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Member postings for Chris Walby

Here is a list of all the postings Chris Walby has made in our forums. Click on a thread name to jump to the thread.

Thread: Electric Grumpy Tigercub
23/01/2021 19:07:31

Hi Peter,

No real issues with the electrics as the motors are small volume compared with IC, no tank so the ESC has loads of space, battery in the fuselage. There are other ways, but George's (4-Max) seems the most elegant although at some point it will light a fire of controversy.

Only real mod is the hatch for the battery as the wires go down the aileron rod hole in the ribs + plenty of room for the servo cables down their paper tube.

The big question will be to leave the Elevator/Rudder as plan or move them back for more flexible location of the battery. My gut feeling is it will need the battery as far forward as possible and if that's the case the servo can go in as plan.

I can't quite see where the nacelles go on the Destiny (only build twins wink) and the planking looks nice. Is it any lighter than rolling sheet or just better and complex curves?

23/01/2021 07:14:54

20210120_193744.jpg

img-20210119-wa0007.jpeg

img-20210119-wa0010.jpeg

And a bit of wiring for good measure before sheeting.

img-20210119-wa0012.jpeg

22/01/2021 22:11:34

Sort of decision time as the covering arrived after a couple of days in the post.

20210120_212323.jpg

Peter’s was yellow, but then I thought tigers are orange and then that go me thinking that bight be hard to ss and the stripes won’t show up. Then I thought it could not be any worse than the Extra Slim Twin that is translucent yellow and appears to change orientation depending on the sun shining through the covering and open structure wing.

The votes are open

  1. Traditional yellow
  2. Tiger orange

Along the same theme I contacted one of my fellow club members who has a film cutter and likes a challenge (not sure if that’s me or the decals). Anyway he has come up trumps with these which look spot on to me.

gtc decals.jpg

And now back to the build

  • Nacelles trimmed to fit the wings
  • Fuselage battery hatch build (planked, now that’s an interesting technique that needs to be practiced once retired as it’s a bit time consuming
  • Fit snakes
  • Fuselage turtle deck formed (balsa sheet dampened and masking taped to formers, once dry then same again on the other side. When both are dry, cut and glue in place
  • Glue and sand motor cowls

I’ll attach some more photos on the next post.

Thread: Extending leads - battery or ESC?
22/01/2021 20:12:07

Before this gets into a raging debate (again) the best bet is to read the manufacturers guidance as they contradict each other. Some say you can, some extend with capacitors and some it it not advised.

Without knowing the make or model of the ESC its just peoples opinions.

Tin hat on and TTFN laugh

Thread: If you ask ten different aeromodellers...
22/01/2021 06:49:58

David,

Turn the question around a bit....What type of flying do you intend to do?

My Laser Acrowot excels at big and small aerobatics and makes me look good with predictable flight characteristics.

If you would prefer something more "manic" with prop hanging capability or the noise of a 2 stroke then perhaps a different engine choice is more appropriate. Nothing wrong with 2 strokes (have two 46's in my Extra Slim Twin and that's for that manic feeling!).

So the question is....what do you fancy sir?

21/01/2021 12:19:33

David,

I have one with a Laser 70 in it and its great, no added lead in the tail and it comes out spot on the target AUW. Flies nice, sounds great and no issues landing.

Servos I can't help with that has not already been said above, but good standard ones should do the trick.

Any question please ask.

Thread: Silly question 3
20/01/2021 12:50:28

Am I missing the point?

Spektrum has model match and this feature has the benefit that if you select one model and trying to fly another it won't let you.

Agreed that you have to have a less than basic TX but far far more worth while once you have more than one model.

IMHO avoid any of the DX.e versions and see if you can pick an old one up. Nothing wrong with a DSM2 TX and plenty of genuine RX's about.

Thread: Silly question
19/01/2021 06:30:32

Rich,

Spektrum has model match which means once you have bound your TX to an RX for a specific model memory the TX/RX will only work on that memory, if you select a different memory or RX it won't bind - a great feature in many respects IMHO as I doubt any of my models have the same settings and there is no chance of getting mixed up.

One minor whinge with the button on the RX, mounting cable tie moved (and depressed the button) and at power up of model would not connect to the TX (as it was in bind mode), sussed it and rebound. Solution was to reposition the fiddly hard to access RX and the cable tie, problem sorted.

