Got one !

[john haz]

Hi Guys,

 

just couldn't resist the temptation & last Thursday bought  a HC B25 Mitchell.

 

Built it up Friday evening, did a few dry run tests sat morning & then went away on a short break.

 

Returned today & thought I should let you know what i thought of it all as a relative newcomer to planes.

 

The manual is written in Chinglish, but has some decent pix & made assembly fairly easy.

 

The kit was all intact & undamaged, with a couple of very minor niggles  - one of the grub screws missing from a motor mount & one of the tail assembly screws missing.  Not a problem.

 

Putting it all together was a simple task with the exception of the cowls, they are ***** to align with the holes.  Not looking forward to removing them any time soon !

 

On it's first spin-up i had only one motor running !!   This was traced to a badly soldered plug on the right ESC lead.  Again, sorted in a few minutes & no major issue.

 

Likes & dislikes:

It looks awesome, can't wait to give it a test flight & have read many hundreds of posts to learn a bit before crashing it

 

The battery bay is the best on any model I have had, simple to remove, on top & the battery 3s2200 fits lovely 

 

Not so keen on the landing gear cycling every time the battery is connected, but my solution is to sit it on a toolbox to allow it to do this.

 

It's heavy !   If there had been an option to buy a kit with no landing gear for hand launch / belly land, i would have bought it.    however, the gear looks so good I'm gonna take my chances until it breaks, then probably rip the lot out.

 

All in all, it's a lot of model for £200 & if i can get a few flights under my belt, i'm sure it will provide hours of fun. 

[Tim Mackey]

Nice one John

[Pete B]

If you are using Spektrum gear, John, try re-binding after you have set the undercarriage to whatever you want it to do when you switch on - it may be the failsafe function. This used to happen when I had retracts on my Sea Fury.

Can't give much thought to this as I'm just looking in for a moment...................

others may know better!

 

Pete

[Tim Mackey]

A few of us have this issue - and rebinding does little or nothing to help in most cases.

It turns out to be the type of servo deployed for the retracts that causes the issue - the supplied spektrum servos with the DX7 for instance are fine, whereas most others are not.

The problem is that most servos will go full travel on not seeing a valid signal from the tx when power is applied - and others simply hold their position. Of course with 2.4Ghz sets, it can take several seconds before the Tx and rx lock on to each other after initial powerup - therefore the servo sees no signal....and cycles as it were.

[Pete B]

Ah yes, that's what it was............seem to remember now it was something to do with electronics..........that's senility for you!

 

Pete

[john haz]

Thanks for the suggestions & advice guys.  

 

I did notice that it will cycle the gear on a "cold" power up, but disconnect the battery & reconnect within 2-3 mins & they don't move ??     It's a niggle rather than a problem, so I can live with it.

 

Had a wattmeter on it last night & at full throttle with a fully charged lipo only got -

26A

280w 

 

Seems a bit low to me for such a heavy model, I hope she can get airborne !

 

Ran it for 4 mins on the ground at 80-100% throttle & the esc's only got slightly warm, battery was ok & showed 11v when I popped it on charge, so I am hoping 5 min flights will be ok on these (this was a 1 yr old flightmax which has been used a lot on my heli's).

 

back soon...... 

[Tim Mackey]

How much does it weigh?

I believe the review model mentioned here a  while back was around 3.5lbs, so you may actually be OK - its no hotliner after all.

Edited By Tim Mackey - Administrator on 17/08/2010 08:35:17

[john haz]

Hi Tim,

 

Not weighed it myself but it's reckoned to be a 4lb model, feels about that too ! 

 

edit:  just seen your edit @ 3.5lb,

 

i'm not at all concerned about it being fast in the air, no clever tricks with it, this one is to fly steady & scale like (I hope).   i was more concerned about getting it up there from the ground.   Seen it hand launched on a video but don't think i would be that brave !!! 

Edited By john hazeltine on 17/08/2010 08:55:16

[Tim Mackey]

I agree, that sort of model needs to ROG to maintain a scale like appearance.

If it does end up at 4lb, then I would be tad worried with 280 watts WOT. 

hats only 70 Wplb, and although I am sure it will "fly" on that, take offs could be marginal, and I always like to have a little power in reserve for those unexpected moments when you just know that a quick burst of power is needed to get out trouble.

It may be worth googling around and checking other forums etc to ascertain exactly how much power its possible to push through the powertrain - thats one thing about RTF models.... you have to do some digging to find out what actual components have been used.

[David Ashby - Moderator]

It'll be fine John, mine flew with 74w/lb but like most twins the sum of the parts is greater....sort of...if that makes sense.

 

The trike u/c means you can apply full power right from the off for take-off but make sure you give the model a good long run before rotating. It's no fighter but moves along well. It has a stall, not viscious but just something to be aware of during the final turns before landing.

 

If you're a subscriber and can see the digital archive then the review is in the August issue.

