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Author Topic: Went flying.  (Read 225047 times)
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tross
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« Reply #1600 on: May 18, 2021, 10:05:02 PM »

What a great flight John.
It hit the climb, cruise, and glide just perfect.
The PGI principles in action.
Good to see you back out and about Larry.
Just like riding a bike apparently.
Thanks for posting.

Tony
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OZPAF
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« Reply #1601 on: May 19, 2021, 05:18:36 AM »

Thanks Tony. It's not quite completely there as it takes the 2 turns to reach it's peak altitude. The optimum would be similar to a CLG launch - 1/2 to 3/4 of a turn to transition. More interesting experimentation required.
 
These stick fuselage models help to get the thrust line passing through the actual CG position with a standard Sig prop/nose bearing - the first requirement of PGI. However I suspect it is still slightly below the CG causing the very slight nose up leading to the necessary slight spiral climb.

The other interesting point about this particular model trim set up is that there is very little Static Stability theoretically. However it is quite stable in flight, possibly due to good dynamic stability from the long tail moment with a large area but light tail .

John

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dosco
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« Reply #1602 on: May 19, 2021, 09:36:28 AM »

The other interesting point about this particular model trim set up is that there is very little Static Stability theoretically. However it is quite stable in flight, possibly due to good dynamic stability from the long tail moment with a large area but light tail .

John



Oooh, that caught my attention.

Could you elaborate on the static stability piece, if you're interested?

Best-
Dave

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OZPAF
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« Reply #1603 on: May 19, 2021, 08:53:16 PM »

Static stability describes the balance of the balance of the forces acting on the model  - wing and tail lift, at a particular angle of attack or CL of the wing for a given CG, and whether the forces have a positive stability effect or the opposite.

However what actually happens during the time the model is being displaced by a disturbance is the area of Dynamic Stability and with models this is largely determined by the ratio of damping forces from the tail to the inertia of the model in pitching.

The calculated Static Margin on my model was very low according to calcs which have have been consistent in the past, while still being stable, thus I suspect that it's large tail on a long tail moment(good damping) and light weight(low inertia) give it good Dynamic Stability.

This is only a brief coverage Dave so I hope it helps. I think you would find some good discussions on Stability in the Model Aerodynamics and possibly glider threads - particularly by John Barker.

John
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dosco
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« Reply #1604 on: May 20, 2021, 11:53:44 AM »

This is only a brief coverage Dave so I hope it helps. I think you would find some good discussions on Stability in the Model Aerodynamics and possibly glider threads - particularly by John Barker.

John

John:
So a long time ago I took a Stability and Control class as part of my aero eng degree. I remember some of the salient points, and your description was on point.

I was curious about how your model exhibited low static stability - which you explained.

I would offer (and as I imagine you're aware) something I learned way back then, which is the computation of Neutral Point can be a bit squirrely. It's a function of locating the Aero Center of any particular surface which can get a bit dicey from a "measure the shape" approach.

Carry on!

Best-
Dave

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OZPAF
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« Reply #1605 on: May 20, 2021, 09:10:54 PM »

Quote
I would offer (and as I imagine you're aware) something I learned way back then, which is the computation of Neutral Point can be a bit squirrely.

Yes that in a broad sense is correct - however by comparing calculated results to actual practice, it's possible to arrive at a better understanding of what is happening as with the model I was flying. Simple models like the one I was flying present less unknowns than more involved ones where the lift effects of the fuselage may be required.

I started a University course in Aero Engineering but was too immature at the time to apply myself properly, but the interest in the theory remains.

Cheers

John
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« Reply #1606 on: May 21, 2021, 10:33:03 AM »


I started a University course in Aero Engineering but was too immature at the time to apply myself properly, but the interest in the theory remains.

Cheers

John


Well, that's an interesting thing to say. It resonates strongly.

I'm now "over the hill" (turned 50 last year) ... and I was an immature jerk for the majority of my "adult" life. I was certainly far too immature to have gone to college, but life being the way it is ... I went, the Air Force paid for half, and then life.

