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From: "Thomas y Reina Jakits" <rijakits@cwpanama.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-1873978@logan.com>
Subject: Re: [FlyRotary] Re: engine mount 4130 vs 304 SS
Date: Wed, 28 Feb 2007 11:30:15 -0500
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Ernest,

I agree, once you stop air-exchange on the inside it cannot rust a lot for 
lack of oxygene.

Question: "Rust Wars" - did you never prime or "SP-400" the frame while 
assembling?
I know primer is just that, primer for paint and should not be considered 
protection, but it is better than nothing?
Wiping with WD-40 helps, but comes fairly fast unless stuck with dust. Also 
when you need to weld you have to clean extra well not have any of the oils 
of WD-40 inthe weld area.

Also just plainly painting the frame any cheap paint is good, 
sand/grind/blast where you need to work and when all is finishes do the one 
time for all blast/clean/etch/prime/paint/polish/IDKW ......

Thomas
"..not pulling your hair, just looking for arguments - I am still in the 
plannig fase, so any and all mistakes you guys ever made and are willing to 
tell, I hopefully will avoid! Thanx"


----- Original Message ----- 
From: "Ernest Christley" <echristley@nc.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, February 28, 2007 10:56 AM
Subject: [FlyRotary] Re: engine mount 4130 vs 304 SS


> Russell Duffy wrote:
>
>> Something Richard Sohn told me, and I soon after found to be VERY true. 
>> The HAZ of stainless weldment will rust almost as easily as mild steel
>> if not properly treated.  It must either be buffed to the original
>> shine, passivated/pickled, or painted.  Since you won't have access to
>> the inside of the tube, going stainless may not get you much.
>>
>>  Hi Ernest,
>>  I can't say I've ever heard of, or thought about this problem.  I know 
>> that the weld will carbonize (I think that's the correct term) if air is 
>> allowed to contact the weld before it cools a certain amount, and 
>> shielding gas can be used inside the tube.  Would this prevent the 
>> rusting you're talking about?
>
> I don't know.  I've just tried to clean up the welds I've made 8*). 
> Richard, can you jump in here?
>
> Lynn, it's actually not very hard to weld stainless.  If I can do it with 
> my Harbor Freight torch, anyone can handle it.  You just use a fairly rich 
> flame.  The test welds I ran broke just like my 4130 welds, right next to 
> the weldment.
>
> Thomas, I don't see the benefit of stainless being the protection of the 
> inside of the tube.  The benefit would be not having to treat the OUTside. 
> Having sandblasted and painted a Dyke Delta airframe after fighting the 
> Rust Wars* for several years while I was putting it together, I would 
> sacrifice a few things not to suffer that pain again.  I wouldn't 
> substitute any old tube into an existing design, even though in a typical 
> tube fuselage the tube diameter and wall thickness are chosen for many 
> reasons other than absolute strength (construction practicality, buckling 
> resistance, inventory simplification, etc).  A switch to stainless would 
> require a clean sheet design, but I think it could possibly be easier to 
> build and lighter when all is said and done.
>
>
>
> *Rust Wars -- you're absolutely forbidden to sweat while welding a 4130 
> frame, not matter how hot it is outside.  If sweat touches the airframe, 
> it must be cleaned immediately with a damp rag followed by some sort of 
> oil.  Each place you fail to treat in such a manner will start turning 
> reddish brown by the next day.  I used to walk around regularly with a 
> scotchbright pad and a can of WD40.
>
> -- 
>         ,|"|"|,              Ernest Christley       |
> ----===<{{(oQo)}}>===----    Dyke Delta Builder      |
>        o|  d  |o        http://ernest.isa-geek.org  |
>
> --
> Homepage:  http://www.flyrotary.com/
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>