pouring boiling water over the bend/dents.

I forgot to say, Welcome to the hobby, RCG and the Scratchbuilt foamies forum!!!!! It's a great addiction!
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Old Dec 14, 2014, 10:34 PM
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Couple of other little things. The CG needs to be between 25 and 30 % of the wing chord. You can see where you have a lot of goodies that will be well behind the CG. I'd notch the motor into the wing a bit to get it a little further ahead. Also make the nose quite a bit longer so you can get the batt well ahead to keep the CG where it needs to be. Also makes more room for your radio gear. Keep the back end as light as possible. Looks good otherwise.
Hope this helps.

Gord.
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Old Dec 15, 2014, 01:50 AM
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looks like a good plane to me

but yes build it light for more gentle flying. and yes the longer the tail boom the better , youll need a long moment arm for stability

you could go for a 10g-20g motor 1300kv to 1500kv and a battery 0f 3s 900mah to 1300mah for starters.

as most parkflyer size planes under 400g AUW
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Old Dec 15, 2014, 06:53 AM
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I wouldn't make the tailbooms any longer as that would exacerbate the CG problem.

Gord.
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Old Dec 15, 2014, 07:28 AM
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Originally Posted by flypaper 2 View Post
Couple of other little things. The CG needs to be between 25 and 30 % of the wing chord. You can see where you have a lot of goodies that will be well behind the CG. I'd notch the motor into the wing a bit to get it a little further ahead. Also make the nose quite a bit longer so you can get the batt well ahead to keep the CG where it needs to be. Also makes more room for your radio gear. Keep the back end as light as possible. Looks good otherwise.
Hope this helps.

Gord.
Yea, I was hoping that once the battery and the rest of the electronics are in place, that would move the center of gravity a bit forward to have it a bit more stable. But I'll try and extend the nose a bit more.
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Old Dec 15, 2014, 07:39 AM
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Originally Posted by balsa or carbon View Post
That looks like a good design ; but for learning how to fly , why not build a PROVEN design beginner RC airplane ? That way when you're learning and you're having difficulties , you'll take away the question of whether or not it's the plane design that's causing the problems . Once you learn how to fly , then build your own design for a second plane .

The scratch-built plane I use to teach first time flyers is the EzFly R3 . It is very stable and can be slow flying if built light weight . There is only one requirement for slow flight ( of ANY plane ) and that is light wing loading . Wing loading is overall weight RELATIVE to wing area . Light wing loading is MAXIMUM wing area with MINIMUM weight .

http://www.rcgroups.com/forums/showthread.php?t=1174874

Here is one of my EzFlys built with an extended wingspan and lightweight electronics for light wing loading . It's so slow and stable , I'm flying with my right hand while filming with my left hand .

Al

https://www.youtube.com/watch?v=VxaUadvhgbc
I'm not to concerned with crashing because I've already ordered a HobbyZone Champ RTF. Which hopefully will get me better antiquated with flying RC by the time I finish this build ( Which probably won't be for a while ).

As the EzFly, I hope I don't come off as stubborn, but I rather create my own design, fail, and try to fix it, than just use a tested design.
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Old Dec 15, 2014, 12:45 PM
Hot glue held together by foam
United States, WA, Vancouver
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Originally Posted by Suixle View Post
I'm not to concerned with crashing because I've already ordered a HobbyZone Champ RTF. Which hopefully will get me better antiquated with flying RC by the time I finish this build ( Which probably won't be for a while ).

As the EzFly, I hope I don't come off as stubborn, but I rather create my own design, fail, and try to fix it, than just use a tested design.
The Champ is an excellent choice for learning to fly .

As already mentioned , for your twin boom design - a longer tail moment ( moving the vertical stabilizers/rudders and horizontal stabilizer/elevator further away from the yaw/pitch axes ) will give you more stability in yaw and pitch . You may have to extend the nose a little to compensate for that .

