David Ovenden

I have tweaked the downthrust and adjusted the top wing incidence very slightly as there apeared to be a very small difference between left and right sides. I will test fly again on Tuesday all being well with the heavier lipos which moves the CG forward just a bit. I am very pleased with the speed and ease of fitting and removing the outboard wing panels. It is just as quick and easy as I had hoped. It's nice when things work as planned - which isn't always the case.

It's looking very nice Colin. Great job.

Well that's my thinking Colin. A forward move of the CG is the "safer" direction. It is easily achieved with a slightly heavier LiPo pack and involves no permanent changes so easy to undo if it doesn't work.

I tried multiple times with tape and it just didn't separate the backing film at all. Scalpel blade was the only thing that worked for me.

Great effort Martin. It's a shame the nacelles build is a bit "bogged down" at the movement but it will all come good in the end. Clearing up the workbench often give the new perspective one needs to push on again with a project. I find that I am trapped in a repetitive cycle of clutter /declutter. I work until my workspace becomes unusable and/or I can find any of my tools because they are all buried under the mess. Then I tidy it all up and everything is fine for a bit until the clutter builds up again. Will I ever develop tidier habits.? Seems unlikely at this stage of life.

In a follow up to the last post. I have checked the plan which shows the CG position at 76mm from the leading edge. The wings are parallel chord and there is no stagger or sweepback. 76mm on a 230mm chord wing means the plan cg is at 33% of mean wing chord. This seemed a little far back. So I've spent 1/2 an hour using the formula in Gordon Whitehead's book "Scale Aircraft" to calculate the CG. According to that formula it suggests the CG should be even further back at 80mm! So my question is am I right in trying to move the CG further forward. Any thoughts?

Well, yesterday's flight proved that 4S power is enough to fly the plane easily. However, it still climbs steeply under full power. The elevator with reduced throw is still sensitive even with 30% expo added. That might suggest the CG is too far back - though it is spot on where the plan shows it. The Condor does fly but not currently in the relaxed smooth fashion I was hoping for. So I will add some more down thrust and move the CG forward a bit (use higher C / heavier LiPo) and see if that improves things.

Thanks Colin. Tomorrow I am taking the model out again for more flights having made a few tweaks. Biggest one is a change from 5s to 4S power as the model really didn't ever need full throttle and climbed strongly at WOT. We will see how it works out in practice tomorrow.

It's tempting John. Especially as I have 5 rolls of silver solartex in stock but no blue!

I started drawing up the plan for the Bobcat wing yesterday. I have settled on 1:6.5 scale which will give 77" wingspan. I will be using my two Enya 53-4C engines but I am hoping to design the model to accept interchangeable electric motor power too. I have two SK3 4250 500KV motors and I am thinking that 13x6 3-blade props with 5S lipos will give equivalent power to the Enya using 12x6 2-blade props. More testing is needed. Once that is sorted I can look at designing the engine nacelles to accept interchangeable electric or glow power modules. In the meantime I better press on with drawing up the wing. I am currently planning on using NACA 2414 wing section at the root changing to NACA 2412 at the tip with 2 degrees of washout at the tip. I am thinking of modelling one of these aircraft as the colour schemes are not too complicated to do.

thanks Frank., I was looking at Devwing and thinking it had some neat features.

Thanks Bob for your recommendation. John, What full 3D CAD program would you suggest? Thanks David

Hi, This question is probably answered somewhere on the forum, but so far a search hasn't led me to it! I want to design the wing for my Cessna Bobcat. I don't need to do a complete detailed plan, but I DO want to be able to plot the wing ribs for the tapered wing with a progressive change of NACA profile from root to tip, and Ideally show spar and LE locations. What would be a suitable app/ program to do this? I am capable of doing it by hand, but like the idea of using the PC to make printing out shapes easier. (Maybe even laser cut ribs??) Who has experience and what to you suggest? Thanks

Thanks for sharing your twin experience Andy. It is always helpful to have input from those with prior experience. I do like the idea of parallel wiring the lipo packs.

