Piper Twin Apache PA23 -150 74"

[Martyn K]

Hi Danny

I suspect that the diode is wired in series with the +ve line from the battery pack. A shottky diode has a low voltage drop - usually between 0.2 to 0.4 volts. However, it needs to be rated for the peak forward current that it may need to carry which could be a few amps

Martyn

[Danny Fenton]

Hi Martyn, No they are not in the main circuit. They are in the red wires from the BEC's to the Rx.

I have found the post where Chris outlined their use in his twin (DH88)

"The diodes are there because I have two ESCs, each with a 3A Switch mode BEC.
So with the diodes, I have two supplies to the receiver, they are kept isolated from each other and even if one SBEC failed and became a short circuit, the other one should soldier on. I've used 5A schottky diodes because they have a lower forward voltage drop than normal diodes.

I can test that each is supplying the receiver by unlpugging one or the other ESC, as long as one stays plugged in, I should have no loss of supply to the Rx.
The telemetry is telling me that the suplly volts is holding up perfectly well while I waggle all controls as hard as I can."

The diodes can be seen as cylindrical lumps in the wiring.

I have ordered some

Cheers

Danny

Edited By Danny Fenton on 18/12/2013 14:50:44

[Martyn K]

Hi Danny

5A forward current rating should be absolutely fine for most purposes. Its a simple and easy fail-safe to implement. You just need to be aware that if you have a circuit fault downstream of the diodes, you may well end up blowing both of them simultaneously. That would not be so good. Without them, you may get high current consumption but enough power flowing to the receiver and other servos while you wonder what to do - just before the battery goes flat

Martyn

[Danny Fenton]

I think this is one of those cases where you can never fully cover all eventualities. But I think it is worth doing so that both BECs can be in circuit. I am not sure if connecting two BECs into the Rx without something to stop the current flowing the "wrong" way is damaging. On a twin would you normally disconnect one BEC?

Cheers

Danny

[Martyn K]

I agree that its worthwhile doing.. What you are trying to avoid an imbalance at each BEC output being fed from the other. It would normally be only a few millivolts providing nothing was dragging one of the outputs down which would probably be within the reverse current handling for the BEC, the problem comes when it gets to be more than a few millivolts which may happen towards the end of a flight if the flight batteries start losing power. Still very unlikely though.

You could also do it with a transistor (or preferably a MOSFET) switching circuit - in those circumstances it could be configured so that the output from one BEC (secondary) is effectively open circuit unless the latching provided by the primary releases and allow the secondary to become active. If you want to be agricultural, you could also use a relay...

Martyn

Edited By Martyn K on 18/12/2013 15:09:15

[Colin Leighfield]

I really enjoy silently following you chaps because I hardly understand a word that you are saying and realise just how much I still don't know. Electronics certainly aren't my forte, and I need to get better. There's clearly no need to attend a university while you are around, even at my decrepit stage in life, I'm enjoying learning. Please keep it up.

[Danny Fenton]

Colin it is great having you and everybody following along, to see the number of views for the thread climbing makes all the time posting worthwhile. I am sure I could get more done if I didn't, but where would be the fun in that As far as knowing what I am doing thats not true, I am just waffling in the hope that Graham A. will never find out and stop me writing for the wonderful tome that is RCM&E

Still messing with lengthening those blessed lighting wires at the mo, so no updates to speak of

Cheers

Danny

[Danny Fenton]

okay all the wiring is routed to where it needs to go, I have some ideas about getting the wiring to wingtips and the removable nose cone without plugs and sockets, but more of that when we come to them. If I can make what works in my head work in the land of reality....

started the upper fus sheeting. It doesn't matter what anybody tells you, you never have enough clamps!

