| Author |
Message |
    
Kevin Dennes
New member
Username: Kdennes
Post Number: 53
Registered: 01-2001
| | Posted on Thursday, February 06, 2003 - 12:51 am: | |
Michael.
I have looked at my shipping list from EAC and it does not state the thickness of the firewall that was supplied but I am inclined to think that the .035" is probably close to the mark. That is just less than 1/32" and I don't think I would like anything less than that, considering the big "grunter" up in front and the amount of fuel being delivered there.
My firewall is installed and therefore I am unable to mic the thickness of it now.
I find it an amazing thing that anyone would ever consider using aluminum as a firewall for such an aircraft as an Express. This is not an aircraft with a little 518 Rotax or the like up there in front.
Regards.
Kevin (from Downunder) |
Jeff Dingbaum
New member
Username: Aviators
Post Number: 8
Registered: 12-2000
| | Posted on Thursday, February 06, 2003 - 09:36 am: | |
I just looked at my early 1990s kit and it is .032
6061-T6 aluminum. yuck. Not only is it aluminum,
but it isn't even alcladed. Not what I want in
my engine compartment. I will probably be going
with the .035 stainless steel.
Jeff |
Allyn Roe
Unregistered guest
| | Posted on Thursday, February 06, 2003 - 09:50 am: | |
Express Aircraft sells CNC cut stainless steel firewalls along with the firewall protective ceramic blanket. For more information call us at (360) 352-0560
Allyn Roe
Express Aircraft Company
|
Gary Markwardt
Unregistered guest
| | Posted on Thursday, February 06, 2003 - 11:10 am: | |
J. Michael: Here is the firewall spacer layout used for my engine (Continental IO-550). Fibrefrax blanket was added with cutouts to clear the spacers.  |
Bill Copeland
Unregistered guest
| | Posted on Thursday, February 06, 2003 - 04:47 pm: | |
It seems to me that the use of G-10 to back up mounting firewall elements is overkill. Besides being hard to use (cut and shape)it is rather heavy for the relatively low mass elements to be mounted. As I recall our heaviest part mounted on the firewall (besides the engine of course) is the auxilliary fuel pump. I assume those using G-10 are not bonding it to the fiberglass firewall and tapping it for mounting screws and bolts, rather than bolting through the part, the stainless or Alum firewall, through the stand - off which preserves the fibre frax thickness, through the fiberglass firewall and into a nut plate attached to the aft side of the fiberglass firewall (essential).
Our solution for the "standoff's" is simple, relatively light and a good use of surplus Q-cell.
Find a 4 to 6 inch piece of 1.5 inch dia PVC pipe.
When you have left over Q-cell - stick it in the pipe. Pack it down. Of course you can simply mix some Q-cell and fill the pipe all at once.
Once the Q-cell has cured all you have to do is push the hardened Q-cell out of the pipe (hint: strike the outside of the pipe sharply in several places), slice off an appropriatly thick "washer", drill a pilot hole in the center and there you have it.
Ours now have over 250 hours on them and they're doing just fine. |
J Michael Johnson
Unregistered guest
| | Posted on Thursday, February 06, 2003 - 05:32 pm: | |
Kevin, Jeff, Allyn, and Gary,
Thanks for the details and opinions. I agree with the unanimous decision that stainless is far superior to aluminum in heat resistance and strength, and, therefore, I plan to use stainless. I am left with the following decision considerations. Is the thin and lighter stainless a better choice because it is plenty strong (compared to the thicker aluminum)and will provide a high temperature barrier and weigh only eight pounds? Or is the .035" stainless a better choice because it is so much stronger than even the thinner stainless and will add much structural strength to the firewall, although it weighs 16 pounds? And, Jeff, here is the price breakdown: .018" approximately $73 plus shipping (Aircraft Spruce) cut in a 4'x 3' sheet;
.035" approximately $65 plus shipping (again Aircraft Spruce and a 4'x 3' sheet); or
EAC -unknown thickness and weight (I'll find out tomorrow) $125 plus shipping but "cut-to-shape".
I'm leaning toward EAC (1) to support Larry & Co. (2) Probably theirs is best combination of strength and weight, and (3) "cut-to-shape" would be a lot easier than finding a way to cut stainless accurately. Am I thinking right? Are there other considerations that haven't been addressed? Thanks again for the inputs! |
J Michael Johnson
Unregistered guest
| | Posted on Thursday, February 06, 2003 - 05:42 pm: | |
Bill, Great idea for the spacers! I already have the PVC pipe and what a weight savings over metal or milled fiber spacers. Thanks, and I hope to see you soon if everything comes together. |
Gary Markwardt
Unregistered guest
| | Posted on Thursday, February 06, 2003 - 06:15 pm: | |
J. Michael & Bill C: Bill has a great idea re: Q-cell spacers. However, having suffered thru a collapsed nose gear issue, G-10 is definitely not overkill on the engine mount spacers in my opinion (four corners & bottom center). Everywhere else, take the weight save. |
wayne
Unregistered guest
| | Posted on Sunday, February 09, 2003 - 05:59 am: | |
I used the KISS principle, spacers made from squares of 1/4" plywood.
Get extra SS .025 for heat shields behind the exhaust, bottom of the fuse. 7"x14". I put a layer of fiberfax under mine. cut it 1/4" smaller than the SS, put a bead of high temp RTV around the edges to glue the mess on along with a few screws. The front edge is joggled to mate with the cowl lip.
