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2012 AK sled build

The 45'd corners weren't cutting it at the back so I'm going to build a CF tunnel extension to replace the last 3' of aluminum. I have a 156x2.5 camo extreme coming so my tunnel was going to end up 6" short anyway.
IMG_3309.jpg
 

Why did you keep the tunnel tapered? I am pretty sure I am going to cut my ears off and make a straight tunnel. Just want to know your reasoning is.

I highly considered a carbon fiber tunnel and maybe I still am. LOL. Do you already have a vacuum bag setup?
 
The square tunnel at the front near the bulkhead is a bad idea. On my previous chassis it dug into the sides of my legs really bad and became very irritating. I kept this one bent at 45's all the way back because I was worried about bending the 7075 at a 90* angle and cracking it, and I figured two bends are stronger than one. Two things I never thought of though are;

- if I leave the corners 45'd, I think the track would hit the corners in the back when fully compressed. The cat skid comes up pretty high in the tunnel.
- If I mount the bumper directly below the second bend, it makes for a fairly low bumper and I think it might look stupid.

One thing I thought of doing was just making a cut up each side of the tunnel behind rear suspension mount and tapering the rear section up a couple more inches.
 
Nikolai said:
The square tunnel at the front near the bulkhead is a bad idea. On my previous chassis it dug into the sides of my legs really bad and became very irritating. I kept this one bent at 45's all the way back because I was worried about bending the 7075 at a 90* angle and cracking it, and I figured two bends are stronger than one. Two things I never thought of though are;

- if I leave the corners 45'd, I think the track would hit the corners in the back when fully compressed. The cat skid comes up pretty high in the tunnel.
- If I mount the bumper directly below the second bend, it makes for a fairly low bumper and I think it might look stupid.

One thing I thought of doing was just making a cut up each side of the tunnel behind rear suspension mount and tapering the rear section up a couple more inches.
Click to expand...
;)!
 
I don't think I have the time to do CF so here's what I'm thinking now. This would solve any track clearance issues, still look good (I think), get my bumper higher off the ground, and allow to me to keep the 45'd corners. It would also save me a bunch of time and labor.

Red - new tunnel extension, matching 45'd corners to keep it looking the same. I'd still use .040 7075.
Blue - existing tunnel, shows the overlap of new extension
Green - obviously the tube work (and there will be more to tie everything together)

Thoughts? Good or bad.

tunnelcap-1.jpg
 
Nikolai said:
The square tunnel at the front near the bulkhead is a bad idea. On my previous chassis it dug into the sides of my legs really bad and became very irritating. I kept this one bent at 45's all the way back because I was worried about bending the 7075 at a 90* angle and cracking it, and I figured two bends are stronger than one. Two things I never thought of though are;

- if I leave the corners 45'd, I think the track would hit the corners in the back when fully compressed. The cat skid comes up pretty high in the tunnel.
- If I mount the bumper directly below the second bend, it makes for a fairly low bumper and I think it might look stupid.

One thing I thought of doing was just making a cut up each side of the tunnel behind rear suspension mount and tapering the rear section up a couple more inches.
Click to expand...

I assume that is because your gas tank was so narrow. I am thinking about running a poo tank that is 15.5 wide, so maybe I will be ok with somethng more straight. I wanna get the weight of the gas lower. Hrmm.
 
Nikolai:

The 153/156 will clear your tunnel if you use your current exhaust setup, but if you go to some kind of tunnel dump, as you know, there isn't much space above the track behind the stock muffler cutout....your drop bracket setup might have an inch or so with a fully compressed rear suspension shock.

Your tipped tail setup should work fine, but what are you thinking to join the sections together? Do you cut slots in your tunnel so it can be bent up to match the angle of the tip up? Basically something to tie the blue and red sections together on the flat part of the tunnel. The vertical sides are easy to mate just like any other extension. Not sure if you need many/any rivets on the 45'd sections.

I considered the tip up for a while, as I was planning an undertunnel that dumped out the back of the tunnel extension, above the snow flap. The plan was to use the Yoshi approximately where the stock unit cut out is and then a 1" x 4" oval tail pipe all the way out the back. Keeps the exhaust heat (and ice build up) under control The 45'd sections pretty much make this a CF/Aluminum debate, neither being easy.

Now I am considering a side exhaust discharge roughly above and slightly behind the air frames. Same oval, only much smaller/shorter, and as usual, its still going to be tight fit. Pretty complicated piece of tail pipe me thinks.

I think the tip up will look very cool BTW!

OTM
 
I like the look when the tipped part of the tunnel tapers from two 45 degrees to one 90 degree, like the Diamond S tunnel. You could make the rear section of an other type of aluminum so it will be easier to bend. The non tipped part of your tunnel is the part taking all the forces from suspension and rider weight. The rear tipped part is more of a fender and will only need to be so strong that you can lift the sled in the rear bumper.
 
Why not just cut the back off and change to tubular for the rest of it? Use coolers (double pass) on the back for enclosing the top of the tunnel.
 
I like the look when the tipped part of the tunnel tapers from two 45 degrees to one 90 degree, like the Diamond S tunnel. You could make the rear section of an other type of aluminum so it will be easier to bend. The non tipped part of your tunnel is the part taking all the forces from suspension and rider weight. The rear tipped part is more of a fender and will only need to be so strong that you can lift the sled in the rear bumper.
 
I believe he isn't going from 45's to a 90 because he doesn't want to bend the material that muchad it's 7075. I dropped off the aluminum today so hopefully have it back Wednesday and he can make some progress this weekend. He better hurry because we still need to slap a turbo on this thing.
 
Wow this is quite the change going from a short track N/A guy to a long track turbo guy. There must be some bad influences around you bringing you to the dark side.
 
hugger70mtnmax said:
Wow this is quite the change going from a short track N/A guy to a long track turbo guy. There must be some bad influences around you bringing you to the dark side.
Click to expand...

He doesn't have a 174" yet...
 
I'm still dealing with the reality of selling the short track. My 156 should be here next week, then it will really set in. On another note, my tunnel extension was bent up today so this should be a productive weekend.
 
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