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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: Laser Engines development.
07/07/2020 11:21:48

At @ £100, a bolt on gearbox conversion would be something I would be very interested in - unfortunately I don't see any way it could be accommodated in my current build [very short nosed Tempest] at this stage so I'm unlikely to be an early customer.

Intrigued by your encouraging news - when will we get an idea of what's developing?

Thread: Motor Ident?
05/07/2020 15:40:08

I've seen your tootling Dick - anything up to 7 kW bursts of less than 2 seconds with 100 mph vertical climbs. Measured figures, not wildly optimistic estimates...


Thread: Flying during pandemic.
05/07/2020 15:29:52

If you're not all gathering together, do the 6 or 30 rules apply? We see it as club members exercising their right to fly in the open air as individuals in the same way that unlimited individuals or households can use parks or beaches if they respect the distancing guidelines. We're not organising meetings in any way although we've laid out the car park to encourage distancing and restricted clubhouse access to one at a time with sanitising rules to allow use of our solar charging facilities.

Thread: Dihedral
04/07/2020 01:12:00

Doesn't dihedral provide an increase in angle of attack of the accelerated wing in yawed flight, providing the majority of the unbalanced lift and hence the increase in bank?

My Extra - mid wing and no dihedral - seems to exhibit very little banking effect with rudder only although it may be that there's some unconscious aileron compensation when flying flat turns - I'll have to try it with the stick locked centrally next time I fly it.

Edit: A bit of duplication - John had posted before I refreshed the page...

Edited By Martin Harris on 04/07/2020 01:38:12

Thread: Carbon Fibre Tubes
03/07/2020 21:19:04
Posted by Erfolg on 03/07/2020 16:56:00:

On the other hand my HK Waco SRE had a aluminium inner wing tube, inside a Carbon outer. Much to my surprise the carbon tube shattered, leaving a wobbly wing. There was a lot more wrong with the model, but that is bye the bye. My repair just used an outer aluminium tube.

I wonder if the reason it shattered was due to the aluminium tube deforming and applying local pressure to the CF? I've had ARTFs with large diameter ali tubes sliding into cardboard tubes which I would assume really only act as guides, the loads being transferred to the wing structure locally at the ribs i.e. the tube is not acting as a significant part of the structure. In fact my well over 10 years old all weather hack electric model [Extreme Flite Extra] uses a relatively small carbon tube joiner and I certainly haven't held back from applying high loads to these models so I don't think an adequately sized tube is a total no no...

Edited By Martin Harris on 03/07/2020 21:20:22

03/07/2020 13:02:18

Do be careful with the carbon dust - it's supposed to be very hazardous to the lungs and quite possibly carcinogenic. Best not to get it into the house or workshop...

Thread: Dihedral
03/07/2020 01:02:40

Although they may give the impression of being flat, Piper Cubs do have between approximately 1/2 and 1 degree of dihedral.

Pendulum stability may be a small factor [there are arguments from people far more qualified than me that it doesn't actually exist] but the levelling effect comes from the differing angles of attack from sideslip induced by bank.

I think you'll find that all high winged aircraft with flat wings or anhedral have swept back wings and therefore need to reduce the high inherent stability which adds a lot of drag and reduces control effectiveness.

Edited By Martin Harris on 03/07/2020 01:04:57

Thread: Laser Engines now closed on Friday's
01/07/2020 17:37:09

Before I escaped from that working nonsense, we had a similar arrangement - although optional - where we could do 5 days worth of work over 4 days which was seen as a way to extend cover hours without paying overtime. Most people wanted Mondays or Fridays off so the day was rotated each week but I negotiated permanent Thursdays for mine as it was our "club day". Long days but well worth it!

Thread: OS 91 surpass disassembly
01/07/2020 16:12:25
Posted by Engine Doctor on 01/07/2020 11:09:24:

I believe another post on here shops pics of their puller

It doesn't actually pull the bearings ,but gives purchase to the bearings so that you can pull or push the bearing to remove or insert them .

This one?

I was planning on turning up a lump of steel to use as a slide hammer below the hex but it's never been necessary - the bearings have come out easily with a wiggly pull...

Thread: Aviation Funnies
01/07/2020 15:55:31

In case of any confusion:


Edited By Martin Harris on 01/07/2020 15:56:26

Thread: Does anyone remember...
01/07/2020 01:06:35

I remember the hours winding the quickstart spring on my Merlin in my dad's garage hoping for more than a short lived brrrrpp until I discarded the quickstart and learnt the art of flicking repeatedly and quickly to get enough heat into the engine. I didn't mind too much as the hard work was accompanied by that wonderful aroma of ether, castor and paraffin.

