Peterf's 1/4 scale Falcon Models Tiger Moth

[Manish Chandrayan]

Good to hear that Peter. If you have already done it could you advice how did you go about bending the lower wing rear metal fittings that has two narrow 90 degree up turned edges?

[ron thornhill]

Hi Manish

You are certainly ripping into the build now, "with the therapeutic riblet fitting". As a matter of interest I bent my lower wing fittings with a tool I have used for years, two bits of power saw blade bolted together one end the job is clamped between the two blades then held with a vice. Of course not every one has power saw blades but any thinish high tensile steel will do. The first bend of course can be done in a smooth jaw vice. I hope this was of some use. Good luck.

[Manish Chandrayan]

Thank you Peter, but could you please explain bit more on how do you go about bending the other side with the tool after you have done on one side?

Ahh! looks like you visited the India site build blog ,

[ron thornhill]

Hi Manish

This is Ron and not Peter it matters not. Well, if you scribe your bend lines then put the outer edge in the vice up to the first line then bend, then put the other outer edge between your two thin pieces of clamping material up to the other scribe mark and bend. The centre section may bow a bit you just have to play with it. That is only my method because it worked for me with what I had at hand

[PeterF]

Ron, that is a good idea for bending the thin sheet into channels.

Manish, No I have not got to the wings, I still have not finished the fuselage.

I have now completed converting my Topflite DC-3 to electric so I now have all glow models converted and I can get back to the Tiger Moth. First things first, I have gone back to the cowl to add some extra blocks onto the bottom P clips to widen the cowl cheeks at the back to make a bit more room for the oil tanks. This has also meant moving the cowl floor pan sideways a bit but it all fits together nicely. The rear of the cowl cheeks at the bottom sits outboard of the undercarriage mount now as with the full size.

I have also started looking at ways of installing my 2000+W motor, and a little tongue in cheek, have shown it with an anti vibration mount. I know what I am going to do and will be making this over the coming few days. Just look at all that room for batteries and the ESC.

Edited By PeterF on 18/11/2015 20:51:40

[ron thornhill]

Looking interesting Peter, I'm curious to see how you change the batteries.

[Manish Chandrayan]

I am so sorry for the mix up Ron and Peter.

Ron thanks for clarifying the metal bending piece.

Peter,

That anti vibe mount is nothing short of stunning. You should have patented it before posting it here, you just lost couple of million pounds.

Yes you will have to fit pads under the cowl latches especially the tank side. I did that. And do not forget to taper the mount to almost nothing towards the front. The plus side of additional bulge is extra room for the air to flow out and cowl cheek bulges on either side provide a perfect baffle to create low pressure for air to flow through

[PeterF]

Posted by ron thornhill on 18/11/2015 23:36:18:

I'm curious to see how you change the batteries.

Ron, you and me both.

I am still not that far forward yet. I now have the motor mounted. One thing I have decided is that if at all possible, I will not cut or carve anything, only make additions so if I do want to go back to a Laser 150 in the future then I will not have problems. Therefore, I have kept the epoxy glass engine mount intact. This has caused me to have to think a bit more about mounting the motor onto the two bearers.

The method I have come up with after some thought was to buy a length of aluminium extruded T section, 1½" x 1½" x 1/8" thick (38mm x 38mm x 3mm thick). I cut a length of this and mounted the motor to it. I then made up another epoxy glass mounting plate from 2 thicknesses of 2.5mm (3/32" board that I have in my bits and bobs box. Careful measurements were taken of the motor length and the right hand thrust. This was drilled to suit the existing holes in the bearers and then the position of the motor worked out before the final holes were drilled. This has come together well. The ESC is going to be mounted just behind the cooling air intake in the nose section of the cowl, the beams for this are glued in.

I have taken the opportunity to test the motor. This has given me 21.5V, 73.0A, 1570W at 6660rpm on a Master Airscrew 18 x 8 prop. The calcualtion for the thrust is 14.7lbs. Expecting the plane to come in around the 16lbs mark gives marginally under 100W/lb which is more than enough. The motor is a Hyperion ZS4035-10. The most amazing thing is I ran this combination through eCalc, the on line electric calculator and that predicted 20.8V, 73.4A, 1524W and 6610rpm. Pretty damn close. The packs are 6S 3700mAh, two in parallel so they are not at all stretched at this power take and I should be able to get some good flight times as it will not need anywhere near full throttle.

