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Member postings for Martin McIntosh

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

Thread: Curare Build
08/11/2012 21:51:59

HI Andy,

I had to shoe horn the ST61 in to get it inverted. Maybe sticking to the original sidewinder method would be wiser but I do not know how the OS silencer would fit in with this. No pipe to worry about though I expect.

Martin

03/11/2012 18:17:28

Hi Andy,

Those look nice wings. Mine are homespun and balsa skinned so yours may turn out lighter. My wing with pipe attached weighs 3.2lb all up.

I would watch out for the CG position with those rear mounted servos though as I see that you are using the originanal type of construction with loads of 1" triangular. Mine is just a hollowed foam top deck and uses forward mounted servos. Having said that I did need to add tail weight.

The complete fus. weighs 5.4lb.

Good luck with your build,

Martin

Thread: Hobbyking Nano Tech Lipo battery problems
29/10/2012 21:36:12

Great news about the HK UK warehouse.

29/10/2012 18:44:18

Hello Peter, thanks for your detailed reply.

Ni and Pb I am very conversant with and have had a lot of commercial training on over the years and accept that you do not get something for nothing: i.e. you need to put in 1.4 times the amount that you expect to get out as a minimum. The rest is just wasted on heat but generally does no harm.

Lithiums on the other hand just appear to take in the same mA/h as the output capacity which is what puzzles me. We seem to be getting back exactly what we put in regardless of (heat) losses etc.

I usually charge Rx Ni packs on an intelligent charger so that I know that the cells are OK and take the expected charge for a given previous usage. A wall wart charger will just thump it in anyway and you have no way of knowing if a cell is down.

The `flashing across` process for an under voltage pack has also worked well for me.

Martin

28/10/2012 21:38:57

I have found the mortality rate of lipos to be very high, either cheapos or otherwise. Indeed I have had a couple of unbranded packs for some years now and they still operate at fullish capacity - not so some of the so called better ones. I try to store most at the recommended 3.9V per cell but even so they just die on me or puff up. I normally charge at 1C, balance the cells and never exceed the discharge rate for the pack . The few nano-tech I have seem OK so far. Overlander Extreme also perform very well.

Note that you will be pushed to find a laptop, mobile etc. using other than Li-on cells, although they do not have the oomph of lipos.

One question that I have yet to find an answer for.

A Ni-cad requires 1.4 times the discharge capacity to charge, so why do Lipo packs only take in as much as you can expect to get out of them? I have put this to a charger manufacturer and could not get an answer.

Had problems with Eneloops as well but that is another story.

Martin Mc

Thread: Dynamic balance on props
20/09/2012 22:51:02

Not read all of that lot yet but from practical experience I have found that up to 16 inch APC are fine. Over that I use wood on petrol motors and static balancing is an absolute must. I usually re-sand to a better shape then balance with coats of varnish, no matter what Brian Winch says. Works for me.

Martin

Thread: Need inspiration for a 26 fourstroke
18/09/2012 15:53:12

I have been using one in a Nihuis 44" Spit for several years. 7 servos. retracts, 3lb 10oz, perfect if it is your cup of tea.

Martin

Thread: Curare Build
27/08/2012 16:10:10

Looks to be a good solution Mark. Pics. would be great.

Martin

26/08/2012 23:39:19

The stress on take-off is backwards and on landing upwards so the springs do nothing at that time. It has surprised me a couple of times when I have had to do a belly landing that the legs were bent back. Must be that the force of a high speed take-off causes more bending than a usually much lower speed landing.

Martin

23/08/2012 23:58:51

Hi Bob,

Took your advice thanks.

The rear end of the pipe just has a screw which must hold it together-new one on me as well but I bought it with the motor. It also has a tube within a tube at the outlet which puzzles me.

I never now use spring loops on retracts as they just cause them to bend back on take off from wet grass resulting in a stuck u/c. Don`t know why I ever did. Just use thicker wire. Oh to be able to fly from tarmac again.

Martin.

23/08/2012 22:31:09

Thanks Steve,

Martin

23/08/2012 18:41:10

David Ashby.

Perhaps you would be kind enough to remove my last post (with the phone No.).

Thanks, Martin

22/08/2012 23:00:52

I would love to have a chat at the Nats and can be found in a LWB hi top white Transit usually parked as near to the hangar bar as possible.

Martin

Edited By Steve Hargreaves - Moderator on 23/08/2012 21:00:57

22/08/2012 22:34:49

Phew, managed it at last but with no text! Thanks.

