Today's Message Index:
----------------------
1. 07:22 AM - New Cowling (Mike Chaney)
2. 10:27 AM - Re: New Cowling (Guy Buchanan)
3. 10:45 AM - Re: New Cowling (Lowell Fitt)
4. 01:19 PM - Re: New Cowling (Lynn Matteson)
5. 01:50 PM - Re: New Cowling (Guy Buchanan)
6. 01:50 PM - Re: New Cowling (Lynn Matteson)
7. 02:32 PM - Rotec TBI-40 injection (sleeved to 36mm) (infow)
8. 06:27 PM - Re: Rotec TBI-40 injection (sleeved to 36mm) (Lynn Matteson)
9. 08:24 PM - Re: Rotec TBI-40 injection (sleeved to 36mm) (infow)
Message 1
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A few years ago I fabricated a new cowling for my Kitfox IV around my Jabir
u 2200 installation.- After many hours of work the cowling looks pretty g
ood.- However, because I-needed to make some needed modifications to th
e cowling over time it is somewhat pieced together.-I would like to fabri
cate a new cowling using the old cowling if possible but-I don't want to
destroy-my current cowling in the process.- This would allow-me to co
ntinue to flying while I worked on the new cowling at a relaxed pace.-
=0A-=0AI'm looking for some possible resources to help me in the process.
- I can't remember if any of the workshops at Oshkosh addressed this issu
e or not.- My last attempt at this involved using the old cowling along w
ith foam and auto putty to get the desired shape.- I then layed fiberglas
s over this cowling to make a mold which I used to make my current cowling.
- I am no expert in this area so any semi-expert or expert advice would b
e greatly appreciated.=0A-=0AMike Chaney=0A1996 Kitfox IV, Jabiru 2200
Message 2
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On 3/18/2013 7:22 AM, Mike Chaney wrote:
> I'm looking for some possible resources to help me in the process. I
> can't remember if any of the workshops at Oshkosh addressed this issue
> or not. My last attempt at this involved using the old cowling along
> with foam and auto putty to get the desired shape. I then layed
> fiberglass over this cowling to make a mold which I used to make my
> current cowling. I am no expert in this area so any semi-expert or
> expert advice would be greatly appreciated.
I can't tell if you already did this, but if you like your current
cowling you use it as a male plug and build a female mold over it, from
which you can pull nice, non-piecemeal parts. You can even temporarily
add to your current cowling temporarily for the purposes of making the
mold, but of course it's much more difficult to subtract.
Here <http://www.cstsales.com/tutorials/fiberglass_mold.pdf>'s a great
description of how to make a mini-mold. A large part mainly differs in
how you support both the male plug and the female mold. For a Kitfox
cowl one problem is keeping the plug stable while you construct the
mold. If you can construct the mold while the cowl's installed this
might not be a problem. If not you will have to install some temporary
bulkheads and stringers. The problem is that fiberglass attachments for
your bulkheads shrink and change the shape of the plug so you want to
first bond a "pad" to the inside of the cowl using a small, distributed
amount of caulk or other soft adhesive. Once cured thoroughly you bond
the bulkheads or stringers to these pads. The internal structure should
provide just enough support to make a good plug. Don't forget to include
some way to support the plug off the ground to free up the plug's edges.
The second problem is that you want the mold to be longer, at each edge,
than the part, so you can trim the edges after you make the part. Again,
making the mold with the cowl on the aircraft may facilitate this since
you could fill all the joints and screw heads temporarily and make the
mold over them, overlapping the part line by a couple of inches. You
make the mold over the screws then come back and fill the screw indents
in the mold very carefully. (You have to make sure you can remove the
mold over the screw heads, though.) Another cool way to alleviate this
problem is to make the mold so that the final cowl is made in one piece,
as in the above mini-example. You then cut the resulting cowl in such a
way as to enable you to use piano hinge to connect the two pieces. This
results in a really cool, fastener-less design. (All RV and Lancair
cowls are done this way.) You still have the problem of the other edges
but this gets rid of the joint overlap problem. (You add shims between
the molds pieces to give you enough additional material for a saw kerf
and edge clean-up.)
As to the free edges you have to find a way to temporarily build up the
existing cowl plug to extend the edges. I've recently done this by using
2" styrofoam insulation board from Home Depot with the facings stripped
off. I bonded three together to make a 6" thick "bulkhead", then rough
shaped them to the inside dimension of the cowl at the free edge, then
cleaned and taped the inside of the cowl edge with aluminum tape, then
bonded the bulkhead to the tape, then filled and faired the exterior of
the styrofoam using art plaster to "mimic" an extension of the cowl. You
then seal the plaster and apply release as you do for the part. You may
be able to use the styrofoam as your stabilizing bulkheads required above.