Edited By David Ashby - RCME Administrator on 17/08/2010 10:24:05

[Vecchio Austriaco]

Hope you have field with a tarmac runway / it doesnt start from Italian grass runways   may be the english grass is cut shorter

 

Is it that one?

 

Flies very nice and scale like. But not much more than 5 minutes.

Pictures taken at ALA Lecco Sunday 2 weeks ago.

VA

[john haz]

Tim:  I have read all 168 pages of one thread on RCgroups (saddo I am) & a few seem to have upgraded the props, motors etc.    Not really found much info regarding power outputs for standard models, except one that listed about the same as me - no flight report on that one though LOL

 

David;  thanks for that.  I guess if that's the standard output then it will be "ok" & not much more.  From everything I have read, it does want some speed before pulling up, so I will have to find a decent surface to try it on. 

 

VA;  Yep that looks the same as mine.   Most of them seem to be identical although with different names on them.

5 mins will do me ok if my zippy 3s handle it ok. 

What i can't understand is all the talk of esc's burning out from overload when mine is barely pulling enough to overload one of them !

 

Not keen on the idea of twin bec feeds, so will invest in a ubec to eliminate this potential problem.     Can't decide if to upgrade the esc's to 30A for added security, sods law says if I do, one will fail anyway LOL

 

Appreciate the replies chaps, good to get more feedback from the experienced. 

[john haz]

to add to the above ....

 

A lot over in the states seem to have changed the props for 10x6 gws props, i think the standard are 9.75x?  & there's VERY little clearance on mine !

 

AIUI  if i change to 9.75x a higher pitch this will give me more speed but no more thrust, can't decide if this would be an advantage on take-off or not.   With the amp draw being so low on mine, if i had room it would have been nice to try 11x7 to see how it fairs.

 

[john haz]

and more ....

 

just doen the same tests with two of my new turnigy 3S/220  & got similar results.

 

Full battery, first hit   312w  & just over 12,000rpm

 

after 10 seconds 294w 11800rpm

 

after a minute or so, very similar figures to the 10 sec

 

 

[ericrw]

Keep the info coming John, I hope to be picking one up tomorrow!  Eric.

[David perry 1]

Ref the guys in the states changing props etc: remember that Americans are inveterate fiddlers and will change anything and everything just " to see " I'd be inclined to trust your figures and the designer and fly it before fiddling. If you don't you'll never have a baseline. D

[Marc Humphries]

@David

I agree - they fiddle just for the sake of it!  They put 600 W motors in glass covered Formosas - why?

 

Remember, a twin engine bomber is not going to tear around the sky like a P38.  My experience with twins (not scale) is that 70 - 80 watts per pound is fine and gives a good scale like peformance.  To give some calibration - a brushed Twinstar with a 7 cell NiMh gives around 50 Watts per pound.

 

Even the huge Boeing B-50 that TN designed works out around these figures - or even less.

 

As Lord Percy would say, "Fly the thing Edmund and be damned with it!"

[john haz]

David & Marc,

 

It all makes sense now    i thought they were doing it because the model needed it !

 

Will take advice from you both & try it "as is".   If it moves along at a reasonable scale speed & has enough power to get me out of rouble, that will be fine, i have a couple of smaller models that will fly st silly speeds when pushed so this one really can be a gentle scale flyer.

 

Dunno when i will get a chance, too much wind right now.  Had my little cessna & mustang out last night & they were ok but too much of a coward to try the lightning or mitchell ! 

[David perry 1]

video, video, video!!!!!

 

 

D 

[Marc Humphries]

There's a video here - scroll to the bottom of the page.

 

Certainly doesn't look sluggish...

[ericrw]

John, I've had a B25 as a birthday present, can't touch it till Sunday though.  However, a sneak glance in the box revealed two unmarked tubes.   I'm assuming they are epoxy mixing tubes.  Is this correct or did you use these or another type of fixative;such as hot-glue.   Eric.

[john haz]

Looks pretty good on the video Marc, but of course it's their own & probably filmed a hundred times to get the right clip LOL    

 

I would love to know if this one is standard, can't believe a 1.75kg model can be hand launched with the power I have in mine

 

http://www.youtube.com/watch?v=cZsTGnGS9QA 

Edited By john hazeltine on 19/08/2010 17:40:01

[john haz]

Eric,

 

The two white tubes are the glue, but it's not a 2 part job, just two of the same.   I thought about using 2 part epoxy on mine but decided that if i used the glue they supply it should hold it together & I stand some chance of removing the wings if I need to ?  (not flown it yet & already thinking about replacing parts LOL).

 

 

[ericrw]

Next question John, what parts ?  Eric.

[john haz]

Parts as in broken ones when I crash it !     I think spares are going to be hard to get hold of in the UK, so I am going to do my best to preserve this one.   If the worst happens, I didn't want the wings fixed in with 2 part epoxy because removing them might cause a lot of damage.   Hoping the standard glue is a touch easier to mess around with.