I failed Calc 3 because of my immaturity. One of the best things to have happened to me, actually.

My GPA was pretty terrible, but I made it through in 4 years and got the piece of paper.

To be fair, many/most technical colleges utilize a variety of academic hazing techniques to weed people out (my school was no exception), so a portion of the blame lies with them.

Best-
Dave

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Starduster
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« Reply #1607 on: May 31, 2021, 04:01:19 PM »

Pretty spectacular morning at Eloy, AZ. got there about 6:00am and stayed until about 10:00. Got too hot to continue. Flew everything I brought:

Last picture, left to right (everything is electric):

Sandy Pimenoff #18

Goldberg Interceptor

My own design F1Q (basically a F1H wing and stab, F1B fuselage, own design electronics pod.

John O'Sullivan Pocket Rocket

Sal Taibi Eaglet

Satellite 450 GLH


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Re: Went flying.
Re: Went flying.
Re: Went flying.
Re: Went flying.
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OZPAF
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« Reply #1608 on: June 01, 2021, 02:15:23 AM »

What a flying session that would have been and all still in one piece. Nice collection. How does the Pimenoff #18 fly?

John
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Starduster
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« Reply #1609 on: June 01, 2021, 10:56:47 AM »

What a flying session that would have been and all still in one piece. Nice collection. How does the Pimenoff #18 fly?

John

Hi John, thanks. Yes, it was a great day. (to be honest, though, I did prang the Interceptor at the last flight of the day. I'm 90% sure it picked up a significant warp due to the heat)

The #18 flies really well, and is fun to fly. I did the CAD work for the short kit that is offered by Bob Holman Plans. I built the prototype from the short kit and have built several since. I built them all as electric, but have been sorely tempted to build one for a Chinese Silver Swallow diesel that I have in a box.

One thing about the #18 is that every one of them that I've built has the same power pattern: after launch, the airplane flattens out for about the first 1 1/2 - 2 seconds. But once it builds up speed, it really climbs well. Here is a link to me launching mine this past weekend:

https://www.facebook.com/100012666609338/videos/1213663502399192/

I really like this airplane and is one of my favorite to fly. I fly it in AMA Electric 'B' (due to the Auto Rudder it does not qualify for 'A')

One last point of interest: For this iteration of the airplane, I used bass wood for the spar and leading edge instead of spruce. I have to say that the bass is really quite a bit stiffer than the spruce. The wing just seems so much more "solid".



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OZPAF
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« Reply #1610 on: June 02, 2021, 01:21:36 AM »

Thanks SD.
Quote
One thing about the #18 is that every one of them that I've built has the same power pattern: after launch, the airplane flattens out for about the first 1 1/2 - 2 seconds. But once it builds up speed, it really climbs well.
It is a little unusual, but looks safe and it is a nice climb pattern. If it has wash in(or differential wash out) on the right panel I could imagine this happening as the speed builds.  Regardless that is a nice climb - almost straight.

John
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« Reply #1611 on: June 02, 2021, 06:14:26 AM »

Hi Rich, looking at your facebook film may I suggest to launch the #18 with a bit more enthusiasm  Smiley, in other words with a bit of a heave to overcome the flattish climb at the beginning. This is a power model, give'em speed right from the start. Don't let the model just leave your hands on his own.

Urs
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Starduster
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« Reply #1612 on: June 02, 2021, 11:39:46 AM »

Hi Rich, looking at your facebook film may I suggest to launch the #18 with a bit more enthusiasm  Smiley, in other words with a bit of a heave to overcome the flattish climb at the beginning. This is a power model, give'em speed right from the start. Don't let the model just leave your hands on his own.

Urs

Thanks, Urs

You are correct, this is one airplane that flys better the harder I throw it. However, I've learned that I can't throw it too vertical, as it does not have the power to weight ratio to continue the climb. If I throw it hard with about 15-20 degrees nose up, it will still stay flat but the time in the horizontal is shorter.
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Tim Horne
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« Reply #1613 on: June 04, 2021, 07:35:06 PM »

This evening I went flying. A simple statement which is common on this forum. However this was the first model flying I have done since the NW Gala at the Manchester velodrome in early March last year.