When you make the mold you do so as in the example, with a part line
"dam" or wall, but made from something really flat. Melamine board is
good for this, since nearly all plywood is warped. (Melamine is particle
board or MDF with a nice plastic coating on it. It's used for shelves
and other kitchen stuff.) Unlike the example above the first layer of
glass should be chopped strand mat. If you use anything woven it will
print through the gelcoat and ruin the surface of the mold. The reason
they didn't do it on the mini-part is because there's no chopped strand
mat that will turn the corners they require on such a small part. (Which
is to say you'll have equal problems if you try to get it to turn hard
corners on your part.)
You will have to make your mold much thicker than the mini mold, above.
(Plan for at least 1/8" total thickness, much thicker than your cowl.)
and you'll have to add bulkheads to stabilize it, taking great care to
pad the bulkheads so any shrinkage in the attachments doesn't "pull" the
mold and distort it.
That's it in short form. There's much more to it in the details, of
course, Unfortunately you can see your existing cowling will be laid-up
for a while, (pun intended,) since you have to use it as a plug, but
once the mold is made you can revert your cowling and get flying again
while you make the new cowl. I don't have any more written resources but
will advise you to look to the model aviation community. They do this
type of fabrication a lot and there's a lot of chatter about it on the
Internet. And some of their aircraft are nearly as large as a Kitfox! A
quick Google "making fiberglass molds" revealed a lot of good
information too, including some video tutorials.
Good luck!
Guy Buchanan
Ramona, CA
Kitfox IV-1200 / 912-S / Warp 3cs / 500 hrs. and grounded
Now a glider pilot, too.
Message 3
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Mike,
I think the trick is to use the original to make a master female mold,
then a copy just as you did on your first cowl. The challenge can be
made easier by using the proper release agents. I have found that
simply waxing the original or mold will sometimes result in damage to
either the original piece or the mold. Typically, I will use wax and
then spray a coat of PVA mold release -
http://www.tapplastics.com/product/fiberglass/mold_releases/tap_pva_mold_
release_liquid/67
You might find it locally. It is water based with an alcohol content
that makes it flow well over the waxed surface. I usually use an old
detail spray gun, but the gun should be cleaned after each use. I have
also put it in a squeeze spray bottle (Windex). The tip needs to be
rinsed as the stuff will dry and clog everything if left too long. If
you will be using it periodically over several days, I would think
removing the spray assembly and putting it in a bottle of water to keep
it moist would eliminate that. The PVA film is easy to remove from the
resin surfaces after separating by simply rinsing or wiping the parts
with a damp cloth. Before other body work or paint the surface should
also be scuff sanded. Another trick from the Lancair book is to use a
lot of paper towles after the lay-up to absorb and remove excess resin
from the lay up. It is surprising how much resin can be removed for a
lighter cowl.
I would suspect your cowl might be out of service for less than a week
and should come from the female master mold blemish free. I have used
it on the surface of finished fabric to fabricate fairings and if
carefully applied it doesn't harm the painted surface.. Another trick I
learned when helping a guy with a Lancair to cover such things as Camloc
receptacle holes and other holes is the typical 3M clear shipping tape.
It is very thin and epoxy will not adhere to it. Small cut circles to
cover such holes will prevent the resin and cloth from penetrating
resulting in a separation nightmare and will leave a very slight
blemish that can be easily corrected with Micro. In my case, I used it
to "mask" around the fairing work area so stray drips can be lifted off
without damage.
Lowell
I am currently working on fiberglass on a project and this is all pretty
fresh. In fact, as I write this, I am about to run down to the local
Tap store for some resin and other materials. I forgot where you are
located - tap is pretty much a Northern California family operation with
some stores in Oregon and Washington but other suppliers will handle
PVA.
Lowell
From: Mike Chaney
Sent: Monday, March 18, 2013 7:22 AM
Subject: Kitfox-List: New Cowling
A few years ago I fabricated a new cowling for my Kitfox IV around my
Jabiru 2200 installation. After many hours of work the cowling looks
pretty good. However, because I needed to make some needed
modifications to the cowling over time it is somewhat pieced together. I
would like to fabricate a new cowling using the old cowling if possible
but I don't want to destroy my current cowling in the process. This
would allow me to continue to flying while I worked on the new cowling
at a relaxed pace.
I'm looking for some possible resources to help me in the process. I
can't remember if any of the workshops at Oshkosh addressed this issue
or not. My last attempt at this involved using the old cowling along
with foam and auto putty to get the desired shape. I then layed
fiberglass over this cowling to make a mold which I used to make my
current cowling. I am no expert in this area so any semi-expert or
expert advice would be greatly appreciated.