For more roll stability , increase the winglet length ( but with less upward angle ) to make a polyhedral wing . That will help keep the plane right-side-up . Once you get comfortable flying it they can be removed/shortened for more aerobatic flight .

And raising the motor/prop higher so the thrust line is above the pitch axis will keep the plane from nosing up a lot when throttle is increased ( if you want the plane to just accelerate straight ahead with maybe a SLIGHT climb ) .

Build light for slow flight . Resist the temptation to add a lot of reinforcement - tanks are tough , but they don't fly well ! Low mass/inertia = low impact damage !

Al
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Old Dec 17, 2014, 11:04 AM
Defies Logic & Common Sense
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Philippines, NCR, Makati City
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BTW if a plane design glides well as freeflight glider is it better chance it would fly well as a powerd rc model. Because thats how i test them.
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Old Dec 17, 2014, 03:26 PM
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Originally Posted by Suixle View Post
As the EzFly, I hope I don't come off as stubborn, but I rather create my own design, fail, and try to fix it, than just use a tested design.
Not at all- the point is that designing, building, and flying are three totaly separate skills and you're much better off learning them one at a time.

Champ will give you flying, EXFly or some other proven model will give you building, and then your own design for designing.

You can do all three at once by entering the hobby with your own scratch built design, but it has the potential to be far more expensive and far less fun. Many that choose that route bail out of the hobby before becoming proficient pilots.

Which isn't to say it can't be done.
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Old Dec 17, 2014, 04:12 PM
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Joined May 2013
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http://static.rcgroups.net/forums/at...2-TBImage3.jpg


Very smart using an old man to point to your plane instead of a dog.... the man probably wont try to eat the plane
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Old Dec 17, 2014, 04:30 PM
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Originally Posted by speedactyl View Post
BTW if a plane design glides well as freeflight glider is it better chance it would fly well as a powerd rc model. Because thats how i test them.
generally, I would say yes. But (there is always a "but" or "it depends" ) What I have found is that when I glide test a plane, it can handle CG farther aft and still glide well versus power on which seems to want the cg a bit forward of the glide setting for the way I like to fly planes. So, I set the CG at about 25-28% of wing chord and when I glide test look for a bit less than flat glide (arcing down over maybe 20ft). That is what works for me. Now one other factor is thrust line; it doesn't affect the glide, but once power is on, it's a big factor, and needs to be considered, so gliding helps but doesn't answer all the issues.

I recommend that folk, especially newcomers glide test their plane before applying power, because it will show up gross errors quickly with (hopefully) less damage than a power on crash, and will show up subtle trim issues that can be tweaked before powering up. After a hundred scratchbuilds, guys may skip it, but when one is starting out, it saves a good bit of grief.
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Old Dec 17, 2014, 07:41 PM
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Originally Posted by rdeis View Post
Not at all- the point is that designing, building, and flying are three totaly separate skills and you're much better off learning them one at a time.

Champ will give you flying, EXFly or some other proven model will give you building, and then your own design for designing.

You can do all three at once by entering the hobby with your own scratch built design, but it has the potential to be far more expensive and far less fun. Many that choose that route bail out of the hobby before becoming proficient pilots.


Which isn't to say it can't be done.
True. I took the hard route anyway learn to design build and fly at the same time.
and my first truely stable flight is on my 4th plane which is EPS and a bipe plane back in 2008-2009.

now there are alot of info on the internet. To do these process would be alot faster.
and some guys cheat things with gyros and stuff to stablize even the most unflyable designs.
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Old Dec 17, 2014, 08:07 PM
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Springer: the last time i did that i only showed my rc buddy a flying wing as freeflight. He told me . Sure it would work . Then added the rc electronis the week later .sure enough it works. After several trims and cg alterations.

the plan is to test every plane i design by freeflight gliding only. The the rc gear can be a later addon

I know theres a thread here thats on freeflight and rubberpower rc conversions.
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