1/4 FlyBaby 84

[propogandhi]

More good new (unless my Watts Up watt meter is on the blink). I run my new 6 cell 5000mah pack fresh off the charger (25.1v) through the watt meter and suprisingly, and a JXF 16x9 prop I was pulling just 45amps at full throttle but getting just over 1000w in output! This I'm very happy with and with my AUW looking now to be no more than 11lbs, this gives me a suggested 90w/lb which I think is more than enough for a model of this type.

 

I may even prop down on the ptich once I've flown her, if she can take it. But for now I just need to get the cockpit area finished and then I'll basically be ready for a test flight, maybe even by next weekend...well, maybe not, but soon anyway.

 

Once she's test flown I'll go about getting myself a new air compressor and finishing her off proper with a good spray job.

 

 

thanks for your advice with the electrics etc gents, it been a great help.

 

 

prop.

[Chris Bott - Moderator]

Prop that all looks like great news, don't you love it when a plan comes together

 

I think you'll probably stick with that prop, because you have that throttle stick to reduce current with during flights to extend flight times.

 

45A from a 5000 will give you 5 minutes, with some spare left over for a go around and to ensure you don't over discharge the battery. 

 

In reality, current draw will average quite a bit less in the air. So you will get longer.

But from your figures, I would fly for leas than 5 minutes, say 3, and then see what your charger puts back in.  From this you can then decide how long a flight you can go for.

 

Cheers

Chris 

[Tim Mackey]

Sounds good prop - do keep us informed on progress

I reckon you will manage 5 -6  minutes easy - do as Danny says , or simply fly until the motor starts to noticeably drop revs at WOT and then land immediately. Whatever that flight time was, set  minute less on your timer for future flights.

[Chris Bott - Moderator]

Do as DANNY says?? Pah! 

[Tim Mackey]

Oy - abuse towards other members is not tolerated on this forum Bott !

[Danny Fenton]

Hi Chris I need all the credit i can get You are right, you said fly for a few mins and take it from the amount you have to top up. I reckon if prop is gentle on the loud peddle he will get a lot more than that. My Chipmunk flew on Friday for 12 minutes and used just over 4000 from a 5S2P 10,000 pack and I did a couple of loops! Unloading is a powerful asset if the prop is right.

 

I am looking forward to hearing the flight report Prop

 

Cheers

Danny

[Tim Mackey]

Double ooops - my bad - I thought the post was from Danny - I must read the things more carefully

In my defence, you are a rare visitor these days Chris - so I almost take it for granted than when anyone is contributing to thread on A123 cells and so on...its Danny

My apologies mate

[Chris Bott - Moderator]

Lol no probs Tim, can't have people thinking Danny and I are the same person though

 

Prop, how far off a flight do you think you are?

We are all really interested now  

[propogandhi]

Hi guy's, well I could in theory have her ready to test fly for next weekend if I spend a few hours a night sort the cockpit etc out. But to be honest I was flying today and it was way to cold, and it really did effect the performance of my lipo's. Plus I'm going away in a week or so's time so I might just wait until March, let it get a little warmer and take my time getting her ready (sorry guys).
 
I must say 5 mins is disappointing! I would hope for closer to 10mins. That said I was only expecting 6-7mins max on my Magnatilla with 5 cell A123's, but I can get 12mins now with mixed throttle. So I'll fly for 5 mins to start with, then see how much I put back into my pack. I can also try the 16x8 prop if I feel I can do with slowing her down a bit when I fly her at WATT. That way perhaps I'll get my amp draw down even further and extend my flight times.
 
Time will tell, if you pardon the pun

prop.

 

BTW remind me how you worked out my flight times based on my amp draw and lipo cap?

 

[Chris Bott - Moderator]

Hi Prop

 

To make it simple, lets say its 50A.

You have a 5000mAh battery, that's a 5Ah  (5 amps for an hour)

 

So if you take current out at 50A in theory it will last 1/10 of an hour or 6 minutes.

But that's every last drop out of the battery and you should never do that with LiPo's 

 

So leaving some in, it's say 5 minutes. 

Actually as you are at 45A it will be longer...

 

However, that is at wide open throttle all the time and with the plane held stationary.

In the air, the current draw will be less. And you will very likely use less than full throttle for most of the flight, this extends flight time too.

 

You will get more than 5 minutes. Maybe a lot more. But only flight testing will really tell.

 

I agree you shouldn't rush things, we can wait..

