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Author Topic: New Model - for OS15FP  (Read 7560 times)
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applehoney
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« Reply #75 on: September 25, 2013, 01:05:34 AM »

 with ear muffs on of course

Huh, I never used ear muffs with my .40's in the past.....

What's that you say ?

Actually, I did sometimes wear ear prortectors; not so much for the noise but to pretend I could not hear those idiots who asked questions while I was preparing to launch
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glidermaster
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« Reply #76 on: September 25, 2013, 10:20:04 AM »

I started to experience a definite hearing loss about half a dozen years ago, ironically after about 10 years without meaningful power flying.
Prior to that I used a heavy set of ear defenders for several years.

Now I have the set in the picture which work well, and can stay comfortably around my neck after the model has gone on its way. I think they were $10 or so.
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Hepcat
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« Reply #77 on: September 25, 2013, 10:58:58 AM »

Glidermaster, John, I am sorry to see your beautiful aeroplane requiring repairs so early in life.  You mentioned in reply #68 that there was an explanation of what happened in the ‘Let’s go Flying’ thread but for some reason such an explanation never arrived at my computer.  I am interested because your opening post on this thread mentioned that you were trying a new washout arrangement.  Did that have anything to do with the dropping of the left wing that you said occurred before the model ‘stacked’?
Hepcat, John.
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glidermaster
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« Reply #78 on: September 25, 2013, 01:47:09 PM »

Hi John,
This wing has washout on every panel - more on the left than the right.
I compensated for this in set-up, but fat fingered a button on the calculator, because I ended up wwwaaaayyy under elevated.
I also ended up switching tails with the Mk.1 version (this being Mk.2) - but I had already rigged the wing and tail mount, and failed to notice that the ply pads under the leading and trailing edges of the tail were different - the difference was less than I first thought, but still accounted for about 1/32" more positive on the tail.

Test glides looked OK, and I had about 3mm movement in the VIT (at the tail trailing edge), so I thought it would at least be safe.

Mk.1 has a standard washin/washout set up - washed out tips, washed in RH inner panel, flat LH inner.

John
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gossie
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« Reply #79 on: September 25, 2013, 06:15:09 PM »

[quote author=applehoney

Actually, I did sometimes wear ear prortectors; not so much for the noise but to pretend I could not hear those idiots who asked questions while I was preparing to launch


Yep, agree with that one. It's awful.
   Couple of years ago running up a Rossi in a new model getting things right,had this fellow just kept talking regardless of my ear plugs in or not.  Not muffs or defenders that day.
When I'm fueling up these Rossi things of mine I can tell when the tank is full when I can hear the fuel start to come out of the very top vent on the tank that goes into the pressure nipple on the rear of the crankcase......can't see it as it's all hidden away.
He is a nice guy, really, but just kept talking about I have no idea what.   In the end I told him I was now totally deaf and could not hear a thing he was saying as I had the plugs in the ears.......not sure if he stopped or not, but I can vaguely remember him standing there with his hands over his ears when the good old Rossi was turning about 28.

I must admit I rather like talking and bulling on.......Remember our session JB?   But when your right in the middle of it..........GO AWAY PLEASE.
  Winding a rubber model with 100 grams X 16 strands always seems a good time to get talked to as well, particularly when getting close to 1000 turns.  I did have a guy kept counting odd numbers and saying other stupid things a few years ago whilst I was winding for a flyoff flight with about 40 or 50 people around both male and female, I shouted "SHUT THE F--- UP and his name......There was total silence and I went on to win that flyoff.
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martynk
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« Reply #80 on: September 27, 2013, 04:55:06 AM »

Getting a bit off topic now, but I am now VERY deaf. I can hear perfectly upto 500Hz but almost totally deaf beyond that (at 2000Hz, my hearing capability is 1/100000th of what it should be).

I cant blame model aircraft engines, my cause was probably too many rock concerts and too much motorcycling (no earplugs). I still ride bikes (now with plugs) but the damage is done and is irreversible. Consequently, I wear very sophisticated and expensive (approx 6000USD) hearing aids. At the best they have restored some of my hearing but in testing I can only hear about 80% of what people say - far worse in a group environment. They are only AIDS not FIXES

Trust me, if you have any doubt - protect your ears

Martyn
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Martyn
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« Reply #81 on: September 27, 2013, 05:03:08 PM »

Wise words Martyn - my hearing loss is all high freq. too, but nowhere near as bad as yours - no rock concerts or motorbikes for me, though, it's all model engine related, I'm certain. One of my earliest memories as a child was being at Chobham with a bunch of people test running engines nailed to trees. I seem to remember crying, too!

