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Author Topic: New Model - for OS15FP  (Read 7574 times)
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glidermaster
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« Reply #100 on: November 10, 2013, 07:23:31 PM »

Hi Adam, another good video!

In my opinon, on the most recent video, the engine slows down less after launch than previously, and then accelerates back to pre-launch rpm quicker than previously.

On the new video one cannot tell if climb pattern is the same, better or worse, and the engine run is shorter in the 2nd video than the first. It is impossible to judge climb height, of course.

Did you make incidence or rudder adjustments when using the 7.5 inch diameter propellor, Adam?

True comparisons are difficult here. Adam's Lucky Lindy is approx. 200 grams heavier than my first OS15P model, and it's bigger, too. I think Robin is correct, for the larger Lucky Lindy a reduction in pitch might be better than a reduction in diameter and a Master 8x3 prop is available.

If they are hard to get where you are, Adam, maybe I could find some and send them over.

John
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Gnu
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« Reply #101 on: November 11, 2013, 12:51:16 PM »

Why would you think that the propeller is the cause of launch induced engine lag? Are you running a suction fuel system? Try pressure if the rules allow. If not, use a smaller venturi and keep the system compact (all tanks and lines near the engine). Use a remote pinch-off rather than looping a fuel line back to the timer. Fuel has mass and when the model accelerates the mixture will go lean.
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glidermaster
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« Reply #102 on: November 11, 2013, 11:12:12 PM »

Because (in the past) we've used the same aeroplane with different props, and done enough flying to eliminate non-prop factors. Most of these observations were from models with crankcase pressure fuel feed.

That's not to say all the things you've suggested don't have an effect though, Gnu, especially fuel system. For instance, I was flying my vintage FAI Night Train earlier in the year, and had the compression set a little bit low. It ran OK and held a peak setting OK, but when I launched the model, the revs sagged slightly. I changed the shims under the head because the engine was a bit touchy, and required that I hold the glow leads on for several seconds to get it to 'come in'. Getting the compression right liberated a little more RPM, and the engine now picks up a little on launch. This particular engine (G15) is the fastest example of the type that I have ever come across, and it`s running (static - before launch) very close to peak power. I think that I might be able to get a better result with a little bit more prop load (i.e. a slight drop in static rpm). We shall see. I am currently using a 7.25 x 3.125. I have another prop of 7.25 x 3.25, and one of 7.375 x 3.125 to try (these are all Buskell original props).

John

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Gnu
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« Reply #103 on: November 12, 2013, 07:13:07 PM »

Sounds like it might be a cooling issue, ie. excessive cooling. Fully loaded at static and at running temperature, it may be cooling beyond optimum as the load is removed after launch. ?? More compression and or nitro? Hotter plug?
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FF Bruce
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« Reply #104 on: November 12, 2013, 08:48:18 PM »

Gnu,
  I've heared the RPM loss that John is talking about.And for the most part it's the prop and the way the motor is set up.Not that your idea's aren't valid they are but I think we are talking about a dia. pitch thing here.On the motors that I remember were timed to turn fast but the prop had a little to much pitch or dia. so untill the motor could get to the desired RPM's there was a lag untill the air speed could let the prop unload and then let the motor run as set up.That's my guess anyway.
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glidermaster
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« Reply #105 on: November 13, 2013, 12:18:27 AM »

Is what I've described contrary to your experience, Gnu?

I'm quite prepared to accept that there may be shortcomings in my engine set up, but some of my related experiences where with my Dad, and he knew all there is to know about getting the best from engines.

He knew a bit about props, too.
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Gnu
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« Reply #106 on: November 13, 2013, 12:57:37 AM »

I dunno. A lag I could understand, but a sag? Maybe just lag and doppler make it sound like the engine is sagging. I'm out of ideas. I used to de-pitch the tips of my props and the engine would wind up all the way up.
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adamescu
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« Reply #107 on: November 13, 2013, 04:53:11 AM »

Thanks a lot Gent's

Jonh, I didn't do any rudder adjustment, not yet, but I will put a little bit left trim on rudder and maybe more wash in ?
Gnu, I am using a suction fuel system with remote pinch-off so I put a "pipe knee" on tank to get more pressure inside.
Well, finally, I´ve found and bought two props Master 8x3, and 10% more Nitro into the fuel, so will see this Saturday on the last event of this year.