For various reasons I don’t do much flying outdoor but there was no excuse today. A reasonably light working day and a sensible finish time meant that I had time and energy; and the weather was amazing. Our flying field is high and will have breezes even when it’s calm in town but tonight it was as close to a flat calm as I have ever known there.

I also have a cellar full of unflown models so I bundled it all into the car and set off.

Unfortunately I am also very “rusty” at getting myself organised for flying. I forgot a number of things of which the most pertinent to this report was the memory card from the camera! The photos were taken on my phone but I would have done more with the camera.

I tried flying almost all the models with mixed success and I now have a long list of repairs and alterations to do tomorrow. I won’t go through the failures but the most promising were; the peanut DR1 which needs more power but managed a gently descending left turn. The Malmstrom “Pushair” looked good but I forgot to make an “S” hook for the pusher prop instead of the usual “reverse S” hook Embarrassed so one flight was all it had. I built a F1N to take to Nijmegen and had some fun hurling it around. I need to learn about trimming it as it tended to dive but occasionally it caught the glide right and looked lovely and slow gliding down.

The best was the Hepcat. This model is quite old (I think I did a build thread for it on SFA!) but like so many of my models it stalled before completion. I finished the single blade folding prop during lockdown last April. In my rush I didn’t even do a test glide, just wound it up and launched. It just flew! Up and off, thankfully not too high and far but I had to chase it and take a bearing on where it landed. I wish John was still here to tell him about it.

The most frustrating things were with the larger two scale models, a Dumas Hughes racer and a VMC Sopwith Triplane. Incidentally, from our field you look down on the village of Flagg where VMC have their unit. If I had remembered my binoculars (another thing I forgot) I think I would be able to see their building. Both these models have been sat in my cellar for a year since being finished. 20 minutes in the car and I got them out and the tail surfaces are doing propeller impersonations Angry. I know why I prefer indoor models. Any advice on how you stop this happening will be appreciated.

Frustrations and failures aside, I had a very pleasant evening and didn’t leave until the sun was disappearing. I saw a couple of farmers in their tractors who waved greetings. A hot air balloon was up about 5 miles away and the main noise was the skylarks and a curlew. If the weather holds I will do it again soon Smiley.
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Pete Fardell
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« Reply #1614 on: June 05, 2021, 04:47:39 AM »

Sounds like a great session, Tim. Nothing lifts the heart quite like outdoor free flight on the right day! I bet John B was looking down and sucking the Hepcat skywards.

Not sure what to do about warps when models go on into new conditions. I know some people put battens along wings and suchlike but that does seem a bit extreme for transporting small rubber models.
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« Reply #1615 on: June 05, 2021, 05:47:05 AM »

I’ve found That there are a couple of things that help keep flying surfaces straight no matter what the atmosphere around them does. The first is good accurate joints. Poor joinery filled up with glue is asking for trouble. The glue will shrink with age and either pull the wood with it or create a void that allows the covering to pull it.

The second point is to ensure that there are no unequal stresses built in when the model is covered. Tissue has a grain and shrinks more one way than the other so make sure the covering is properly aligned With the grain running the same way on both sides.

Avoid covering light structures in mid air as it’s easy to thumb in stresses when you are teasing out the wrinkles. I prefer to tape the tissue to a board. Apply glue stick or dope and the drop the frame down onto the tissue flat. For curved upper surfaces I roll the frame onto the tissue from TE to LE on a flat surface.

Finally don’t over tension. These days I’ll use a coat of thinned weak dope and then non shrink for subsequent coats. Sometimes I don’t even bother with the weak dope. Just Water spray and non shrink dope.   Pre shrinking Esaki on a frame helps with light structures.

