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Member postings for Rob Lewis

Here is a list of all the postings Rob Lewis has made in our forums. Click on a thread name to jump to the thread.

Thread: Great Service - RCWorld .co.uk
23/01/2015 18:52:47

RCWorld has been my site of choice for a couple of years. Never had any problems that haven't been instantly resolved, and as Stevo said, postage is always reasonable and quick.

Thread: Bombardier Q400
17/12/2014 09:02:11

Must admit i don't know too much about this yet, wasn't at work last night or today.

From what i have read, it seems passengers were saying there were popping sounds and sparks and flames coming from the back of the engine. I'm assuming it was surging, a compressor fault or such.

All in all sounds like it was well handled by the crew. Once the fire is out, it is a non event. The Dash flies perfectly well on one engine.

Thread: Replacement Car
17/12/2014 08:42:23

I got a new car a few weeks back. Initially i was thinking of a 3 series GT as a friend has one, but it was a bit out of my price range having only been released last year. Last car was an old 3 series BMW hatchback, and wanted something bigger but not an estate.

I ended up getting an Audi A5 5 door sportback. Loads of room in the back with the seats down, and a huge boot lid to get them in and out.

Thread: Bombardier Q400
05/12/2014 19:10:53

Absolutly fantastic Simon,

When its in the air you can't tell it from the real thing.

So pleased for you that it all worked out.

24/11/2014 22:08:22

Looks fantastic Simon. Just like being at work......

Can't wait to see a vid if it flying

Massive yes from me.

Thread: Fantasy Formula 1
21/09/2014 22:55:07

Highest score 2 weeks on the trot teeth 2. I'm sure it won't last though.

Thread: When is a pusher prop not a pusher prop?
18/09/2014 13:07:13

Hi Peter, I was having a think about our discussion and think i may have realised where we crossed wires.

When you were talking about the leading edge of the prop being closest to the engine on a pusher, i think you were refering only to the pitch of the propellor?

I was talking more about the aerofoil shape of the prop. Obviously the prop to all intent is just a rotating wing and has a leading and trailing edge. My thoughts are that although the pitch of the prop was okay and produced thrust in the correct direction, the aerofoil section was opposite to that needed for the pusher prop. So when rotating the prop was leading with its aerodynamic trailing edge, like trying to fly an aircraft with the wing on backwards.

Maybe that will clear things up? (Or open an even bigger can of worms?)

Either way, its great to get the Windbag in the air. There is definately a lot of drag from the Flexifoil, with full throttle applied it climbs at about a 45 degree angle and i think that is mostly because of the wing holding it back. The guys at the club loved seeing it fly as well.

Rob

Thread: flexifoil windbag
17/09/2014 21:14:26

Well i discovered the problem with my Windbag with help from some other forumites...... The pusher prop i was using was moulded opposite to the way i was expecting meaning it was running backwards (leading with the trailing edge), see my pusher prop thread for a more detailed explanation. Basically it was developing much less thrust than it should.

A simple fix of replacing the prop and she was airborne and 20ft up before i'd blinked. A few trimmimg flights later and it was flying around lovely. Unfortunately it rolled over and broke the canard on the last landing, but its a quick fix.

Thanks for your help guys thumbs up

Thread: When is a pusher prop not a pusher prop?
17/09/2014 21:07:02

Well the good news is, the Windbag flys. Used the 11x6P and she was airborne within about 10 meters. Can't believe something so simple kept it grounded for so long. At least it was a cheap fix. Bad news was it rolled over on landing and broke the canard, only a couple of hours work to repair though. All in all a sucessful outing.

smile

17/09/2014 14:47:37
Posted by reg shaw on 17/09/2014 14:23:03:

Hi rob, thats a familiar looking machine you have there!! Its exactly the same as the old 'Windbag' from I'm guessing the late 80's early 90's. I remember mine fondly but sold it on a few years ago.

Are they still available?

Ian.

Yep its the same machine Ian. I stumbled across the old plans and have always been keen on things that are different. I brought a 2nd hand Flexifoil Stacker 6 kite from ebay and built the rest.

I've still got the plans saved on my laptop if you fancy a copy. I had to print it out on loads of A4 sheets and tile them together but it got the job done. PM me your email address and i'll forward them on if you like.

17/09/2014 14:43:05

Hi Peter. Just going back to your first post, you said that a pusher prop will have the leading edge closer to the engine. I'll repost the pic so that we don't have to keep scrolling to the top.

img_20140916_161911.jpg

Both of these props are pusher props, and both are placed the same way up. My understanding is that the top prop, the 10x7P, if mounted so the surface we can see is next to the prop washer / nut, will have the props aerodynamic leading edge furthest from the engine and hence will be leading with the trailing edge first when the engine is running counter-clockwise.

Conversely the lower prop, an 11x6P when mounted the same way will have the aerodynamic leading edge closest to the engine as you described, and will be leading with the leading edge when the engine is running.

If as Chris suggested the 10x7P is turned over, so the face we see is against the prop driver, then the prop will lead with the aerodynamic leading edge as required.

I've probably over described a lot of this, but it just about makes sense to me.....

Have we crossed paths or am i not understanding your explaination fully?

Cheers Rob

17/09/2014 13:14:25

Thanks for the detail Peter. When the top prop was bolted to the engine i had the writing pointing away from the engine as i normally would, so when the engine was running counter-clockwise (viewed from front) in effect the prop was running backwards with the trailing edge leading into the airflow. If i flip the prop over and have the writing facing the engine then it becomes the perfect pusher as you described with the leading edge closer to the engine.

