Tim Cheal
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Posts posted by Tim Cheal
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Hi Colin
Sorry I got dragged away earlier. Imagine the wing sitting above the cub with the left wing forward of the perpendicular to the fuselage
And the wing has dihedral.
As the aircraft accelerates along the line of the undercarriage track (straight ahead for the fuselage) then the aircraft will tend to roll right). As your instructor experienced. This is equally true of the undercarriage is fitted at an angle to the fuselage (and of course the wing).
As the weight comes off the fuselage the aircraft is no longer constrained to track along the line of the undercarriage track, and so ‘weathercocks’ to present a more balanced wing profile (in fact the fuselage is now crabbing). Hence the roll stops once airborne.
This all may be complete rubbish, but something to consider.
Tim
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Colin, indeed.
With that in mind are you sure it was in the middle, and not offset to one side?
Sorry about the wing departure Stevo!.
Tim
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Sorry Colin, I didnt answer your question.
Its the dihedral that causes roll with yaw (as does sweepback, but there shouldnt be much of that on a Cub!). It actually effectively changes the angle of attack but its easier to think of this as pushing the wing sideways (at 90 deg to normal flight) through the air, one wing will have airflow hitting it on the bottom, but the other side has airflow hitting it on the top (you will need to imagine the first half of the wing is not in the way). The one half will want to rise, and this is dihedral stabilising the model.
Hope that helps.
Tim
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Thnaks Stevo
Colin, Is the wing bolted on? It may be that next time it is level and the problem has gone away (perhaps a wire trapped underneath for example)!
Tim
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Was thinking about this one.
I am with Ken.
It could be that either the undercarriage is offset, or the wing not perpendicular to the fuselage, or not 'level' (it should have equal dihedral each side), or even the wheels not at the same height (causing a 'bank' while on the ground).
In these cases , once airborne I believe the aerodynamic force would straighten the wing out.
In the case of an undercarriage not tracking straight, once it is off the ground aerodynamics will straighten it all out to least drag and aileron trim sort out any unwanted roll. But on the ground, the aircraft track may be dominated by the tracking of the undercarriage, hence inducing a roll in the same manner as yaw does (secondary effect is roll) when airborne.
For a wing not perpendicular the aircraft may sort this out once airborne to effectively straighten the wing (although the fuselage would now 'crab'.) If the dihedral is not equal I suspect the same may happen, but now the fuselage would be 'banked' for the wing to be straight.
Do let us know what you find out, because most of the time it is nothing like what we think it is causing these things!
Good luck!
Tim
Edited By Tim Cheal on 07/04/2014 17:49:36 tt get rid of a smiley thingy
Edited By Tim Cheal on 07/04/2014 17:50:11
Edited By Tim Cheal on 07/04/2014 17:50:36
Edited By Tim Cheal on 07/04/2014 17:51:15
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Terry
I have just completed my 16th flight with my Tutor. I love it, and it is much admired by my colleagues.
The only criticism of the model, and the area I would look closely at before you get the engine and cowl installed, is the nose leg. Its very nice that it is sprung, but more than once it has turned off centre by up to 90 degrees in the air and taken some careful landings to prevent it digging in and noseing over. When the grass was really wet it slid along nicely, but as it dries out there is more resistance and today's first landing was nearly a complete flip.
There appears to be 3 areas to consider. The first is the securing of the noseleg restrainer to the firewall. I would make sure these are done up very tightly, and with some kind of threadlock. Second, is the nose wheel and spat security to the noseleg, again make sure this is really tight. The third is the securing of the sprung bit of the noseleg to the short solid stub that slides into the firewall retainer. 3 allen grub screws fulfil this task. But they can allow the noseleg to turn if not fully secured. I recommend that you undo these screws,dismantle the nose leg, file some flats for the grub screws on the stub and reinsert them with either some very good locktight or some cyano. I have resorted to cyano today and hope that they will hold this time.
I hope that helps.
My son (ex Manchester UAS) confirms that it the Tutor is 'soloed' from the RHS.
Tim
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I have a question with regards to this issue that one of you may be able to help with.
The article on the rather nice (and unconventional) Corsair states that it flies "with no vices". But, the airborne picture at the bottom of Page 46 shows the aircraft with a massive rudder deflection to the right, and possibly a small amount of aileron, also to the right. It also looks like the wheels are just retracting, so I have assumed this is just after take off. So, my question is:
Is that amount of rudder deflection a mix with aileron to make it turn, or is there something else going on?
