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Thread: <Archive Thread> Building the EX3 - Tips & Hints

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  1. #21
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    Jul 2015
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    Broken Arrow, OK
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    Default Re: Building the EX3 - Tips & Hints

    ENGINE COWL

    FINISH MANUAL, Page 4-21, Section 4-24. They have updated the manual and actually included several of my photos from here. They suggested a different way from marking the cut line in the manual here and it's actually simpler than my way but gets to the same results. So the manual method is fine but I do go ahead and add a layer of tape on the outboard........ forward side of the cowl before cutting. I use a dremel with cutting wheel, so this tape edge gives the dremel blade a good, straight guide to follow. I just put the thicker, green tape down with the edge over the line I marked with the compass.

    Here is a video of it. Note that it's my original way of marking the cut line. https://youtu.be/4BC6sgIavbQ

    The old manual and the video is for an EX2 so won't work either. On the EX3, you have to install the prop spinner bulkhead which mounts behind the prop before you can properly measure the cowl distance from it to the back of the spinner. That means the prop/spinner bulkhead has to be installed first. In the EX2, you don't have to install the prop since the spinner bulkhead can be simply placed in place to measure and then easily removed because it doesn't have to mount to the prop.

    HERE IS MY ORIGINAL METHOD OF MARKING THE CUT LINE

    So the problem or difference is that we don't have room to slide the cowl up forward enough to get the aft edge in forward of the boot cowl forward edge. Normally on the EX2, you can slide the cowl up over the front of the engine flywheel all you want which makes it easy to slide forward enough to simply mark the edge of the cowl to cut from the front edge of the boot cowl but with the EX3, the distance between the front of the cowl and the back of the spinner mount is only about .025 (not far enough to get in front of the boot cowl so you can mark the cowl cut line) .....which is right where it should be AFTER being cut to fit the boot cowl. So here is what I figured out to do to get it right.

    I have attached 3 pdf pages on the cowl where you can see hardware, etc. These aren’t in the manual anywhere at this time, so be sure to download and print.

    These EX3 cowls come with all the nutplates already installed and ready to go. The cowl is almost ready to fit and only requires a very small amount of trimming, so be careful not to cut too much.

    You will probably need some help to install it. First place several wraps of tape around the edge of the boot cowl (just aft of the "lip" that the cowl will go over) to protect the paint and a layer on the inside lip of the boot cowl as well where the cowl will fit over. Be sure and get that first tape over the boot cowl painted are (not the lip area) nice and flush with the front at the lip.

    NOTE: YOU WILL PROBABLY NEED TO ENLARGE THE COWL UP BY THE PROP BULKHEAD TO ALLOW THE SCREWS/NUTS OF THE BULKHEAD (where the prop mounts to the prop bulkhead) TO NOT HIT THE COWL. JUST SEE HOW FAR THE BIG OPENINGS ON THE TOP AND BOTTOM HALF NEED TO BE ENLARGED TO LET THOSE BOLT/NUTS TO NOT HIT IT. You'll need to check it and then remove and trim it before proceeding so you can slide the cowl completely forward up against the bulkhead when measuring for the cut as explained below. DO THIS BEFORE INSTALLING THE COWL AND MARKING THE CUT LINE BECAUSE IT WILL LET YOU SLIDE THE COWL UP CLOSER TO THE SPINNER BULKHEAD.

    Put a mark on the tape on the boot cowl where the center of the boot cowl is (the overlap point) then find the center of the cowl my tape measure and place a mark there on the edge next to the boot cowl center mark. When installing, be sure and you match the 2 center marks together so the cowl is centered on the boot cowl.



    P1060486.jpg
    (Black line on masking tape is the center of boot cowl and the small, silver mark on the black bowl is the center of the cowl)


    Start by laying the top cowl piece up on top of the engine and then work the bottom piece up into position. I used some 5 lb weights on top of the cowl piece right where it meets the back, center baffle/rubber seal area to keep it down. It will overlap the boot cowl just a small amount. You will notice it's a very tight fit at that point where the baffle just above the oil cooler is and weights help hold the rubber over until it kindof forms to cowl and you get the bottom half on. If you left the baffle seals off like recommended earlier, then you won't have to use the weights.



    P1060490.jpg
    (Weights on top of the cowl over the oil cooler area of the baffles. Not needed if seals left off for now)


    The bottom half will have to go as far forward as possible behind the prop spinner bulkhead so you can work the front baffles under it and then slide it back. Keep working it, it will be stiff but it will fit.

    With the top of the cowl centered on the boot cowl center mark, go to the front and be sure to get the cowl centered around the prop spinner bulkhead. You can look/measure the distance between the bulkhead and the edge of the cowl and also the screw that joins the 2 sections together and be sure they are about the same. Here is the left side, just make the right side the same amount of distance.


    P1060488.jpg
    (Left side of cowl looking from the front. Make the right side the same distances)


    Then go to the side and look at the distance between the cowl and the spinner bulkhead and be sure it's equal distance on the top and the bottom. Be sure it's pushed as far up towards the boot cowl as possible.