I have now added short turn downs to my exhaust pipe ends to shoot it away from the fuse bottom. This has helped the noise and vibration along with keeping the belly cleaner. |
Bill Copeland
Unregistered guest
| | Posted on Sunday, February 09, 2003 - 08:18 am: | |
Gary: You are absolutely correct about retaining G-10 for the engine mount standoffs. A p.s. to my previous post re: Q-cell standoffs, my Bro reminded me that we added a bit of milled fiber to the Q-cell when we made ours.
Wayne: We installed stainless steel plates on the bottom of our fuse behind the exhaust exits also. Worked only marginally. Our final solution was to weld a 6-8 in addition to each tail pipe, angled down about 10 - 15 degrees. Now no exhaust on the bottom at all and it does help the noise.
|
Douglas Hoff
New member
Username: Dhoff
Post Number: 17
Registered: 05-2003
| | Posted on Sunday, October 31, 2004 - 11:02 am: | |
My firewall is starting to make me nerveous. It seems to have a "buckle" above the mounts for the nose gear, plus it is doing the same thing around two of the engine mounts. This started about a year ago but is definately getting worse. I called the factory a year ago when it started and they said not to worry, that they do this. However I'm starting to worry and would like to know if anyone else has had simialr problems and what they did about it. Any other suggestions?
Thanks,
doug Hoff
|
Allyn Roe
Unregistered guest
| | Posted on Sunday, October 31, 2004 - 12:36 pm: | |
Doug,
There is a layer of insulation between your stainless firewall cover and your actual fiberglass firewall. This can leave a voided area for the stainless to "buckle". To be safe, I would do a good inspection from the inside on your fiberglass firewall. |
ali moghaddas
New member
Username: Amoghadd
Post Number: 10
Registered: 09-2003
| | Posted on Monday, November 01, 2004 - 10:19 am: | |
If you are using stainless(Alpha= ~9.6 micro in/ in/ deg), the thermal expansion for 130 deg delta t(200 F- 70 F), for a 48" wide panel is 60 mils.
That means, one should have at least 1/16" gap between the panel and the fiberglass wall to eliminate buckling of the panel.
The gap should get RTV ed to eliminate leakage and added insulation.
Ali |
wayne
Unregistered guest
| | Posted on Monday, November 01, 2004 - 05:47 pm: | |
that's all well and good and may be why it is buckeling as it gets hot. But you DONT want it sliding around, as the mount bolts should be tight to the FW. |
Ted Gaston
Unregistered guest
| | Posted on Tuesday, November 02, 2004 - 08:13 am: | |
"I called the factory a year ago when it started and they said not to worry, that they do this."
Doug, as you well know, I worked at "The Factory" for over 4 years and never saw what could be described as "Buckled" stainless at the engine mount attachment points.
You need to carefully inspect the inside structure to ensure that the engine mount gussets are intact. Also, take the weight off of the gear and check the engine mount bolt torques. The way this engine mount attaches to the firewall does not result in insulation between the mount pad and the solid G10 material.
If you could take some pictures it might be helpful.
Ted |
Douglas Hoff
New member
Username: Dhoff
Post Number: 18
Registered: 05-2003
| | Posted on Wednesday, November 03, 2004 - 07:52 am: | |
Hi Allyn & Ted-
I sure appreciate your reply; it's really nice to hear from you! I'm sure that there are many others like me that have been wondering how you're doing and hoping the best for you.Thanks also to Wayne and Ali for their reply!
Do you know if the firewall was strengthened after my plane, which was the first with the io550? John Klenke thoguht that it was beefed up at some time. I don't have it home now but will try to get you some pictures ASAP. It's in the Spearfish FBO as I was getting bad readouts on my Visions system. The mechanic there looked as you suggested Allyn and said that it appears that the washers are trying to pull through the firewall, so in the least I'm going to need some suggestions as to how to remedy that.
Thanks again, and my best to everyone.
doug |
Roger Spencer
New member
Username: Roger
Post Number: 11
Registered: 05-2001
| | Posted on Tuesday, February 08, 2005 - 07:34 pm: | |
Doug, Have you solved your firewall/mount problem?
I'm about ready to start on my firewall forward installation. I've found nothing on glassing the forward side of the fiberglass firewall to the fuselage sides. When bonding the upper and lower fuselage together it only requires 2 layers of bid to bond the firewall to the fuselage. This joint takes engine mount loads into the airframe not handled by the gussets and center support and must withstand the vibration as well. I can't imagine that this is not glassed prior to installing the insulator and metal firewall. How has everyone handled this? I was thinking 4 layers of glass.
Once the insulation is placed on the firewall and the metal installed what has everyone used around the perimeter of the metal firewall to seal it? |
wayne
Unregistered guest
| | Posted on Wednesday, February 09, 2005 - 05:10 am: | |
I used 4 layers in front. sealled the SS with red high temp RTV after installing the mount for the last time. |
Doug
Unregistered guest
| | Posted on Wednesday, February 09, 2005 - 07:39 am: | |
Hi Roger-
I sent some pictures to John & Bill at Express and am waiting for a reply. If they decide it's airworthy I'll probably fly it to Gower, where Bill is, for a better look. If you'd like the pictures and my correspondence send me your email address and I'll get you that information. Larry (Express) did the firewall work on my plane so I can't tell you how many layers it had, but if I were you I'd go with 4. To me the nosewheel is poorly designed and puts too much stress on the firewall when landing.
Best of luck with your project, doug |
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