Flick forward [ouch] more than 40 years and I built a Phantom Mite from a downloaded plan around a Merlin that was given to me by a work colleague and I was amazed by how easily it started and ran. The only problem was getting a little dizzy after a few circuits - I'm sure that never happened back in the day!

Thread: Sanwa old 35mhz servos
30/06/2020 10:06:37

As Pete says, black wire corrosion associated with damp storage. If anyone needs to engage in storage of models in an outbuilding or similar, the best precaution is to remove the battery and store it indoors as the battery is where the dreaded black wire corrosion originates.

I've often wondered whether we we should have standardised on switching the negative wire rather than the positive side - that would tend to protect the wiring and components, in bad cases, beyond the switch.

Thread: OS 91 surpass disassembly
29/06/2020 19:31:57

Heat, piston at the bottom of the stroke, gloved Mk 1 thumb down the bore, wiggle to break the seal and Robert should be your mother's brother...

29/06/2020 19:12:08

There's no plug, Steve. I've pushed them out with a small piece of hardwood as per Jon's suggestion but a bit of heat softens any caster that might be causing sticking as well as expanding the barrel. Normally, if one is reluctant to come out, I pop it in the oven at about 150 degrees C for 5 minutes and give it a bit of a twist [wearing gloves] which normally releases it. Then once the piston and crank are out, back into the oven and a sharp tap on a block of wood should see the rear bearing dropping out.

Although you can wiggle the piston and con rod out of a few 4 strokes without disassembling them, I don't think it's possible on the OS 90. I assume you know that to separate them, the gudgeon pin comes out of the hole in the back of the barrel - I find that suitable self tapping screws inserted by hand will grip the PTFE pad and the internal bore of the pin enough to wiggle and pull them out without marking them. Don't lose the tiny PTFE pad!

29/06/2020 18:36:50

Plug holding the liner? I can't recall anything like that but yes, some heat should do the trick.

Thread: Does anyone remember...
29/06/2020 12:47:58

As a young boy in the mid sixties, my "mecca" was Bold & Burrows in St. Albans which was a wonderful emporium combining model related stuff and electronic components extending over several premises close to the town centre. I can't remember how much domestic appliances came in to the picture - wasn't interested in them at the slightest - but they expanded into the premises of a former department store and the model department took over the top floor with all manner of household goods over the lower floors - and a general tool department in the basement, if memory serves me right. I remember drooling over the wondrous radio controlled section while eking out my pocket money to buy balsa and accessories for free flight and control line models. Unfortunately, I suspect that ambition overtook reality and after a few years the firm folded. In recent years, I've become reacquainted with the chap behind the counter since my earliest memories and he now flies at our club about 15 miles from St. Albans on occasions.

Even in the relatively small city of St. Albans, there were multiple model shops throughout my childhood and into the later years of the 20th century - very different now when they are at least a half hour trip in the car to get to.

Those were the days when a visit to the town centre could provide some interest instead of being the modern sterile mixture of chain outlets, charity shops and estate agents. There were all manner of tool, toy, model, junk and speciality shops in every high street. Even in land-locked Hertfordshire, St. Albans had - next door to B&B - a chandlery, run by an elderly lady of "character" who would have given Norah Batty and Ena Sharples a serious run for their money!

Edited By Martin Harris on 29/06/2020 12:58:44

Thread: new to wash out
27/06/2020 21:34:41

Get steaming...

No, don't drown your sorrows but try to introduce the necessary deformation by steaming the aileron structure and twisting gently. There's little to lose and it may save you building a new pair of ailerons.

Edited By Martin Harris on 27/06/2020 21:35:01

Thread: The Lockdown Restrictions Have Been Relaxed. Who's Been Flying?
26/06/2020 23:48:28
Posted by Erfolg on 26/06/2020 15:38:27:

one of the now diseased mags,

Oh no! Has Covid 19 spread to magazines now?

Thread: new to wash out
26/06/2020 21:44:29
Posted by john davidson 1 on 26/06/2020 21:21:44:

Regarding Eurofightesr and such being unflyable without a computer, why do MODELS of them fly perfectly happily?

Probably due to having a more forward C of G and/or smaller control movements?

Thread: Blue Foam
26/06/2020 14:54:54

I think the important news is that Floorspan is being manufactured again, albeit under a new name. As long as the density is suitable, hopefully smaller quantities will trickle through to modellers in due course - as may be evidenced by the post from RC Plane Flyer above.

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Q: The effects of Coronavirus

 Yes - for the first time
 Yes - but Ive bashed balsa before
 No - Ive existing projects on the bench
 No - Im strictly an ARTF person

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