Warbird Replicas Ju88 Night Fighter build

[Ron Gray]

@alan psimilar to my thoughts! I’m thinking of cutting mine out of some fibreglass sheet and using a 2mm bolt for the hinge pin, not because it will be stronger but because it will look better. After all, the only reason for thinking about this in the first place is because this is such an obvious feature on the full size. Having said that I have to remember that these Warbirds Replicas are very much ‘stand off’ scale. I may ultimately decide that it isn’t worth the effort!

[Eric Robson]

Edited July 9, 2021 by Eric Robson

[Glynn]

Very Nice flying Eric.

[Eric Robson]

I could not get text on the video was taken today from a mobile phone. A really great flying machine. Thanks again Richard.

[Ron Gray]

Very nice Eric, looking forward to getting mine finished and in the air.

[Ady Hayward]

Nice flying Eric. I found with mine that dropping a just a couple of degrees of flap made the plane feel a lot better when flying scale like. The 88 is a lovely plane to fly

[Eric Robson]

Thanks Glynn, Ron and Ady. flying it yesterday in perfect conditions and no one there to take pictures. I did have a problem with it a few weeks back when I took off and at about 30ft operated the retract switch and the motors cut. it hit the ground hard but tough as old boots it did not sustain much damage. I thought I must have caught the engine cut off by mistake but after rebuilding the front end and nacelles I took it up to a good height and operated the retracts, the motors cut again so I dropped the wheels and they restarted. I took it higher and tried again, this time the motors kept running then after 2 circuits died. I shut the throttle and opened it again and they restarted. and got the plane back onto the strip. I checked the esc's and they seemed ok but I replaced them. The trannie was checked and there was no cross functions all switches doing what they should,  then on ground checks with the props off it happened again, it was on Spektrum radio so I changed the system to Futaba and have not had any more problems. It may be the rx as I have flown other models with the Spektrum without problems. Now that it has had 8 successful flights with the Futaba gear I will refit the glazed nose and bomber canopy. 

[Eric Robson]

This was after the motors cut. It looks worse than it was, there was only a tip of the wing that was damaged and the rear of the fuselage was ok

Edited July 11, 2021 by Eric Robson
added some text.

[Trevor]

Ouch! Glad you've got it operating reliably now Eric. Are your retracts powered through the receiver? If so, I'd guess your problem might be caused by a dip in supply voltage as the retracts operate. This would be worse if the retracts encounter resistance before reaching the end of their travel so it might be worth checking that the wheels don't bottom out in the nacelles when retracted. Even if your Futaba receiver is more tolerant to voltage dips, it would still be a worthwhile risk-reduction exercise.

 

Also, If you are using the BECs in the ESCs, it's really easy to use one of them to power the retracts (and maybe flaps) and the other one to power the main flight controls - just pull the red wires out of the appropriate  receiver plugs and join them all together.

 

Sorry if you know all this already!

 

Trevor

[leccyflyer]

That's a great tip Trevor. Thanks.

[Eric Robson]

Thanks Trevor, I have considered using a separate 6v battery for the controls it would not be a problem as the plane fly's on half throttle, the wheels don't bottom out but the legs are long and with the oleo and the wheel it must be a fair weight to pull up

[Ron Gray]

@Trevoryour post has just reminded me that I need to do something similar with my BF-110. It’s a bit more complicated as I am running SBus to a decoder in each nacelle and then out to the flaps, ailerons and throttle. The retracts are separately wired (to allow me to power them separately) but at the moment pick up power from the Rx. I need to change that so that they get power from the sound system battery but as that is 3s I need to add a BEC. Oh the joys of leccy!

[Ron Gray]

@Eric Robsonthat looks nasty, glad it looks worse than it is and will soon be up again.

[Ron Gray]

Thought I'd post a few shots to show that I'm still working on the JU! I've spent a lot of time working on the nacelles, not just the ply covering but strengthening the joints to take the extra load of the I/C motors hanging off the firewalls.

 

Nacelles are locked into the wings with a sunken plate so marking it out and cutting the foam out using my soldering iron foam cutter.

 

 

 

 

Plates stuck in place using Gorilla Glue brown and using the nacelle frame to help keep them I'm place whilst the glue dries.

 

 

Then the nacelles epoxied to the wing and stood on the firewalls to make sure they line up!

