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ARIXTRA Build Thread by ISAAC NAJARY

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Old 11-11-2012, 05:40 AM
  #126
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Hi Itzik,
The way your Motor and SC are positioned, maybe a small opening on the back of the bally-pan will improve cooling by creationg s short exit pass for the air...
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Old 11-11-2012, 08:40 AM
  #127
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ORIGINAL: amram

Hi Itzik,
The way your Motor and SC are positioned, maybe a small opening on the back of the bally-pan will improve cooling by creationg s short exit pass for the air...
Amram
Hi Amram,

The way the ESC is positioned provides enough cooling to the ESC but it also serves as an air deflector which aims the air to the motor battery and helps to speed up the air passes around the motor battery.

I like the motor battery to have air cooling as much as I can.

Best regards,

Isaac Najary
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Old 11-11-2012, 10:01 AM
  #128
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

HI
OK, I understand your point. Don't you concern that the air passes to the battery area is relatively hot as it comes from both Motor and ESC?
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Old 11-11-2012, 10:19 PM
  #129
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY


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ORIGINAL: amram

HI
OK, I understand your point. Don't you concern that the air passes to the battery area is relatively hot as it comes from both Motor and ESC?
Amram
Hi Amram,

You were right if we were talking about something like air-conditioner radiator, but in our case the contact surface of the hot elements (the motor and the ESC) is so small compared to the air mass that is passing through so the air temperature rises very little.

As long as the temperature of the air passing though the battery is lower then the battery temperature itself it is still good.

Best regards,

Isaac Najary
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Old 11-11-2012, 11:30 PM
  #130
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Hi
I am not sure I agree with your air cooling analysis but for sure I have learned something from that…
Thanks
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Old 11-12-2012, 01:41 AM
  #131
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

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ORIGINAL: najary


(...) As long as the temperature of the air passing though the battery is lower then the battery temperature itself it is still good.

Best regards,

Isaac Najary
Not completely true... that's just one factor to take into account; you have to consider also air flow (or how much air pass passes licking the battery surface) and battery mass. The diff. of temperature DT has to be also evaluated considering the air flow too... big flow => small DT allowed; small flow => big DT NEEDED
In any case, and from the constructive point of view; take good care of air intakes and (specially) air exhaust rather than air temperature.
There are several gold/thumb rules to apply here...
regards;

G.

PS; Issac, thanks for posting so detailed photos and building tips; really appreciated.
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Old 11-12-2012, 07:42 PM
  #132
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Something tells me Isaac would know if his cooling methods were not working properly. He's got quite a few of these builds out there and is familiar with his power setups.

The truth of the matter is that we don't know the mass flow of air through the plane, nor the temperature, let alone the Y+, Reynold's number, and subsequent heat transfer coefficients. Most of what we see is trial and error; there are not many people doing detailed 3D modeling of model F3A airplanes.
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Old 11-13-2012, 01:34 AM
  #133
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY


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ORIGINAL: najary


Quote:
ORIGINAL: nonstoprc

Najary,

Wonder permanently gluing the chin cowl to the fuse is an option once the landing gear work is done. Seems that could increase the rigidity and may save some grams.

Enjoy your every building step!
Hi Nonstoprc,

I considered to do that in my Osmose, and decided not to, because:

1. The chin cowl is very soft and it will not increase much the rigidity.

2. It maybe saves only 2-3 grams.

3. You will no have good access to the motor, the landing gear and to the ESC.

4. The joining between the fuselage and the chin cowl will be problematic as far as the finish is concerned.

Best regards,

Isaac Najary
Najary,

I installed my jeti spin 99 on my Visa, in front of the battery pack, on the battery deck and behind the Neu f3a motor. The esc is barely warm after landing with normal 7-8 minutes of flying. So I would not worry about cooling the esc. Setting up an air channel for the motor, as you did, is a good idea.

The Visa does not have a chin cowl at all. Once the landing gear is installed (relatively painful to drill the access holes for the landing gear mount screws), I found there is no reason to access the fuze from the back. A chin cowl, and it's mount hardware would add some weight.

Regards,






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Old 11-13-2012, 01:43 AM
  #134
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY


Quote:
ORIGINAL: gaRCfield

Something tells me Isaac would know if his cooling methods were not working properly. He's got quite a few of these builds out there and is familiar with his power setups.

The truth of the matter is that we don't know the mass flow of air through the plane, nor the temperature, let alone the Y+, Reynold's number, and subsequent heat transfer coefficients. Most of what we see is trial and error; there are not many people doing detailed 3D modeling of model F3A airplanes.