Back in the UK many years ago a kid, standing about 5 metres away, shouted "Is that going to be noisy, mate?" just as the front of the F1C was heading for the starter. A split second later he got his answer.......
I don't like the noise of F1C - it's gone too far, I think, and we should have done something about it 20 years ago. One can't un-ring a bell though, can one.

OS15FP models are fine, though - to sort of head back to topic!

John
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glidermaster
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« Reply #82 on: October 17, 2013, 10:20:05 AM »

I got out for some more flying, and flew the repaired OS15FP model yesterday.
I put a 1/16" shim under the leading edge of the wing - and this time it survived!

This is now an easy model to fly.
I think this thread is probably complete!
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Badgerbill
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« Reply #83 on: October 19, 2013, 04:59:48 PM »

I can't resist adding a postscript to this string, involving, as it does, Glidermaser and his use of ear defenders.

It would have been 1980 - maybe 1981 - when I accompanied John and his father to the Poitou contest in France. The Buskell family had booked a gite as a nice change from staying under canvas, and John and I shared a room. Separate beds I hasten to add.

I was more or less unaware at that stage of life that I was prone from time-to-time to snoring, but the extent of the problem became apparent when the alarm went off in the early hours so we could get to the flying field in good time, and I shot out of bed, expecting Glidermaster to have been similarly shocked awake, only to see him blissfully asleep with his ear defenders on...
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glidermaster
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« Reply #84 on: October 21, 2013, 11:29:30 AM »

I had forgotten that, Bill!

I think it was 1987, though - just after the first Poitou World Champs.
Ah yes, those were the days................
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RobinB
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« Reply #85 on: November 07, 2013, 02:16:20 AM »

John, what prop are using with the 15FP?

Robin
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glidermaster
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« Reply #86 on: November 07, 2013, 11:46:53 AM »

Robin,
I am using a Master 8x4 cut down to 7.5" diameter. It seems to suit the OS15P well - Dave Clarkson recommended them.
To be honest, I haven't experimented much, but the prototype was flown on a APC 8x4 for a while. It seemed a bit too big, though.

I like the props Bruce Hannah and others are using on their OS III 15 models - a Norm Poti 8x3.5 glass prop (I think).

John
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adamescu
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« Reply #87 on: November 08, 2013, 09:33:55 AM »

Robin,
I am using a APC 8x4 in my Lucky Lindy - Os Max 15 FP powered and its works very well /15200 rpm/

https://vimeo.com/63476176

Adam
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glidermaster
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« Reply #88 on: November 08, 2013, 02:09:55 PM »

Thanks Adam, that's a good video.

Watching it a couple of times, I have some observations (this is just opinion, not criticism);

In my opinion, 15200 RPM is a little on the slow side for this engine, and is well below peak power.
After launch the engine slows down, indicating that the propellor is loading up, not unloading. I prefer to select a prop that does the opposite - i.e. there is an increase in engine revs at launch, so that more power is being delivered by the engine to the propellor, not less.

Lucky Lindy is an FAI model from 1960, and most of my flying the last couple of years has been with vintage FAI models from the late 60's. I am flying 2 with Super Tigre G15s, both with the same propellor (self made). On Night Train it is almost an ideal prop, and you can hear it 'bite' on launch, the engine speeds up, and the model accelerates pretty well. I think it could possibly take just a little more pitch.
On Trad Lad, there is no audible pick up, so I think I'm at the limit of what the engine can deliver, and I need to explore my box of propellors a little more, and find one better matched to the airframe/engine combo.

John
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adamescu
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« Reply #89 on: November 09, 2013, 03:20:27 AM »

John, thanks a lot for your opinion-advice.
When I saw your previous reply in this thread about props, I decided to put this video here with all informations, because my LuckyLindy /650Gram/ is a little bit lazy but stable.
Tomorrow I can try Master 8x4 cut down to 7.5" diameter to reach a peak. I have a question regarding the  fuel /the proportion of the consisttence /  what is best for OS15FP and about peak RMP ?
Best regards
Adam

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RobinB
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« Reply #90 on: November 09, 2013, 06:49:44 AM »

I have a couple of good standard FP15s and another with a Nelson plug conversion.
On 25% nitro, the standards give 14,400 on APC 8x4 (0.33) and 17,500 (0.35) on APC 7x4.
The 'Nelsonised' one gives 15,500 (0.38) and 18,000 (0.38) on same props.
The figures in brackets are bhp values from a chart produced by Gordon Cornell some years ago.

OS quote a max. power of .41 bhp @ 17,000 for the 15FP and LA.
I just have the $20 optical cheapo tach that's sold under different brand names - I think OS have better equipment!
Also, their test engine probably wasn't just picked off the production line.