 

 

Reinforcing strips epoxied to the nacelle framework and the veneer covering, it ended up being a very stiff construction

 

 

 

Thin ply covering stuck to top of nacelles with small screws as temporary 'clamps'. I didn't need to wet the the ply but the screws certainly helped!

 

Edited July 11, 2021 by Ron Gray

[Ron Gray]

I'm using Richard's new design retracts so this called for quite a bit to time to work out how to fix them in place (due to the box framework) and what angles to set the oleos to so that they aren't raked too far forwards and allow the wheels to retract quite deeply.

My approach was to use the holes already drilled in the side of the box framework as mounting holes so I threaded these for 5mm bolts. Ply stiffeners were glued to the outside of the framework 

 

 

But fitting them this way meant that I had to make some spacers to take up the space between the nacelle frame and the retracts box section. I 3D printed these (why not?!!)

 

 

Recesses cut out in the wing to take the wheels when in the retracted position

 

 

The supplied retracts didn't quite give me the correct positions for the oleos when down or retracted so I resent the 'spring' to give me what I wanted

 

 

Very little of the wheel protrudes below the underside nacelle covering (you can also see where I had to extend the plastic nacelle covers as I couldn't get them to fit!)

 

 

Nicely positioned when down

 

 

[gillyg1]

Nice job Ron, like you say alot of working out, be worth it in the end.?

[Eric Robson]

3 hours ago, Ron Gray said:

@Eric Robsonthat looks nasty, glad it looks worse than it is and will soon be up again.

Actually it is together Ron,  the damage was done a while back. I put the ply reinforcing on the inside of the nacelle sides to take up the gap due to not having a 3D printer. but I do have slack arse trousers , A length of 4mm screwed rod may be an alternative for the front mounting bolts as it is difficult to get to the nuts on the inside.

[Ron Gray]

That's why I threaded the holes in the alloy box! The bolts will either have shake proof washers under the heads or thread lock.

 

Glad you've got it together and share the same taste in male attire!

[Ron Gray]

I got the build sufficiently advanced that I could put it together to check the C of G which determines where I will mount the servos for the tail end. As anticipated it is a bit nose heavy so I can locate the 2 servos at the rear although I may change them for slightly smaller ones than the standard ones I had planned on using.

 

[martin collins 1]

Pictures of it assembled please Ron ? 

[Eric Robson]

I had 5 flights today with the Ju88, after replacing a suspect motor everything went well, landings could have been better.

 

Edited July 13, 2021 by Eric Robson
wrong vid.

[Ron Gray]

Glad its back up and flying again Eric and it looks like it's a 'go to' 'plane for you?

[Ron Gray]

@martin collins 1I didn't take any photos of the loosely put together bits but I'm going to do it again later so will take some then! In the meantime here are some progress photos, not necessarily just to do with the I/C side of things!

 

Having looked into the Frise ailerons in a lot more detail (for that read a LOT of time) I've decided against them. The problem I encountered was that to get them at least something like scale, i.e. with the hinge line notably below the aileron's surface I just couldn't position them correctly; its a combination of aileron thickness and width. I've not totally ditched the idea and may come back to them later, after the initial flights.

 

So, ailerons and flaps sanded to shape and hinged

 

 

Flap servos added (I 3D printed a plate for them to sit on/in)

 

 

My usual 3D printed servo fixing plates

 

 

 

Which sit neatly in the provided ply servo boxes

 

 

Wing location dowels fitted, drilled holes through former, positioned wing, dowel hole locations marked in wing LE and dowels glued in wing using Gorilla Glue (brown), wing repositioned with plastic sheet in between to prevent any excess glue sticking the wing to the fuse!

 

 

Whilst not included in the kit (?) wing fairings formed using triangular balsa with saw cuts and wetted to form to the wing profile (note plastic sheet in between to protect wing veneer from water, will be left in for when I glue the fairing pieces in place)

 

[RICHARD WILLS]

On 10/07/2021 at 12:56, Ady Hayward said:

Nice flying Eric. I found with mine that dropping a just a couple of degrees of flap made the plane feel a lot better when flying scale like. The 88 is a lovely plane to fly

Fabulous picture Ady .

That view is something our brave lads would not want to have seen !

[Ron Gray]

No, they would have much preferred this:

 

 

 

Sorry Eric!

Edited July 15, 2021 by Ron Gray