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Member postings for Martin Harris

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

Thread: Slite v2 spoiler box
12/11/2019 13:36:31

I think the pictures in Andy Sephton's build thread show a similar arrangement? Is it perhaps just sanded to shape once the centre section is completed?


Perhaps a PM to Andy if he doesn't see this thread?

Edited By Martin Harris on 12/11/2019 13:37:23

12/11/2019 13:12:19

They need to be JPEGs and uploaded to your albums first.

Thread: Non parallel wing ribs - Terminology?
12/11/2019 12:46:58

Wikepedia also states [in a different article]:

"A further consequence of the new rules for airframe stress design was that a new way of harnessing the lifting force of the gasbags had to be found. Wallis's solution to this problem later led to his innovative geodesic airframe fuselage and wing design for the Wellesley, Wellington and Windsor bombers."

My interpretation is that the gas bags were slung using wires arranged in a criss-cross arrangement using geodesic principles - i.e. following the shortest distance between 2 points on the surface of the object - and Wallis developed this thinking to the lattice structure formed from aluminium channels [forming the shape rather than following it] which he named Geodetic Construction.

We're probably departing into semantics and in fact, Alan only stated that Wallis developed geodetic construction while designing the airship. Whatever, the principle certainly worked and many Wellingtons returned with structures still providing sufficient integrity after being hit by enemy fire that would have downed many other types.

Edited By Martin Harris on 12/11/2019 13:03:12

12/11/2019 12:25:47
Posted by Alan Gorham_ on 12/11/2019 11:51:46:

I think it's a common misconception that Barnes Wallis designed the Wellington. I think that it was designed by Vickers chief designer Rex Pierson using the geodetic construction that Wallis had developed when designing the R101 airship.

I stand corrected - I always assumed Barnes Wallis lead the design team.

Didn't Wallis design the R100? However, I don't believe the R100 used geodetic construction although the gas bag lifting loads were supported by wires arranged in a geodesic configuration.

Edited By Martin Harris on 12/11/2019 12:28:14

12/11/2019 11:36:40

Best known example was the Wellington bomber designed by Sir Barnes Wallis of bouncing bomb fame. It results in a very high strength to weight ratio. Many years ago, I owned a share of an SHK glider which used a form of geodetic construction for the 17 metre wings - the main spar in each wing only extended to about 8 feet...

Thread: The Gov't, CAA, BMFA & UAV legislation thread
11/11/2019 14:11:02

As a precaution, I've downloaded my BMFA membership certificate and the relevant exemptions to my mobile phone. Nothing to fear from the boys in blue and no scraps of paper to blow away!

Thread: Ebay sellers...
11/11/2019 10:41:23

That's the Black Mountains Gliding Club at Talgarth - a rather "compact" site where the performance of the 235hp Pawnee is rather useful. Let's hope they've kept it in better condition than the model. I had a few tows behind it in the mid 80s...they've certainly had their money's worth!

Thread: Autumn is been flying ?
10/11/2019 22:35:39

Chris omitted to tell you that we had a small invasion to contend with on Saturday - seems the CAA are taking a heavy handed attitude to compliance issues...

whatsapp image 2019-11-09 at 18.54.09.jpeg

In truth, one of our neighbours wanted to do some filming and we were happy to oblige.

Thread: The Gov't, CAA, BMFA & UAV legislation thread
10/11/2019 22:17:45

Why speculate on matters under active negotiation? We've already been told that buddy boxing and instruction under close control are being discussed - until we hear that such arrangements can't be incorporated there's little point speculating whether little Johnny [or Jemima] would need to sit a test before being given a taster on a casual basis.

10/11/2019 21:41:59

Plus one on the above, Andrew.

To all the doomsday merchants - if you want to do the test - go ahead...costs nothing but I shan't bother.

I'm more than happy to wait until after the next BMFA/CAA meeting when I expect things will be much clearer - club AGM isn't until early December and I expect to pay my additional £9 with my renewals.

I'll worry about bombshells if they ever arrive - until then I'll continue to enjoy my flying as normal.

Edited By Martin Harris on 10/11/2019 21:44:04

10/11/2019 18:45:31
Posted by Mike Etheridge 1 on 10/11/2019 17:00:53:

If you were all to take the test, the administration task could be sorted out in a week and you could all start to daub your Operator ID's on the sides of your planes prior to the election and Christmas!.