Cheers

Chris 

 

[propogandhi]

Well, for the hell of it I tried the 16x8 tonight. At WATT I was getting 930W for 39amps which equates to 85w/lb. Again I still feel this would fly the model nicely, she's no aerobat, so I may even try the 16x8 to start with and increase my flight times a little too. What do you guys think?

 

 

prop.

[Danny Fenton]

I think you should go for it. the time you really notice not having the power is when you get into trouble and need to gain height quick. but if you plan your flight in advance it should be fine. You could even try a few fast taxii's to see how it feels, I bet its airbourne before 2/3 throttle even on the 16 x 8 (though you know I would prefer a higher pitch lol).

 

Should be great to see, any chance of a video of the maiden?

 

Cheers

Danny

[propogandhi]

If I can get someone to do it at the time, then yes, maybe. Won't be great quality mind you, it will be taken on my digital compact if they don't have there own. That said they shouldn't need to zoom in that much, she's quite a size. That's also a worry, the patch at Wanstead is exactly that...a patch! I think it will be ok, but maybe I'll find a bigger strip to test fly her.

 

prop

[Chris Bott - Moderator]

Propo I personally would go with the 16x10.

 

You can use the 45A if you need to, and a few clicks back with the throttle stick and you soon bring the current down..

[Tim Mackey]

I certainly wouldnt drop to 13" - either stick with the 16 X 10, or the 16 X 8 as I originally suggested - I reckon either will be fine - the 10" giving greater pitch speed of course, but at the expense of duration

[propogandhi]

13" was a typo, I meant 16".

 

 

prop

[Terry Whiting]

Prop,

 

I built the 1/4 scale bipe, (now sold) admitted a little more draggy than your 's, but was no problem getting in and out of a 60m patch.

I sold it because i was going electric, but now reading your thread i'm beginning to wish I hadn't as she was a fantastic flyer and a wonderful camera platform.

 

By the way, if your digi compact has the ability to switch to manual focus do so, then  set the focus at infinity, just use zoom as required. The result is much better quality.

 

Best of luck on your maiden   

[propogandhi]

Hey Terry, note taken re: the field size.

 

Tell me, do you remember the AUW of your flybaby bipe? It would be interesting to see how much lighter mine is, if at all!

 

 

prop.

[Terry Whiting]

Prop

 

Yes,     The  AUW was 11.25lb and my power was a   Laser 100.

Another club member built one previous to my build and was almost 2lb heavier.

He used a Laser 150 + some nose weight. I scaled down the wood  especially in the tail area and ended up having to make provision for my flight pack 6" rearward of the lower wing TE.

 

More I think of that model the more sick I feel for selling her.  

[propogandhi]

Sorry for the painful memories, but thank you for the info. So If my Flybaby comes in at no more than 11lbs, then she should fly well I suppose. Would you describe her as a floater at that weight? What was she like in stall?
 
prop.

[Terry Whiting]

Prop.

Your wing loading at 11lb would 23-24 oz and still make it a floater have no fear, as for mine with the extra wing area came out about 18oz.,  the stall it was a non-event, she would slowly sink. In  15- 20mph wind I could make is sit stationary as a kite by juggling throttle,elevator , and rudder.
Luckily as it was a club member who made the purchase he still lets me have some stick time 

 

I remember the plan giving both build versions.    

 

[propogandhi]

Terry, I'm just getting the Flybaby ready for its test fly this Thursday. I don't suppose you happen to remember how far the CG was back from the lower L/E do you? I've just come to the conclusion that I don't yet know exactly were it should be!

 

 

prop.

[propogandhi]

Actually not to worry, I forgot I had another thread on this build on rcg and within that some chap from the States posted the c/g for his Dynaflight 1/4 flybaby. The only this is its in inches, which other than for wingspan, I do not use. Can some please clarify what

"3 5/8 aft of the leading edge" converts to in mm. I've got a rough idea but I'd like to be sure.

 

With all this converting in mind would someone care to convert the throw settings taking from the above kit into mm too please:

 

 

I'm being lazy I know, but you wiser gents know inches like the back of your hand...so please spare a little time for a mainly metric  man

 

prop.

[Terry Whiting]

Prop,

 

Sorry, can not remember,  but you would be safe at 25% of the chord being  a parallel chord wing.

To answer your question,      3 5/8" ==== 93mm.

 

What is the chord measurement of the  wing? 

 

TW 

[propogandhi]

Ok, the cg is now basically right and the wind screen is on, and with that she is now air worthy, but by no means finished. So Today's the day, I'll hopefully report back this evening with good news and a half decent video.

 

prop.