Precedent Stampe 1/4 Scale

[john stones 1 - Moderator]

Lucky fella indeed. She'll slurp a bit of fuel, take plenty. ?

[cymaz]

Good luck with the maiden....keep us updated 

[Peter Jenkins]

11 minutes ago, john stones 1 - Moderator said:

Lucky fella indeed. She'll slurp a bit of fuel, take plenty. ?

John - lucky indeed!  I got 10 mins per tank full when running in.  That's full throttle and using the needle valve to alternatively run at max then rich to cool off - as per OS instructions.  As I'm not expecting to use much more than half throttle most of the time and to have a only slightly rich mixture I reckon 12 mins might be safe.  However, as I'm used to 7.5 min flights in aerobatics I'll probably set the timer for 8 mins and see what comes out of the tank on landing.

 

Cymaz - thanks.  Will post on the outcome.  BTW - I was surprised at the weight and as I will be using less than 0.5 Kg of fuel I will be under the magic 7.5 Kg limit for max height restricted to 400 ft.

[Steve Dunne]

Hi Peter, The Precedent Stampe is a lovely model and a delight to fly!

One word of warning - a warning I was thankfully given before I built mine: this model was designed in the 1960s for sedate flights with a soft .60 engine.

It was definitely not envisaged to perform aerobatics other than take-off, fly round and land very gently. There are no wing braces between starboard and port wings, the wing rigging is functional. Wings folding during a loop is not uncommon on unmodified models.

Hopefully your friend will have added wing bracing - so you can ignore my comments, but just in case...

 

Other than that - a beautiful model that flies well and is very impressive in the air. Enjoy!

 

Steve.

[Peter Jenkins]

Hi Steve

 

Thanks for the warning.  I have not asked my club mate whether he strengthened the wings but looking at the AUW of 6.7 Kg I suspect not.  It was not my intention to do aggressive aerobatics with the Stampe - my primary flying being F3A aerobatics with electric powered 2 mtr airframes.  I've seen videos of model Stampes performing lomcevacs and whilst these tend to be almost stalled manoeuvres and so don't generate the lift forces that a high speed and tight pull out would my intention is to fly around sedately with the odd roll, loop and stall turn thrown in.

 

The OS 155 is very much an engine destined for another aeroplane with the Stampe being used to run it in gently.  

 

The wings don't seem as strong as my Bucker Jungmann (60" span with OS91 FS pump).  That has survived loops, rolls,  cubans but I've not gone for any negative G or snap manoeuvres!

 

I will proceed with caution!

[Nick Somerville]

10 hours ago, Peter Jenkins said:

I checked the CG and it is on the rear wing bolts of the top wing.  This seems to be the safe place for the CG.  Hoping to fly it tomorrow.

Started out with my c of g there but she wouldn’t flare well, so moved it back 5-10mm and so much better both flaring and looping. Alternatively make sure you have the rates on the elevator high as you come in on finals.

[Peter Jenkins]

Thanks Nick.  I'll bear that in mind.  I discussed the aircraft's CG position with the original builder/pilot and he said it flew fine with that CG. We shall see!

[Ron Gray]

I am planning on filming this so stay tuned!

[Jon H]

I borrowed an OS155 for testing vs the laser 155 during development. It was a nice engine, good power and very easy to use. Fuel economy wasnt too bad either. I dont know what prop you have fitted, but i would be looking at an 18x6 assuming the OS will handle it. 

 

I have a higher elevator rate for landing as well as my model starts to loose elevator power at low speed. I cant do much with the c/g though as i already have a smidge of down trim for level flight at half throttle. Its not a big issue as i use a high rate for landing on most of my scale models anyway. 

[Peter Jenkins]

Hi Jon APC 17X10.  I do have an 18x8 as well but that has a much larger hub (presumably to allow 4 bolt prop hubs) so the spinner had to have its prop holes enlarged and I've not had the time.  It turns the 17x10 at 7,500 rpm but thst's after only 3 tankfulls through it.  OS recommend flying on a slightly rich setting reducing richness over the next 10 flights.  So that's the aim.  The 17x10 will fly it too fast so need to manage the throttle accordingly - just like in F3A!

[Jon H]

I can tell you fly pattern ? 17x10 not going to work at all. For a model like this you want 6, maybe 8 inches of pitch at the most and you need as much diameter as you can get. There is a shed load of drag on a model like this and you need thrust to overcome it. A high pitch prop like that will likely be stalled most of the time due to the very low speed of the model and thrust will be very poor. 

 

7500rpm is also very slow for running in an engine. I would recommend a 16x8 or 17x6 for running in a 155 but i would need to check the OS book to see what they suggest. Certainly 16x8 and 17x6 are the run in props i recommend for the Laser 155. When i tested the OS 155 i found it did high 8000's on 16x8 and this is the sort of rpm i would suggest for running in. 

 

I would strongly recommend a change of prop. 17x6 for max power, 18x6 will likely work well too. In my testing i found the OS was slightly better than the laser on smaller props like the 16x8, but the laser gave better performance once loaded with bigger props. Just the nature of the two engines. In either case, 18x8 was too much for the OS i tested but the laser just about handled it. 

