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grs-pms(at)comcast.net
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 Posted: Sat Jul 01, 2006 2:39 pm Post subject: 601HD cowl |
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I'm starting to fit the cowl to my Stratus-powered 601HD. My firewall-forward kit, including the cowl, was purchased in early 2000. My builder's handbook calls for 20mm clearance between the lip of the cowl and the (extended) surface of the front face of the prop extension. Is this enough for easy removal of the upper half of the cowl? It seems a bit tight to me.
How about the number of cowl fasteners? My builder's manual calls for 4 Dzus fasteners per side. That seems skimpy to me, particularly with them bearing in fiberglass. How does the cowl retention system hold up after a couple hundred hours of flight? Should I reinforce the fiberglass at the fastener locations? Would Camlocks be better than Dzus fasteners? ( I think I know the answer to this one already, but I'm asking anyway.)
How about trimming the lower cowl to clear the oil pan and the valve covers? Any tricks to make that easier?
I'll appreciate any advice on fitting and retaining the cowl, particularly from builders with a number of hours on their planes. Thanks in advance.
George
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larry(at)macsmachine.com
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| Posted: Sat Jul 01, 2006 3:55 pm Post subject: 601HD cowl |
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George,
20mm is close, but the front pins for the cowl will be within 3/8-inch
of the rear edge of the prop if you use a Warp Drive. For this, my
upper cowl is still easy to remove and
replace. The number of cowl fasteners is just right, and then of
course, you've got several over the top too. I prefer Dzus to the
Camlocks. Simpler installation. After 85 hours, my cowl is still in
great shape. No reinforcements needed if you've a good fit.
I added aluminum side covers to get clearance for the exhaust and they
are just enough to do the job. The only trick to getting the engine
clearance for the oil pan is to make a deeper cowl or raise the engine.
My engine mount is 1-inch higher to clear the pan and tilted down by the
1/4-inch thickness of a spacer at the Stratus upper mounts as well as
being able to align the spinner with the upper cowl surface.
Invariably, you'll consider cutting away more lower cowl than you'll be
comfortable with, so I'd recommend you make the cowl pan deeper between
the exhaust side covers.
Unfortunately, I'm painting and the plane is apart for the process, but
I do have a page on the website on the cowl which shows the modifications.
Larry McFarland - 601HDS at www.macsmachine.com
George Swinford wrote:
| Quote: | I'm starting to fit the cowl to my Stratus-powered 601HD. My
firewall-forward kit, including the cowl, was purchased in early
2000. My builder's handbook calls for 20mm clearance between the lip
of the cowl and the (extended) surface of the front face of the prop
extension. Is this enough for easy removal of the upper half of the
cowl? It seems a bit tight to me.
How about the number of cowl fasteners? My builder's manual calls for
4 Dzus fasteners per side. That seems skimpy to me, particularly with
them bearing in fiberglass. How does the cowl retention system hold
up after a couple hundred hours of flight? Should I reinforce the
fiberglass at the fastener locations? Would Camlocks be better than
Dzus fasteners? ( I think I know the answer to this one already, but
I'm asking anyway.)
How about trimming the lower cowl to clear the oil pan and the valve
covers? Any tricks to make that easier?
I'll appreciate any advice on fitting and retaining the cowl,
particularly from builders with a number of hours on their planes.
Thanks in advance.
George
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bryanmmartin
Joined: 10 Jan 2006
Posts: 1018
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| Posted: Sat Jul 01, 2006 4:13 pm Post subject: 601HD cowl |
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The higher air pressure inside the cowl holds it out against the fuselage skin around the firewall so eight dzus fasteners hold it in place pretty well. My lower cowl slides in between the L angles riveted to the firewall and the fuselage skin and are held in place by four dzus fasteners. The upper cowl is held in place by the cowl pins that protrude from the lower cowl at he nose and four dzus fasteners, two through the side skins and two into the lower cowl. The fasteners I received from ZAC weren't long enough to go through two layers of fiberglass so I cut out a small piece of the lower cowl on both sides where the fasteners go and riveted and glassed in two strips of .025 aluminum to attach the dzus springs to.
Getting the lower cowl to fit is a major bit of work. The cowl was actually designed to fit the rotax so you have to cut away a bit chunk of the lower cowl to fit the subaru. Installing the bumps over the valve covers wasn't too hard but it took a lot of work to fit around the exhaust and oil pan. I ended up just gradually trimming and test fitting and trimming until the lower cowl fit. When I was done, I taped some polyethylene foam to the bottom of the engine and exhaust and building up new fiberglass to fit around these protrusions. I threw away the oil pan scoop ZAC sent me, I just couldn't get it to fit right. I built my own scoop to cool the pan. I still have some "temporary" aluminum lips at the rear of the cowl to improve the flow of cooling air. I put them on nearly two years ago during phase I flight testing to get the oil temps down. Someday, I will replace them with fiberglass. I've been too busy to fix such cosmetic issues so far.
