Motorpowered Sailplane... darkside... something

[Doom]

Hey Guys,

this might be my first ever posting in a forum so please be forgiving if some stuff is not classical forumtalk. Why I am posting is because I started my first scratchbuild. Well to be correct, I scratchbuilt a few planes from the FT series already (FT 3D, FT Versawing Blunt Nose, FT Racer) but this time I wanted to do the whole constructionprocess as well. But doing it on the computer oder drawboard would not be comforting for me so I just made a few sketches of what I wanted to achieve and started building right away.

What I came up with so far is most of the fuselage, the wing (very rudimentary yet) and parts of the stabilizers (even rudimentarier then the wing). Wingspan will be around 140 cm, length so far is 80something cm. All the sizes I calculated from a scheme sheet where it said how long the fuselage has to be for a glider with that and this wingspan, stab areas and so on, very helpful.

What I would love this to become is a slightly smaller but still epic radian pro kind of glider. In the beginning only aileron, no flaps, but would love to add them later. First I thought it would be nice to mach the wings detachable, but I think my scratchbuilders knowledge is not there yet I will try to fly this thing of a NTM Motor with 1200 kv and 250W and a 9x5 folding Prop. Power should be delivered from a 1500 mah 3 cell. By now my feeling is that it will be also able to carry a 2200 3 cell (of which I own a few).

My plan is that when the plane is done and flying well I want to finalize the plans for it (only using foamboard) und upload them here. How do you guys usually make your plans? What software are you using? I was planning on using adobe Illustrator since I have that on my work laptop.

Here now a few pictures of the status quo:




Ok folks, looking forward to a lot of interaction with people who share the passion for building, flying and crashing planes

Also, them bananas in the pictures are sooooooo delicious...

 

[marc60]

Did you use the bananas to form the nose? Great shape

 

[stay-fun]

Looks awesome dude! Is it going to be a mid-winged glider? So you won't need too much downthrust on you prop (if at all)?

 

[Doom]

Hey Marc, actually now that you mention it... that whole discussion makes me kind of banana

Thanks stay-fun, actually now it stil looks crappy, but it is only the prototype when it works out I´ll do plans, then it´ll look nicer I think it is going to be a high-midwing kind of thing. I hope i can come up with a motor mount that can change the angle of the prop. Otherwise it´ll be a lot of try and error

Will keep you posted!

 

[stay-fun]

Ah, the multiplex acromaster has quite a neat way of changing the motor angle (in any direction!). It's a metal firewall that mounts onto the nose using 2 screws, and has 4 additional screws in the firewall that just rest against the motor mount. By adjusting how far these 4 screws go into the firewall, the angle of the firewall relative to the motor mount is adjusted:

http://smallpartscnc.com/image/cache/Multiplex 19x30 378-800x600.jpg
http://static.rcgroups.net/forums/a...2344571-12-thumb-Motor Mount.jpg?d=1234743189

Maybe an idea? (you don't need to make it that complicated with side AND down/up thrust, just up/down is prob fine)

...or you just add shims

 

[aiidanwings]

I like to say rudimentarier.

 

[Doom]

Haha, yeah, I´m so happy that at least somebody recognized my superpower: Grammar

 

[TEAJR66]

You could tape the fire wall directly to the plane. Then as you want to adjust thrust angle, use washers to shim the motor mount on the fire wall. From the looks, thrust and drag lines are not that far off. It should not require much down thrust. Looks good. Good luck.

Is that a beer on the table? hehehehe

Be safe and have fun,
Tommy

 

[Doom]

Hey Tommy,

it is Ice Tea, the drink, not the rapper/actor. And that special Ice Tea is the reason why I was up until 3:00h am last night... black tea... AAAAH!!! I am so tired at work right now..

Thanks for the kind words I was just thinking of a way to be able to change the thrustvector with just one screw for every direction. So there is two Firewalls one is attatched to the plane the other one to the firewall (see the Pic) On the backside there is screws to change the angle in every direction. What do you guys think?

 

[TEAJR66]

I like the idea. What holds the two panels together at a pivot point that lets the mount move as the screws are adjusted? Washers between the motor mount and fire wall is simple. I have used it a couple times and I liked it because it worked. I have had a few ideas for adjustable firewalls to use when I am doing my scratch designing, but keep coming back to shims behind the mount.

