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Geez, after buying a $200 Vividia borescope to look at my valves (see Aug 24 in this thread), I was just reading about this one (pic) for $29.  The previous problem with these cheapies was that they were not flexible enough to stick them in the plug hole and bend them back to look at valves.  A Vans owner says this one can do it.  It could probably be glued to a piece of bendable wire and inserted into the cylinder.  

Why do this?  Regular Lycomings have notoriously-poor valve stem lubrication.     https://web.archive.org/web/20050217090118/http://www.prime-mover.org:80/engines/Marvel/tbo3.html   So the valve stems wear and the rocker arm pushes the valve head off center.  Heat does not transfer evenly around the valve head to the valve seat, the valve head gets heat-stressed and a piece breaks off, or the head breaks off.  What you don't want to see is a half-moon discoloration (pic).  There is a really bad case in this video  https://youtu.be/x6OyfoV1Z2I

 

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Photo 2013-01-02 01.51.23 PM.jpg

Edited by Kent Ashton

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That is a very sad looking head.

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Some words on filling:  I have painted three canards and several cars and bikes and made about all the mistakes you can make so perhaps I've learned some things.  My buddy who is repairing and painting his Cozy came up with this problem (pic).  He says "I have sanded the primer to #2000 grit and I see pinholes [again].  What to do?"

He has two problems:  He did not kill the pinholes before priming and he is sanding the surface too smooth for further paint to get a bite.  For me, there is a logical order to painting a canard, that if followed will result in fewer mistakes.  Here is mine:

1.  First, do your filling and sanding to get the surface perfect, and sanded down to about a 320 grit.  Along the way, use a stiff aluminum bar marked up with a big Sharpie.  Rub the bar perpendicular to the chord.  The bar will leave oxide and Sharpie smudges on the high spots.  Sand them down a little and repeat until the smudges are everywhere evenly.  On curved surfaces like the nose, I use stiff, flexible things like welding electrodes or old bandsaw blades held over the surface to find high and low areas.  View the surfaces from many angles with lights at different angles.  The mistake here is usually thinking you are ready for the next step but you are not.  Primer/surfacers will not fill pits and deep sanding scratches.  Undetected defects are usually present.  We have to fix those here before priming.  To find them, I spray the whole surface will a thin mist of black sandable rattle-can primer and sand it all off.  That will usually show many undetected defects.  Fix all of them except pinholes.  Sometimes a new layer of filler over the whole surface is the easiest path.  Sand to about 320 grit.  Repeat as necessary.  It is a mistake to sand smoother than 320 grit.  Now your surface is truly flat and smooth but there will be pinholes.

2.  Fill the pinholes with the "Cory Bird epoxy wipes method"--three to five wipes with straight epoxy allowing it to tack up between wipes.*  The wipes will fill the pinholes but they will leave hard ridges and runs that will need sanding flat.  IMO, the reason you don't want to sand finer than 320 grit prior to the wipes is that straight epoxy wants to clump-up due to surface tension and a very slick surface will help it clump.  Also, it's hard to leave any epoxy when wiping a very slick surface so you can't build up any thickness.  My objective with the wipes is to get enough thickness of straight epoxy that I can wet sand it flat without going through it.  Sanding through the hard wipes may expose more pinholes.  Sand the hard wipes down to 320-400 grit.  Now my surface is smooth, has a thin layer of epoxy and pinholes are filled.

3.  Epoxy is a pretty good primer for a topcoat if it has the correct bite but I usually spray a sandable primer/surfacer and wet sand that to about 400 grit.  Now I'm ready for a topcoat.

*NOTE:  Cory, who built a championship airplane, said a 36 grit finish was just fine in preparation for the epoxy wipes    http://www.ez.org/t/cp77-p4   He used the wipes to fill big sanding scratches.  I find it better to work those out to a finer surface.  Cory suggests a 3-4' sanding spline.  I usually get good results with an 18-20" board but I have not won any Oshkosh awards.  ?

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Thanks for the tips Kent!  What are you representing in your photo... the way it should be done or the way it shouldn't be done?  I see two scratches, some uneven micro around the NACA, and an uneven gap.  It still looks fast... if mine looks that good I am going flying.

Edited by macleodm3

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1 hour ago, macleodm3 said:

Thanks for the tips Kent!  What are you representing in your photo

My friend was showing me his pinholes but now that you mention it, maybe they are not pinholes.  Below is what I usually see as pinholes (pic).  They are larger and paint does not want to bridge them.  My friend's look tiny; I don't think I've seen that.  Maybe my friend just has some texture problem with the primer and just needs to sand more.  I dunno.

 

pinholeswarm.jpg

Edited by Kent Ashton

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To close the loop on this, my friend said he sprayed a thin coat of primer on his "pinholes" and sanded to 500 grit and doesn't see them anymore, so maybe it was just the texture of his primer and 2000 grit sanding giving that effect.  Normally you can spray gallons of  paint over a pinhole and it will just laugh at you.

However, with sandable primer I have occasionally swiped the wet primer with an old credit card when a swarm of pinholes appeared.  It filled them and the primer could be sanded flat but it  was more work.  Best to kill them before priming.