Edited By PeterF on 21/11/2015 17:53:42

[ron thornhill]

That's a clever idea Peter, but, although there are twelve bolts holding the motor on it is still hanging on an 1/8 inch piece of ally, I personally would have put an angle bracket on the top to give a bit more rigidity, just a thought.

It's good to see you back on the build.

Ron

[PeterF]

Ron, I had a think about your comment, I am not worried about the tensile strength of the aluminium, but after you commented I realized that the set up I had could suffer from fatigue due to vibration in the vertical direction as the mount tried to flex around the junction of the T shape. Therefore, I have added an L section above the epoxy glass plate to the back of the T section. That should stiffen it up as there are now 2 points that it would have to try and flex around, much less likely. Although there are 12 bolts, the load passes through 3 sets of 4 in series. This epitomizes the usefulness of these forums. Brilliant.

The next stage is starting to think about mounting the batteries. I have this set of 8 batteries and they are used in 3 other planes, I am not about to go and buy a set for the Tiger Moth alone, therefore I have to make something to fit them. The first step was to try and put them on the top of the engine bearers per Manish's suggestion earlier. Unluckily although they git at the back and in profile, they are too wide as the cowl tapers in towards the front. It would have been great to have had them fit like this. Moving them around in various positions gives the set up in the final photo as being the best compromise. There will be lots of room for the cables between ESC and battery packs. I will start to build the box to fit them like this. I need to come up with some method of having a robust floor, I do not want them ejected onto the cowl base if I have a hard arrival. Probably something like some beams coming out from the firewall and supported from the engine bearers at the front

[ron thornhill]

Sorted Peter.

Can't help but notice a very tidy workshop or is all the very useful stuff piled out of view.

[Manish Chandrayan]

Peter

How about the space meant for the tank in IC version? You could fabricate a tray and suitably support it. Even the tank needs a suitable enclosure to support it.

The battery pack could either be slid in the tray through front cockpit or from front after removing the nose bowl. Since you do not have an engine hanging in that space, the space could come in handy for locating the battery pack.

[Manish Chandrayan]

Ron,

How was your experience with the lower wing fittings interface with fuse?

I have run into some minor issues where if I align the rear metal fitting on the wing to epoxy board fitting on the fuse, the fittings on the front spar are off by about 1/16 or so. And then again I am also worried that if I glue in the wing side of epoxy board fitting on front spar, the angles do not match. Both the fuse fitting and the wing fitting are glued flat but the wing root will have an angle and I fear this may not be an ideal situation. Wish I had not epoxied in the front fuse fitting earlier, that would have made life so much easy now.

[ron thornhill]

Hi Manish

Yes the mountings did need a bit of fettling, as you can see the bottom of the rear mounting is angled. I drilled clearance holes in the epoxy fittings the soldered a nut under the rear wing fitting and epoxied a nut under the front fus fitting. Just because there made that shape it dose not mean they have to stay that shape, you wont see them once the wing is on. well hardly.

[Manish Chandrayan]

Thank you Ron, for those pictures. My fitting alignment at the front is just a bit off (when rear fittings are aligned). Since my wing fitting is yet to be glued in I think I will fettle the slot in the rib so that the fittings align and then pack up the slot suitably. I plan on pinning the piece with some carbon pegs as well just to be sure.

How did you set the dihedral angle on top and bottom wings?

[PeterF]

Here is the answer to life the universe and where to put your batteries. A battery box built to go down between the two engine bearers, the hole in the ply plate has been increased in length to accommodate this. The battery box sits onto the firewall at the bottom of the hole that was cut out for the glow fuel tank. This has been deepened a little to take the batteries and give clearance to the top of the cowl. There should be good air flow around the batteries, but only drawing 37Amps peak from 3700mAh batteries with flight load much lower should not stress them at all anyway.

One answer re the workshop is "A tidy workshop is the sign of a tidy mind". The real answer is that I have had a good tidy up with the move to electric, I am sure things will degenerate now I am back building.

[Manish Chandrayan]

Good bit of lateral thinking there Peter. Glad to see it sorted out. Replacement of those battery packs would be an easy task with removal of hinge pin on one side and flipping cowl top.