On Jul 1, 2006, at 6:37 PM, George Swinford wrote:
| Quote: | I'm starting to fit the cowl to my Stratus-powered 601HD. My firewall-forward kit, including the cowl, was purchased in early 2000. My builder's handbook calls for 20mm clearance between the lip of the cowl and the (extended) surface of the front face of the prop extension. Is this enough for easy removal of the upper half of the cowl? It seems a bit tight to me.
How about the number of cowl fasteners? My builder's manual calls for 4 Dzus fasteners per side. That seems skimpy to me, particularly with them bearing in fiberglass. How does the cowl retention system hold up after a couple hundred hours of flight? Should I reinforce the fiberglass at the fastener locations? Would Camlocks be better than Dzus fasteners? ( I think I know the answer to this one already, but I'm asking anyway.)
How about trimming the lower cowl to clear the oil pan and the valve covers? Any tricks to make that easier?
I'll appreciate any advice on fitting and retaining the cowl, particularly from builders with a number of hours on their planes. Thanks in advance.
George
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--
Bryan Martin
N61BM, CH 601 XL, RAM Subaru 150 hours in the air.
do not archive.
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_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive. |
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grs-pms(at)comcast.net
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| Posted: Sun Jul 02, 2006 9:34 am Post subject: 601HD cowl |
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Larry and Bryan:
Thanks for your cowl tips. I think I'll open the clearance from 20 to 25mm or so and add a few more fastener locations.
Any additional comments and advice still welcomed.
George
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larry(at)macsmachine.com
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| Posted: Sun Jul 02, 2006 1:11 pm Post subject: 601HD cowl |
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George,
The Dzus fasteners are easy to install just as you see in the link
below. I've put my cowl on the exterior of the aluminum fuselage which
puts the springs
inside attached to the aluminum. I did a large dimpler for the dzus
fastener stud and if you decide to go with them, let me know and I'll
make one
up for you and send it no cost. The simplicity of dimpling to use A4s
for the springs is really easy once you use a template.
http://www.macsmachine.com/images/cowling/full/Dzusspring.gif
http://www.macsmachine.com/images/cowling/full/Dzusdimples.gif
http://www.macsmachine.com/images/cowling/full/Dzustools.gif
I believe the cowl comes off much easier because the number of studs are
held to a minimum. It's way stronger than it looks.
With more studs, you'll fight alignments in the installation and daily
access. With the number I used, the cowl comes off in about 30-seconds
and goes back on in about 45-seconds.
The exhaust clearance tubes were formed using a large rubber mallet on a
piece of aluminum over a heavy wall 2-inch steel tube that was smooth
on the outside. Any diameter from 1-1/2 to 3-inches would work. Put the
tube in a vise and lay the aluminum over the tube and start working it into
shape.
http://www.macsmachine.com/images/cowling/full/cowlfairingsinside.gif
The bumpouts don't need to be anywhere near as large as the ones
provided and you can do a layup of a smaller fiberglass bumpout using
the one
sent with the cowl, adding your own flange. I've got a 1/4-inch
clearance on the nearest side owing to engine offset angle and the
leading cylinder.
http://www.macsmachine.com/images/cowling/full/cowlcheekinstall.gif
If you need any other specific details, you only have to ask.
Larry McFarland
George Swinford wrote:
| Quote: | Larry and Bryan:
Thanks for your cowl tips. I think I'll open the clearance from 20 to
25mm or so and add a few more fastener locations.
Any additional comments and advice still welcomed.
George
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grs-pms(at)comcast.net
Guest
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| Posted: Sun Jul 02, 2006 2:22 pm Post subject: 601HD cowl |
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Larry, the Dzus dimpler would be very much appreciated.
I've been looking at the oil pan "bump" that Zenith sent. The flange
doesn't much match the contour of the lower cowl, does it? They could do
better, if they gave a damn. I can see that I'm going to have to learn
fiberglass work, like it or not, and I don't.
---
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larry(at)macsmachine.com
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| Posted: Sun Jul 02, 2006 4:32 pm Post subject: 601HD cowl |
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George,
Fiberglassing isn't so difficult to learn, but do wear a 3M
organic/charcoal respirator when you work with the resin.
The respirator will keep you safe as well as eliminate your having to
smell the stuff in process. Nowdays,
I get deathly ill if I don't have the respirator on with the resin
container lid off. Do wear latex gloves.
Acetone will cut the stuff better than anything. You need more guidance
on doing fiberglass, I can summarize it
for you, or you can read up and get there off the Internet. If so, let
me know when you get there.
Larry McFarland
George Swinford wrote:
[quote]
Larry, the Dzus dimpler would be very much appreciated.
I've been looking at the oil pan "bump" that Zenith sent. The flange
doesn't much match the contour of the lower cowl, does it? They could do
better, if they gave a damn. I can see that I'm going to have to learn
fiberglass work, like it or not, and I don't.
---
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