Sam James Cowl Inlet Ring Installation

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bullojm1
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Sam James Cowl Inlet Ring Installation

Postby bullojm1 » Thu Nov 06, 2008 10:28 am

I know a couple of you have Sam James cowls or are thinking about going that way. This cowl installation is not very well documented on any web pages / forums, so I thought I'd take the opportunity on RivetBangers to show you guys how I did mine.


The first thing I took care of was making sure the top and bottom cowls matched up in the front. My left side was good, however, the right side's top cowl needed to be built up a little to match the bottom. A little microballoons mix fixed that up nicely. I am pretty impressed with MicroBalloons. This was my first time using it and it goes on easy and really sands off easily. Great for building up areas in a lightweight manor! The only problem I had with them was how much I made in my batch. With one pump of the epoxy I had a huge amount of micro slurry by the time I was done. Oh well, its only money wasted (I haven't worked out an equation for how much $/pump epoxy costs me yet!). Here is the end result:

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Once the cowl halves lined up, I needed to enlarge the inlet holes to accommodate the size of the inlet rings. I simply put the rings against the cowl and drew a line around the perimeter of the ring with a thick sharpie. The thin sharpie had a tough time coming into contact with the surface of the cowl.

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And the end result:

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I went at the fiberglass with the dremel tool (builder BEST friend) with a drum sanding wheel to enlarge the hole to the diameter of the ring

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In case you didn't know, the rings aren't permanently attached to the cowl. They have a groove in them that you need to mold the mating pattern into each cowl half. When you install the bottom cowl, you adjust the intake ring to sit in the groove of the bottom cowl (the ring is attached to the baffle/plenum by a flexible neoprene connection). Then the top cowl goes on and locks the ring in. So, I needed to build up the inside of the cowl with flox (flocked cotton and epoxy slurry) to contour to the groove in the inlet ring. Sounds simple right? Well, there are certain things you DON'T want to do. The two specific things you don't want to do is glue the two cowl halves together or glue the two cowl halves together!

To keep the epoxy exposure to the inlet ring to a minimum, I used packing tape to cover the front and back of the inlet rings.

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Now onto keeping the cowl halves from sticking together. The Sam James instructions recommended putting clay in between the cowl halves, and I thought that was just genius. Simple and effective.

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Now I didn't want to just worry about the cowl halves sticking together -- I also knew I needed to pure a flox mixture into the inside of the cowl to seal the rings in. If I just poured it without any provisions, it would bond the two halves of the cowl together. So I used some more clay and made a little dam out of it between the two halves of the cowl.

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Next on the list of things I didn't want to happen was the flox to bond to the inlet rings. To take care of that I covered the exposed metal with wax.

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Next was the actual installation and fiberglassing. Gravity is your best friend here. I didn't want to mix the flox too thick for fear it wouldn't gravitate to the groove. I didn't want to too thin either because that would increase the weight and cause it to ooze out of any small gaps between the cowls or between the inlet ring and the cowl. So anyways, I placed the cowl on the floor with the front on the ground.

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I used some smaller boards and shimmed them to be flush with the intake molds on the cowl. I put some wax paper on the boards in case any flox oozed out.

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Finally I put the rings in place and filled the front of the cowl up with flox. It was amazing how much epoxy/flox it took to get these things set. I think I used about 8-9 pumps.

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In the end I was pretty happy with how it turned out for the night. It wasn't all that much work, but it was a fair amount of preparation. Tonight I get to see if I can get my cowl halves apart!
Mike Bullock
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Postby cjensen » Thu Nov 06, 2008 10:32 am

Great write up Mike! I've been following closely on your site each day as well...I'm thinking about starting my cowl this weekend...

8) 8)
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Postby bullojm1 » Thu Nov 06, 2008 10:39 am

Thanks Chad.....I can see the end of the cowl in the near future. I still have some slight issues with the hinges being difficult to put the pins in. I think that's a simple fix by shimming the hinges with some flox (Fiberglass is my new best friend......can you say "Composite" for my next homebuilt? ).