Best regards

Adam
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Gnu
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« Reply #108 on: November 13, 2013, 03:22:31 PM »

Let us know the result of the changes.
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glidermaster
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« Reply #109 on: November 13, 2013, 04:08:58 PM »

Yes, Adam, let us know how it goes.
Just be aware that, depending on the temperature at your event, higher nitro can make starting difficult.

However, that advice applies more if hand starting!

John
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adamescu
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« Reply #110 on: November 17, 2013, 06:24:12 AM »

Ahoj,
thanks to all, I can say that Master 8x3 is the best choice that I can get, with 17500 RPM Lucky Lindy accelerate much better much than with APC 8x4
https://vimeo.com/79565663
and some more video from our event shoot by my junior
https://vimeo.com/79565868 - The Lucky Lindy powered by OS 15 LA - by J.Jirasky - also tried Master 8x3 and climb was much better ...
https://vimeo.com/79565869 - The Top Banana by C.Patek - MP JET .061 Diesel
and one powered by Rapier
https://vimeo.com/79566332

Wink

Adam
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glidermaster
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« Reply #111 on: November 17, 2013, 10:55:06 AM »

That is great adam, junior is pretty good with that camera!
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martynk
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« Reply #112 on: November 18, 2013, 05:28:19 AM »

That Lucky Lindy is very nice. What period model is it?

Martyn
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adamescu
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« Reply #113 on: November 18, 2013, 06:42:48 AM »

Thanks Martyn,

The Lucky Lindy - Larry Conover was a winner of F.A.I. Power Championships in 1960 - after 12th Flyoffs

http://aeromodelismovolarlibremente.blogspot.co.uk/2009/06/lucky-lindy-de-larry-conover-usa-1957.html

Here are some more pictures of my ship

https://picasaweb.google.com/adam.jenik/GEODIZZY#

Ahoj

Adam
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martynk
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« Reply #114 on: November 18, 2013, 08:47:15 AM »

Thanks Adam

That means that it would qualify for classic power in the UK. Interesting design with those triple fins as well.

Martyn
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adamescu
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« Reply #115 on: November 23, 2013, 08:07:41 AM »

Hello all,
Ive just found a very interesting prop on the APC web for free flight, for example 7.625x3.25 // 7.8x4
//  8x3.75W and etc., maybe good one for OS 15FP ?
Do you have any experiences with this prop ? material ?  it is twice as expansive in this special category as a standard prop for example 8x4 .
Thanks a lot
Best regards
Adam
« Last Edit: November 23, 2013, 08:49:59 AM by adamescu » Logged
Scottl0413
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« Reply #116 on: November 24, 2013, 07:24:14 AM »

Adam, the 7.8 x 4 apc is the prop of choice hear in the states for high performance .21 engines, i.e. Rossi's, K&B 3.25's and 3.5's, super tigre Series X .21's etc. APC's 8x4 tends to come apart on rpm's over 20K!!

Scott
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glidermaster
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« Reply #117 on: November 24, 2013, 11:33:47 PM »

I've never seen them, but I think 7.625 x 3.25 sounds about right for an OS15FP.
Of course, the airframe makes a difference too, but it would be worth trying, I think.

John
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glidermaster
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« Reply #118 on: August 02, 2016, 01:42:22 PM »

This thread has been silent for a while now, but when I moved house last year the wing of the OS 15 model got damaged when I dropped another box of models on it.
Anyway, I recently turned this little pile of balsa and spruce into a new wing. A bit of tissue, and I'll be ready to go again.

JB
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Re: New Model - for OS15FP
Re: New Model - for OS15FP
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gossie
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« Reply #119 on: August 02, 2016, 05:51:14 PM »

Sweet JB.   And no black balsa in the mix.   How unusual, but oh how nice.
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glidermaster
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« Reply #120 on: March 02, 2017, 11:10:39 PM »

Back from my first trip to Fab. Feb. at Lost Hills.
I picked up a 2nd in Vintage FAI, but it didn't go so well with this model.

Still in the trimming stages, this is what happens when the timer doesn't work...........
........ inevitable really, when you don't start it.
Luckily the ground was soft, or it could have been badly damaged.......
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gossie
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« Reply #121 on: March 03, 2017, 03:03:04 AM »

Oh dear me, but man made, man can fix it.

You have answered my question elsewhere....."How did Night Train go?"  Well done.
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