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Member postings for Piers Bowlan

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

Thread: Baby Flea
17/08/2018 13:36:23

That is really excellent Max, looking forward to the pull out plan in the magazine, if that is your intension. It will be a very popular build I'm sure. Do you think a 30 four stroke would be suitable in a conversion?

Thread: Great Service - But!
17/08/2018 12:55:47
Posted by David Mellor on 17/08/2018 11:59:02:

"It seems most of us know and acknowledge the problems of pollution but accept it"

If so, do you think that "acceptance" is what each of us needs to change?

The reason I ask is to do with the psychological implications. Surely if a particular proposition is accepted then its very acceptance defeats any further mental effort to help change the proposition?

We can all individually do 'our bit'; buy vegetables lose from a farmers market (locally produced), cycle to work (where possible), and compost our garden waste. All worthwhile stuff but the big policy changes need to be orchestrated by governments, that is their function. So how do you suggest we change 'acceptance' as a mindset and how would that play out in reality? Write to your MP or take part in 'green' marches/rallys? How many people with families and busy careers have the time to get involved with such things, let alone be inclined, considering the political baggage that often accompanies such 'green' organisations.

The tide is turning, awareness of the problem has never been higher and sustainability is the buzzword. It is just a question of whether things are changing fast enough?

Thread: Flaps
15/08/2018 19:02:08

I think that video should come with a health warning:- Don't try this at home!

15/08/2018 17:27:37

Yes Nigel, 'if have power on you have a big dose of prop blast over the inner section of the wing' not only that but the prop slipstream will be rotating causing a different angle of attack between the two wings and therefore asymmetric lift and drag. Probably more importantly, the increase in lift produced by the flapped inboard section of the wings will cause the centre of lift to move inboard, reducing lateral stability, which at the stall will exacerbate any tendency to drop a wing.

Yes, I thought talking about 'stalling speed' will cause apoplexy in some people. Apologies all!

15/08/2018 15:04:21
Posted by Martin Harris on 15/08/2018 11:43:52:
In terms of handling with flaps deployed, although there may be some negative effects from disturbed airflow, as the effective angle of attack is higher at the flapped part of the wing I have always felt this gives less tendency to tip stall as the inner part of the wing stalls a long way before the outer parts - i.e. using flaps provides wash out...

Selecting flap effectively increases the camber for that section of the aerofoil. The coefficient of lift increases as does drag for that part of the wing. The more cambered section (inboard) will stall at a lower airspeed than the tips so the tips of the wing will tend to stall first as they have a less cambered aerofoil. That is my understanding and is what I experienced when I instructed on C152s many year ago.

I would demonstrate a clean stall first followed by a power-off stall with flap and finally a power-on stall with flap. The clean stall was usually pretty benign in a C152. The stall with flap at idle power might provoke a bit of a wing drop but the stall with power and full flap would often provoke a rapid wing drop and autorotation into an incipient spin if you didn't correct in good time with opposite rudder. In truth the C152 didn't spin that well. The important thing was to keep the slip ball in the middle at the point of stall, particularly with flap out. With flap and power it was critical. My conclusion was that flap increased the likelihood of a wing drop (tip stall).

Edited By Piers Bowlan on 15/08/2018 15:14:58

15/08/2018 12:12:08
Posted by Biggles' Elder Brother - Moderator on 15/08/2018 10:44:03:

At larger angles, 40 degrees plus, they don't provide lift they just make drag - lots of lovely drag!


Not wishing to be picky BEB (!) but at larger angles, at 40 degrees plus for example, flaps still provide the same lift they do at 20 degrees deflection, it is just that they produce a lot more drag as well (not instead of). Perhaps that is what you meant? In other words the stalling speed will be the same at 40 degrees as it will at 20. This assumes that all other variables like wing loading and air density remain the same. Aircraft with efficient double slotted fowler flaps for example, will also experience a small further reduction of stalling speed with greater flap deflection but still the principal effect will be an increase in drag with large flap deflections.

Thread: The Big Guff.
15/08/2018 09:33:34

Ask ten modellers how you would build The Big Guff and you will get a dozen different answers! Personally unlike David (Mellor) I wouldn't bother adding carbon strip or towes for that matter. If you are intending to use quarter inch Bass wood for the upper and lower members with full depth webbing, it will be massively stronger than this slow flying, lightly loaded model will ever require. The question that David asks is a valid one. Would 1/4 x 1/8 basswood be sufficient - and without carbon reinforcement? After all, the original design used an all balsa spar glued together with balsa cement and carbon fibre hadn't been invented!

I would give some thought to how the two wing panels are joined. The dihedral braces on some of these early designs are somewhat fragile by modern standards, think, Super Sixty (howls of protest on the forum!). A lot of leverage with large wings, should they suffer an arrival rather a landing, so make sure there are not any stress risers.

With a short nose moment, why put any servos in the tail, just use wire trace and pull pull cables? That way you can use any servos you like in the fuselage without fretting about the weight. Personally, I would use a wire U shaped joiner for the two elevator halves, more reliable than a piece of wood.

I think the Laser 75 will be more than adequate! Personally I would go electric and stick the LiPo vertically behind the motor bulkhead. No C of G issues even if you covered the entire rear fuselage with birch ply wink 2.

Thread: Servos
14/08/2018 10:45:28

Servos;- horses for courses really! For small models I have purchased quite a few of these, as I have found them to be reliable, powerful (for their size) and I haven't received a dud one yet! For slightly larger models I generally use Hitec servos, notably HS 82MG and if you want something a bit more powerful a HS225BB is a good budget servo. Just my 2p worth.