I ask because I have used rudder/aileron mix on my piper cub, but never to the degree the picture shows?
Regards
Tim
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Thanks Pete
There is (a circuit to land), honest. Its just before the cocked off nose wheel drags the model off to the right on landing (only poor thing on the Seagull Grob Tutor is the nose wheel which rarely drives the model in the desired direction, but loads of up elevator takes the weight off the nose and its then not too bad on wet grass!).
I didn't know that about the other RXs, I shall give it a try.
Tim
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Santa did bring me the Spektrum GPS telemetry module. It has taken a bit of internet searching and faffing, but today I managed to get a file to download,convert it to a Google Earth file and display it on Google earth:
Its fairly simplistic, but on Google Earth you can see distances, slew to horizontal view, or plan view to see where you have been over the ground etc....
The application to do all this is some software available free. It also presents the telemetry data in table or graphical format, as per this:
All great fun really (for someone a bit sad like me!).
Although the HITEC GPS data looks great I have too much Spektrum kit to swap it all over, so I am glad I went the Spektrum GPS route as the great advantage is that I only have to take the SD card out of the side of the transmitter to download the file rather than removing, or at least accessing, a receiver every time.
Thanks to those that contributed or took an interest.
Tim
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I decided on the Spektrum Telemetry module so just waiting for Santa to deliver!
Thanks for all your help guys, Ill let you know how I get on.
Tim
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Count me in too please.
Happy Christmas.
Tim
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Thanks Guys
I am torn now as I like the telemetry idea, but it will only work to download data when I have the telemetry active to send the data to the SD card (DX8) (I only have 2 telemetry capable RXs (AR8000), the rest are Spektrum 6200 or 6210s).
The SM one will store the data to look at later but will need extracting from the device itself.
Have I got this right.
Any advice?
Tim
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Actually Fly Boy 3 I don't think that's a daft question at all.
The answer is that no aircraft I know has such an instrument, but it is entirely possible. As BEB implies it rather depends on the type of aircraft. Small aircraft have a centre of gravity chart of the aircraft envelope and it is the pilots responsibility to ensure that the fuel, people and bags are loaded within the aircraft's 'envelope'. This is normally pretty broad, but it is often possible to get outside of it, which can cause difficulties.
Large aircraft are normally loaded by a team in accordance with a load plan, and a computer generated load sheet provided to the flight crew. It remains the Captains irresponsibly to check the aircraft is in balance but the options are pretty broad. Commercial airlines are striving for an aft CofG to improve fuel efficiency so knowledge of the actual CofG would be worthwhile. Moreover, the trim set for take off depends on the actual CofG, and this is calculated for each take off individually from the loading figures provided by the loading team. This relies on accurate recording of the weight of what is loaded and it being put in the same place in the holds as stated on the load form. You can imagine what would happen if the weight is declared wrong on the loading information.
I recall an accident in 1999 where a Focker 27 crashed on approach to Jersey. If I remember rightly it was loaded too far aft, and when the flaps were lowered for landing it pitched up. The problem is one of control. With the CofG aft there may not be enough forward control travel available to stop the aircraft pitching up, causing the forementioned angle of attack to increase and a stall to develop. Recovery from such a stall is difficult as there is insufficient forward stick available.
But the load "shifting" form its position is also cause for concern. Google "
Hope that helps
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Fantastic, thank you for the steers. I apologise for not finding the UK outlets you have listed, a Google search was not fruitful of UK sites, but I can see that they are available.
Dizz, Can I ask if the Spektrum data can be uploaded to a computer in the same way that the SM Modelbau GPS logger appears to be able to be. To be honest, it is not so much the telemetry (although that looks very very useful) but the download I am after.
Many thanks.
Tim
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I note that in the US you can buy a Spektrum GPS Sensor (SPMA 9587) for around $99, but there is no such device on the Horizon Hobby.co.uk site.
Does anybody know anything about this unit being released in the UK, or can anyone recommend anything they use for GPS tracking. I was after something that would track my flight and download to a computer afterwards (Hobby King had such a thing but it didn't look like it got very good reviews, especially for uploading data to the computer).
Any ideas gratefully received.
Tim
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Count me in too please.
Tim
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The weather was most kind today so I managed to maiden the Tutor.
I had trouble with the cheap spinner. The back plate did not have any 'bite' on the APC prop that I used for the maiden and it therefore slipped a lot. Removing the a spinner helped, hence the picture below is 'spinnerless'.
