cartercg

Juan, great video, and very interesting to see the inside of the plane during flight. I agree that it would probably be a good idea to prevent some of the wire movement, especially the Rx battery leads as all of the movement can't be good. At least you have a dual bat setup so if one wire breaks you won't crash.

I got your message, thanks again for the feedback.

It would be great if you could post the throws you're using for spins and snaps. Perhaps you can measure them next time you're flying the Citrin. The distance the rudder moves at the top, elevators at the ends of the stab and ailerons at the inside.

One difference I'm finding with my Citrin is that she has a tendency to want to bounce on landing i.e. as the rear starts to touch down the wing creates lift and she takes off again. I think it may be largely due to my replacing the stock gear with a carbon one with more flex, as the replacement gear is about 1 inch longer than the supplied gear. It may be that the additional angle on the wings is then causing the problem (I'm using a MK tail wheel that is not very long). Perhaps I need to make the tail wheel a little longer so that she sits a bit more level? Or is this a tendency with the bipe? I have more than enough prop cleranace so lengthening the tail wheel won't be a problem. Has anyone had a similar porblem where lengthening the main gear resulted in this tendency?

Regards
Clint

cartercg

So I lengthened the tail wheel by about an inch and the fuze now sits a bit better. See below pics:

The plane before lengthening the tail wheel (spats are now red!). You can see that it sits at a fairly large angle. Raising the tail by an inch will help.

Original tail wheel (MK).

Modified tail wheel. It also gives the stabs a bit more clearance as they sit close to the ground. Hopefully the stabs will now also talk less abuse from stones etc thrown up by the wheels and prop.

My son Thomas with his RC toy - fortunately they're cheap at his age......that will change if he ever wants for fly F3A and dad has to equip two planes!!!!

grantb

Da man already HAS two planes [>:] [>:] Wolfgang's Peridot A-plane from the 2011 world champs and now the Citrin[:@][:@]

Thomas is well set to inherit the Peridot[:'(]

cartercg

He's not even allowed to touch the Peridot!!! Like Grant mentioned it was Wolfgang Matt's A plane at the Worlds at Munice, and still has the FAI markings and Matt's numbers, branding etc. It's a special plane from a sentimental perspective, and it flies great. I'm running a bit more positive incidence and forward CG compared to how Wolfgang had it set up. Stall turns and spins are fantastic, as are snaps and rolls. It carves through the F13 really nicely, but the knife edge parts need a lot more rudder work as compared to the Citrin.

cartercg

Ok, some feedback on the flight characteristics of the Citrin.....

I started with the CG at the recommended location, but found it tail heavy. This was especially noticeable on landing. Moving the main flight pack forward an inch moved the CG forward about 10mm and that improved the tracking. The plane was less prone to bouncing on landing.

With a light motor like the Pletti Advance, one needs to move everything as far forward as possible so that the required CG can be achieved. My 1135g Hyperion packs are now sitting about 25mm from the back of the motor, and will sit right up against the motor if I save another 35 to 40g with a lighter prop. So anyone building this plane should move everything as far forward as they can. I did and even so my flight packs are sitting far forward in the fuze.

I tried different aileron differentials, but zero differential seems best and the feedback I've got from other pilots agrees with that.

I'm still paying with the CG and it's early days, but it looks like she will come to the canopy on both knife edges. Moving the CG back to prevent this seems to cause other compromises. I expect I'll end up with a Rud-down elev mix, but not more than a few percent.

Rud-Aileron coupling is superb. Even during a knife edge loop I hardly had to breathe on the aileron to keep her exactly on KE. If is does end up with some mix it will probably be less than a percent.

My only real "irritation" thus far is that the left wing drops when pulling and pushing. Upright and inverted she does not roll, so aileron alignment is very good and she is not carrying noticeable aileron trim. It points to a slightly heavy left wing (the stabs are parallel with the main wings and incidences of both stabs are the same). On some thinking on the cause I realised that the Elev servo wires, Rx, Emcotech switch and Spin 99 are all installed on the LHS of the fuze. That's at least 150g on average around 80mm from the centreline of the fuze. It equates to probably about 10g of wingtip weight and may be the cause of the "heavy left wing". I've move the Rx battery to the RHS of the fuze, and for the next flight will strap the main battery about 10mm offset to the right of the fuze centre line. Hopefully that will balance her laterally and the wings wil stay level when pulling and pushing.

