2000 GMC FastBack AeroCap Project

[ChazInMT]

Craig, Just guessing here, but that radius on the boat hull looks to be about 2 feet. The radius on my cap averages 6 inches. Even at funny angles, some part of the plywood is going to have to bend to that radius. I don't think even door skin would go that far without splintering. The plywood I tested is 3/16" mahogany. Still a great idea though.

[Christ]

If you wet it, plywood will bend almost in a 2" radius 180* without cracking. It's a PITA to steam large pieces, though.

You can use Lauan for your bed fairing, that bends pretty nicely with just a warm wet rag and a few minutes of working with it.

If you're semi-decent at wood-working, kerf-cutting your wood will also let you bend it and keep a smooth upper surface.

[MetroMPG]

I think this now qualifies me as an Assistant to the Helper of a Novice Shipwright Apprentice.

Thanks for the LOL.

Driving impressions? Tuft testing? (Too much to hope for?)

[ccrider]

wow chaz that came out great i hate to think how many hours it took you to build. my cap is a simple design and it took me allot longer than i thought it would take to build. it is a shame to cover up all that work. you should stain it up and put it on your building resume. HA

[ChazInMT]

Well, It is Finished. The result is not too bad. I now know exactly what Fubeca is speaking of when he says, "It looks better in Pictures than it does in reality", the heatshrink is a pain to work with and mistakes show up. Careful as I was I needed to patch 5 holes. So far only positive comments from all who have seen it. I'm tempted to put it on that Toyota truck web site that was not too kind to Bondo's AeroLid to see what they think.

I took it for a test flight and have to say I was underwhelmed. I went 95 miles, 85% highway, and got 16 Mpg in a very, very crude method of filling up, takin er for the drive, then fillin er up again. I was averaging about 73 Mph cause that’s what I normally do. I'll obviously need to take readings over a few full tanks worth of driving to refine what gains I may have made. I want to get 17 to 18 Mpg on the highway for my trip. So what ever other tuning I can do to get there I will. I plan on going just 70 when I travel, and my tire pressures will be amped up. I am going to fill in some holes in the lower air dam and block some of the grill. I think this should allow me to meet my goal. I would have expected to get 14.5 MPG from past experience. I don't have a scangauge.

The AeroCap changes the dynamic of the interior sound for sure. It seems like I hear a lot more road & tire noises, so the general pitch of the sound is higher. When I first drove out, it was very noisy. I remembered that along the way, I set the cap forward enough on my bed when I mounted it, that it was touching the rear glass a little bit. I didn't think it was a big deal and planned on adjusting it later. I realized driving out, a lot of the noise was probably due to all the noises the cap was hearing and generating, were being conducted through the rear window....doh. So when I pulled off to turn around, I climbed in, took a few minutes to loosen the mountings up, and scooch it back. That helped a bunch.

I dunno if I'll take the time to A B A, but I'm very curious about how tuft testing will look so expect that within a week.









Charlie

[Christ]

Looks great!

Are you gonna make a mold and maybe sell a few if there's any local interest?

[Fubeca]

It does look good!

How did you seal where the flat meets the curve at the rear of the cap (or did you)?

I assume your truck has a mechanical engine cooling fan? What gear ratio are your axles?

[ChazInMT]

Thanks Christ & Fubeca.

1) No plans now to make/sell, I am going to be doing my "Day Job" starting in 3 weeks which will have me going from MT to NY til mid may working at nuke plant outages.
2) No seal yet, I'm going to get some black caulk and undo the 7-8 screws holding it together and seal it that way soon.
3) Mech fan, Gears? How do we find that out? I bough this truck used.

[Fubeca]

For the fan, just pop the hood and check it out. A mechanical fan is bolted to the front of the waterpump at the front of the engine.

The gears is a little tougher. There might be tag on one of the bolts that holds the front or rear differential cover. Otherwise you can manually check it or look up the VIN here Comprehensive GM VIN Decoder

My 2006 has electric fans and a 3.42 axle ratio. I can easily get 17 on the freeway right now with my topper and the weather.

[ChazInMT]

Sorry, meant to say "Mech Fan. Gears?"
I'm a fairly apt mechanic, changed the waterpump muhself on this beast in fact, so I know she be a mechanical fan.

The VIN shows 3.73. rear dif ratio. That would be better than 3.42 wouldn't it?