Since I’ve been following these regimes I have had no problem with twists even though my steel barn modelling shed gets extremes of hot cold and humid at different times of the year
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« Reply #1616 on: June 05, 2021, 06:05:58 AM »

Unfortunately I am also very “rusty” at getting myself organised for flying. I forgot a number of things of which the most pertinent to this report was the memory card from the camera! The photos were taken on my phone but I would have done more with the camera.
Thanks Tim. We're off for a big session at Luffenham tomorrow and I just found my memory card in the computer. I'm bound to forget something but as long as it's not rubber or diesel fuel, should be able to improvise. I'm taking about ten models in a four-model car. It's saying 2mph at the moment - hope the grass isn't too long.
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Russ Lister
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« Reply #1617 on: June 05, 2021, 06:14:46 AM »

Great that you got to fly, Tim  Smiley

It was a pretty miserable day when I went to VMC's unit ... the higher ground was in cloud!
You must have one of the highest flying fields in England?!
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Tim Horne
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« Reply #1618 on: June 05, 2021, 06:43:18 PM »

ZK, Thanks for the tips. I already do some of them, but I haven’t tried the method of applying the part to a piece of taped down tissue rather than laying the tissue over the part and then endlessly pulling and smoothing to try to get the wrinkles out. Next time I will give this a go.

Bill, I’m glad the comment helped as a reminder. My memory card was in the computer as well!
Looking forward to seeing pics from Luffenham.

Russ, I had a look at the OS map and the 405m (1328’) contour goes through our field! There are plenty of slope soaring locations in the area as well but of course they like a bit of wind!

I spent the afternoon doing repairs and alterations and am now looking forward to another opportunity to get out. The forecast for tomorrow is 4-5mph so I might see if I can escape for a while Smiley.
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« Reply #1619 on: June 06, 2021, 03:08:06 AM »

That sounds pretty high to me, Tim! .... especially when you compare it to my old slope soaring site:

https://en.m.wikipedia.org/wiki/Old_John

I use what I think is the highest road in Leicestershire on the way to work .... 802 feet .... we are not big on altitude in Leicestershire!
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« Reply #1620 on: June 06, 2021, 03:24:07 AM »

Quote from: Russ Lister
I use what I think is the highest road in Leicestershire on the way to work .... 802 feet .... we are not big on altitude in Leicestershire!
No, but Leics can do steep.  Clack Hill* at Mkt Harborough.  A blast cycling to Harborough from Desborough, not quite so easy on the way back. Smiley



*426' / 129m
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« Reply #1621 on: June 06, 2021, 03:40:08 AM »

Quote from: Russ Lister
I use what I think is the highest road in Leicestershire on the way to work .... 802 feet .... we are not big on altitude in Leicestershire!
No, but Leics can do steep.  Clack Hill* at Mkt Harborough.  A blast cycling to Harborough from Desborough, not quite so easy on the way back. Smiley



*426' / 129m

Yes! ... a route I drive quite often. I used to train on the A6 ... but usually out Loughborough way from Leicester. I can't recall if trained out that way at all.
I came my traditional way back from 'Skeggy' last weekend ..... brought back memories of dragging myself up the climb by Belvoir Castle on my ride from Mablethorpe to Leicester in the late 70s. That's a pretty good climb too!
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tross
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« Reply #1622 on: June 12, 2021, 07:01:12 PM »

There's some great flying going on in this thread for sure.

The 18" Vampire was flying on rails today. Shocked
It does finally come down but has not been found. Undecided

https://youtu.be/DZg0Ja-NWnU
Can be viewed in hd if that helps. Cool

Tony
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« Reply #1623 on: June 12, 2021, 07:15:31 PM »

Well Tony that was a very pleasant experience. Thanks for sharing the successful flight with us . Just amazing how that got down. Certainly a natural flyer. You must build another one.
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« Reply #1624 on: June 13, 2021, 06:05:59 PM »

Thank you FLYACE1946.
For sure those long flights are hard to catch.
They can be camera shy. Grin
Working on a re-build.

Tony
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