F-18 upgrade ??

[stuey]

I dont know about it being certain, but my Eurofighter and Habu seem to go away ok into the wind. The Eurofighter I can just about get my hand around the bottom on the CG for a straight and level shove, the Habu I use an underarm lob slightly nose up. I have a couple more EDF models that probably have about 1:1 that I have only ever bungee launched, but I will try a handlaunch if I can get a decent grip.

I think having a decent amount of thrust with an EDF model is essential for me, it doesnt have to be the fastest ever model but a Jet should fly like one imo. I have ended up on 4S packs with all of them now, with a well chosen setup it can have the performance and duration (if you use the throttle stick!)

[john haz]

Cheers Stuey,

 

Every bit of advice is great for me.  We all make our own minds up & i know nothing is cast in stone, but I have learnt so much from the guys here, I know it's saved me a lot in repairs. 

 

Using the throttle is something I have just started to do more this weekend, I love to fly full chat, speed is addictive, but I'm just learning that seeing how slow a plane will fly is interesting too

 

Got home at 3:30pm today, been at the field since 11am & managed to use 19 batteries with only one minor accident launching the Jetiger  -   it NEEDS wind to get airborne, if it's too calm that one is staying in the car !

 

 

[john haz]

Well, my 4500kv motor arrived today & after sorting out the sabre, I thought it was going to be a 15 min job to get the F18 upgraded.   No, it's never that simple is it

 

The new motor has a 3mm shaft, I have two shaft adapters for a 3mm shaft, but neither of my impellers work on them

 

The only one I had that would fit the shaft adap was a 70mm impeller  

 

OK, no problem, i will buy a new impeller, or a different shaft adapter, or maybe even a whole new 64mm fan unit suitable for 3mm ..........  Even that isn't easy unless I wanted to spend silly money on one !

 

Why can't these things be standardised a bit    It makes prop planes look easy ! 

Edited By john haz on 13/12/2010 20:46:06

[john haz]

Job sorted (I hope)

 

As per my other thread, i butchered a shaft adaptor & made the 6 blade impeller it all fit

 

All back together & on test I got 360w on a 3 cell 2200 (relocated to a new hatch on top, behind / under the canopy).

 

Holding it upright it will almost hold it's own weight, so hoping she gets away ok.

 

COG seems to be on the second moulded line back from the leading edge of the wing (top), I am guessing it's a bit tail heavy at this so may have to add a touch of weight in the unused battery bay.

 

Tim:  where did you set your COG in the end ??   I saw your message questioning this yourself but not certain what you decided was best in the end ? 

[Tim Mackey]

Sorry John, darn ISP troubles have left me with no internet or phone for the last 2 days!

On this old picture, you can see thin white line just aft of the wing l/e.....thats the sweet spot.

Be warned, my first attempt to fly her with the 4s resulted in a complete lack of elevator authority, as the COG had shifted just 1 cm forward of this....so DONT get her nose heavy.

 

[john haz]

I thought you were a bit quiet this week Tim, assumed you had gone away to see Santa

 

That mark is interesting, looks a lot further forward than the 23" from the nose I have been reading, but if it works, that's good

 

Obviously I don't want it too tail heavy, had bad experiences with that in the past, but I also know that hand launching a nose heavy edf isn't too easy .....  sweet spot is what I need !

 

With the std fan, upgrade motor & a 3S behind the pilot, my cog is about here (black line)

 

 

 As much as it pains me to do it, i will have to add some weight up front !

 

Thanks for the help, again  

 

 

Edited By john haz on 16/12/2010 08:00:24

[Tim Mackey]

Yes, it does seem a bit rearward - however with so many so called correct locations, it may well be OK- I have only flown mine with as shown and it felt about right tbh.

[john haz]

I think if yours flew as you have shown, I will pop a bit of ballast in the nose & try it.

 

Would you suggest a level elevator (straight edge along the tailplane & elevator) ?

 

Obviously I'm edgy about maidening this one, it looks so nice I really don't want to break it first throw.  Pretty confident i can handle it ok in the air IF it's trimmed somewhere near right.   I will ask a friend to adjust the trims in flight for me, then at least if it rolls or pitches, I can hold it under control & he can trim.

 

Looking forward to flying this one and the sabre with the new setup, just gotta wait for the weather to improve ! 

[Tim Mackey]

Yup, level the elevator with the tailplane, or a tiny bit of "up" - and as for the flight...it was a doddle apart from the launch. Once she is up and away it flies real smooth and steady, like a much bigger model TBH.

[john haz]

It's good to hear it might fly nice Tim, can't wait to get it in the air.   I'm just hoping the first launch goes ok, once I get it trimmed & know how to launch / land it, I will be a happy bunny.

 

I have done the elev - rudder mod, and managed to get it balanced without adding weight (lots of hacking around, the canopy is now removable & the batt sits under it.   I had to evict the weeble from the office but have tinted it black which I prefer

 

Maybe next week