Full boat tail on a Matrix

[Weather Spotter]

Jim, you did not make me feel bad. I want your results with my build time line and skills, aka short and less exacting. It was my choice but I wish I got your result with my work

I just might have to try the shelf idea.

34 degrees is cold? I could paint at that temp drop 15 degrees and that was my shop. fiberglass took 2-3 hours to stop dripping and 12 or so to full cure.


I had a freeway test run today. It is just fine at 70 MPH. I found that I can hold 60-64 MPH now with 40-42 MPG. That was what I got at 54-56 without the tail. I can get 42-44 MPG at 55 MPH and 44-46 MPG at 50 MPH.

I think my sweet spot has gotten larger and moved up a few MPH. Without the tail it was 47-53 MPH. Now it is like 48-55 MPH.

As I went down the freeway at 55-60 I had lots of cell phones out (taking pics I would think).

[Weather Spotter]

Well I had two tanks with the boat tail on. Both were this weekend and neither were fair tests. My first tank was with my testing / video runs. It also had some fast driving in 4" of snow which murdered mu MPG. The second tank was half show driving and the other half was fast driving due to a schedule out of my control.

I did find that the under belly pan collected slush by the wheels and broke. No slush was getting over re axle but plenty got tossed up by the tires and found a way in top if re belly pan.

This tank I am on now is much better representation of what it can do. I am pulling 40 now (tank is only at 60 miles) I am still seeing that go up by. 5 -1 mpg per day. I think that 45 is not out of the picture.

I am sure the tail has bumped up my sweep spot to 52-58 which helps on the highway. Around here the minimum speed on a third of my commute is 55 but I range from 60-55. So this bump is a big plus.

[alohaspirit]

curious why you dont fill up more frequently


(different strokes for different folks)

but i fill mine around the 150-200 mile mark

[Weather Spotter]

Two reasons,
1 I do not drive a whole lot which is the best way to save gas
2 its cold out so I fill up when needed say every 300-400 miles or 1/4 of a tank left.

[alohaspirit]

(I drive about 5k/year myself)

but I can certainly understand not wanting to pump gas in cold weather

[Phantom]

Good work for the squeaking get some foam tape and attach it to the tail and see if that helps. For the snow sticking on the back attach a short lip at the bottom edge of the tail about 1-3" out from the current ending point and possibly make terminate an inch or so from the corners. You can then adjust till you get it how you like it or remove it, if it does not help.

[Weather Spotter]

Well after some driving the last two weeks I have noticed that I smell exhaust when I crack the windows to vent out the fiberglass smell. My tape was also starting to come off. So I took the tail off tonight.

i put in some lag bolts to use as lift points and use a come a long to hold the weight as I unhooked it and pulled it off.

I noticed right away that my aluminum foil heat/ exhaust protection had crumbled. I think that it touched the exhaust pipe in one spot and tore. From that rip I was getting exhaust into the tail whenever the car was under a negative pressure. I fixed this issue by making a galvanized steel heat guard/ exhaust deflector.

Then I went to work on my gaps. I marked the aprox size while the tail was on the car. I used foam pipe insulation since it is long, cheep ($1 for 12') and is closed cell (water resistant). I put this along the whole edge of the tail/ car surface. Then reattached the tail.

With the lift I can get the tail on and off all by my self. It is a bit longer and takes some crawling in and out of the car but I can do it. I use a needle nose vice grip to hold the nut while I turn it from above.

I will get/ upload some picts latter.

[NeilBlanchard]

Building stuff is complicated, that is for sure.

Your post made me wonder if there would be any utility in extending the exhaust pipe up to the rear fascia of the boattail? This would (slightly) pressurize the wake zone, and it would help avoid leakage into the car.

Where are you seeing the heat?

[Weather Spotter]

I will try to get a pic of what areas the heat damaged as it will be hard to describe. Its -10F out right now so it will have to wait

I think that extending the exhaust would add a great amount of work for no gain. What I should do is cut it off early and tuck the muffler in better.

[JasonG]

If your eyebolts go into wood, may I suggest you get some tee-nuts.
They have little teeth that hold them in so you dont need to climb in and out. Oh, and their cheap !