I had a very near miss on the weekend when after the first flight I was changing the main flight pack and noticed the 4mm bullet on the +ve of the speed controller was sitting at a severe angle. I stripped off the heat-shrink and see photo below. Basically it looks like there was a hot spot in the connection which caused the solder to heat and the entire connection almost failed. This is the first time I've had such a failure/situation. I was lucky as a dead stick in the wrong part of the sky could have ended really badly. Looks like a few more seconds of power when it was hot could have caused a complete failure as the end of the battery lead was just attached to the bullet. You can see in the photo how it had pulled out of the bullet and the solder has melted onto the outside of the bullet.

Jason Arnold

What size bullet is it?

They shouldn't do that....

Regards,
Jason.

cartercg

They're 4mm bullets. I've been using them (as have other pilots) for years without issue.

cartercg

I managed to get in a few quick late afternoon trim fights. As mentioned in a previous post I shifted the main flight battery right of centre to compensate for the Rx, switch and speed controller installed on the left hand side of the fuze (see first pic). I'm pleased to report that it solved the heavy left wing tendency, and she pulled and pushed with wings level.

I'm not keen to have to install the packs like this indefinitely so moved the speed controller to the right hand side of the fuze. It should roughly balance of the Rx, switch, Rx battery and stab to Rx leads that are installed on the left hand side of the fuze. I should then be able to install the packs in line with the centre of the fuze (2nd pic) and not have a heavy wing issue. I see from Juan's video with camera inside the plane that he has a similar setup.

I'm running the CG about 13mm forward of the recommended CG. I'm finding the plane tracks, snaps and lands better. Before it felt very tail heavy (to me). It's comming to the canopy on both knife edges, and I'm starting to mix that out as I don't want to move the CG any further back.

Dre

My Feedback: (2)

Another Citrin data point...

The as-received weights are posted in the image below along with a comparison to my Amethyst. The RTF weight using the usual Futaba equipment, TP5000; Hacker C50-14XL Comp; Master Spin 99; TP910 Rx battery and Jaccio regulator and the heaviest prop I would ever use on it (APC 21x14 @ 129 grams) is 4973 gr.

I did reinforce the landing gear area as Clint noted at a cost of about 15 gr - I have seen too many airplanes with the stock gear plate arrangement damaged.

Also as noted by Clint one needs to be careful with balance. I was able to balance the airplane at the recommended CG location and have some forward margin.

The flight charcteristics are quite similar to the Amethyst, although I think it flies better than the Amethyst in terms of having neglible roll or pitch couple with rudder and has a more overall balanced control feel, in particular the yaw sensitivity is less. Snaps are even better. Only a few flights so far however I sense no alignment or trim issues. The recommended CG (115mm from bottom wing LE) appears to be a just fine. Looks big in the air.

Regards,

Andre

grantb

Hi Andre,

My "out of the box" weights were:
Top Wing: 555g
Bottom Wing: 570g
Left Stab: 99g
Right Stab: 103g
Fuz: 929g
Screw pack, servo and engine mount: 81g
Spats: 26g
Gear: 117g

Total comes out at 2480g

Somehow I score on the fuselage but my wings and stabs seem a lot heavier than yours. Still a net weight difference of 50g and Clint's Citrin was about 40g heavier than mine out of the box !!!!

Can you please post your TP5000 weight?? With the TP5000's and the APC it seems a small miracle that you have made weight[8D]

Grant

PS: Another thought. Did you weigh everything on the same scale? Could you weigh the TP5000's on both scales, if you used more than one? Your weights are consistently about 7% below mine except for the fuselage. Just made me think that you might have used a 2nd scale for the fuselage.

Spillmann

Hi

My Citrin weighs 3800g (RTF without battery).