 

Oh and you can forget the 4 bolts on the prop. Just use the middle one. Multi bolt prop hubs are the work of the devil and we dont even use them on our biggest V twins. There is absolutely no need for it on a 25cc engine. 

Edited August 19, 2021 by Jon - Laser Engines

[Ron Gray]

According to OS, prop sizes are 16x8 - 12, 17x8 - 12.

 

Peter, if you want a 17x6 or a 17x8 to try I can bring them with me.

[Jon H]

How strange. The OS120 4 stroke manual recommends up to 18x6. I wonder why the 155 is so limited ? 

 

Not that it matters. I would slap an 18x6 on and go for it. If its runs over 7500rpm then its fine anyway ? 

[Martin McIntosh]

This site is driving me mad. I just submitted a lengthy reply and it just sat there saying `saving`.

Here is the gist of it.

My Stampe was built from the Precedent kit and I soon realised that the wing centre sections required 1/8th birch ply braces. I throw it round doing anything I can think of and have not managed to break it yet. I have even put springs in series with the flying wires because I got fed up with them breaking.

Original power was a Laser 155 but I wanted it elsewhere and fitted a 180, both on the same 18x8 wood prop which I still use. Build weight was 6.2kg and cg 1" in front of the upper wing TE.

[Nick Somerville]

180 and a 20x6 Menz on mine which is perfect.  
Interestingly my first Stampe 23 years ago was the Precedent one, which I built as per the plan with no flying wires or beefing up of the centre section and with no problem despite spirited flying.

On my current Slec modelled Stampe I beefed up the ‘fragile’ area and added scale flying wires (50lbs trace wire which won’t break before the fittings) yet I now fly with more care!!! Definitely an age thing ?.

[Richard Acland]

I find that most people tend to overpower their models and therefore do not replicate the scale speed of the model. My Precedent Stampe is powered by an SC 90 FS and flies superbly. I think the plan showed the original to be powered by a .60 two stroke. As may have been mentioned before the tailplane incidence on the plan was miles out. Ever since I have had to fly with a mass of elevator down trim. I dont know if anyone else has experienced this.

[cymaz]

I think we all have down elevator when we fly Stampes!

[Jon H]

I have to confess i would not want to fly mine on less than the 180. Its just perfect with takeoff at half throttle and full power only needed for large loops. I cant imagine trying to fly one with a 90 unless it was really light. That said, at 16lbs mine floats and floats so if it was any lighter it would probably float away!

[Martin McIntosh]

RA, glad that I am not the only one flying with more down trim than would normally be used as total movement. I have heard that there were two versions of the plan and guess who got the bum one. It does not seem to affect the performance in any way.

The prototype was flown with a geared Meteor 40 I believe, then a 60.

Have also tried a 19x6 to get better loops but not really any noticeable difference other than it did not have enough speed in a four point or slow roll.

[Peter Jenkins]

12 hours ago, Jon - Laser Engines said:

I can tell you fly pattern ? 17x10 not going to work at all. For a model like this you want 6, maybe 8 inches of pitch at the most and you need as much diameter as you can get. There is a shed load of drag on a model like this and you need thrust to overcome it. A high pitch prop like that will likely be stalled most of the time due to the very low speed of the model and thrust will be very poor. 

 

7500rpm is also very slow for running in an engine. I would recommend a 16x8 or 17x6 for running in a 155 but i would need to check the OS book to see what they suggest. Certainly 16x8 and 17x6 are the run in props i recommend for the Laser 155. When i tested the OS 155 i found it did high 8000's on 16x8 and this is the sort of rpm i would suggest for running in. 

 

I would strongly recommend a change of prop. 17x6 for max power, 18x6 will likely work well too. In my testing i found the OS was slightly better than the laser on smaller props like the 16x8, but the laser gave better performance once loaded with bigger props. Just the nature of the two engines. In either case, 18x8 was too much for the OS i tested but the laser just about handled it. 

 

Oh and you can forget the 4 bolts on the prop. Just use the middle one. Multi bolt prop hubs are the work of the devil and we dont even use them on our biggest V twins. There is absolutely no need for it on a 25cc engine. 

Hi Jon

 

If you are going to comment on another manufacturer's product, the least you can do is to read the manual before telling me I've got it all wrong!  I was following the advice in the OS 155 manual.  They state that you can use any of the stated props for running in.  The go on to tell you how to run the engine in by running the engine after start at WOT and using the needle valve to alternate between max rpm and period of rich running.  They say do this for 2 tankfulls and then go and fly with a slightly rich setting and gradually lean the needle until after 10 flights the needle is at optimum.

 

As you will have seen from Ron's post, 18 inch props do not feature.  However, I decided to get an 18x8 but it came with a wide boss which I said I guessed was for a 4 bolt setting.  You tell me not to bother with a 4 bolt setting - I'm not stupid you know!  The OS only has a single threaded shaft but when I'd looked to use APCs on my petrols they didn't come with a wide enough boss.

