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Chris's ChtiCat Racer

A real fun Depron Indoor 'Thingie' based on F1 aero!

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McG 696906/11/2017 18:18:56
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1615 forum posts
714 photos

Hi again,

While waiting for the small electrical bits to arrive, I still have enough to take care about.

I covered the acetate thrust fairing with some yellow laminating film to have it ready to be glued in. I fact, as the ChtiCat is a small thingie, I’m going to use some cut-offs from the Ballerina deco scheme.

850_fairing_dryfit01_900.jpg

Gaston insisted to have a dry fit of the bits available so far. I was surprised that, when curved, the acetate is really steardy, stronger than 3mm Depron would be anyway. Also the reduced thickness seems to be a nice advantage to fit it nicely against both sides.

Next step will be to create an additional small square former, half way between the front and the top deck with a concave cut out for the fairing. Allowing less torsion of the front end will (hopefully) avoid Don’s kind of ‘destruction’.

858_fairing_dryfit02_900.jpg

I also did laminate the small vertical mount after giving it a quick LE rounding.

If you have a closer look, the LE of the top deck received a thin 6mm strip cut out of a tongue depressor. Getting ready to stick all those bits together now.

Hakuna matata

Chris

BRU - BE / CTR Bits #2 Control

Don Fry06/11/2017 19:03:49
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1814 forum posts
25 photos

McG, sorry not been following post. Mine runs on a HobbyKing Donkey motor/controller. Runs on a 3s 800 battery. Prop is as big as you dare, pitch is as big as you dare.

You need huge exponential, as it corners in a controlled skid. You watch the skirt, they can flip, and you try to run them just below flip point in the turns. Don't shut the throttle, no aerodynamics with no throttle. Don't open the throttle, they flip in the corners. And they are at least 3 times faster than anything that flies in the hall. Collisions are frequent, as they all are in one plane.

Mine was destroyed last Sunday. Enjoy.

Hint, the battery MUST BE LOCATED IN THE TUNNEL BEHIND THE MOTOR. Failure to do this will cause excessive flipping. Don't know why. 

Edited By Don Fry on 06/11/2017 19:07:24

McG 696907/11/2017 10:55:39
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1615 forum posts
714 photos

Thanks for visiting and for your advises, Don.

That HK Donkey Combo looks like a very nice solution and it even follows the 2204 motor/10A ESC race regulations. yes Are you using the 1700KV version?

Thank you regarding the battery location, my intention is indeed to have it on top of the ESC on a tray just behind the firewall.

I'm using a XXD 2212 as I already had a few of those and they were very cheap at €4,80/piece...

But now I'm getting a bit worried as the max power of a 2204 on 3S is just under 100W and the 2212 gives around 95W on 2S, up to 170W with a 3S Lipo. I expect my 'thingie' to weight around 200gr, say 250gr with a 2S 850mAh...

So on 2S, I will be around 190 W/lb ! Of course it's not an airplane... but, am I building a 'dragster' then? frown

As I am really inexperienced, the first purpose to build the ChtiCat was to get some Tx sticks practice during the winter months... Well, maybe I should build a second glider right away... angel

Hakuna matata

Chris

BRU - BE / CTR Watts (What's) Control

Don Fry07/11/2017 11:51:08
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1814 forum posts
25 photos

Chris, Yes I use the 1700KV unit. It is robust, and good value. I have just weighed my debris, and it's 225 grams with its 800 3s battery. It has a 7 by 4 prop, which is good for the basketball court sized gym my club uses. You balance accelatation to top speed, and slowing it again into the corners, as you slow it by reducing the throttle, not closing it. Close the throttle, equals no control.

Another tuning modification, is changing the size of the Velcro pieces on the bottom. It has the effect of changing the centre of grip, so you can balance it in the turns, as it drives like an old fashioned Porche 911, and swaps ends if provoked. Remember, winners are first past the line, not the fastest.

I might suggest you make a sacrificial foam bumper , velcroed on, to go on the front end. The front end has a hard time, and any reduction of g force in a crash is good.