Thread: Sand n Seal
17/01/2021 12:36:54

Hi,

IMHO won't touch the stuff (if its the water based version), tried it out on a bit of balsa sheet compared with the "solvent" based before committing to the model. The water based version made the balsa warp/twist and it never went back to its original flat sheet. The solvent based version didn't move at all.

For the risk of setting a twist up I'll stick with a smell for a short period of time.

But each to their own.

Thread: Electric Grumpy Tigercub
16/01/2021 13:40:53

Had to have a bit of a chuckle as I finished of the last of the motor stand off’s as it was a bit of touch and go with the ali stock (leftover included). Dad would be proud with the lack of waste and no option of making a mistake.

.20210114_182627.jpg

Talking about the nacelles I was having a think about making them removable and added a ply plate against N1 then screwed it from the back. Okay it will be fiddly when all assembled, but at least won’t mean breaking the cowl to remove it.

Nacelles have proved a little more interesting as I was intending on to strap the ESC to the stand offs, but when it came to the cowl construction its was obvious that's not going to work. The ESC's can go where the tank has vacated and that brings me on to the cooling requirements. Perhaps a small chin scoop on the cowl and another scoop where ESC will live. The back of the nacelle underside is sloped and a larger exit scoop should work ok

20210116_114403.jpg

Balsa glued to get the general shape and I'll add a more for the shape/scoop.

20210116_121843.jpg

….Order the covering film....

Thread: Workshop comfort
15/01/2021 08:01:00

JT, Good questing and I don't think I have an answer as such having experienced the same effects of the cold. I have a lathe in the garage/workshop where I have been building however last night I need to make some spacers with the result of standing still at the lathe for a couple of hours. There was no need to move around until the end and then a good impression of the Tinman was evident until joints were warmed up.

My garage sufferers large temperature gradients with it being pleasant at bench height, but very cold at floor level and moving around keeps the blood flowing to the legs and standing still the opposite effect.

If anyone has a solution other than a fan heater (too directional) or storage heater (as the workshop heats up quickly, does not need to be on all of the time) I would like to hear from you. The only thing I can think of is the workshop type electric radiant heaters, but again directional and a bit of a fire risk if something is left too close.

Thanks to all who have contributed, food for thought and I'll be trying out some of your advice.

Thread: It is flying related Flight
14/01/2021 10:48:13

but what happens if the aircraft is less efficient at the lower mass without retrimming? will it have less or more drag?

IIRC gliders sometimes carry water as ballast to suit certain weather conditions and beat others without ballast over a measured course/time?

How complex can we go without formula laugh

Edited By Chris Walby on 14/01/2021 11:17:17

Thread: Watts/lb misleading?
14/01/2021 07:33:45

Slightly off topic, but IMO its a guide and thus only a guide for general consideration. A good starting point however the more performance (extreme in any direction) then the less useful it is.

I had a funfighter and fancied the need for speed....in the end it was pushing 400 w/lb but really went little faster than the original set up. Due to quite a thick wing, frontal area and high drag it was never going to go fast no matter how much power was dissipated by the electric set up.

If the model has a high wing loading or low lift wing as part of the design then the power train will be designed to match the performance required, my ham fisted attempt achieved little compared to designs that are intended to fly fast in comparison.

I think the really clever/good designs are those that achieve very wide ranges in flight performance without any nasty traits. They are easy to spot.....so they are very popular with model flyers.

Thread: Electric Grumpy Tigercub
14/01/2021 07:14:14

On to wing joining and this went without issue, the drawing says dihedral of ½ inch under each tip although I was told that in previous thread discussions it should be an inch under each tip. I went with the drawing and the supplied brace on the basis that it was easier and generally more dihedral make it more stable right way up and less when inverted! Off topic but I have loads of fun with my foamboard Nutball (flying disk) with massive dihedral trying to fly inverted with rudder and elevator only controls! Look at supports for the aileron servos mounting plates (more of that later).

20210111_171215.jpgPS - Nacelles dry fitted as I was still working on the first LE strip, but more on that later.

14/01/2021 06:46:43

On with the build and having moved more static useful items (rubbish, parts, materials for other projects and tools) from the end work surface I set the SLEC building board for the fuselage assembly to start. This has the benefit of allowing work on the wings and nacelles all to be progressed at the same time!

Fuselage would be easy except as this will be electric it will need a battery hatch in the nose.

20210103_172531.jpg

I want the flexibility to move the lipo between F1 all the way back to under the LE of the C of G even to the point moving the rubber/elevator servos by a bit (deal with that later).

The plan is to make F1 and F2 out of ply and open F3 out to allow the lipo to pass through in either orientation.

