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tonyrenshaw268(at)gmail.c
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 Posted: Thu May 29, 2014 9:24 pm Post subject: Key Sanding................and Instrument Panel ventilation |
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Gidday,
I want to air a hypothesis that key sanding does NOT matter what grade of paper, so long as you dull it off. The premise is that by roughening you are removing the gloss, and increasing the surface area. I am aware that the heavier the grade of paper you use, the more likely you are to damage the glass fibres within the matrix. So, I don’t want advice on Grade of paper, but I do want to ask whether people think that this could be true:
“ I believe there is a likelihood that whether you use 240 Grit paper, or 60 Grit paper, that the substrate will increase in surface area by the same amount”.
Thats my debate.
I also believe there is a likelihood that the amount will be twice the surface area, but I don’t know how to mathematically prove it, however I’d like it explained in simple terms, what the actual formula is in someone else’s view. In fact I’ll go a step further and hypothesise that it is
1/2 surface area of a circle MINUS the are of the diameter of a similar radius circle.
I’m going to retract double, and reckon it is closer to a 50 % increase.
Any takers? Anyone had enough red wine to give this consideration? There might be two guys out there in the Cottswalds, but they will probably just argue between themselves, so I thought I’d air it to the greater Europa community.
Regards
Tony Renshaw
P.S. I have an instrument panel fan, a computer fan, and I am wondering where would be the most advised place to put it? I am thinking midway between the main panel and the radio stack, behind the mono wheel gear retraction handle rebate, on the RHS. Whatdoyareckon?
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John Wighton
Joined: 18 May 2010
Posts: 241
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| Posted: Fri May 30, 2014 3:55 am Post subject: Re: Key Sanding................and Instrument Panel ventilat |
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Tony,
Not sure on where the surface area discussion is going - or the objective.
Regarding the panel, l installed 2off fans in a carbon frame above the 6 pack/EFIS hybrid panel in G-IPOD. This is the highest point hence hot air will collect here. It performs the de-mist function in the cockpit (no other heater is fitted).
I can send some pics if needed.
Regards
John
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_________________
John Wighton
Europa XS trigear G-IPOD |
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Fred Klein
Joined: 26 Mar 2012
Posts: 503
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| Posted: Fri May 30, 2014 8:33 am Post subject: Key Sanding................and Instrument Panel ventilation |
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On May 29, 2014, at 10:23 PM, Tony Renshaw <tonyrenshaw268(at)gmail.com (tonyrenshaw268(at)gmail.com)> wrote:
| Quote: | | “ I believe there is a likelihood that whether you use 240 Grit paper, or 60 Grit paper, that the substrate will increase in surface area by the same amount”. Any takers? Anyone had enough red wine to give this consideration? |
…too early in the morning for the wine…intuitively, as I imagine a field of a given size covered w/ hemispheres…an approximation of grit paper...as I imagine the surface area of the hemispheres as the hemispheres diminish in size…I cannot escape the conclusion that the total surface area will increase in inverse proportion to the diameter of the hemispheres…
…nonetheless…I can think of better reasons to avoid 60 grit when key sanding…
| Quote: | | P.S. I have an instrument panel fan, a computer fan, and I am wondering where would be the most advised place to put it? I am thinking midway between the main panel and the radio stack, behind the mono wheel gear retraction handle rebate, on the RHS. Whatdoyareckon? |
I reckon putting in 3 those 120 mm computer fans (at) $10 each were the was easiest decision I’ve had to make regarding my panel…I’m uncertain at this time whether or not I’ll use the little louvered vents intended to direct airflow towards the windscreen.
F.