Edited By Manish Chandrayan on 27/11/2015 08:41:44

[PeterF]

I have finally got back to the build and have decided to tackle the control cables for the rudder and elevator, rudder first. I made up some thimbles to go through the loops in the wires. I’ll cover making the thimbles in the following post. Pictures show the fittings made up from sheet brass, these were in the kit of parts from Falcon, just needing to be folded around the bolt. I have also soldered the two halves together to stop them opening up. For the adjustment of the rudder cables I have a set of 4 very nice turnbuckles from Mick Reeves, not perfect scale but will look OK on the model. I am still waiting to get the right bolts to attach them to the brass fittings, slight oversight on my part. Once everything was attached, a quick check with the Rx connected to the rudder servo showed the correct 2.5” displacement on the rudder. I had already worked out the geometry and chosen the hole on the servo arm and the APE settings on the Tx to get the right movement and for once, I got it right.

Rear control arm, brass fitting and thimbles

Rudder bar, brass fitting, turnbuckles and thimbles

Cables connected to the rudder

Cables connected to the rudder bar

Rudder works, turn right

And turn left

[PeterF]

The full size model has thimbles in the loops on the control cables to stop the cables wearing as they rub within the fittings on the control horns. The kit does not include anything and is set up for you to just bend the wire through the fittings. In an attempt to add some scale details I have made up my own thimbles, a few hours work to make the 16 required for the model. The cabling supplied in the kit is about 0.7mm diameter. The holes in the fittings and turnbuckles are 1.6mm. I sourced some 0.8mm ID x 1.5mm OD brass tube, 3 pieces 300mm long being plenty.

I filed a small slot in some hard balsa to rest the brass tube in. I put some soft steel wire around 0.6mm diameter through the brass tube, placed the brass tube in slot in the balsa and filed the top half of the brass tube away using an ordinary metal working file. I lifted the soft steel wire from the tube and then ran a small triangular file down the slot left in the brass tube to clean it up. The steel wire is put in the middle to give the file something to work the brass tube against and to file it completely away. The first attempt did not sue the wire and as the top oif the brass tube thinned down it deformed inwards making life difficult.

The next stage was to bend the end of the brass tube around a 3mm steel bar in the vice. I found that I did not need to anneal the brass tube. However, I did hold some steel cable in the slot to try and help keep it formed. I found that I needed to hold around 1cm of straight length on the one side to keep the bend formed well.

However, I only needed about 5mm straight length for the thimbles, so I made a jig up from some scrap ply to cut off the bent section at the right place. This left me with thimbles with uneven legs, so I then had to cut the longer leg down to suit the required 5mm length, again using the ply jig. In the end I used one complete 300mm length and about 50mm from the second tube.

The previous post shows them being installed. They can not be completely bent together until they have been installed.

Brass tube with steel wire inside in slot in balsa ready for filing down

Brass tube filed down, steel wire visible

Brass half tube cleaned up ready for bending

End of half tube bent to form the thimble

Collection of uneven thimbles

Collection of completed thimbles

Close up of a completed thimble before installation

[cymaz]

Clever idea

[PeterF]

This is the photo of the completed thimbles after the long side had been trimmed, I accidentally used the same one twice in the post above.

[Manish Chandrayan]

Peter, you have motivated me to give the thimbles a try. I am using 1/32 7x7 cable from Vogelsang

I had also got the the smallest thimbles they had assuming it would be suitable for the Tiger but alas those were too large for our use.

I have been also contemplating getting these from UK. They look to be suitable. To see the thimbles scroll down the page.

But before I order I will try and make a few from copper tube, that should be easier to work than brass

[PeterF]

Manish,

I had looked at those from the ship modelling site but the one type did not look the part even though they had then at 0.8mm ID, and the better looking ones may have been to large. My issue was the turnbuckles only had a 1.5mm ID hole so I could not accept anything larger, so making my own guaranteed a fit. I chose brass tube because you can usually get it in thinner wall than copper. I also looked on the ship modelling site for the shackles as I need them for the upper elevator guide rod, but looking at the full scale of the plane I am modelling showed that it had a shackle made from plate not bar, so I will make my own for that.

Peter.

[Manish Chandrayan]

Thank you Peter, that information would save me some money

[PeterF]

That was a neat idea - not sure how the post got orphaned though.

Posted by ron thornhill on 29/01/2016 13:18:41:

Hi Peter just thought you may be interested with what I did with the turn buckles. I bought two lots, one with eyes and one lot open ended then swaped one end of each making easier to fit on with just a split pin. Your thimbles look brilliant, didn't think of that, too late now.