Thread: Laser 180 Petrol
14/08/2018 10:30:10

Thanks Ron & Jon, that is encouraging news. The best news would be info on when the first production engines will become available. I have an NGH 38 that was destined for my World Models Pa 25. I would much rather fit the Laser GA30 but with other projects on the go the Pawnee can wait until next year for it's engine, no problem.

14/08/2018 06:44:20

Jon, have you done any testing regarding the GA30 noise levels when turning the 17X8 wood prop? I just wondered if it was any noisier, or no different to, the Laser 180 glow?

Thread: Diesel fuel - local
14/08/2018 06:03:35

I would give Sussex Model Centre a call and see if they can post it. It's about 37miles from Portsmouth to Worthing so alternatively you could drive over to pick it up, if you had a couple of hours to spare. Cheaper than having four gallons of fuel couriered over but then again you may end up spending a lot more once you get in the shop!

Thread: Chorus Gull
14/08/2018 05:43:27
Posted by David Hayward. on 13/08/2018 20:15:34:


it's the tapered section element that I could do with some advice on. The ribs will be produced by the sandwich method. It appears to me the wing section should taper top and bottom from root to tip; this means I cant just build with the ribs from root to tip down on the building board as this would mean only the top of the wing would taper.


What this means is ribs from the root to the tip will have to be gradually spaced off the building board, also bearing in mind building in the necessary washout.


Firstly is my thinking correct? Secondly, if this is correct, is the easiest way of achieving this by including tabs on the ribs to provide the required spacing?


No David, I don't think it is. I don't have the plan in front of me but just pin the lower spar to your building board and glue your ribs to that, not forgetting to pack up the trailing edge, - progressively increasing spacers to the tip to create the required washout. Don't build the wing 'off the building board'.

I am not a fan of foam wings but the Bill Kits foam wing cutting service looks very good value if you follow the link provided by Kevin. It might save you time and heartache if you are not comfortable building a tapered, washed-out wing. Good luck.


Edited By Piers Bowlan on 14/08/2018 05:45:40

Thread: Why not 'cut and glide'?
13/08/2018 09:30:19

I was slope soaring a simple 2 ch flying wing (Zagi) from the South Downs a few years ago. A woman came up to me and said that she had been watching my plane fly and said 'It is so quiet, where is the engine?' I said it doesn't have an engine, it is a glider. 'But', she said, 'you have a controller, how does it fly?' I said that it is just soaring in the rising air that is blowing up the slope. The 'controller' is just so that I can steer the model around the sky. It will continue to fly for as long as the wind blows (almost). She looked at me totally non-plussed with a look of bewilderment and scepticism. In her eyes I was clearly lying, as what I was doing was impossible; magic was at play!

Edited By Piers Bowlan on 13/08/2018 09:32:19

Thread: Scottish Aviation Twin Pioneer CC Mk 2
11/08/2018 15:24:19

Collisace, I find it hard to believe that such a large model will have a one piece wing but I could be wrong. If you are up to building this twin electric monster then making the outer portions of the wings detachable (outboard of the nacelles for example) should be easy-peasy for you. SLEC make these tubular wing joining tubes in various sizes which are ideal for detachable wings.

Having had a look at this model on the Sarik site, if you look at the side elevation of the Twin Pioneer in flight and enlarge the image, you can see what look like screws just outboard of the engine nacelles. Three piece wing. Fuselage looks like a doddle, just a lot of it!


Edited By Piers Bowlan on 11/08/2018 15:39:00

Thread: EU. LBT
10/08/2018 11:10:07

Important point - Any V8 or D series gear imported or sold pre the 2015 change remains legal to use in the UK.

Edited By MattyB on 09/08/2018 17:55:11

So if you use a V8 or D series Rx, which you bought last week, and if someone wished to prosecute you for a non-compliant Rx then the onus would be on them to prove that it was purchased post 2015? How could they do that?

Thread: RM Aerobat
10/08/2018 10:52:17

Nice work Nigel, what servos are you using?

Thread: BMFA 2018 Nationals
10/08/2018 10:48:03

Sadly I can't go to the Nationals this year, I was looking forward the evening 'chuck and duck'. I agree, the new arrangements look more appropriate, judging by what I have see on uTube channels of the event in previous years..

Thread: Why not 'cut and glide'?
09/08/2018 14:02:17

'Why do some models have a wide flight envelope and others don't?' Design:- wing loading, aerofoil used, available engine power, high lift devices fitted, configuration, aspect ratio, intended purpose, to name only a few.

Edited By Piers Bowlan on 09/08/2018 14:04:58

Thread: EU. LBT
09/08/2018 13:18:55

Wow! Thanks for that Pete yes

Thread: Why not 'cut and glide'?
09/08/2018 12:25:00
Posted by Toni Reynaud on 09/08/2018 12:03:56:

Everyone should have done this at least onece - it's part of the A test as a Deadstick Landing. Also I for one have a great deal of difficulty primarily controlling speed of descent with the throttle - the lag between throttle management and speed of descent change is quite long. Perhaps I don't fly and practice enough.

I think the problem is exacerbated with models that have a large pitch change with power leading to a less stable approach. If you can set the model up to have a small pitch change with power with some mixing or, dare I say 'engine down thrust' (not wishing to be controversial here!) life will become easier. A nice calm day helps too.

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