Vecchio, thanks for correcting me on that one. Good pics, yours or the original?

Andy, I would lengthen the u/c by 1 inch if using a 12 inch prop for a taildragger set up from a grass strip.

Also make the tailwheel leg a little longer than I did.

22/08/2012 22:25:35

curare 018.jpg

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curare 009.jpg

curare 008.jpg

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curare 001.jpg

 

Edited By Chris Bott - Moderator on 23/08/2012 08:40:25

22/08/2012 20:32:25

Well, I have managed to get quite a few pics in my photo albums, but the tutorial stops short of saying just how I am supposed to get them on this thread. Sorry, but you will just have to look at`my albums` until someone guides me in the right direction here. Hope that they clarify the brake build.

Any ideas anyone?

Martin Mc. (complete computer idiot)

21/08/2012 21:19:53

Hi Mark

Thanks for your reply. I must admit that I did not study the Magic too closely re the exhaust because having all my models and gear nicked after the 1979 WC`s I lost all interest in competition flying apart from one attempt with a model with a swan neck and top enclosed pipe which was not successful.

Hanno had a huge array of switches on the back of his Tx, presumably one for each maneouvre requiring the brakes, which was beyond the electronics knowhow of most of us. I only use them for landing at the moment and they are a real boon for getting down in a short space.

I remember Mike Bone well. Unfortunately, although he was an excellent flyer, mainly because he could rarely get his engines to start/run properly! He used HP`s at the time as I did. Please say hello from me if you are still in touch.

I scaled my model from the original RCM&E article. It was quite simple since everything including balsa sizes is in inches. I noted that the `Prototyp Miss Springfield` had lots of strips of Solarfilm added to the fin/rudder where he had obviously experimented with areas/ angles to get it just right but the plans show these bits in rather too exact inches. Seems to work though.

He used a Webra slider carb but wether it was a Webra motor I cannot remember, but do remember him saying most forcefully at the time `zis is ze best carburettor`.

I have some Webra RE 61 bits lying around if anyone wants them but will require new pistons/liners.

Martin

21/08/2012 01:25:13

Hello again,

Mark, if you use a rear exhaust motor then it must exit via the swan neck where the noseleg used to be surely? Otherwise the pipe would have to go down the side of the fus. instead of underneath.

That is why mine had to be a tail dragger. Also I now have to fly from a grass patch which is not very kind to noselegs.

Since in the seventies I was at the top of the aerobatic tree I must also disagree about setting up the noseleg shorter than the mains. This was just not so. They were set level so that the wing incidence was at the flight angle on takeoff thus the model would fly off the ground rather than leap off which would have cost a lot of points. Landing was achieved by gently setting the main wheels down first then letting the model sink on to the nosewheel. Getting these right was worth megapoints.

Andy,

The post by Mike was a reply to my previous one. The colour scheme is as described on the RCM&E plan, orange and green, so it must be mine!

The flap/brakes are a real pain to make and fit but well worth the effort. Note that mine are the 1977 version with six holes in each brake: not the one shown in the article. I have set them in to be in line with the TE since we all use two aileron sevos now and a strip linkage does not have to run through them. They are 1/3 up and 2/3 down as measured from the upper surface with the hingeline central. On operation there is is slight pitch up from level flight but if you do this in a turn it is not noticeable. Servo slow would sort this.

What ever you do, do not use piano wire in tubes to operate them as it will rust and sieze, use brass tubing only. Silver solder the horns to the tube if you can. The hinges are a couple of tinplate straps on each side soldered to the tubes, some holes drilled then epoxied to the flaps when you are absolutely sure that everything is in alignment.

The brake part can be made from GRP, ply or alloy. It needs to be set in to follow the wing contour.

Hope to get some pics. of this here if I can work out how to do it again.

I would make the gear 1" longer if going from grass as the prop. clearance is minimal (tail dragger only of course).

Martin

20/08/2012 16:11:58

Hi all,

Finished my Curare about six weeks ago. If you wish to see it go to the GBRCAA forum, retro aerobatic comp. 2012, page 7 and a description on page 8. Built from scratch, foam surfaces and top deck.

Martin Mc.

Thread: Don't just stand there, get one up!
13/08/2012 22:51:47

OK thanks for that info. I normally use the Perkins ones on other models but do not recall seeing a Spit. shaped one, but then again I am not going to be too fussy after that nasty mishap. I shall get one of those.

Cheers, Martin

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