If you get that thing built and functionally repeatable, I would like to see the design. Let me see some of that Deutsch Engineering!

Enjoy the tea brother. Be safe and have fun,
Tommy

 

[stay-fun]

Hmm, I guess the way you set it up now, requires your pivot in the middle of the firewall, right? Can you do that?

I've made an alternative pivot setup:



This way, you can shim the middle top screw to get the desired downthrust (don't forget to shim the bottom screw as well, to allow side thrust). Now you can adjust the two top side screws to get the desired side thrust.

Yes it may not be perfect, because you need to shim to get the downthrust, but at least (hopefully) it's kinda sturdy... After all, there's going to be quite some weight on that firewall, and thrust...

What do you think?

 

[Doom]

I tell you what I think right away. I am really amazed how helpful and supporting everybody is over here. This is the best Forum. Your Idea looks quite nice. I want to try and make this a setup that is built and used very easy. So your Idea is pretty helpfull since it is less screws. I think I will try and make prototypes of both and post them here.

Thanks buddy, actually not one of my friends or family is into the hobby so now sharing my ideas with such kind people is a blast to me!

 

[TEAJR66]

Ok, here it is. Now someone needs to build it and let me know if it works.

Be safe and have fun,
Tommy

 

[Doom]

Hey, great, how did you do that so fast? But one thought. If both firewalls are put together with springs (is that the correct plural) isn´t that going to generate vibrations? I wanted to join bith together with the 4 Screws that come in from the front after you achieved the angle you wanted with the screws from the back to fixate both firewalls.

 

[stay-fun]

I am really amazed how helpful and supporting everybody is over here.

No problem dude, I love helping people out. I'm also the only one in my family doing this stuff (my dad is into model trains though - but it's quite different). (oh and btw, I live in the US but I'm from The Netherlands - I have no family on this continent at all!)

I've got a new idea again. Since the orientation of a plane can be defined by a minimum of 3 point (screws): have one screw in the middle bottom, shimmed. Then at the two upper corners: the screw goes through the motor mount, and a locknut keeps it in place. A bit loose, so the screw can turn. Then, use a locknut which is sunk into the firewall (glued or whatever), and screw it in there. Now you can simply turn the screw to adjust the distance of the motor mount to the firewall. You only need the top 2 screws to be adjustable.

I think it's even more simple and better than my previous idea

 

[stay-fun]

Ok, here it is. Now someone needs to build it and let me know if it works. View attachment 26575

Be safe and have fun,
Tommy

Looks pretty neat man! But... There is the weight of the motor/prop, which will compress the bottom springs... Unless you use really tight springs I guess...

 

[TEAJR66]

If you compress the springs completely, the mounting will be rigid. Let out the bolt (or bolts) that gives the angle adjustment you want and there should be minimal vibration on a balanced prop/motor combo. Plus this is only temp while you find the proper angle. So after a few flights, affix the permanent motor mount. One key is to have the holes in the motor bracket the exact diameter of the bolts. The springs provide the back pressure to reduce vibration. This is a tractor design. for a pusher, there would be some modifications

Anyhow. Just an idea. Thank you for giving me something to work on to occupy my time.

Be safe and have fun,
Tommy

 

[marc60]

I think the traction of the motor whilst running will be enough to prevent the weight from compressing the springs?

 

[TEAJR66]

Weight compressing the springs wont be an issue.

1. the springs will be compressed as much as can be and still allow for the angle of the mount. The springs are just there for back pressure so the mount does not slip around when not under torque and thrust.
2. It is a mount for a tractor configuration, the thrust will pull the forward motor mount out to the extent that the screws allow the motor to travel.

Use blue Loctite and the bolts wont loosen on their own and will still be adjustable.

Just a concept. There is a starting point. Someone build it and make it work.

Be safe and have fun,
Tommy

 

[Craftydan]

For fear of this being thrown back in my face (I've been accused of this within the last week) . . .

Neat, but a little over-engineered, doncha think?

This can be accomplished with a small stack of thin washers and a single firewall, allowing you to spend your weight budget elsewhere . . .

. . . oh wait . . . that's what you suggested at first