The James cowl is definitely some extra work to do over the Van's cowl from what I have seen and read on other builders logs. However, I think its totally worth it from a possible speed increase, but more so, the LOOKS :o!

My big suggestion with the cowl is walk away from it if you get frustrated. Have something else to work on so you can go back and forth to it and not lose any building time. And lastly, feel free to buzz me if you have any questions about it. As always, I am happy to help out fellow builders.
Mike Bullock

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Postby dons » Thu Nov 06, 2008 12:41 pm

This info is great Mike. I am very much interested in using a SJ cowl and reading posts like this help dissolve some of the mystery of doing something slightly different than normal. I'm still thinking about the prop extension issue, but since acro isn't really a priority for me, I don't think it will be show stopper at all. I like the idea of the looks and efficiency of the SJ cowl and plenum. Thanks for posting that.
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Postby bullojm1 » Thu Nov 06, 2008 12:56 pm

dons wrote: I'm still thinking about the prop extension issue, but since acro isn't really a priority for me


If you go with their "Short" cowl, you don't need a prop extension. However, you can only use the short cowl with a vertical induction intake (All carb'd engines or the vertical fuel injection systems).
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Postby dons » Thu Nov 06, 2008 1:00 pm

Yeah, I should have noted I'm looking at the long version and a horizontal injection, but even the short cowl looks good.
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Postby bullojm1 » Thu Nov 06, 2008 1:12 pm

Don-

OK, glad you already knew. One thing that I found out later is Whirlwind sells an extended hub version of its constant speed prop for the same price as their standard hub. I might of gone with the long cowl if I would of known that from the getgo!
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Postby DanH » Thu Nov 06, 2008 2:14 pm

<<With one pump of the epoxy I had a huge amount of micro slurry by the time I was done. Oh well, its only money wasted (I haven't worked out an equation for how much $/pump epoxy costs me yet!).>>

Hi Mike,
Since you like glasswork, consider the purchase of a scale to mix your epoxy by weight instead of volume. A scale will allow you to mix any laminating epoxy (West, Aeropoxy, etc) plus structural adhesives like Hysol and T-88, some of which are too viscous to pump or they entrap air.

I use an old balance beam gram scale just because I've had it 20 years. These days you can buy a nice digital gram scale for $20-$25. Easily pays for itself in the epoxy you don't waste. I routinely mix as little as 10 grams with perfect accuracy.
Dan Horton
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Postby bullojm1 » Thu Nov 06, 2008 3:03 pm

DanH wrote:Since you like glasswork, consider the purchase of a scale to mix your epoxy by weight instead of volume. A scale will allow you to mix any laminating epoxy (West, Aeropoxy, etc) plus structural adhesives like Hysol and T-88, some of which are too viscous to pump or they entrap air.


Dan-

Great suggestion! I really find I waste a lot of resin with the mixing of the microballoons.
Mike Bullock

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Postby rv8or » Thu Nov 06, 2008 4:16 pm

Thanks for the write-up Mike. VERY informative, and takes the mystery/dread out of the SJ Cowl work in my future


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Postby flytoboat » Fri Nov 07, 2008 10:07 am

Mike,
Great looking work. I'm sure many people will benefit from your documentaion.
From your research, how much of a speed increase can be reasonably expected from using the SJ cowl/plenum over stock Vans?
Thanks,
Don
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Postby bullojm1 » Fri Nov 07, 2008 10:14 am

flytoboat wrote:From your research, how much of a speed increase can be reasonably expected from using the SJ cowl/plenum over stock Vans?


Don-

I haven't found anyone who has taken off a Van's cowl and replaced it with a James cowl to get some real numbers. Sam James says a 7-10 MPH increase is possible with the use of their plenum AND cowl. I don't know how much each individually gains you. I know that Pete Howl (RV9A) recently put a homemade plenum on his Van's cowl and didn't see any speed increase at all. So I don't know how much the plenum itself adds. As of right now I am not planning on going with the James plenum. I am planning on fabbing up my own fiberglass intake adapters that go from the round James inlet rings to the Van's baffles.