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Yeah... I see pinhole swarms in my micro too.  I am not worried about them... I'll fill them with raw epoxy like you mentioned.  How big of a pinhole can you fill with the raw epoxy?  Most of mine are small (1/16") but a few are larger perhaps 1/8" or 3/16" diameter.

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50 minutes ago, macleodm3 said:

Yeah... I see pinhole swarms in my micro too.  I am not worried about them... I'll fill them with raw epoxy like you mentioned.  How big of a pinhole can you fill with the raw epoxy?  Most of mine are small (1/16") but a few are larger perhaps 1/8" or 3/16" diameter.

I don't have any exact numbers.  Three wipes for me will fill or almost fill a 1/8" pit.  If they are large pits they don't exhibit the same surface-tension pull-away as pinholes--they are just holes to be filled.  Sometimes I  go around putting dots of wet micro on them that I sand down later.  Or I might put a dot of wet primer-surfacer on them when they show up during priming (argh!) and sand them down later.

Here are some pics you might find interesting  Pics 1,2: after several wipes.  The result is not as flat as you might think although I squeegeed pretty thoroughly.  I believe it's due to surface tension causing the epoxy to clump or maybe I just needed more squeegee.  Pics 3,4: I marked off low places and pits after the first application of micro and sanding.  I would probably not try to patch those and just lay down a new layer of filler but the red marks will be helpful because they will show through when sanding and tell me I am filling the low spot and not leaving the filler too thick.  Patch-filling is problematic because the batch hardness changes and it's hard to get a patch flattened to match the surface around it without sanding the surrounding area low. Pic 5: I find it useful to pre-fill low places and high places before doing the whole wingl.  It is hard to fill a low spot like a spar-cap trough while trying to get an even layer of filler over the entire wing.  Same for high spots.  Best to pre-fill them, sand them flat, then do the whole wing.

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I was wondering why Google's "+" search feature wasn't working.  It was very useful to put "+" in front of search words and Google would reliably search for all the words.  That went away when Google wanted to use the + character for Google+.  However, I found out recently that Google's Advanced Search feature will do that but there's a trick to get there.  

For example, I wanted to find images of throttle cables:  Do a Google Image search for anything.  When the search results come up, select "Settings" at the top of the page and go to "Advanced Search".  Change or put your terms in "all these words" and you'll get a lot more pertinent results than a generic search.    LIke this:

https://www.google.com/search?as_st=y&tbm=isch&hl=en&as_q=longez+throttle+cable&as_epq=&as_oq=&as_eq=&imgsz=&imgar=&imgc=&imgcolor=&imgtype=&cr=&as_sitesearch=&safe=images&as_filetype=&as_rights=

Google+ has gone away but I don't think the + character has been restored yet.

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I talked about my homemade smoker back on page 5 which was not very successful.  Since then I've upgraded to an Akorn Char-griller https://www.chargriller.com/collections/kamado-grills  a cheap version of a Big Green Egg kamado cooker.  The Chargriller is steel--about $290 from Walmart, Lowes, etc versus $750-$1000 for the true ceramic smokers.  It's one of the best things I every bought!   I just mound up some charcoal briquets and apple wood, give it about 20 minutes to come up to temperature and it will cook for 3-5 hours+ with very little tending.  Yesterday I added a Pitmaster IQ110 found on Craiglist.    https://pitmasteriq.com   It is a little temp-controlled fan that keeps the cook temperature perfect.   Mostly I cook St Louis ribs (3 hrs) or brisket or  the occasional chicken or spatchcocked turkey.  They have all come out great.  Must try a pizza sometime.

There are plenty of Youtubes of folks cooking delicious these on these kamado grills.  Check them out.

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Kent, do you think it would be good for curing smaller layups?  ?    

When my parents got into smoking / slowcooking - they went way overboard...  but the flavor was good (be careful of wood selection - it makes a HUGE difference in flavor!).

M.

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Saw this question below on a FB page.  None of the answers suggest comparing the pressure differential above and blow the cylinders with a relatively simple water manometer setup.    https://www.canardzone.com/forums/topic/18661-kents-long-ez-project/?do=findComment&comment=61602   I would guess his cowl exhaust area is too small.  It is certainly smaller than you see on most airplanes.  He has a big opening around the prop but there looks to be a flywheel blocking that path.  I don't recall the rule-of-thumb exactly but I think it says the exit area should be two or three times the inlet area.  Also the top of the cowl looks tight to the tops of the cylinders.  Those restrictions might be creating backpressure that restricts flow.  In my experience above, I moved the cowl exhaust opening to a better place  but did not change the intake size.  That improved cooling considerably--it just allowed the air to get out.

 

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Further on the airplane above:  I'm a little surprised that his oil cooling is OK since the flow has to make a 80 deg turn against the baffle and get compressed to go out the slot which looks to be only 1/3rd the area of the cooler.  He seems to have a dedicated intake duct for the cooler.  These things are interesting to speculate on.  If he made the cooler exit more efficient, it would likely make the cowl bigger but maybe the drag from a larger cowl would be offset by less cooling air being used for the cooler.

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