    P1060487.jpg


    When it all looks good, I pull the cowl back away from the boot cowl pretty much as far as I can until it touches the back of the prop spinner bulkhead and check to be sure it's still centered on the bulkhead by looking at those screws on either side again and make them even.

    The EX2 had alot of excess material and we made 2 cuts....the 1st to get it close and the 2nd to get it a perfect match. On the EX3's, the cowl is cut very close to being perfect so there is no room for error. We will only measure it and cut it once, so it has to be right this first time.

    With the cowl touching the spinner bulkhead probably on both of the sides and being sure you still have the cowl centered on the top where it meets the boot cowl and at the front around the prop spinner bulkhead, then:

    take another piece of 1" masking tape and align the aft side of the tape with the aft side of the 1" tape we wrapped around the boot cowl (the top part just before the lip). Remember, the forward edge of this tape is right on the edge of the boot cowl lip or right where we want the finished cowl to meet up with. BUT..........remember, our cowl is now pushed forward towards the prop by about 1/4". The aft side of this tape is touching the aft side of the boot cowl tape but the forward edge is overlapping onto the TOP of the cowl. So this forward edge is now the same line around the cowl as the boot cowl lip edge is.

    So then we are going to take some 1/4" fine line tape and run it around the cowl keeping the aft edge of it perfectly aligned on the forward edge of the 1" tape we just put down. This will now give us where we will cut the cowl on the forward side of this 1/4" fine line tape and it should give us a perfect fit up to the boot cowl.

    Before we do this, take some regular masking tape (like the thick, green tape) and run it up perfectly flush with the forward side of the1/4" tape where we will cut and then remove the 1/4" fine line tape and the 1" tape it was butted next too. The aft side of this tape is the area we will cut and remove. By cutting 1/4" off then when we slide the cowl back it should butt perfectly with the boot cowl lip.


    P1070122.jpg
    (Here you can see all the tapes installed. There is the 1" tape totally on the boot cowl that is aligned with the front edge of the lip; then a 1" tape on top of this tape that is aligned with the aft side of the bottom tape and going over onto the top of the cowl; then the 1/4" tape forward of the front edge of this 2nd 1" tape)


    P1070121.jpg
    (Here you can see the 3 layers of tapes and we will cut forward of the RED 1/4" tape here. NOTE that in this diagram and the way we do this is with the cowl pushed forward until it equally touches the back of the spinner bulkhead).

    You could also just use the compass set to 1” and mark the cowl with the pencil with the sharp end following the aft side of the boot cowl tape but I was afraid of scratching the paint and I could not see the pencil line on the black carbon fiber of the cowl very well, so I just used the tape.

    I like using the Dremel tool cutoff wheel and just pull the cowl further back away from boot cowl as far as possible and then I slide a piece of aluminum between the cowl and engine/boot cowl before cutting.....or you can remove it and cut it. I take a few Popsicle sticks and put under the cowl to hold it out away from the boot cowl as well. If you are uncomfortable using your Dremel tool like this, you may just remove the cowl and cut it on the bench.

    Also will have to cut out the cowl at the bottom around the gasolator. Cut enough out so that you can get your fuel strainer cup up into the gasolator to pull fuel samples later.


    P1060492.jpg

    To get it to fit completely under the gasolator without bending it, you will have to cut it more, all the way down to get it to fit.

    After making the cut on the cowl, slide it back up so that it fits in the top, center where your center marks are on the boot cowl and cowl and put masking tape to hold it in place. Go around both sides pushing/pulling the cowl until it is up flush against the boot cowl and putting enough masking tape to hold it as you go. Mark any place that may need additional sanding or filing if any places are "humped" towards the boot cowl. After removing the cowl for paint, I will take some a long file or sanding block and go around the cut edge to smooth it. If you mess up and cut into the cowl, just fill it with some of your body filler and sand it down.

    After it's all tapes up, use cowl #2 figure attached here and make the measurements on the cowl. Start with making the hole on the side that connects the upper and lower half at the boot cowl. It should be .50" from the boot cowl side and .50" up from the cowl joint.


    P1060495.jpg

    From that mark, measure up 5.3" UP from that mark towards the center. You should get a perfectly equal 4 segments ending at the dead center at the top. If not, move the top one over enough to have it centered on both cowls (boot cowl and cowl). Do the same for both side. This will leave you will 9 places, including the 2 joint marks on either side. Then remove 1 cleco at a time and drill with a #30 through each hole and re-cleco.

    After removing the cowl, I'll drill the cowl and center hole in the boot cowl lip with a #19 bit and then countersink it enough to make the dimpled washers NAS1169C6L fit flush and then install the nutplates MS21059L06 with MS20426A3-4 rivets into the boot cowl. DONE!
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    Last edited by Daveembry; 03-31-2022 at 12:27 PM.
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

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