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  #341  
Old 12-18-2015, 09:58 AM
Av8torTom's Avatar
Av8torTom Av8torTom is offline
 
Join Date: Nov 2009
Location: Yardley, PA
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Default Router????

Oh man, you should have watched this...

https://www.youtube.com/watch?v=OtKQbM9laC8
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  #342  
Old 12-18-2015, 11:29 AM
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Michael White Michael White is offline
 
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Location: Cartersville, Georgia KVPC
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Andy,
Two thoughts...
1. Does your wife's router have a shop vac fitting? If so, you can buy her a nice shop vac for Christmas...to go with the router of course...
Seriously, a vac would help with the mess. If the router has no vac fitting, you could get one of the girls to hold the tip of the vac near (but not too near) the router as you make the cut to suck up the scraps. Getting the oldest girl to help would be best, and I'm sure she would love to help Daddy work on the plane.

2. The 6" diameter on the inner lip may seem too big, but if you do the math it will give you just about the same area (28 sq. in. each side) as the standard Van's cowl inlet (25 sq. in. each side). If you then throttle the exit per Dr. Dan's previous posts, you should have plenty of cooling for just about any flight regime without creating speed/drag issues.

Regards,
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  #343  
Old 12-18-2015, 02:22 PM
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LettersFromFlyoverCountry LettersFromFlyoverCountry is offline
 
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Cripes, if my wife gets on here and finds out you got your wife a router, that racheting wrench set sitting under the tree I got for her is going to look sad.

Thanks a lot, pal.
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  #344  
Old 12-22-2015, 09:37 PM
crabandy crabandy is offline
 
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Location: Ottawa, Ks
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Unfortunately BillL was right, there is a bit of a twist in the baffling. Seems the right front of the baffling is 1/4-3/8 inch lower than the left front. I'm sanding off the foam I glued to the fiberglass plenum and gluing foam to the baffling instead.


I think I've finalized my inlet shape and size. I originally planned on using the existing inlets, but to better my odds of more cooling I decided to:
-make the inlet area larger
-move the inlets outboard
-move the inlets forward
-use round inlets

I ended up with 5.75 ID per inlet with 25.97 sq in versus my stock size of 21.29 sq in, SJ large rings have 16.8 sq in per inlet. Being fixed pitch I generally climb out at 130 knts as a compromise between horsepower, climb rate and cooling. At 130 knts my stock Vi/Vo should be .54, with the new larger inlets it will be .45. At 90 knts the stock Vi/Vo should be .77 with the new larger inlets at .65.

I used a 7/16 outer lip and a 3/16 raduis inner lip for the ring I plan on bonding to the front of the cowl. I routed a 7/8 core box into some HDPE then routed the middle of the groove out.


I routed out another disk to fit the hole and then used a 3/8 core box bit to make the inside radius. I used a finish nailer to tack everything to the bench.


The new ring with the smaller inner radius next to the full 7/8 diameter ring I made first, the OD of the smaller ring is .75 inch less.


The 3/4 inch smaller outside diameter of the new ring appears to be easier to blend into the existing cowl, just my uneducated opinion.
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Last edited by crabandy : 12-22-2015 at 09:41 PM.
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  #345  
Old 12-23-2015, 05:54 AM
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Michael White Michael White is offline
 
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Lookin' good Andy!
Can't wait to see the finished product.
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  #346  
Old 12-23-2015, 01:40 PM
crabandy crabandy is offline
 
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Quote:
Originally Posted by Michael White View Post
2. The 6" diameter on the inner lip may seem too big, but if you do the math it will give you just about the same area (28 sq. in. each side) as the standard Van's cowl inlet (25 sq. in. each side).
Michael,
Just curious if the inlet area quoted was from a smooth horizontal induction Van's Cowl. I found my vertical induction on cowl inlets were considerably smaller than a friends RV7 with the smooth bottom horizontal induction cowl. Just curious if all the smooth bottom cowls have a larger inlet area than the vertical induction. I did some glassing to get the inlets to match up while fitting my cowl, I think I inadvertently decreased my inlet area while doing this.
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  #347  
Old 12-31-2015, 05:03 PM
crabandy crabandy is offline
 
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Location: Ottawa, Ks
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I lightly peened the outer surface of the prop flange bushing in several places with a center punch and pressed it in with some all thread as recommended by Saber, I also used some red loctite. I'm not positive it will hold and will test tighten with some scrap tubing in case it comes loose. The availability and price of oversized bushings leads to having someone with a lathe turn down an indexing bushing to the size I need as my next option.



I mounted the prop to find my clearance from the back of the prop blade to the front of the inlets, since the spinner portion of the cowl is flat and equidistance from the prop I used it as a reference.
The inboard right side is 1 1/8 inch aft of the prop blade, the left side is 1 3/32 inches. The outboard side is harder to measure accurately due to the blade sweep and lip of the inlet but the left outboard side is about 15/32 further aft than the right outboard side.





I mounted a yard stick to the split line of the cowl and hot-glued some foam to represent the closest point of the rear of the prop blades. I marked center lines on the round cardboard with some vertical tick marks to play with different locations, I also made some marks on the spinner portion of the cowl for outboard/inboard measurements.



This moves the inlet out quite a bit from the original location, I'm shooting for 3/8 inch aft the prop blades on the inboard side of the inlet.

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Last edited by crabandy : 12-31-2015 at 05:06 PM.
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  #348  
Old 01-04-2016, 12:14 AM
crabandy crabandy is offline
 
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Location: Ottawa, Ks
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Best build session I've had all year.....last couple of months included! Mr. Baby is down for a solid nap while the oldest 2 are actually interested in learning how to apply math with tape measures, ratios (mixing epoxy) and power tools while the 2 year old plays in the bucket of soapy water......
Here's the blank slate so to say, its been the front of my plane for 2 flying years and attacking it with 60 grit and sloppy epoxy has been the biggest hang-up of this project.



The girls and I figured out how to measure and scribe an arc in some foam and the 5-1 ratio of epoxy to hardener. They painted on some dry micro and we stuck our foam blanks onto the cowl.





While we were waiting for the cowl to dry my oldest daughter and I made some templates for the flanges of the plenum. After gluing the plenum top to the foam on the engine baffling I sanded the edges down to make up for the width of the fiberglass, we'll see how it fits.





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  #349  
Old 01-04-2016, 12:37 AM
crabandy crabandy is offline
 
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Location: Ottawa, Ks
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I whacked the excess foam off with a drywall saw.



When I originally fitted the cowling I used a 3/16 inch gap between the spinner and the cowling, I'm using the flat face of the cowling behind the spinner as my reference plane. I used a 1/4 inch piece of Masonite over the flat spinner area to give me the proper height, I used a flat piece of oak with some sandpaper glued to it to sand the foam down. I used an 1/8 inch piece of cardboard to further cut down the right side which was slightly closer to the prop. The





It left me with about 11/16 gap between the flat spinner area of the cowling and the front of the rings, the left side foam height is 3/8 inch higher than the right side. The aft edge of the prop is about 1 1/8 forward of the flat spinner area of the cowling giving me about 1/4-3/8 inch clearance between the prop and inlet rings....I hope.



Inlet rings epoxied in place.

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  #350  
Old 01-04-2016, 06:54 AM
BillL BillL is offline
 
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Location: Central IL
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Looking Good Andy! Don't forget about prop blade clearance. I don't know about Cato, but others can come back even with the back of the spinner (or more for the older Hartzell composite CS). The right side is closer due to the engine angle. (I see you knew that!)
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Last edited by BillL : 01-05-2016 at 02:23 PM. Reason: Silly Bill - the picture was right there!!
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