Equipment:

Hacker Q80-13S
Hacker/Spin 99 Opto
Marquet Spinner
Mejzlik EL 20x13 (weighs less than 40g)
Futaba R7008 receiver
Futaba BLS-153 (AIL/ELE)
Futaba BLS-551 (RUD)
PowerBox DigiSwitch (6.5V)
TP 900mAh 2s1p r/c battery pack
MK Tail Gear
MK Foam Wheels
Oxai hardware package

Jean-Claude

cartercg

Well the final weight of mine without main flight pack is 3855g with the following equipment:

Plettenburg Advance
Hacker/Spin 99 Opto
Mejzlik carbon Spinner
Mejzlik EL 21x13
Futaba R6208SB receiver
Futaba BLS-153 (AIL/ELE)
Futaba BLS-451 (RUD)
Emcotech Rx switch/regulator (7.2V)
Hyperion 550mAh 2s1p r/c battery pack
MK Tail Gear
Tettra Foam Wheels
MK ball links with Central Hobbies titanium ends and carbon rods for linkages

But's it's difficult to really get a feel of the relative weight compared to other completed Citrins as we're all using different scales and a 1% error in the measrement is very significant.

Clint

Dre

My Feedback: (2)

My heaviest TP5000 pack is 1167gr. The airplane was weighed with that. The TP5000 is a 10s brick which is a bit lighter than 2x5s.

For reference my Amethyst came in at 4997 with all the same equipment EXCEPT with a Falcon 21x14 (weighs 40gr.)

Some things I did to keep weight down: Used Ti bolts for LG and motor mount; did not use any heavy duty servo extensions; took out all servo wire connectors and shortened servo leads to minium; servos mounted without grommets using Al screws; replaced rudder cables with Kevlar; replaced elevator horns with Ti bolts and MK type post; replaced tail wheel and ground weight out of tail wheel bracket; used 9550 servo for rudder; reduced ESC power leads to minimum; also forgot to mentiuon earlier that I am using a Marquett spinner with Hacker insert (the lightest spinner you can get). It all adds up.

As to the scale used. It is 3kg scale and the same used for all weights. It is calibrated against a known weight. The big parts are weighed and the weights are summed. This can lead to an accumulated error, however, I have checked my weight process using a friends research grade 5kg+ scale and I was with 7gr @5kg. In summary I do not think I have a scale issue.

Weight differences - one less or extra pass with the clear coat and you are there.

Regards,

Andre

Jetdesign

My Feedback: (8)

Hi Clint,
Thanks for sending me the link to this thread. Your motor mount looks great, and I just happen to have a sheet of 2.5mm carbon plate in the mail.

Can you comment on the 20g weight of the front mount? Did that include screws? The aluminum mount weighs 19g for both pieces, but with silicon tube and screws, total weight is 41g. If I can do custom mount for same or less, I would like do something similar.

Thanks!

grantb

My mount was done in the same way as Clint's. In fact he made most of it and helped me fit it too. My build thread is on Avcom. There is quite a bit of banter but the motor mount starts here http://www.avcom.co.za/phpBB3/viewto...rt=90#p1097936. You can skip most of the posts and just look out for the photos.

My final weight on the front mount (2.5mm plate) including epoxy is estimated at 23g and the rear mount (1.5mm brace and tabs with 2.5mm centering ring) came out at 8.5g (Probably under 9g with epoxy) All in for 32g. This does not include the 3 x 4mm Allen head screws to secure the motor to the front mount.

I was really taken by the F3AUnlimited mount and intended to use it. Looks really neat but unfortunately the 41g does not include the fixing structure to secure it to the airframe (another 10g I'd guess) and with the Citrin we just don't have the extra weight spare to play around with.

cartercg

Hi Joe,

Grant and my mounts are basically identical so the weights are essentially the same as what Grant has posted. The front mount (like Grant and I did it) is only really necessary with the Citrin as there is no front nose plate to attach the F3A front mount to. Using the F3A mount would have still required the installation of a front carbon structure, plus the additional mounting bolts etc. As we had to put a front plate in anyway, it made sense to make it such that it directly attaches to the motor and does not require the F3A mount as well.

In your case if the plane has a traditional front nose then the F3A front mount should work great and I really would not bother with trying to make a completely new front mount.

Clint

grantb

Maidened my citrin this morning at JOMAC (Johannesburg Model Aircraft Club) this morning.

Final weight was 3788g excluding the Hyperion 4600's. Ready to fly at 4920g. My basic kit started about 40g less than Clint's. Not sure where I made up the other 30g, mostly, I'd guess, by running a 4 wire system to the elevator servos.

