Reinforcing engine mounting holes

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FrankFuss · 11-18-2009, 11:02 PM

Is it a good idea to reinforce the firewall around the engine mounting holes, like with CF dowels, so as not to crush the plywood, or am I just being anal, or both? :25:

66stang · 11-18-2009, 11:06 PM

Use a nice size washer!

jlb · 11-19-2009, 12:00 AM

Washers work fine if you're using nuts and bolts but I prefer using blind nuts (or T nuts as some call them) which eliminates the loose nuts and simplifies things somewhat.

sweetpea · 11-19-2009, 12:20 AM

I do this on all my aerobats.....probably overkill.

I use a holesaw and drill out some plywood. Then I put the blindnuts into that. I then glue them to the inside of the firewall. I then take a 1/8 flat piece of alum and cut it in 2 strips. 1 goes on the top and one goes on the bottom of the motor. This spreads the load across the motor box.

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classclown · 11-19-2009, 01:35 AM

	Quote: Originally Posted by 66stang
	Use a nice size washer!

+1 on the washers = LESS WORK!!!!

bodywerks · 11-19-2009, 01:39 AM

All you really need to do is not over-tighten the bolts. Many people crank the bolts down in an effort to keep them from coming loose, but crush the wood in the meantime. They only need to be torqued to 50 inch-pounds or so. then safety them with safety wire or simply put a bead of silicone around the head of the bolt(assuming you use blind nuts on the other end) to secure it to the surface.
What you want to do with the CF stuff is a good idea, but 1/8" hardwood dowel works better. If you're going to do the fender washer technique it is a good idea.

bodywerks · 11-19-2009, 01:42 AM

	Quote: Originally Posted by classclown
	+1 on the washers = LESS WORK!!!!

MORE WEIGHT!!!!!

classclown · 11-19-2009, 02:02 AM

Sure its more weight, if you use those grade eight nuts and bolts.

66stang · 11-19-2009, 02:12 AM

You could also use the nylon nuts, or thread locker.. But don't use thread locker on a nylon nut!!

Superrmario · 11-22-2009, 10:42 AM

I am doing the same and came to the forum to see if there was any answers.

88" WH Edge 540 with a DA 50 going onto it.

The firewall was in good shape, but the guy that i brought it from had a G62, so he put a wood block on the front as a stand off. I tried like hell to get the wood block off without damaging the firewall, but it cracked.

I replaced the firewall with aircraft quality 4 ply, plywood. Used 30 min epoxy to hold the sides and the firewall in the joiners, and the clamped it down. I took it one step further by drilling 1/16th holes in the side of the motorbox into the actual firewall, and epoxying 1/16th carbon fiber pins in. I have heard of a varity of hold downs, but I think I may go with the fender washer way. My only problem now is getting the fender washers to fit with the tristock in the way.

Any ideas?

sinergy · 11-23-2009, 09:52 AM

	Quote: Originally Posted by bodywerks
	MORE WEIGHT!!!!!

Where did you get those blind nuts?

Tired Old Man · 11-23-2009, 11:26 AM

Grind off the side of the fender washers to fit the tri stock. Requires a little more effort to hold them in the correct position as the nuts are tightened up but only for a moment.

Superrmario · 11-24-2009, 08:06 AM

	Quote: Originally Posted by Tired Old Man
	Grind off the side of the fender washers to fit the tri stock. Requires a little more effort to hold them in the correct position as the nuts are tightened up but only for a moment.

Thanks for the info. What it did was just the opposite as I didn't see this post. I sanded down the tristock to fit the washers, the
n applied thinned epoxy over the tristock to harden it to he corner.

I think it may hold up.

crazyjoe · 11-24-2009, 10:28 AM

	Quote: Originally Posted by sinergy
	Where did you get those blind nuts?

True Value, Lowes, Ace hardare, Home Depot

classclown · 11-24-2009, 11:14 AM

	Quote: Originally Posted by crazyjoe
	True Value, Lowes, Ace hardare, Home Depot

You forgot to add Uncle Bob's house of nuts.