The second prop by contrast would need to be bolted to the engine with the writing facing outwards for the leading edge to be closer to the engine. This was what caused the confusion.

Incidently this is for a Flexifoil windbag that i have built

img_20140806_190934.jpg

The plans call for a 0.40cu engine. I have a Super Tigre 45 on it that i had in my spares box. With the 10x7P on (running backwards) i was getting around 11,000 RPM at full throttle, so should be more than enough power for the model, if the prop is correct.

Tonight i will try the 11x6P or maybe the 10x7P backwards and see if it makes any difference. Thinking about it logically, it makes sense that power would be down with the prop effectively running backwards, so hopefully all problems will be resolved tonight.

I brought 2 of the 10x7P's but from the same supplier at the same time (always carry a spare), they are both the same, but i guess they could always have been a bad batch?

As with Ian and Chris I assume clockwise tractor props are available, will have to do some research and see if it sheds some light.

16/09/2014 20:57:33

Posted by eflightray neath on 16/09/2014 20:42:28:

As this 'Propeller Selection' forum is in the 'Electric Flight' group of forums, I assumed wrongly frown

Oops.... When i started the thread i just scrolled down the "select a topic" list and thought prop selection sounds about right. Didn't realise it was in the leccy section. My appologies.

Could well be Chris. Thats what it looks like. I don't have the packaging anymore but the writing on the prop just says 10x7P which is the same format as on the 11x6P. Just checked the site i brought from and theres no special info attached to the prop either. Who knows....

16/09/2014 20:33:40

Some interesting points.

efliteray - Its an IC engine so reversing the motor or folding props are out....

Dave - In the pic above both the props are with the writing facing up, and they are both APC pusher props. So the top one would have the writing facing towards the engine and the lower one would have the writing facing away from the engine for them to work. I couldn't say which one is the norm as they are the only 2 pushers i have ever brought, just seems strange to me that there doesn't seem to be a convention. Either that or i have stumbled across a somehow mismoulded prop.

16/09/2014 19:07:06

I've never seen IC props being fitted backwards (writing towards engine), but looking at it now that definately seems the only way that prop will work. Strange that they are from the same range of APC pusher props but are different.

Either way at least the lack of thrust should be sorted and the model should fly this time round. thumbs up

16/09/2014 18:05:14

You know what....I hadn't even thought of turning it over. Doh..... I've always used props the way round as shown, with the writing pointing outwards. The other side of the prop has the cutouts at the hub as usual, i guess theres no reason it can't be mounted upside down so to speak.

You learn something everyday... Cheers Chris

16/09/2014 16:41:07

I recently built a model that needed a pusher prop. I brought the required prop, a 10x7P and although i thought something looked strange i thought "it must be right".

Anyhow long story short i haven't managed to get the model in the air yet, with the thought being lack of thrust or too heavy / too much drag.

One thing i decided to change was the prop. I ordered an 11x6P and realised what was wrong with the first prop and maybe why the model hasn't flown....

img_20140916_161911.jpg

The top prop although labelled a 10x7P looks to me like a clockwise rotating tractor prop. As i was using it as a pusher, it was effectively rotating backwards, with the trailing edge leading. I'm betting it would be a lot less efficient rotating backwards.

Its not just me is it?

Thread: flexifoil windbag
14/09/2014 11:45:15

Thats was my thought, not enough power or too much drag. The first attempt at flight i did have the body on, but all attempts after that i had the body removed to try and remove some drag. The rear axle sits behind the spar by about an inch or so, but this is as per the plan. I was thinking about moving this forward slightly, but too much and the prop would hit the ground on rotation.

I had assumed that the Stacker 6 kite i brought was the same as the windbag kite. But by the sounds of it the gauze opening is smaller on my kite. I guess this could make a difference, although Roy is using the same kite and obviously had success.

I have a Thunder tiger 46 on another plane that is in for repairs at the mo, i may change the engines over and give it another go to see if a bit more power helps it.

14/09/2014 00:05:12

Hi jeremy,

I forgot about the canard. It was the only bit i changed, i made it out of balsa, 3/8 thick if i remember. And i bolted it to the canard mount rather than using bands. Initially i set the incidence as per the plan, with the elevator going the right way - moving down for up command.

Its hard to describe but when trying to lift it off the ground, even with full up the nose would almost bounce. It would start to rotate but then give up and drop back to the ground. Even using the whole length of our strip which is about 500ft of tarmac..... Perhaps there isn't enough power from the old engine i'm using?

Edited By Rob Lewis on 14/09/2014 00:06:18

13/09/2014 22:24:50

I brought myself a Flexifoil Stacker 6 kite off ebay with the intention of building a windbag, and over a year later i finally got around to it....

img_20140806_190934.jpg

Unfortunately it seems i have built a racing car that drags a parachute around with it. Despite the kite inflating it just will not rotate. sad

If anyone with experience with anything like this has any tips i'd be more than grateful?

It is built as per the plan and is powered by an old Supertigre 45 with a 10x7 pusher. On opening the throttle, the kite inflates and i'm sure it is getting enough speed that it should fly. I pull back the elevator and the nose starts to lift but thats where it stops. There either isn't enough lift from the kite or not enough power to get it airborne. I've tried changing the incidence on the canard to give more lift but to no avail. The plan said that a decent 0.30cu engine would be sufficient, so even if my 0.45 is a bit tired it should still have enough grunt.

I'm planning on trying a different prop, maybe an 11x6, but i doubt just changing that will make a huge difference. Other than that i am stumped........ Any ideas?

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