Cheers

Danny

[Martin Roberts]

Hi Danny, you are getting close - how about a few 'exploded' shots, showing the 'whole model' as is so we can all see exactly where you are at - doesn't need to be pretty, I'd send you a few more clamps - but Santa might beat me there - just remember it is not a case of not having enough anything else - it's a case of not having enough space to store all the stuff and still have enough space to work. My double car garage is full to the eye balls LOL

Marty

[Danny Fenton]

Hi Marty, we all need more "stuff" clamps especially. don't you just love these plastic jobbies? everybody has em much more versatile than the clothes peg. I would be chuffed if Santa bought me more of these. Should be the freebie with magazine subscription renewal

Ton has suggested a built up wing tip, I am waiting to see if it is possible before I cut foam.

I will get the fus sheeting done and then we will maybe do a posed assembly morale shot

Cheers

Danny

Edited By Danny Fenton on 18/12/2013 22:45:46

[Ton van Munsteren]

Hi Danny,

Great job and Iam sure a buildup tip will work just fine.

Will send the drawing of the parts the comming days.

Cheers

Ton

[Danny Fenton]

Thanks Ton that will be good news, I didn't fancy sanding a couple of square foot of foam

Carried on with upper fus sheeting, really like this 2mm balsa, just the right thickness

Cheers

Danny

[Martin Roberts]

Danny & Ton, could always sand down a block of hard balsa for the tip - na! - just kidding, unfortunately being down here we don't get the freebies, or I would have subscribed when the building jig was up for grabs..... I do admire your sense of art - the colour scheme you so patiently applied when clamping the fuz was to say the least impeccable LOL, mine are big black so-and-so's... Didn't you use a stringer behind the side panel join, or did you misalign the bottom panels to the stringer? Could be a good detail or notation to utilize for the final plan. I also like using 2 mm, as it is firmer to work with and still sands back to about 1.6 finish if you're not too harsh, so there is still enough meet for the glass to hang on without going concave between the bulkheads.... now outside to bash some Australian Hardwood into shape on my deck or I won't live til Xmas.....Marty

Edited By Pete B - Moderator on 19/12/2013 09:55:52

[Danny Fenton]

Hi Marty, good luck with the the hardwod, not that I think you will need it unless its for the Christmas Barbie Still can't get my head around Christmas in the middle of summer.

The reason there is a strange line where the upper sheeting meets the lower is that the I sheeted the lower in 3/32 or 2.4mm. The discrepancy will sand away

Cheers

Danny

[Danny Fenton]

A little more sheeting. For those of you new to this lark, and I am no expert but there are a few ways to bend/curve balsa. They include steaming, wetting, and using a chemical to shift the Ph away from 7.0 (neutral) This can be vinegar or amonia. I use amonia, though it does pong a little innitially.

Ammonia and vinegar (vinegar I have never tried by the way) break down the bonds between the cells and make the wood extremely pliable. Water or steaming does not break down the cell bonds and is therefore less effective. However water/steaming will leave the wood slightly stronger, though I have never detected any difference once thouroughly dried.

Here you can see one way to approach sheeting, in this instance I have trued the edge of the new sheet and glued it using CA to the previously attached fuselage sheeting. I then apply some amonia along the line of the curve, I use a 1/2 wide paintbrush. Allow a minute for it to soak in, then use masking tape to hold it in place while it dries.

Once dry carefully lift the edges and apply glue before finally fixing down.

Doing the above has a drawback, but as long as you are aware of it then its not an issue. If you CA to the existing woodwork the area of balsa along the join will be harder and may not bend readily. To solve that in this instance I chmfered the sheeting slightly, and will therefore have a slight ridge along the glue line. Because of the wood thickness this is easily sanded flush. This may seem like a disadvantage, but it does allow a really tight joint against the adjacent sheeting.

Cheers

Danny

[chris larkins]

One simple method I have used in the past for lighting wires on removeable wings etc is to use self adhesive copper tape (sold as slug tape). This is very easy to solder to and is then simply stuck down onto the two mating faces (its wafer thin) then as the wing or tail etc is secured in place the connection is made and hey presto the lights are on. Just be carefull that on a foam model you solder first then stick in place otherwise the heat melts the foam ( I know, I've tried), The pictures below should show what I mean, there are obviously 2 copper strips on the fuselage wing seat that match up with those on the wing.