11-18-2009, 11:02 PM	#1
FrankFuss Gettin' Lower! Join Date: Sep 2007 Location: Littleton, CO, USA Posts: 71	Reinforcing engine mounting holes Is it a good idea to reinforce the firewall around the engine mounting holes, like with CF dowels, so as not to crush the plywood, or am I just being anal, or both? :25:

11-18-2009, 11:06 PM	#2
66stang Fly it like you hate it! Join Date: Jan 2006 Location: Collinsville, IL Age: 44 Posts: 4,434 Awards Showcase Total Awards: 3	Re: Reinforcing engine mounting holes Use a nice size washer! __________________ *I call Craven my sugar daddy!*

11-19-2009, 12:00 AM	#3
jlb Gettin' Lower! Join Date: Nov 2007 Posts: 64	Re: Reinforcing engine mounting holes Washers work fine if you're using nuts and bolts but I prefer using blind nuts (or T nuts as some call them) which eliminates the loose nuts and simplifies things somewhat.

11-19-2009, 12:20 AM	#4
sweetpea If you can't HUCK it BLING IT! Join Date: Jan 2006 Location: Just Moved.......Hampton VA Age: 37 Posts: 9,269 Awards Showcase Total Awards: 2	Re: Reinforcing engine mounting holes I do this on all my aerobats.....probably overkill. I use a holesaw and drill out some plywood. Then I put the blindnuts into that. I then glue them to the inside of the firewall. I then take a 1/8 flat piece of alum and cut it in 2 strips. 1 goes on the top and one goes on the bottom of the motor. This spreads the load across the motor box. __________________ Offical Member of Team Caribou Lou "Some people spend an entire lifetime wondering if they made a difference in the world. But the U.S. ARMED FORCES don't have that problem." ...Ronald Reagan

11-19-2009, 01:39 AM	#6
bodywerks Bad-ass Super Contributer! Join Date: Jan 2006 Location: Tucson Age: 36 Posts: 5,229	Re: Reinforcing engine mounting holes All you really need to do is not over-tighten the bolts. Many people crank the bolts down in an effort to keep them from coming loose, but crush the wood in the meantime. They only need to be torqued to 50 inch-pounds or so. then safety them with safety wire or simply put a bead of silicone around the head of the bolt(assuming you use blind nuts on the other end) to secure it to the surface. What you want to do with the CF stuff is a good idea, but 1/8" hardwood dowel works better. If you're going to do the fender washer technique it is a good idea. __________________ Gmoney and Smarks are spooners

11-19-2009, 02:02 AM	#8
classclown Bad-ass Super Pooper Join Date: Mar 2006 Age: 44 Posts: 2,200	Re: Reinforcing engine mounting holes Sure its more weight, if you use those grade eight nuts and bolts.

11-19-2009, 02:12 AM	#9
66stang Fly it like you hate it! Join Date: Jan 2006 Location: Collinsville, IL Age: 44 Posts: 4,434 Awards Showcase Total Awards: 3	Re: Reinforcing engine mounting holes You could also use the nylon nuts, or thread locker.. But don't use thread locker on a nylon nut!! __________________ *I call Craven my sugar daddy!*

11-22-2009, 10:42 AM	#10
Superrmario Man Up!! Join Date: Feb 2009 Location: The beach, in NJ Age: 32 Posts: 781	Re: Reinforcing engine mounting holes I am doing the same and came to the forum to see if there was any answers. 88" WH Edge 540 with a DA 50 going onto it. The firewall was in good shape, but the guy that i brought it from had a G62, so he put a wood block on the front as a stand off. I tried like hell to get the wood block off without damaging the firewall, but it cracked. I replaced the firewall with aircraft quality 4 ply, plywood. Used 30 min epoxy to hold the sides and the firewall in the joiners, and the clamped it down. I took it one step further by drilling 1/16th holes in the side of the motorbox into the actual firewall, and epoxying 1/16th carbon fiber pins in. I have heard of a varity of hold downs, but I think I may go with the fender washer way. My only problem now is getting the fender washers to fit with the tristock in the way. Any ideas? Last edited by Superrmario; 11-22-2009 at 11:05 AM.

11-23-2009, 11:26 AM	#12
Tired Old Man Bad-ass Super Contributer! Join Date: Jul 2006 Location: California Posts: 4,323	Re: Reinforcing engine mounting holes Grind off the side of the fender washers to fit the tri stock. Requires a little more effort to hold them in the correct position as the nuts are tightened up but only for a moment.

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