Is this enough for a 1/2A Beginner Ringmaster?

[HugoW]

Hi,

I downloaded and printed the plans, have the balsa, and even found some dope in the shed to seal it. But I don't want to use a Cox anymore, and I found these in the shed (quite near the dope, BTW):
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8478
http://www.hobbyking.com/hobbyking/store/__4204__TURNIGY_Plush_10amp_9gram_Speed_Controller.html
I found a good source for a timer.

Now I think the Beginner Ringmaster should weight very little, and combining this set-up with a 500mAh 2S pack should get it airborne. Or is this too small?

Please advise,
Cheers,

Hugo

[Tim Wescott]

It looks like it may be a bit underpowered to do the full pattern, but it should go around in a circle fine, and perhaps even do the round maneuvers.  Particularly if you build light.

If you have a means to measure current, put the biggest prop on it that'll have it pulling less than the rated 8.5A and see how it does.  Then go from there.

[John Rist]

Check out :  http://stunthanger.com/smf/index.php/topic,37540.0.html   

Looks like a good 1/2A setup

[eric rule]

Black Tiger   BT2836C  - 1300 kv motor with 3 cell 1300 mAh battery, 20 amp ESC combined with KR Governor will produce 250 watts of power. That will provide competition level performance on a model weighing up to 26 oz.

[HugoW]

I am sure it will, 250W was more than enough to power my Multiplex Fun Cub! (OK, I upgraded to double that for more Fun, but anyway.) Where did the 26 ounce come from? That is 737 grams! I'm building a half-A Beginner Ringmaster...

My set-up will weigh:
20 grams motor
9 grams ESC
50 grams 3S 600 LiPo
79 grams
I found a prop that gives me a static power level of about 95W, the plane should weigh about 150 grams when done.

Yours I guess will weigh about:
70 grams motor
18 grams ESC
100 grams 3S 1300 LiPo
188 grams

I will give this a shot, I can always upgrade to a bigger set-up. This plane is only to get me started. After I learn a bit I will want a better plane anyway, but first let's do circles and change height without crashing.

Cheers,

Hugo

[eric rule]

The 26 oz is the total weight the 1/2A system will handle with competition level power. Based upon our research we have found that you need 150 watts of power for every 1 pound of model (that's the aircraft plus the power system). Here's the math: RSM .061 electric system produces 250 watts of power. 250/150=1.667 pounds X 16 =26.6 oz (754 grams).

Since the weight you are going to have to move around the circle is 229 grams (8 oz) due to using the 600 mAh battery and a model that only weighs 150 grams (I'm not sure that I have ever seen a Baby Ringmaster that came out at only 5 oz) you only need 75 watts of power so you should be Ok with the system you outlined.

[Tim Wescott]

Black Tiger   BT2836C  - 1300 kv motor with 3 cell 1300 mAh battery, 20 amp ESC combined with KR Governor will produce 250 watts of power. That will provide competition level performance on a model weighing up to 26 oz.

That might be a bit much for an aircraft that really should weigh in at 6 ounces or so.

[HugoW]

Thanks Tim, your reply came in just when I was typing:

I think 26 ounces / 750 grams on a 1/2A plane cannot fly. The 1/2A planes I can find are about 20" wingspan, wing area 65 - 70 square inch. Let's for the sake of easy math say 78 square inch on 26 ounces, one ounce per three square inch. That won't fly as far as I know.

The wood work on my Beginner Ringmaster is done, it weighs 37 grams now. Plus hardware plus set-up, my aim is lowered from 150 to 130 grams. 6 ounces is 170 grams, so I should be OK with my set-up.

Cheers,

Hugo

[HugoW]

Just thought I'd share a pic of my handy work so far...



42 grams as she stands. 130 target minus 79 set-up minus 42 grams = 9 grams left for paint and controls. That isn't a lot of room... Anyway, 130 is an ambitious target, I don't mind going over slightly.

Hugo

[Tim Wescott]

If you can hold the weight down to 130g, your 50 watts of motor may actually do the job nicely.  The rule of thumb for large planes seems to be 7W per ounce on average, 11W per ounce peak.  For smaller planes it's more like 10W per ounce average, and I haven't a clue of the peak value needed (more than 11, probably).

Here's my Beginner Ringmaster on the scale (that plywood is not part of the weight you see -- the number on the scale is all plane).  In addition, I've got a Beginner-Ringmaster-Like-Thing for comparison -- it's got less wood and no landing gear, which is probably where the 20 missing grams went.

Finish on both of these planes is a few coats of clear dope, then tissue, with colored tissue (and decals, in the case of the Beginner Ringmaster) for trim.  It's light, and it looks pretty good.  Hinges are sewn on after finishing (I always finish first and then hinge).

Both of these are promising fliers, but with problems that keep them hanging on the wall -- the Cox one won't stay running inverted, and the Wen-Mac one won't keep line tension inverted.  But for flying level in a circle and then falling down from dizziness, they're great.

[Keith Renecle]

Hi Hugo,

Your Beginners Ringmaster looks good so far. If you look at the method I used on my 1/2A stunter you can see a neat way to install the electric stuff. If you need more photos I did take a lot when I was building. The governor timer may sound like an overkill but the constant speed makes for such nice flying especially in wind. The shut-down feature when you jam the prop is also worthwhile. Even with the prop saver sometimes the prop still stays on the shaft and jams the motor.

I've owned and flown a lot of 1/2A models that were Cox powered and none of them flies as well as this electric one. The weight is 170 grams or so, but I reckon that the foam and paper covered wing is heavy so I could knock off another 20 grams with a built-up wing covered with plastic film. On a flat wing you can stick the battery under the outer wing with some Velcro. The motor needs to weigh around 22 grams with a Kv of 1900 to 2000 to spin a small diameter prop like the 6 x 5.5 APC I used. Slower than that needs more diameter and then ground clearance becomes an issue. Have fun!

Keith R

[HugoW]

Thanks for all the info, I think I can continue with the power system. I have very different question, though. I don't know if I should start another topic about this elsewhere on the board or do it here to keep this plane topic complete, so I ask here. If this is wrong, please let me know.

As you can see the wood work is done. Now I will need to finish the plane. I had planned to use three layers of clear dope, one thinned 50% and two full coats. Decorate with a permanent marker, and done. Now I also read for instance Tim about putting on tissue. Would this add a lot of strength? How about weight? I don't need to fuel proof the plane as the electrics I plan to use run on electricity and magic smoke, not on fuel. Could I leave the clear dope behind and use tissue directly? Would I still use dope on the tissue, or some other applicant?

Cheers,

Hugo

[Tim Wescott]

Tissue will add some strength and a lot of good looks for little weight (certainly less weight than if you try to fill the grain of the wood with dope alone, or if you try to paint color trim).

If all you want to do is to waterproof the thing and go fly, then your plan will work just fine.

I recommend dope if you think you'll ever find yourself in the company of nitro-powered airplanes.  There are other finishes that will protect the plane from water, but that won't survive fuel spills, exhaust fog, and getting handled by hands with castor oil on them.

[HugoW]

Thanks! I will not go near anything oily / smoky anymore, so that's not a problem. I just learned I can seal the wood with nitrocellulose lacquer and sand that back. I think I will stay away from tissue for now. This first plane is just to get me and my son going, if we like it I will certainly build something bigger and better.

Cheers,

Hugo