Incidentally, my Max III 15s also pull 18,000 on APC 7x4, albeit with 40% nitro.

So, Adam, your 15,200 sounds quite good, but our tachometers may not agree.

I think John is right, and a 7.5x4 could be worth a try.
However, as your hauling up a 650 gm Lindy perhaps a pitch reduction is the answer.
The problem I've found, though, is that 8x3 props are hard to find.

It's a guess as to how much your engine can pick up after launch - 500? 1000?

I use APC props as a common 'yardstick' for comparing different engines, and I've noticed
that the 8x4 loads the engines more that other makes. I've just started trimming an FP15 aeroplane
using an S-2 Series Master 8x4, and it definitely picks up after I launch.
Next time out, I'll try and remember to tach it.

Robin
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glidermaster
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« Reply #91 on: November 09, 2013, 11:08:49 AM »

That's all very good data, Robin.
I can't recall rpm for my OS15FP engines, but they are both standard engines. I use a fuel with approximately 15% Nitro (20% oil) - I say approximately, as I watered down some 25% nitro with straight, and wasn't very careful doing it - I run this in an OS20FP as well.

I have found that they run OK on 5% nitro, but are not happy on straight. Nitromethane is expensive in most areas of the world, and OS being a world brand, I suspect they are optimized for low nitro - say 5-15%.

What weight is your Lucky Lindy, Adam?
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glidermaster
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« Reply #92 on: November 09, 2013, 11:28:26 AM »

A thought occurs, matching props to planes - actually memories.
I produced a 5.5x3 1/2A prop many years ago, in carbon and glass. On my models which at the time were 275 sq ins, 7.5 oz models (Cox TD 051 - UK 1/2A) they were OK, but nothing spectacular. For whatever reason, I gave one to Alan Parker who was flying a 240 sq in 5.5 oz model, and he had spectacular results. Revs were very similar to my engine (21k ish), but he got a pronounced audible acceleration on launch - maybe over a thousand RPM (I'm guessing).
My Dad tried one on his 280 sq in model - weight 8.5 oz - his engines were Kustom Kraft, and turned 22k, but it sagged on launch by 1000 rpm.
My Dad's prop is 5 1/2 x 3 1/8, turning pretty similar rpm to my prop, and he got an engine acceleration on launching his model. That prop was very good on my models, but not very good at all on Alan's lightweight.
I still use this prop.

I don't understand what's happening, though.
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RobinB
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« Reply #93 on: November 09, 2013, 03:43:38 PM »

Something to do with the mass of the prop?
The greater the rotating mass, the more energy is needed to accelerate it.

I'm right on the edge of the area where I know what I'm talking about,
so I'll venture no further  Smiley

A missing piece of the puzzle: have you any idea what prop Alan used originally?

Robin
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glidermaster
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« Reply #94 on: November 09, 2013, 05:23:19 PM »

No Robin, and it was a while back, of course.
It would have been one of the standard offerings - circa 1990 - possibly APC.

Russel Peers also had some of my props - and didn't like them...........
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« Reply #95 on: November 09, 2013, 05:25:11 PM »

My guess is that any engine that slows after launch is fuel starved. Not a prop issue.
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glidermaster
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« Reply #96 on: November 09, 2013, 05:51:04 PM »

No, sorry Gnu.
We did enough flying with these various props to eliminate that possibility.

John
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FF Bruce
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« Reply #97 on: November 09, 2013, 06:09:27 PM »

John I don't think APC props came out untill 1993 or 94 most used Cox props or a glass verison of it.In FAI,Bartills 7X3.5 prop untill 78 or so then we
made glass Cox copies.
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glidermaster
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« Reply #98 on: November 09, 2013, 11:02:43 PM »

You're probably right Bruce. Maybe Alan was using the black Tornado with white stripes on the blade tip.
It getting to be quite a long time ago now!
I still have some of the props I designed, but recently I made some more of my Dad's prop for one of my old Cox 1/2A models. Dad's prop is quite superior on that model.
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« Reply #99 on: November 10, 2013, 03:17:44 PM »

Ahoj,

I had a flight today with my Lucky Lindy (650 Gram weight - OS15FP)  with APC 8x4 cut down to 7.5" diameter which made power 15350 RPM, but  after the launch the engine still slows down.  I use a fuel with approximately 10% Nitro (20% Castor) - it watered down Cox 25% nitro  with straight 85/15, and I wasn't very careful doing it, just a mix of left overs Cox and FAI fuel.

https://vimeo.com/79035927

Thanks for advice

Adam
« Last Edit: November 10, 2013, 03:56:10 PM by adamescu » Logged
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