Mike Chaney
1996 Kitfox IV, Jabiru 2200
Message 4
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In addition to what Guy and Lowell have said, there is another way to
go...see if Pete at USJabiru still sells the Skyfox cowl made for the
Kitfox IV and the Jabiru engine. That is what I bought back in 2005
when I ordered my engine. There is still a bit of work to do to make
the cowl-to-windshield transition compatible, but for about $600
(2005 dollars) it's already shaped, and fits the engine like a glove.
The Top half overlaps the bottom with a "joggle" and the fit is
pretty good, but will take some cleaning up with a file or sandpaper.
The air inlets are properly sized for the 2200 engine, and there is
an opening for the oil cooler air. See picture of my cowl during
fitting.
If you still want to make your own, there is a tape that Spruce
sells..."Fiberglass 101"... which is pretty good for less than $30,
and which explains the use of parting agents, dealing with sharp
corners, etc.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062
Prince prop 64 x 30, P-tip
Electroair direct-fire ignition system
Rotec TBI-40 injection (sleeved to 36mm)
Status: flying with 1417 hrs... (since 3-27-2006)
On Mar 18, 2013, at 10:22 AM, Mike Chaney wrote:
> A few years ago I fabricated a new cowling for my Kitfox IV around
> my Jabiru 2200 installation. After many hours of work the cowling
> looks pretty good. However, because I needed to make some needed
> modifications to the cowling over time it is somewhat pieced
> together. I would like to fabricate a new cowling using the old
> cowling if possible but I don't want to destroy my current cowling
> in the process. This would allow me to continue to flying while I
> worked on the new cowling at a relaxed pace.
>
> I'm looking for some possible resources to help me in the process.
> I can't remember if any of the workshops at Oshkosh addressed this
> issue or not. My last attempt at this involved using the old
> cowling along with foam and auto putty to get the desired shape. I
> then layed fiberglass over this cowling to make a mold which I used
> to make my current cowling. I am no expert in this area so any
> semi-expert or expert advice would be greatly appreciated.
>
> Mike Chaney
> 1996 Kitfox IV, Jabiru 2200
> www.matronics.com/contribution _-
> ===========================================================
Message 5
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On 3/18/2013 10:44 AM, Lowell Fitt wrote:
> You might find it locally. It is water based with an alcohol content
> that makes it flow well over the waxed surface. I usually use an old
> detail spray gun, but the gun should be cleaned after each use. I
> have also put it in a squeeze spray bottle (Windex).
These things
<http://www.walmart.com/ip/Preval-Spray-Gun-Corporation-267-3-Piece-Preval-Paint-Spray-Gun-Kit/21284518?ci_src=14110944&ci_sku=21284518&sourceid=1500000000000003260430&adid=22222222227000000000&wl0=%7Bmatchtype%7D&wl1=%7Bnetwork%7D&wl2=%7Bifmobile:m%7D&wl3=21486607510&wl4=%7Baceid%7D&wl5=pla&veh=sem>
are great for spraying PVA. When I was a pro the fab companies used them
quite heavily.
Guy Buchanan
Ramona, CA
Kitfox IV-1200 / 912-S / Warp 3cs / 500 hrs. and grounded
Now a glider pilot, too.
Message 6
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In addition to what Guy and Lowell have said, there is another way to
go...see if Pete at USJabiru still sells the Skyfox cowl made for the
Kitfox IV and the Jabiru engine. That is what I bought back in 2005
when I ordered my engine. There is still a bit of work to do to make
the cowl-to-windshield transition compatible, but for about $600
(2005 dollars) it's already shaped, and fits the engine like a glove.
The Top half overlaps the bottom with a "joggle" and the fit is
pretty good, but will take some cleaning up with a file or sandpaper.
The air inlets are properly sized for the 2200 engine, and there is
an opening for the oil cooler air. See picture of my cowl during
fitting.
If you still want to make your own, there is a tape that Spruce
sells..."Fiberglass 101"... which is pretty good for less than $30,
and which explains the use of parting agents, dealing with sharp
corners, etc.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062
Prince prop 64 x 30, P-tip
Electroair direct-fire ignition system
Rotec TBI-40 injection (sleeved to 36mm)
Status: flying with 1417 hrs... (since 3-27-2006)
On Mar 18, 2013, at 10:22 AM, Mike Chaney wrote:
> A few years ago I fabricated a new cowling for my Kitfox IV around
> my Jabiru 2200 installation. After many hours of work the cowling
> looks pretty good. However, because I needed to make some needed
> modifications to the cowling over time it is somewhat pieced
> together. I would like to fabricate a new cowling using the old
> cowling if possible but I don't want to destroy my current cowling
> in the process. This would allow me to continue to flying while I
> worked on the new cowling at a relaxed pace.
