Chris's Webbit

[David Davis]

What does your model weigh Chris?

[Chris Bott - Moderator]

Hi David

 

2lbs 1oz now. That's with a 2200mAh 3S LiPo.

 

That reminds me it has just charged.

My last flight was exactly 10 minutes. Of all sorts of flying styles.

Charge put back in - 1083mAh.

[Chris Bott - Moderator]

Downthrust. How much is too much? I adjusted this at the field this evening until the model carried on straight and level along the same line no matter what the throttle setting.

Seems to work well as a setting so I don't think I'll change it.

 

Here's an attempt to measure it, I made it about 8 deg relative to the wing centre line.

 

[Big Bandit]

Spot on Chris, Hopeing to maiden mine this weekend, so I'll dial in some down thrust. I'll measure mine as well, the wings are nearly finished.

 

Cheers,

 

Chris.

Edited By Big Bandit on 14/04/2011 21:57:11

[Chris Bott - Moderator]

It will be interesting to know how much down thrust you need Chris, this just seems really excessive to me.

[martin Rowley 1]

Chris,

Clever bloke!I'll be interested to see it fly this weekend if I get the chance to get out!

Martin

[Pete B]

Nice one, Chris - your determined efforts to add 'lightness' have really paid off with those flight characteristics

 

My mate Terry has a Webbit (unflown as yet) which, to me as a leccy flyer, seems far too heavy for its size. He also has a Boomerang which is enormously heavy for its size and, for a trainer, flies a bit like a guided missile - surprised it hasn't got a braking parachute!

 

I'm no aerodynamics guru but, regarding the downthrust, could it be that the 'V' tail has some negative incidence, or the characteristics of the 'V' tail affect the overall dynaics of the aircraft? This doesn't seem to tie in with your finding that inverted flight needs little elevator, though???

 

Pete

[Chris Bott - Moderator]

Thanks Martin, not sure about clever, more like "got away with it". I'm afraid I'm away for the weekend so won't be out. That should mean the weather will be great for everyone else though...

 

Pete I'm no guru either, I agree with your theory. As it flies well with no power then I think the incidence is OK. So I do wonder whether it's a peculiarity of the V tail. To be honest, now it works I don't really care

 

[Biggles' Elder Brother - Moderator]

Well done Chris - hansome looking model and glad to read yo sorted your problems.

 

BEB

[Alan Dorrell]

Hi All,

 

My Webbit is now cvered and I am about to install my hardwear. Hopefully wont take too long.

 

I, ve just had a bit of a pear shaped ten days and missed both good flying weather and building time. It is mainly down to this TV change over, plus a bit of a poorly wife.

 

I was wondering about things like exponential on flaps and elevators. You know it is said to have more up than down on ailerons as down creates greater drag, and on elevators as up is more used and important than down.

 

Now, I used to fly C/L aerobatics and carefully built my models with absolutely parallel thrust lines and incidence, because I flew inverted as much as the "right" way up. I have been assuming the same is more or less true of the Webbit. I have a M.A.N. plan somewhere, some thirty odd years old, where the designer, one of the editors, maybe Walt Schroeder, carefully placed engine wing and stab / elevator on the same datum line. I must dig it out.

 

Anyway, that's my tuppence worth for now. Comments will be appreciated.

 

Cheers. Alan.

[Chris Bott - Moderator]

Hi Alan

 

I forgot to mention that I've taken out virtually all my aileron differential now, mainly because roll rate was poor with only one aileron doing most of the work. And my ailerons are half the size of standard.

 

I would always have elevator going the same amount up and down.

 

As for expo, that really is a matter of personal taste. If I have too much for example, I loose "feel" for the model. I put in an input, its not enough so I add a little more and get too much, if you know what I mean.

 

So on mine at the moment, I have 30% expo on ailerons and elevator.

[Alan Dorrell]

Hi Chris,

 

Of course, you have flaps taking up a bit of aileron space. My Webbit is pretty much bog standard except for being electric. I bent up and soldered the under carriage yesterday and am fairly chuffed with it. Photos soon.