 

I am not looking for maximum performance in this instance since the 155 is probably overkill as the 120 is nearer true scale but still much more powerful that real life.  I very much doubt the prop will be stalled since if it were there would be no lift generated but I felt a goodly amount of thrust when I was ground running with the 17x10 fitted.

 

Could I suggest that you read threads more carefully and refrain from passing on your views with the Laser engine tag on your name on other manufacturers running in recommendations and props.  It would also be helpful if you didn't take a dig at me by saying "I can tell you fly pattern".  We've discussed your comments before on my Mustang thread where you decided to take me to task in using an OS 120 as it being too powerful for the model.  If you knew anything about pattern flying you would know that we are used to dealing with grossly overpowered aircraft so that we can fly vertical manoeuvres at constant speed and we never use power on downlines.

 

I have been flying in competition aerobatics for 10 years and now fly the FAI schedule.  I help to teach people to fly aerobatics and I've just written a book on aerobatics that seems to have gone down well - see the September issue of RCM&E.

 

Please could you stop your knee jerk reaction when you have read one of my posts?  I am happy to take constructive criticism but not snide comments.

[Peter Jenkins]

I'm afraid that I ran into plumbing problems this afternoon and after the 155 burst into song it then started to die, coughed and ran backwards!  Operating the kill switch fixed that but after that despite a lot of help from Ron we couldn't get a cough out of it.  We then noticed fuel dripping out of the cowling.  On removing the cowling, it was clear that there might be a small split in one of the fuel supply pipes - the builder had put in two tanks, one high and, the supply, one low.  There were a lot of bubbles in the fuel lines so I called it a day and will replace all the piping and try ground running again.  If that's still iffy, I'll replace the top tank as it's a tinplate one and cannot be opened unlike the small plastic bottom tank.  Should have done that in the first place but this is very much a side line for me so doesn't get much time devoted to it.  Sorry scale fans but F3A comes first, at least until the end of September.

 

Once I get the plumbing sorted out, Ron and I will get together to get a video of the first flight.

[Jon H]

um...

 

Not sure why you are so bent out of shape Peter. 17x10 is a pattern prop, the little winky face did signify some humour, you know a light hearted jab? i assumed you knew what that was. Clearly not. 

 

As for the rest,  i know how OS recommend you run engines in. not sure why you mention it as i didnt say a word about the tuning aspect and none of what i suggested was a major contradiction to the book. i even said i needed to check it to make sure i wasnt totally wide of the mark..so i am really not sure what your beef is. Its also possible i know enough to disregard their manual? maybe? I run all my OS engines on 15% oil not 18% like they tell me. They are all very happy with that and nothing has exploded. We can have a crack at saito too if you like. I use a 15 inch prop on my 45 and that isnt in the manual. It too has not exploded. Just because i work for laser it dosent mean i dont know anything about, and should not comment on other brands of engine. Engines are engines. Variations on a theme, but mostly they are all the same when it comes to general operation and their overall requirements. I have also repaired/rebuilt more engines of all brands than i can remember. I have even upgraded some with parts i manufactured myself. As such i will continue to comment as and when i choose unless its something i know nothing about. 2 stroke tuned pipes for example.

 

The prop multi bolt thing, you said you had not had time to mod the spinner. Implied you were going to use the multi bolt hub. Reading it again it seems you meant the prop cut outs. I read prop holes as holes..as in holes for multi bolts. Misunderstanding there, not sure why you are so upset by it though. 

 

I had forgotten the mustang thread and now this all makes sense as you are clearly still upset about it. Then as now you keep going on about F3a like its somehow relevant to the conversation. I design and build engines, I also have one of these models, have flown scale for over 15 years and spend my day recommending things to customers so one would assume i am qualified to recommend a propeller or two and suggest good RPM for running in an engine. You wrote a book? great, im sure its very helpful for those wanting to fly F3a. Aerobatic FAI ninja? very impressive...not got much to do with Mustangs, Stampe's and engines though. The 120 was and still is excessive for the Mustang, 17x10 will be sub optimal for the Stampe, 7500 is slow for running in an engine of this type. Just because a thing works in F3a dosent mean it works for scale. I have had aerobatic guys use our 155 for models and recommended them 16x10. WWII guys i recommend 17x8, Tiger moths etc 18x6 or 19x6. When i tested an OS155 i found it generally similar to the Laser. Not as good at large props but generally very close. With that in mind i recommended what i thought were the two best props for the job in an effort to be helpful and maybe pass on a little knowledge. A shocking crime i know, but its what i do. 

 

 

 

 

[Ron Gray]

???

[Martin McIntosh]

Just my 2P worth, when I bought an OS 91FX the instructions recommended 14x10-11. It scarcely ran at all on a 14x11 and will only turn a 14x6 happily. Strict Japanese noise limits no doubt.

[john stones 1 - Moderator]

O.S 91fx, lovely engine, mine turned a 16x8 in my Cermark Pitts, sweet as a nut.