It will sharpen you, 5 minutes and my eyes dry out, no time to blink.

McG 696907/11/2017 19:21:19
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1615 forum posts
714 photos

Hi Don,

It's really great to receive some feedback when one gets a bit into trouble. So thanks a lot for it.

I guess I wasn't to far away with my 'guestimate' of 250gr then. The 2212 is about 20gr heavier and I'm planning to laminate the beast with 40 micron vinyl. That could come very close.

I'm taking good note of your handling procedures and I'll start to invest in Velcro strips as I've raced 911s in a former life. So, I see what you mean... wink

An emergency foam bumper sounds like a very welcomed idea as well.

Thanks again

Hakuna matata

Chris

BRU - BE / CTR Velcro Control

McG 696908/11/2017 18:13:25
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1615 forum posts
714 photos

Hi to all,

A large 'cloud of flue' seems to be covering the area here and with some fever handicap, I had to cancel my visit to La Grotte today.

I've been making some (little) progress with the scheme markings though and they are nearly finalized now.

I have some question for the Leccy Gurus. I've been reading quite often that attention should be given not to increase the length of the wiring between battery and ESC, giving a preference to lengthening the wires from the speed controller to the motor. Right?

My problem with the ChtiCat is the other way around due to the lack of available space. So, is there a problem making the motor/ESC wires shorter?

I would have thought "No" as the resistance of the wires will only get lower, but I prefer to ask before committing. Any advice, please.

Hakuna matata

Chris

BRU - BE / CTR Ohm Control

Don Fry08/11/2017 18:52:14
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1814 forum posts
25 photos

No.

But re making it pretty, these things have a really hard life. A nasty trick Is to corner inside a victim. And because there is a victim to lean on, you can open it up coming out of a bend. Victim ends up in the wall. Newton's laws rule.

Remedy is a judicious lifting of throttle. Then the aggressor understeers across your front, then swaps ends trying to get grip before hitting the wall.

McG 696909/11/2017 09:40:54
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1615 forum posts
714 photos

Thanks again, Don.

I'll cut the ESC wires to the appropriate length as soon as I receive my connectors.

Concerning "making it pretty", I'm convinced a ChtiCat can have a really hard life, but then on the other end, I can't imagine sending a brave soldier naked to the front line, especially if it's a 'kamikaze' mission... angel

As for victims to lean on or getting assaulted by other beasts, chances are pretty non existing. I presume I will be just by myself with the thingie. wink

But then, the real danger will be when the walls decide to start crossing my intended track... surprise

Hakuna matata

Chris

BRU - BE / CTR Track Control

 

Edited By McG 6969 on 09/11/2017 09:55:09

Don Fry09/11/2017 12:29:51
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1814 forum posts
25 photos

You will not make it to General then.

Edited By Don Fry on 09/11/2017 12:32:22

Iris Vieghe09/11/2017 19:04:35
46 forum posts

My eyes love the 'pretty' part. heart Maybe I am shallow? I am not 'technical', that I know. So all I can say about this 'machine' is whether I think it's pretty or not. So keep on working on the pretty part too. You may not make it to General but you will be forever my Captain. Ay ay sir!

- Iris

BRU - BE /Aesthetics control

McG 696910/11/2017 07:44:09
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1615 forum posts
714 photos

Thanks both , I had a large smile smiley reading your comments.

I'll probably never make it to General, Don...

... or maybe not even to The LotH's Captain...

... but then, I'll stick to "Saving Private Chris"... wink

Hopefully I can get back to La Grotte today, but the connectors didn't show up yet.

Hakuna matata

Chris

BRU - BE / CTR Rank Control

McG 696914/11/2017 17:55:36
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1615 forum posts
714 photos

Hello everybody,

I managed to get to La Grotte again and could finally resume the ChtiCat build.

While having some spare ‘virus’-time, I started pondering (slowly) about the rudder design of the thingie.