Thanks Joe; I just wanted to add something i though "good to add". Actually is not a big deal to put some numbers to the cooling here but as you pointed: 1- Trial and error is still valid enough; 2- Isaac has more than enough experience on F3A building.
So; let's go ahead watching his great thread.

Cheers;

G.




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Old 11-13-2012, 05:17 AM
  #135
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY


Quote:
ORIGINAL: najary

Here is a structure with I developed after deep thinking about the forces applied on the landing gear mount.

The all idea here is about making the landing gear mount as light as possible but still strong enough that you can be secure that in hard landing it won't broke.

It is a very frustrate feeling to brake the landing gear mount as a result to a sudden strong gust of wind especially in competition.

I have this structure in my Osmose and in my Xigris and it was proven as strong to survive over 2,000 landings with naturally some of them were pretty hard landings.

The total weight, including gluing to the fuselage and 4 screw-nuts is 30 gram (728-698).

Best regards,

Isaac Najary
Isaac, would you mind sharing where you purchased (or how you made) the carbon fibre honeycomb panels? What weight carbon fibre is used in their manufacture?
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Old 11-14-2012, 05:14 AM
  #136
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Hi Isaac

I really like to see your work.
Waiting to see it at the field!

Mark,
Isaac and I buy our honeycomb at this [link=http://www.acpsales.com/Panels-Sheets-and-Laminates.html]website[/link]
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Old 11-14-2012, 10:08 AM
  #137
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY


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ORIGINAL: ram_z

Hi Isaac

I really like to see your work.
Waiting to see it at the field!

Mark,
Isaac and I buy our honeycomb at this [link=http://www.acpsales.com/Panels-Sheets-and-Laminates.html]website[/link]
Which thickness of panel is Isaac using for these gear boxes?
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Old 11-14-2012, 10:04 PM
  #138
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Quote:
ORIGINAL: MarkGrabowski


Quote:
ORIGINAL: ram_z

Hi Isaac

I really like to see your work.
Waiting to see it at the field!

Mark,
Isaac and I buy our honeycomb at this [link=http://www.acpsales.com/Panels-Sheets-and-Laminates.html]website[/link]
Which thickness of panel is Isaac using for these gear boxes?
Hi Mark,

It is 1/8" and 1/4" http://www.acpsales.com/Sandwich-Panels.html

And allso this:
http://www.hobbyking.com/hobbyking/s...MM_Thick_.html

Best regards

Isaac Najary
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Old 11-16-2012, 05:07 AM
  #139
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Hi  Isaac,

this my first post on RCU becose i'm new member.
i hope you will continue with your build thread becose i'm wery interested, and you do it weeery good !
would like to build one, but i'm living in thailand now, so not easy to import ...have to wait until i go back to visit my country (switzerland) and after i will order and bring with me.

tanks
andrea
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Old 11-16-2012, 08:07 AM
  #140
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Old 11-16-2012, 07:53 PM
  #141
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

In the previous post, did you move the wing tube, or cut in the wrong spot?
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Old 11-16-2012, 11:08 PM
  #142
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

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ORIGINAL: gaRCfield

In the previous post, did you move the wing tube, or cut in the wrong spot?
Hi Joe,

That was a cut in the wrong spot caused by a measuring mistake.

Best regards,

Isaac Najary
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Old 11-17-2012, 12:27 AM
  #143
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Sure that must have been the happiest part of the day!
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Old 11-18-2012, 05:29 AM
  #144
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Hi Itzik.
Last 2 photos of post 140 are extremely nice. 'TA'ANUG LIROT..'
Thanks
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Old 11-20-2012, 09:59 PM
  #145
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Old 11-21-2012, 04:46 PM
  #146
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Is the repair made from balsa that has been glued to that ply 'bracket' and the fuse? I don't mean to pick on the mistake - it is a learning opportunity as the repair is in a fairly critical area. I may encounter something similar if I end up playing with my wing tube/ socket / incidence when I build my foam wing cores.
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Old 11-22-2012, 11:03 PM
  #147
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY


Quote:
ORIGINAL: gaRCfield

Is the repair made from balsa that has been glued to that ply 'bracket' and the fuse? I don't mean to pick on the mistake - it is a learning opportunity as the repair is in a fairly critical area. I may encounter something similar if I end up playing with my wing tube/ socket / incidence when I build my foam wing cores.
Hi Joe,

First the balsa patch has been glued to the fuselage and were sanded align with the fuselage inside.

The ply bracket has been glued after that.

Best regards,

Isaac Najary
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Old 11-23-2012, 07:54 AM
  #148
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Old 11-23-2012, 10:44 AM
  #149
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Default RE: ARIXTRA Build Thread by ISAAC NAJARY

Thanks Isaac, this thread is awesome.
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Old 11-23-2012, 10:28 PM
  #150
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