[img]cid:05FD6BC6-B1BC-4F63-81AB-52AC232C4141[/img]
[img]cid:F96001A5-A7C6-420D-AA08-D330CD06781D[/img]
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spcialeffects
Joined: 29 Aug 2012
Posts: 306
Location: Kent
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| Posted: Fri May 30, 2014 8:59 am Post subject: Re: Key Sanding................and Instrument Panel ventilat |
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Hi john, I'd be interested in seeing a few pics please. Thanks Frank
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tonyrenshaw268(at)gmail.c
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| Posted: Fri May 30, 2014 3:00 pm Post subject: Key Sanding................and Instrument Panel ventilation |
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Hi John,
Re Key Sanding, I suppose the purpose is to legitimise why we do it, and its because I’ve been doing work on the very thin sandwich skin of the fuselage. The cloth in question is so thin, and I believe any strong Grit will compromise the structure, so it got me thinking about what the goal really is. I reckon the goal is to abrade the matrix resin, without compromising or ideally even touching the entrapped glass, and in essence increasing the surface area in the process. I then wondered academically whether there was any difference in the surface area between one Grit and another, and I don’t believe there is, SO, when key sanding, any grit will do if it roughens the surface and dulls it off. Thats all, just an academic exercise, but I know there are smarter guys than me on the list, so I asked.
re: Instrument Panel Venting, I have kindly been sent a few photos but am always desiring seeing how others have done things, so yes, I’d love to get some photos. Thanks John.
Regards
Tony Renshaw
On 30 May 2014, at 9:55 pm, John Wighton <john(at)wighton.net> wrote:
| Quote: |
Tony,
Not sure on where the surface area discussion is going - or the objective.
Regarding the panel, l installed 2off fans in a carbon frame above the 6 pack/EFIS hybrid panel in G-IPOD. This is the highest point hence hot air will collect here. It performs the de-mist function in the cockpit (no other heater is fitted).
I can send some pics if needed.
Regards
John
--------
John Wighton
Europa XS trigear G-IPOD
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=424022#424022
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richard collings
Joined: 08 Jul 2011
Posts: 73
Location: warwickshire england
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| Posted: Sat May 31, 2014 3:27 am Post subject: Key Sanding................and Instrument Panel ventilation |
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Hi Tony
If you have mounted the instrument module on rubber bushes as we discussed
earlier you will have created a vent all along the top, if heat is an issue
you can fit a fan or fans on the underside of the instrument module both
sides and drive cooler cabin air up into the module and let it exit across
the top. It could also act as a demister and it keeps the fans out of site.
Best wishes
Richard
G-CGZV
By the way you were right I can't count only 5 brackets hold the top engine
cowl on !
--
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tonyrenshaw268(at)gmail.c
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| Posted: Sat May 31, 2014 4:52 am Post subject: Key Sanding................and Instrument Panel ventilation |
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Hi Richard,
Now thats a good idea, to push cooler canin air up through the panel. I am about to mount the panel on the rubber bushes, and working on replicating the cowl setup. Just keep sending all your good ideas downunder.
Regards
Tony Renshaw
Photos to follow.
[quote] On 31 May 2014, at 21:26, "Richard Collings" <rcollings(at)talktalk.net> wrote:
Hi Tony
If you have mounted the instrument module on rubber bushes as we discussed earlier you will have created a vent all along the top, if heat is an issue you can fit a fan or fans on the underside of the instrument module both sides and drive cooler cabin air up into the module and let it exit across the top. It could also act as a demister and it keeps the fans out of site.
Best wishes
Richard
G-CGZV
By the way you were right I can't count only 5 brackets hold the top engine cowl on !
--
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Scudrunner
Joined: 31 Aug 2012
Posts: 26
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Fred Klein
Joined: 26 Mar 2012
Posts: 503
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| Posted: Mon Jun 02, 2014 8:30 am Post subject: Key Sanding................and Instrument Panel ventilation |
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…thanks for the tip…I’d not considered possible reflections…the dark grey louvers will definitely go on…f.
On Jun 2, 2014, at 9:14 AM, Scudrunner <howardbrooksster(at)gmail.com> wrote:
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Just an observation for those fitting fans etc in the top of the instrument panel; I mounted a box under here recently and used four stainless steel screws. In flight they resulted in four very annoying reflections in the canopy - I recommend keeping everything up there matt black or dark grey. [Embarassed]
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=424213#424213
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