Pretty much flew off the tarmac without any help. A click of left and she was happy. Both Clint's and my Citrin seem to need some up trim which can be dialled out with the adjustable stab.

Last picture shows cartercg's and my Citrin together.

GlennO

Hi Guys,

I have just completed my Citrin and have flown it on the weekend.

Mine has a Q80 14xs with a spin 99.
I have started with a 21x14 and 20.5 x 14 prop but have found with the hotter conditions here in Australia 30c degrees plus last weekend, that the Spin 99
shut down as it over heated. I have mine mounted on the side of the fuse, basically in the center of battery tray - similar to what most people have done.
I made my battery tray out of composite board and it is removable. The final weight for the tray was 29 grams.

I am concerned that it is not getting any direct cooling so I'm considering move to below battery tray and maybe open up a inlet hole below the main engine ducting for direct
cooling to the speed controller.

Mine came in at 3810g as I kept my installation very basic and light. I plan to use TP 5000 packs.

I've only had a couple of short flights so far, but first impressions are that it has incredible rudder power as most people have stated, and it rolls incredible well.
I hope sort out the cooling issue and do some more flying with it this week.

regards GlennO

cartercg

Hi GlennO,

Congrats on your new plane. I've managed to get a fair number of flights on mine now. Great flying plane but it does tend to get blown around in the wind, especially cross winds. Although it can fly nice and slowly I have found that flying it close and slow gets punished in strong cross winds. So I'm now flying mine at around 165m and reasonably fast as with a mono. I have found it then tracks better requires a lot less pilot workload.

I'm running a pletti advance with trimming now at 24deg. My spin 99 is mounted in the same manner and even with an ambient of 30 deg it is cool to the touch on landing. I'm surprised yours is overheating. Our summer is getting into full swing here so our temps are probably similar. I have two small air exit holes in the fuse at the bottom of the landing gear area as per the pics on the oxai site. I'd suggest you consider creating those exit holes before moving the speed controller. Hope that helps.

Clint

cartercg

GlennO, looking at the pics you posted, you seemed to have cut away a large amount of the bottom air scope that forces air upwards towards the motor and speed controller. That may be the route cause of your overheating. Consider installing a scoop that forces the air upwards.

Clint

GlennO

Hey Clint,

Thanks for the info on the exit holes, I hadn't seen those pictures and I must admit that it did seem strange that there where no
exit holes cut when I received the plane.
I will cut them and also add a depron deflector under the motor to hopefully get the air up and around the controller.

We're going to be seeing 40 degree C weather here soon so I need to get the cooling issue fixed.

Thanks again Clint,

Cheers GlennO

Dean Pappas

Hi Andre,
Have you put the ship up on a straight table and measured all the incidences?
I sure would be curious.
thanks,
Dean Pappas

GlennO

Hi Clint,

I made the changes as you suggested, cut exit holes near U/C, fitted a scoop below motor to force air upwards, moved the ESC up slightly on where it was
but It seems to have not made a whole lot of difference.
The ESC is still very hot to touch even in Ambient temperatures of around 25 degrees. I compared the temp difference with my Pegasus which also has a Q80 and
spin 99 with a 21x14 and the Pegasus ESC temp was around 35 degrees compared with 65 degrees in the Citrin with the 14xs Q80.
I was running a 20.5 x 14 then switched over to a 20x13 to see if i was loading the prop too heavily however I saw no temp drop on the smaller prop either.

I am now considering moving the ESC to below the battery tray just to see if this makes any difference. Below the battery tray may get better direct airflow.

cheers GlennO

Dre

My Feedback: (2)

I find the cooling in the Citrin to be the best of any e-powerd airplane I have had. I have only the small exits behind the LG as described and no special duct work. Everything runs cool. I use a Spin and it is up front behind the front air scoop, so blocked from direct airflow. After a flight It is warm to the touch on a 95 deg F day (about max temp we see). My point here is that I wonder if there is not something wrong with your ESC?

Regards,

Andre

GlennO

Hi Andre,

I am starting to wonder if there may be a problem with ESC too. I might switch it with the one that is currently in the Pegasus to find this out.

You say yours is behind the air scoop up front, is it mounted say level in height with the bottom of spinner?

cheers GlennO