 

Mind you, all this talk of rolls etc., I am still happy just to be able to take off and land. I am still flying, when I get out flying, my Arising Star. My initial motive for building the Webbit was to have a handy, smaller size model I can take down to the field and fly with a minimum of fuss. I had been thinking of buying a Wot 4 Foamy E when I saw the charity build thread. I have been really enjoying it because I am definitely an addicted builder. And I will bet, to be honest, I expect the total cost of the Webbit will have been more than the Wot 4 might have done. The fact is, I had this thirty year gap from aircraft modelling, but since taking it up again about three and a bit years ago, I have three and a half artf's, six scratch builts and an unfinished Little Toot. I shall start my Webbit 52 in a week or so's time, but I also have the full kit for Tony Nijhuis's Lizzy, a kit fot a three channel Popsie, plans canopy and cowl for a Fairy Firefly and plans and ambitions to build Miss Lizzie, Mustang FAI, an enlarged Javelan and a raio assisted Windy Aint It.

 

By the way, I dug out that MAN plan. I t was by Walt Schroeder and he called it "Eyeball"

 

Cheers for now. Alan.

[Mowerman]

Looking at the downthrust seems very similar to my Piwakawaka (a bit like a slightly smaller Webbit)

[Chris Bott - Moderator]

Thanks MM.

 

I'm still tempted to try it with less again, it just looks wrong.

[Andy Muckley]

Hi chris i have a quetion? I dont get what it means in the instructions about the tork rods and the grooving of the wing. Hope this makes sence

[Chris Bott - Moderator]

Hi Andy.

 

Torque rods! Quite an old method to operate ailerons from a central servo.

If you intend to use two servos mounted out in the wings somewhere, then don't worry about torque rods.

 

If you do want to use them, they can usually be bought at a model shop or made yourself.

Bought is much easier.

They consist of a tube which glues along the trailing edge, the hole down the tube is in line with the hinge line. So you have to groove the balsa to let the tube in, if that makes sense?

 

The tube has a metal rod down it.

The outer end (for each aileron) is bent at 90deg straight back, so it goes in a hole drilled in the aileron. The inner end is bent at 90deg straight down (for a high wing model). This end is usually threaded and has a fitting on it for a pushrod clevis.

Once one is in for each aileron, the central servo is connected up with short pushrods and operated the ailerons via the torque rods.

 

Quite a long explanation, is this what you were wondering?

Cheers

Chris

 

 

 

Edited By Chris Bott on 24/04/2011 10:53:31

[Chris Bott - Moderator]

Andy if you need more, I just found a book with some great drawings and words on the subject, just shout and I'll scan them and post them.

[Andy Muckley]

Hi Chris thanks for that understud, only using one servo so will go with that, i think my old trainer uses the tork rod method so will take a look at that for referance thanks chris

[Danny Fenton]

Hi Andy one gotcha that we have all probably fallen for when doing torque rods, rub some vaseline on the wire where it goes through the tubes. When you epoxy the tub to the trailing edge any epoxy in the tube will make it bind really badly, the vaseline should prevent any epoxy causing too much trouble.

I bet everybody on here has had that happen at some time

 

Cheers

Danny

 

[David Gilder]

Andy.

 

Regarding the Torque Rods...

 

Have you had a look at the Wings Build. It is all explained in there!!!

 

Webbit example build - Wings

 

Dave

[Chris Bott - Moderator]

Davids explanations in the wing thread should be all you need

But just in case I've tried scanning that book and started a thread here

In trying to keep the file sizes down the scans are not brilliant, but something might just help.

[Andy Muckley]

Ch eers Danny good tip and also found by making a mistake you also need a right and left one easy mistake to make but soon bent it the right way

[Andy Muckley]

Hi David will look now, as i haven't seen your thread yet thank you

[Chris Bott - Moderator]

Off to fly VeeBit again this afternoon

Wish me luck!

[Chris Bott - Moderator]

Two lovely flights with the Tiger Moth this afternoon and three er.. flights with the VeeBit.

 

First two VeeBit flight went fine actually, as long as I stayed below 3/4 throttle. Above that I still have unpredictable torque problems. Landings were good too.

 

Third flight doesn't count, I thought I had tons of battery left in the previous battery but evidently didn't. Low Voltage cutoff kicked in soon after takeoff with the nose up at 45deg. Kicked the nose down and carried on for a straight on deadstick. landed a long way out and hit a strip of longer grass that flipped her on her back.

Third real flight went OK but was fighting the wind and really couldn't pull any smooth manoeuvres. Roll trim seemed quite a bit out so decided to land to see if the bad landing had moved or broken anything. Again the tufts flipped her over. Now I have a small split in the rear fus just below the V tail so I called it a day.