Pic deleted.

I have managed a first flight with the Curtiss Condor. I used 10x6 3-blade props. Both motors were standard rotation with no sidethrust. There was a small torque pull to the left on take-off but easily manageable with a bit of rudder. As Chris rightly says "it's what it's there for". Given the advice here, and my experience with the Condor, I will stick with the same standard rotation and no sidethrust for the new Bobcat project.

Thanks Jon & Nigel for your very helpful input., That is what I was tempted to do. It means I will set up both electric motors and I/C engines with standard rotation. Then I don't have to find matching opposite rotation props and don't have to re-time the Enya. Whilst I imagine it will work in terms of allowing it to run "backward", I can't believe it will run exactly the same as the standard motor would. As I now have three Enya 53-4C engines to choose from, I will concentrate on finding which 2 run closest to each in terms of max rpm and transition across the mid-range.

Having completed my Curtiss Condor twin project I'm planning my next model. I'm going to do a Cessna T-50 Bobcat twin. My intention is to design it to have interchangeable I/C and electric power modules. With electric its easy to have one motor with standard rotation and the other reversed with a "CCW/pusher" prop to avoid the torque issues. I wondered about doing the same with the I/C powerplants so the flying dynamics of the model would be the same with either electric or I/C module fitted. So her is the question. I now have 2 Enya 53-4C engines that I will use in the model. I found online the following diagram for retiming the Enya for reverse rotation. Anyone tried it? Is the re-timed reversed rotation engine likely to run very differently from the standard rotation engine? Would it be better to to have them both on standard rotation and concentrate on reliable engine set-up so neither of them stops? There is a video of someone who has done this on YouTube but the engine is only seen running on the bench and is not properly set up in the video so its hard to tell how successful it was in reality.

I'm watching this thread carefully. It looks as if this Rustin product could be very useful for glow-engined models if it can deal with 10% nitro fuel.

Really interesting build Nick. Fantastic workmanship and great photos.

Simply elegant DD

Took my PT-19 and Veron Hawker Tomtit for a turn in the spring sunshine..

I now have some forked oleo legs from HK. They are nicely made, but unfortunately they won't really take the required 3 3/4" wheel without some modification. (In fact even a 3 1/2" wheel binds on the fork) Still they may do to create at a prototype set-up to prove the viability of a scale retract system for the Bobcat.

Went out with my Phoenix 2000 glider to get my hand in again. Then did the maiden flight with my Curtiss Condor. Lovely, sunny and warm this morning with only a light breeze.

Thanks for your kind comments . I hope many of you have managed to get out flying today and to enjoy the fantastic warm weather. Once you have got back home and put your planes away I would like to pick your brains. The Condor test flight was pretty successful with no nasties but a few issues to resolve. Most obvious was that there was way too much elevator throw. Fortunately flicking in the low rate (70%) made things manageable but still more than ideal. I have now adjusted the throw at the servo (inside the fuselage) so that should be OK. Secondly, there was a marked tendency to climb under full power so I dialled in some down trim, but the nose would drop when the power was off. So it sounds like more down thrust is needed? Or is there just too much power from the 5s lipo pack? I didn't need full throttle to take off and almost all the flight was 1/2 throttle or less. So maybe 4s would be enough? The model weighs 4.7kg but there is 1200W from the 2 motors at full throttle. After a 4 minute flight the 7000mah lipo was still showing 74% so it is not power hungry. The weird thing is that on landing both YEP 60A ESCs were "double beeping" which notifies Low voltage. However, measuring the LiPo pack showed all 5 cells at 4.0v. The ESC is set for "slow down" at 3.2v per cell. So something is very off there. Because of this issue I stuck with just the one flight. Any thoughts. I have a dedicated separate 10a UBEC so maybe I ought to fit that rather than rely on the ESC BECs? Your thought appreciated. David