>
> I'm looking for some possible resources to help me in the process.
> I can't remember if any of the workshops at Oshkosh addressed this
> issue or not. My last attempt at this involved using the old
> cowling along with foam and auto putty to get the desired shape. I
> then layed fiberglass over this cowling to make a mold which I used
> to make my current cowling. I am no expert in this area so any
> semi-expert or expert advice would be greatly appreciated.
>
> Mike Chaney
> 1996 Kitfox IV, Jabiru 2200
> www.matronics.com/contribution _-
> ===========================================================
Message 7
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| Subject: | Rotec TBI-40 injection (sleeved to 36mm) |
G'Day Lynn...
I have a question in regards to the Rotec TBI-40 injection! How has it worked
out? What do
you mean - sleeved to 36mm? Was the TBI-40 to big? I was thinking about the
TBI-40... but
Rotec recommended a TBI-32-2 instead!
Ron
:--)> Rotec TBI-40 injection (sleeved to 36mm)
Message 8
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| Subject: | Re: Rotec TBI-40 injection (sleeved to 36mm) |
Hi Ron-
Yes, it has worked out well for me. When I first looked at the TBI-40
at Oshkosh in 2009, Paul (from Rotec) told me that the -40 would
probably be a bit too much throat area for my 2200 cc Jabiru engine,
and that I might have to restrain the throttle opening by 1/4" or so.
This is because the TBI-40 was originally designed for their 2800 cc
engine, and therefore the throttle opening needed to be larger for
that size engine. I did this for a while, but later on, I made a
sleeve that is a push fit into the air inlet...before the slide
throttle. Because that area of the TBI is slightly tapered, it was
fairly simple to turn out a sleeve on my lathe that would push into
the air inlet, and could not be sucked further into the
airstream...works great, and I also have a sleeve that is 35 mm
inside diameter that I made at the same time, for testing purposes.
When I got the TBI, I got the round rear housing, to slide right into
where my Bing was, but in building various intake manifolds, I
decided to get the -3 rear housing, the one with 4 bolts, so I could
more easily adapt to the manifolds I was designing.
I noticed that Rotec was selling the 32 mm's for VW, etc. If you get
too large a carb/TBI, the air speed through the device will not allow
proper fuel atomization, thus the reason for making the smaller units.
Here is a shot of the sleeve in place, as viewed from the air inlet end:
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062
Prince prop 64 x 30, P-tip
Electroair direct-fire ignition system
Rotec TBI-40 injection (sleeved to 36mm)
Status: flying with 1417 hrs... (since 3-27-2006)
On Mar 18, 2013, at 5:32 PM, infow wrote:
>
> G'Day Lynn...
>
> I have a question in regards to the Rotec TBI-40 injection! How
> has it worked out? What do
> you mean - sleeved to 36mm? Was the TBI-40 to big? I was
> thinking about the TBI-40... but
> Rotec recommended a TBI-32-2 instead!
>
> Ron
>
> :--)> Rotec TBI-40 injection (sleeved to 36mm)
>
>
Message 9
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| Subject: | Re: Rotec TBI-40 injection (sleeved to 36mm) |
Hey Thanks Lynn!
:--)> Hi Ron-
:--)> Yes, it has worked out well for me. When I first looked at the TBI-40 at
Oshkosh in
:--)> 2009, Paul (from Rotec) told me that the -40 would probably be a bit too
much
:--)> throat area for my 2200 cc Jabiru engine, and that I might have to restrain
the
:--)> throttle opening by 1/4" or so. This is because the TBI-40 was originally
designed
:--)> for their 2800 cc engine, and therefore the throttle opening needed to be
larger
:--)> for that size engine. I did this for a while, but later on, I made a sleeve
that is
:--)> a push fit into the air inlet...before the slide throttle. Because that area
of the
:--)> TBI is slightly tapered, it was fairly simple to turn out a sleeve on my
lathe that
:--)> would push into the air inlet, and could not be sucked further into the
:--)> airstream...works great, and I also have a sleeve that is 35 mm inside diameter
:--)> that I made at the same time, for testing purposes. When I got the TBI, I
got the
:--)> round rear housing, to slide right into where my Bing was, but in building
various
:--)> intake manifolds, I decided to get the -3 rear housing, the one with 4 bolts,
so I
:--)> could more easily adapt to the manifolds I was designing.
:--)>
:--)> I noticed that Rotec was selling the 32 mm's for VW, etc. If you get too
large a
:--)> carb/TBI, the air speed through the device will not allow proper fuel atomization,
:--)> thus the reason for making the smaller units.
:--)>
:--)> Here is a shot of the sleeve in place, as viewed from the air inlet end:
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