It seems obvious now that the fastest air movement is located at the inclined extractor part. Well it seems that the designer made the rudder less reactive - with a rounded off bottom part - precisely at that area. frown

862_rudder_def_900.jpg

So, I decided to increase the rudder width by 10mm (+/- 18%). The white foam part in the pic.

Then I changed my mind by having a smaller width at the top and a larger one at the bottom. The yellow/fluo laminated rudder. It looks a bit like a gentle 3D beast now. wink

As the rudder hinge will be a simple clear strip of lamination it’s easy enough to change it later on if needed.

As I wrote before and as the fin already shows, intensive use of the Ballerina vinyl off-cuts is the motto here.

864_liposeat01_900.jpg

I also prepared the battery tray - ie foam laminated with acetate - behind the motor mount with a space underneath to receive the speed controller. Only a dry fit shown here.

866_liposeat02_900.jpg

The other good news is that I also received the missing little bits including the Lipo & ESC connectors. Hopefully I can have some better progress from now on.

Hakuna matata

Chris

BRU - BE / CTR Virus Control

McG 696915/11/2017 19:04:14
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1615 forum posts
714 photos

Hi again,

I made a start right away at getting those tiny connectors out of their bags and got the soldering equipment out of the drawer…

After some really disastrous first results, I quickly switched to measuring and cutting some vinyl lamination and progressed with sticking that to the ChtiCat as I experienced the pleasure of a lot more success.

Unfortunately, I forgot the camera at La Grotte - I suspect that happened before during the Ballerina build - but I officially promise to post a lot of them (say?) tomorrow… blush

Hakuna matata

Chris

BRU - BE / CTR Pic Machine Control

Don Fry15/11/2017 19:22:15
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1814 forum posts
25 photos

Chris, I admit I have consumed a fine Bordeaux with my dinner of lapin aux prunaux.

But, regarding the rudder, this is the fastest thing in the hall. If a plane is airborne, you are travelling at at least twice as fast, and that is in the corners. And it has a huge rudder, to give some control when it accelerates from zero, but once running the rudder throw is small. So you program big exponential. Mine is iro 50 60 %.

Don't over think these things,

I don't know if I will rebuild, build another. My hall, a basketball court is challenging. If it was bigger, I would enjoy tuning it. But running them is a brutal war game.

McG 696916/11/2017 08:07:59
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1615 forum posts
714 photos

Hi Don,

Well, The LotH and I shared a 'Plateau de Fromages' and a - too small - Spanish Epulum Gran Reserva 2009...

Regarding the rudder mod, I'm just trying to find out if it would give a better response at 'low' speed - or not... and yes, I'm convinced a lot of expo will be needed at higher speed.

I still have to learn how to bind and configure my old Tx. blush I guess I will be crying for help around here quite soon now.

And later on, I can already project a very suicidal 'maiden glide'... frown

Hakuna matata

Chris

BRU - BE / CTR Expo Control

McG 696916/11/2017 19:31:00
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1615 forum posts
714 photos

Hello to ‘all’,

… well at least, if there is still somebody out there?

Anyhow, we’re back in biz’ness. Especially Gaston as he loves this part of a build as much as I do.

Not much ‘literature’ needed here. Just have a look… and hopefully enjoy.

871_colour01_900.jpg

876_colours05_900.jpg

878_colours06_900.jpg

883_colours08_900.jpg

890_colours09_900.jpg

The pontoon is totally finished but fuselage and fin are just a dry fit.

Questions always welcome of course.

Hakuna matata

Chris

BRU - BE / CTR Deco Scheme Control

Stephen Jones16/11/2017 20:36:12
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2396 forum posts
1388 photos

Are you hoping it`s going to be a one horse race with that color scheme wink

Steve

Max Z16/11/2017 20:38:38
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385 forum posts
175 photos

Nice decoration! I am sure it will dazzle the competition......cheeky

Max.

AndyD16/11/2017 21:25:15
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628 forum posts
438 photos

looks like a winner to me,fantastic scheme.

Andy G.17/11/2017 12:51:48
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321 forum posts
179 photos

Looking Very Dazzling! Tempted to put one of these on my build list!..

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