I am about to start working on the lower cowl. I have a whirlwind prop and put the 2” spacer on the prop flange. Does anyone have some pictures of your install and how you trimmed the cowl.
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I am about to start working on the lower cowl. I have a whirlwind prop and put the 2” spacer on the prop flange. Does anyone have some pictures of your install and how you trimmed the cowl.
My story is here. You may find it useful.
Thanks Tom, I will go look as soon as I finish this.
That looks like great work. I think I will have similar problem with distortion of boot cowl, and now I have an answer for solving that if it happens.
Very helpful. Thanks. Is that a Whirlwing prop?
Steve
I’m at that stage right now. I’ll take some photos but all I did was put the extension on, centralise the cowls using clecos to hold the cowls tight and then traced around the perimeter of the extension. That gives me decent clearance all round to account for engine movement under load.
David, if you have any photos, I would love to see them. I am going to go investigate my firewall/boot cowl first (going to get construction manual and see when it says to install the nutplates. I hope to put in the spinner plate and get the cowls taped into place and marked.
There are “scribe lines” on the upper cowl and possible the lower cowl too. I only looked briefly before calling it a night. Am I supposed to trim the lines where the upper/lower cowl come together before starting this process? Also, it looks like the cuts (notching) on the front of the lower cowl have been done already. The edges are rough, but I am not sure if I need to remove more material.
If I take a picture in my iPad, can I upload it directly, or does the file size need to be reduced? I am going to try to post picture if the front of lower cowl.
Tom, are you flying yet? Last I heard about a year ago you were ready.
Yes, I've been flying for over a year.
To answer another question. Yes I have a whirlwind prop.
Unfortunately, I forgot to take any photos. My build is 150 miles away and I've just gotten home after a weekend of work on it. Sorry about that, but I can tell you what I did, if that helps ....Quote:
Originally Posted by Flyboy66
Do as you say you're about to do; i.e. fit the boot cowl first and trim that IAW what the manual advises. When fitting the cowls, I started with the lower cowl and followed the manual exactly as described. In setting the position, I had the engine in and held the lower cowl central by attaching to a circular disk I'd attached to the engine ring gear (I have a Lycoming 0-233 engine - don't know the setup if you're fitting a Rotax). That disk was also used in order to get the correct length for the prop extension fitting. After everything was centralised and the cowl trimmed, I then drilled 1/8" holes and cleco'd in place (I held the lower cowl in place with clamps up to this point).
When it came to fitting the upper cowl, I trimmed to the scribe lines along both sides, thinking all would be good. BIG mistake. What I should have done (and subsequently did after fixing my stuff up) was place the upper cowl in position, centralised with the lower cowl at the ring gear location, THEN trimmed the upper cowl. That would have prevented me from having to get handy with some fibreglass and put back what I'd trimmed off !. So strong advise, DON'T trim to the scribe lines unless you're sure they represent trim lines for your build. Once it's fitting up well, drill off and cleco in place. Then you can start drilling off for the camlocs.
This where I'm at right now and it's how I did it, so hope this helps. Others may have done things differently, but this worked out well (eventually) for me.
Yeah don’t trim to scribe lines or you will be way off. I am also at this point. Use masking tape to get a perfect fit. Lay a piece of tape up to the edge that you want to have the top cowl mate to on the lower cowl. Place top cowl on and then match edges of masking tape. Then you now have a trim line that will match. Depending on how off it is you may need to trim to get it within the thickness of the tape so you can see the edge. I have some photos on my build log that may explain better.
You don't have too much choice on where to trim the top edge of the lower cowl where the joggle is; you can't trim away too much of the joggle.
The cowls are trimmed. I have a little sanding to make the edges uniform, but was surprised how easy it was for a knucklehead like me. Yes, it took a number of install, measure, remove, trim...repeat. But it is done.
Thanks to this thread, I think I have a handle on this. Appreciate more tip's and pic's if you got them. :)
This pic is before trimming.
I have to do some minor epoxy work to smooth things out around the air inlets but I got it where it needs to be!
After re-reading the manual and other posts and pic's. I temporarily bolted my 2" extension and my spinner backplate.I temporarily glued two 1/4" pieces of wood spacers to the front of the lower cowlI leveled the plane for and aft and set the lower cowl to the aircraft and moved the cowling forward so the 1/4 spacers were just touching the backplate of the spinner.
When I placed the top cowl on it was apparent that A LOT of material would have to be removed. Well over an inch had to be removed from the FRONT of the top cowl. I removed the tabs as they were never going to fit no mater what I did. That made adjusting the top much easier. I'll add aluminum tabs when all is done. I did have to clean up the joggle transition in the front of the lower cowl. Also trimmed the inner opening risers on the lower cowl where the tabs used to be.
After all this, I just kept removing material mostly from the top cowl, FRONT ONLY and a little from the front sides just so it matched with the forward joggle line.
Now that top is in line with the spinner plate, I can now finalize the side and rear cuts.
Whew! :p