No need to take any test to get an operator's registration - they just want 9 shiny coins of the realm and anyone providing them along with their details is then considered capable of building/assembling,maintaining and authorising a pilot to fly their model.

Thread: Charge rate ???
10/11/2019 15:16:01

Unless there's something very unusual about these particular batteries, the recommended charge rate for LiPos is 1c i.e. 6A or 6000mA

What sort of an authority has told you to limit them to 1/3 C ?

Edited By Martin Harris on 10/11/2019 15:16:45

Thread: Best Heating Option For Your Hobby Shed
10/11/2019 13:55:24

I've started burning red diesel again since starting a new build and the heater continues to impress. What I like is how quickly the air temperature in my not particularly well insulated double concrete garage increases to a comfortable level for working. Fuel costs are so much lower than my previous electric heating (plus consumption is physically obvious) and there are none of the humidity issues that bottled gas caused when I tried that.

Thread: The Gov't, CAA, BMFA & UAV legislation thread
10/11/2019 13:47:42

This poses an interesting possible defence to a charge of failing to display your registration - if the label must be removable, what happens if it "must have come off during the flight somewhere - honest Guv"?

Thread: Average current draw
10/11/2019 00:24:55
Posted by John Wagg on 09/11/2019 19:07:15:

Noted Simon, Thanks.

The Ni-Cad is from about 1994 and the Ni-mH is fairly new but got cooked on a fast charge, Might use the Ni-mH but not the Ni-cad.

Currently (pun intended blush) the Ni-cad does over 2 hours but not done a full test on the Ni-mH yet.


1994 NiCd giving in excess of 4/5 of its rated capacity? Bring back (good quality) NiCds...

I'd be happier using that battery (after a black wire corrosion check) than a new budget NiMH although I favour LiFe where my servos allow them.

Thread: Autumn is been flying ?
10/11/2019 00:05:29

Lovely flying conditions this morning but rain from lunchtime. Luckily I went this morning rather than my usual Saturday afternoon session but unluckily the club generator needed attention resulting in losing some flying time.

Thread: The Gov't, CAA, BMFA & UAV legislation thread
09/11/2019 21:57:48

I keep seeing references to pilot registrations by the existing certification route "expiring" after June. As these registrations will be issued on the strength of competence indicated by possession of approved qualifications and independent registrations on the strength of having passed a test "on the day", why would either expire "mid term"?

As I see it, the end date simply aligns with the introduction of new EASA legislation and the CAA are simply granting a period until then in which registration for 3 years can be made using your existing qualification.  When these expire, who knows what regulations will have evolved...

Perhaps this is too logical but I haven't seen anything stated in official documentation to contradict my assumption.

Edited By Martin Harris on 09/11/2019 22:01:19

08/11/2019 19:28:25
Posted by Nigel Heather on 08/11/2019 19:10:34:

If the CAA have now defined ‘special tool’ as ‘any tool” why haven’t they updated the very document that they ask people to refer to as preparation for the test?

Steve's words were:

"... we will be updating the service with the following:"

(my bold)

Edited By Martin Harris on 08/11/2019 19:30:15

Thread: CAA BMFA
08/11/2019 19:04:39

I'm tempted to say, "So what?" In the unlikely case that the CAA rescind your pilot validity, issued as an Achievement Scheme certificate holder, just take the test!

Thread: The Gov't, CAA, BMFA & UAV legislation thread
08/11/2019 18:51:16

Surely it's as clear as day!

The BMFA (etc.) obtained a concession "There will be no requirement to place any registration numbers on the exterior of model aircraft, but they must be carried in an easily accessible location (within a battery hatch for example)."

Steve has informed us that the CAA are refining this to "Where it is not possible to display your operator number on the outside of your drone or model aircraft, you may instead attach it on the inside- within a compartment that can easily be accessed by anyone, without the need for any tools or specialist equipment."

The BMFA have a meeting with the CAA on the 14th where I suspect this will be discussed. I wouldn't expect (or put any faith in) any statement until after this meeting.  As things stand, your competition scale model will need to have a hatch built in to it to contain the number which, although a nuisance and right royal pain in the backside in the case of an existing model, shouldn't be beyond any competent modeller.

Edited By Martin Harris on 08/11/2019 18:59:41

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