In the end, the James cowl costs me about $314 over the Van's cowl (including shipping). Using 5 MPH as a conservative guess to the speed increase, I only paid $63/MPH. And its not only top end speed I gain, but efficiency across the whole operating range, so I will save a little gas no matter how fast I fly.
Mike Bullock

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Postby dons » Fri Nov 07, 2008 11:13 am

Heh Mike, thanks for the tip on the Whirlwind. I hadn't been considering them yet as I was leaning towards the M1B/Hartzell combo from Vans. So many choices (good thing I have LOTS of time).
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Postby bullojm1 » Fri Nov 07, 2008 11:36 am

Last night I continued my work on the intake rings. First I took the cowl off the floor. The first thing I noticed was some of the epoxy separated from the flox and flowed down to the wax paper I had sitting below the intakes. I am really glad I put wax paper down because if not, I would of had the cowl glued to some wallboard! Also, another benefit to the epoxy doing this was the front of the cowl was now perfectly aligned to the front of the intake rings! It's nice when you get something for free! Here is a pic to show the front of the cowl where the epoxy ran to:

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It took about 1/2 to get the cowl halves apart because of some minor bonding. No big deal, I just worked it slowly with a razor blade. Here is a blurry shot showing the groove molded into the cowl:

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I took another 1/2 to clean up the mold as well as get out all of the modeling clay and clean up the intake rings. Here is a shot of everything put back together:

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The left side was looking great, but the right side had some slight gaps going on:

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I used a dremel tool with a sanding drum to knock the grooves down a little on the cowls to try to make the cowl halves get closer, However, I didn't want to take too much off because then my rings would be loose and look funny. In the end, I ended up with a little gap, but that can be filled easily later on.

Finally I put the cowl back on the fuse to check the fit. Everything looks great. I declare the intake rings FINISHED! Not bad for two nights in the shop.

Image
Mike Bullock

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Postby cnpeters » Fri Nov 07, 2008 12:38 pm

Excellent write up. Mike - please keep it up! I, too, plan on going the SJ route and appreciate your lucid commentary.
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Postby TomC » Fri Nov 07, 2008 3:59 pm

Mike,

Looks like you are progressing quickly. One question. Is there a patch on the side of the induction air cavity? Is this required to clear part of the engine?

Thanks,

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Postby bullojm1 » Sat Nov 08, 2008 12:25 am

TomC wrote:Looks like you are progressing quickly. One question. Is there a patch on the side of the induction air cavity? Is this required to clear part of the engine?


Tom,

I did need to make a "bump out" on the lower cowl to clear the mixture arm of the precision fuel servo for my IO-360. I documented this modification in this thread:

http://www.rivetbangers.com/forums/viewtopic.php?t=3000
Mike Bullock

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Hinge Pin

Postby capflyer » Sun Nov 09, 2008 7:03 am

Mike,

Great write up on your ring install. I converted my Vans cowling using Sam's rings and front inserts so now it looks very similar now to the Sam James. I picked up a couple kts but the real reason I did it was because I retrofitted on his plenum.

In any case, it is really easy to make your cowl hinge pins go in and out from the cocktpit. It took more time to let the epoxy dry for the knobs on the pins then making the instillation guides.

Looks like your somewhere in MD. I am at GAI so stop by to take a look at how I did it or I could come by if your close enough and help you out.

The clean cowlings look so much better without seeing the attach point in the front for the pins.

Mike R.
Gaithersburg, MD
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Postby bullojm1 » Sun Nov 09, 2008 9:51 am

Hey Mike-

I would love to come by and check out your RV. I live in Reisterstown, about 20 min away from DMW. If you want a free lunch, fly up to DMW and I will buy! That's the least I could do for the priviledge of stealing ideas.

I will PM you with my contact info.
Mike Bullock

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RV7Guy
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Thanks

Postby RV7Guy » Sun Nov 09, 2008 1:18 pm

I'm getting ready do the glass work on my friends SJ cowl on his 7. How to do the rings just wasn't computing. Thanks for the visuals. Now it is clear.

Thanks,

Darwin N. Barrie
Chandler AZ
Darwin N. Barrie
Chandler AZ
RV7 N717EE


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