20210103_171943.jpg20210110_112305.jpg

Then build the fuselage with the intension to cut the top off F2 to form a hatch from F1 to F3 as I need the length to feed the lipo in and then move it about to achieve C of G

I’ll add a photo of the fuselage shortly once I get back in the workshop.

 

 

Edited By Chris Walby on 14/01/2021 07:09:49

11/01/2021 11:19:09

Thanks for the feedback and having checked it would appear that the incorrect conversion (Trump) factor was used resulting in a wildly inaccurate wingspan, the correct size should be 1346 mm.

Piers, I have PM'ed you regarding your question.

The build continues with assembly of the nacelles and the wings.

20210104_192548.jpg

20210106_193845.jpg

Only mod to the nacelle was a large hole cut in N2 to allow the ESC control wire through as the power cables will traverse via the unused aileron pushrod/bell crank rib holes. I'll be using in wing aileron servos just in case I fancy a bit of flaperon or differential later on. Oh and I made the motor stand-off on my 1940's Myford lathe.  

Nothing to report on the wing build, all standard assembly with just the wings to join and nacelles to fix later on.

Edited By Chris Walby on 11/01/2021 11:40:18

10/01/2021 07:56:58

Lets start the build and hope I can keep the building work with the pace of posting updates

Things to consider pre-build

  • Canopy from Steve at Vortex, big thanks as there was so waiting due to COVID 19 but no rush and good job
  • Modification of the cowls/nacelles to suit the electric set up
  • Modification to the fuselage for the battery access

Nothing major and looking at the drawings it has Peter's signature design/construction style throughout which is reassuring from the experience gained from the Ohmen build and limited overall experience.

I will be using the plasterboard and plastic sheet method of bas board and dusting down the SLEC board for the fuselage once I have cleared enough bench space. I thought I would get clever and attach the drawings on both sides of the plaster board which does limit the “I just need a peek to check that” if there is balsa and pins stuck in.

20210101_133915.jpg

10/01/2021 07:55:01

Boring for the experienced builders out there although I would like it to be helpful to those like me who don’t have decades of building under their belt and want a proven good flyer

Cheat 1 – Kit purchased from Sarik last year

Cheat 2 – Electrical bits purchased from 4-Max last year

Cheat 3 – Read through all of the build logs here to gleam any information I could

For those that aren’t familiar with Peter Miller’s Grumpy Tiger Cub its vital statistics are:

Wingspan: 53in (2125 mm)

Weight: 4 lb 11 oz( 2.126 Kg),
Wing area: 500sqin( dm
2
)
Wing loading: 21oz/sq ft ( g/dm
2
)
Servos: 4max 2x 10g and 2x 45g)

Retracts: Fixed
Motor: 4-Max 3035 870Kv

ESC: 30A x 2 + 5A UBEC

Prop: 9x6 tractor and pusher

Battery: 4 S 3700mAh (I have 4S3300 so will use those)

Calculated thrust (4max) 4.6 lbs (weighs 4.68 lbs) 2068g

Calculated speed 62 mph

10/01/2021 07:53:45

gtc flying.jpg

Well folks as the club mass Ohmen build edged towards completion last year a couple of us thought about the next build. If you don’t know already then it will soon become apparent that I have a preference for ic twins and although this build will be electric it is at least a twin.

There are already a few build logs here for ic versions (as per the original design) and electric plus scaled up with retracts and flaps, but for me it will be a straight as possible standard build.

Thread: Please check my setups
09/01/2021 19:59:31

IMHO there is a few ways to tackle ic and electric power plant set ups

  • Follow designers recommendation including where the designer uses another supplier
  • Research the model in question and what others have used or similar set ups
  • Design it yourself using motor calc software

I have used all three depending on the model of interest although as Peter uses 4-max and George is kind enough to publish all of the set ups for multiple designers it makes the task easier.

There are a couple of benefits of using 4-max IMO and they are firstly the quality, secondly George will tell you if stuff is in stock or when its coming in and thirdly if you have a problem he will help you out.

PS I had a problem a few weeks ago with a delta twin that George had supplied the props, motors, UBEC and ESC's for and after about 10 minutes on the phone he and identified were the problem was. After I had corrected my TX mix issue all was well and my point, there was nothing wrong with the 4-max kit.

There is always someone who will tell you they got it cheaper from somewhere else, well that's ok, but if the UBEC/ESC dies on you its not just the cost of the component to replace.

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