[Danny Fenton]

Hi that's an excellent idea, and is along the same lines as I was thinking, though I was thinking of a flexible spring contact on one surface, rigid on the other. Your tape idea is an excellent and should work well with what I was thinking. I will see if I can find some "slug" tape. Why is it called this, may I ask?

Those curved sections I showed earlier are finished, and the gap has come out pretty good. Wish I had done the bottom this well

Cheers

Danny

[chris larkins]

I think gardeners stick it round the circumference of plant pots as apparently they get a static shock if they try to move over it so repels them.

[Danny Fenton]

Thanks matey, I have some on order

Managed to get some more top sheeting on....

the shape is lovely, and flows just as the full size. Not a straight line anyway

I have never built a model with a cabin and side windows. I am in a quandry as to the side windows. The panels Ton has designed give the window sizes, but I cannot see how I can make them work, certainly not in the material that they are made of

I have a feeling that the side windows are going to need to be vacu-formed. So the next question is how to make the plug? Rob from RBC has made a plug for the front windscreen, and as you can see the shape is good. Unfortunately the clarity and quality isn't quite there. I will drop Rob a mail and see if he has any thoughts.

So suggestions on a postcard, while I finish sheeting the top and front section

Cheers

Danny

[Martin Roberts]

Hi Danny, no postcard - message in a bottle LOL, for thought and planning..... you need to make the side ribs for the cabin less 2 mm, form up an new side frame and layup the new 2mm dummy skin, which is now (outside) a plug matching the inside of the cabin wall, I am sure that Ton can send an alignment template for the cut out sections of window less say 0.5 mm all round and cut the window panels in 1.5 mm sheet then fix onto the plug using the template, now when you vac the new window 0.3mm clear or black, it will fit almost flush minus say 0.2 mm inside the outer skin, I am sure Ton could model that up in about 3 minutes including the strong ply stringers top bottom and middle (nice and strong for the Vac as is the 2 mm dummy skin, Marty

[Danny Fenton]

Hi Martin, that sounds like a plan. I will be able to do something similar without Ton needing to do that by simply building the side of the cockpit. I have enough drawings to do this I think, I don't want to pile more work on my friend, it is Christmas after all

I will keep going with the sheeting and simply make the rectangular side pieces that are missing, sheet and glass them.

Thanks for that. I like your plan

Cheers

Danny

[Ton van Munsteren]

Hi Danny,

Sorry for my late reply, did see your post earlier on the side windows but had to go to my mate for building on my new glider and his Autogyro.

Did make some pics from the drawing on how the window part should go,

The idea was to first place the window part and than build the planking against it, but he that was my thinking.

Here some pics ;

But Iam not sure if that would work the way I have designed it specially looking at the way the ply is cut, in cad it all looks so easy

Keep up the good work the apache looks great

Ton

[Ton van Munsteren]

Danny,

Did forget to mention, don't hasitate asking that is what Iam here for mate.

Just let me know what you need to fix this the easy way for you.

Ton

[Martin Roberts]

Hey Ton, what is that software you're using?

Marty

[Danny Fenton]

Hi Martin, Ton was using Rhino, I am pretty sure he still is. He has to export the drawings as .dwg so that I can open them in Turbocad and print them to scale. I cannot afford Rhino!

Ton, the rear side window can be made from flat PETG so there is no worry there. it is just the front side window on each side. If you could build in 3D the rectangular section I have missing, then I can make a plug and vac form them. I have heard from Rob and his method is very neat for making the plug.

"I made a 3d design of it, milled out of foam ,then vacuumformed it , took out the foam , pour in moulding material , sanding it to approx grid 400 , then we have a vacuum mould"

He doesn't seem keen to make the plugs for the side windows though.

Morale boosting shot

Cheers

Danny