It flew nicely and pretty straight from the start (just a small amount of aileron trim required). The model handled well, but I didnt take it beyond loops and stalls.
I tried stalls with flaps up, mid and full and only at full was any wingdrop tendency noticed. I elected to land without using any flaps, and after one flight bought it home to check all the fasteners/spats etc... All seems well. I may get a better spinner, has anybody replaced the Seagull one, and can you recommend any spinners with a similar profile.
Tim
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Is it overweight?
Tim
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Great News Mike.
Was the performance noticeably better with the .91?
Tim
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Hi Mike
I hope you got the Tutor sorted and flying again.
I managed to complete mine last week, and this weekend have put all the decals on ready for its maiden (I thought about doing it the other way around but the weather wasn't good enough today so I cracked on with the decals). My thanks to the guys on the forum who tipped to wet the model with water with a small amount of washing up liquid before applying the decals to allow a bit of movement around for positioning, this worked a treat.
Here it is all ready to maiden:
Tim
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Craig
Hopefully this picture will help:
And here is my recovered model (just washed, so those are soap bubbles!)
Tim
Edited By Tim Cheal on 15/09/2013 11:42:58
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There was a thin line of different coloured wood above where the torque rod lies, so in the centre section of the wing from where the torque rod disappears at the servo end to the inboard end of the aileron.
Hope that helps.
Tim
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Craig
I had the same issue with the torque rods. Once you have cleaned off the covering you will find the wood has an inserted strip of a different colour. By cutting this out with a Stanley knife, (a thin dremel tool would work great as well) I was able to lift the torque rod form the servo link end to repair. I was able to remove them from the ailerons then without terminal damage so I could use the same aileron again. The torque rods travel through plastic tubing and in my case it was all rusted up, so the whole assembly was turning in the wood when the ailerons moved. By careful manipulation I was able to free it all up and use the same torque rod and assembly. I then replaced the wood I had removed with a strip of balsa and covered over.
As for slow speed flight as discussed in my original post here, and the responses, my Acrowot does not drop a wing either, but getting it slow enough consistently to land at my club was difficult. Hence the flaps, which are used for drag, not lift, which means I can approach steeper (there are lots of trees around my flying site!) It also lands slower, which has helped on those rare calm wind days.
I covered mine with the control surfaces still attached. This proved fine with the elevator and rudder, but the ailerons were really tricky and on one flight there was an awful noise then suddenly a piece of Oracover departed the model; I had lost one of the aileron coverings in flight. So I think your plan is best.
Good luck with the refurb.....
I have some pictures, but they are on the other computer, so I'll add them later.
Tim
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Craig
My Acrowot was looking tired after last summer, so I did exactly the same and recovered it in Oracover. I was able to repaint the cowl and clean up my canopy so they remained the same. But, and to keep some originally I phoned Chris Foss and he was very helpful in supplying some "Acrowot" decals at a very reasonable price, but I also had some additional items supplied by Tim at model markings.
I found that since the recovering it is really slippy and will not come down in a clam wind (to be fair my OS46LA is inside the cowl and it leans off a lot during flight and I need to run it a little rich, which means I cant get the tickover down to optimum without it stopping at the bottom end!). So, I replaced my single aileron servo with 2 (side by side) and added some flapperons to add some drag for steeper approaches. Not everybody will think this is a good idea, but I have found it has helped immensely in calm winds. I have to admit, that due to limited movement of the down going aileron at full flap travel the roll control is less than when they are up. It has caused me some difficulty on one approach, but I leave them up when it is 'windy' and use them in calm winds. I am not sure if others have had the same problem, but it really is slick when covered with a nice shiny finish!
I too like the carbon undercarriage, but I would fix it with nylon bolts - I put something about this in another Acrowot thread. I also took the opportunity to fiberglass the inner fuselage by the undercarriage mounts to strengthen this area prior to recovering. So far the nylon bolts have done their job, breaking when they needed too!
Good luck with the refurbishment.
Tim
Piper Cub trainer rolling to right on take off.
in Beginners
Posted
Thanks for letting us know Colin. Sometimes the small things seem really important (anybody who has raised teenagers may recognize that!).
It can be really frustrating when you cant fly because you cant get an instructor, but the satisfaction of knowing you can go to the field and fly alone safely is well worth the wait.
I still believe my suggestion is plausible, but back in me box for a few months!
Tim