95 GMC pickup streamlined (aerocap and wheelskirts)
 

http://ecomodder.com/forum/attachmen...p;d=1420918558

Hi fellow modders, its about time i joined you all and participated in this deadly site... ive been lurking for too long. I had been thinking bout an aero truck topper for year or too before i got 'er done...
It is made of wood with a rubber skin on top, was thinking of wood skin, but couldnt justify the time or extra weight. It has been on the truck for 3 months now and i love it. I drive out of town on highway most days of the week, and have noticed slightly lower revs at cruising speed of 100km/hr. I cannot test l/100kms as have a hole in top of my fuel tank, but it must help. Sure keeps the snow out of my gear, and get some good headturns!
I can also drive 110 with the topper up, and the next step is using it to push the air over the "new" trailer... and some rear wheel skirts of course.

What do you all think?
Feedback appreciated

http://ecomodder.com/forum/attachmen...p;d=1421635974

Hey, welcome! Nice pics too. I can't believe this greeting got missed given the cool project it presents. I'm sure people would love more details on the rubber covering and how you did it. I don't think I have seen that here yet. And what do you mean "hole in the top" of your gas tank? I hope that's just a missing cap, or maybe a lead foot! ;)

Looks good! I bet it has a bit more power pulling the trailer now!

Thanks California98civic for the welcome. Its a fairly similar shape to many of the truck toppers on here, maybe with a longer overhang at the back. Which just happened as i built it because i used 10 foot strips of wood, then standing back looking at it, i decided to keep it long for aero benefit.
construction is using 1/2 inch ply and studs ripped into about 3/8" strips... see photo, then lots of PL premium and narrow crown staples. The rubber is hard to name as my buddy has a roll of it and gave me a big chunk. It is between 1/16th an 1/8th thick and has a grid of fibre inside it. It doesn't stretch much so had to have a join along where the side meets the top. I stapled it on with a T50 electric staple gun. Pretty simple construction, hardest part was figuring out the "arches".
And the gas tank issue is a leak! But in the top half of the tank... it will take 50 litres no problem, but i can't measure full to full. Shes not the most efficient vehicle on the site but i need the 8' box for work and now towing the trailer too. And the price was right! Free.

Dirty dave: thanks man, im pretty stoaked on how the shape turned out, and yea it must help a little pulling the trailer, but watch this space... i would like to have the topper 'up' to punch the hole for the trailer, semi style! I have tried it already but it needs a little refining (work)

The magnum is our new family wagon, and i am currently doing a mpg test on it stock, on a trip from saskachewan canada to los angeles... 2850 kms each way. So far im pretty happy, it rides nice and smooth and is returning under 10litres/100kms... doing the speed limit which is 80mph in places on I15. Its the "small" 2.7l V6. Would love to bellypan it and maybe rear wheel skirts etc. I do like the low stance and tapering shape, feels stable in the crazy crosswinds!

Belated welcome, rumdog!

Very cool! That's a good looking cap - nice work. My only suggestion would have been to build in a radius at the side/top transition. Complicates construction, but ensures a smoother flow transition between those surfaces.

Are you going to stick around? Garage entries/fuel log?

---

I missed it too! (Just edited the thread title and embedded a couple of rumdog's pics to guarantee more eyeballs.)

Nice cap! It looks so clean!

I'm curious about the hinge setup.

EDIT: never mind, I figured it out.

Cheers MetroMPG, are you talking about the cab to topper transition ? Yes i know what you mean... maybe i can gap fill with a thick foam strip, but i don't want to touch the cab as it makes funny noises!
Yea for the hinge i used HD gate hinges and a 2X4 frame.
And yes i plan to stick around! I am still out of country in the magnum... back soon. Love this like minded community! And thanks for tweaking my photos

I actually meant the transition from the "triangular" side pieces to the top surface.

Ahh right, it is not as sharp a tranny as it looks in the side photos, i will take a pic when im back. But i hear you... smooth is good!
Next is rear wheel covers and side skirts, will look up the site for mounting ideas. I like the look of bamzippows

Sounds like you're having fun. Not knowing my actual fuel economy would drive me nuts though (hole in tank preventing fill-ups).

What year is it? Thinking: ScanGauge or equivalent...

Its a 95 with efi... i was thinking the same thing today! I am data curious! The topper can come off easy with 2 guys, it would be nice to know a base line mpg for my daily 20 min highway commute.
Hey metrompg i think you are right - that tranny is abit too sharp from the topper top to side, next model will be smoother. This is a quick and rough proof of concept for me, thanks for the input. The second one will be way easier!

Ive been doing lots of brainstorming and image surfing for air dams and side skirts, i would like to lower the bottom edge of the truck to reduce underbody flow - more so on the sides. Medium airdam up front, lowest in front of the wheels.

Think ill use Plastic sheets, as coroplast doesnt like -30 C, gets super brittle. Hope i can find black! Hmmn conveyor belts are black, i like what dave did to his F 350

Youll have to excuse my mix of units, i went to school in metric but now work in inches and feet.i use Kms and litres, until a recent roadtrip down into the States. Where gas is CHEAP man - $1.69 a Gallon! Sheesh. In NZ its about that for a liter!

The Magnum did great on the recent trip to california... ie. didnt breakdown, and avoided a collision nicely. It was a big winter trip for the family and we were lucky with clear weather throught the mountains most of the time. 6555 kms all up. Around 10.3 l/100km or 23mpg doing 80\85 mph and 9.7 l/100 or 24mpg doing 65\70mph. Both using mild truckdriver technics of looking ahead and minimising breaking, slowing on climbs a bit, timing lights. Car was FULL! Not great figures but good to know a starting point. Its my wifes vehicle! So mods will have to be a step up from my truck (with 590,000kms) - where i can slap on some panels to cover the rust.

Subbed. I love your cap. It looks like a canoe.

tank leak
 

Cap looks great.Thanks for doing that!
As to the tank leak,if you can get access to it and locate the offending spot:cleaned,scuffed,and dried,it can be cold-sealed with JB-Weld 2-part epoxy.
I've done a few.
Then you could top that puppy off and finally know what the cap is doing.

I just found the thread too.
If you're set on another round, just cut a softer curve in the ribs, position the stringers so there is a continuous 3 or 4 inch gap, roll a roll of flashing metal, cut lengths and roll them (on a cyclone fence or with a skate board in a gutter), then bend it to fit your already-finished frame and rivet or staple it. Or little screws.

Try pulling the rear side tight first and pull the wrinkles toward the front corner.

Woohoo! I got mentioned! ;)

Welcome to the forums! Sorry fer being late to the party... :(

My builds have started from a simple idea to try something and learn from them. Hopefully you will find the time and enjoyment from learning and applying the skills from everything you do. The rear wheel skirts came after my belly pan and side skirt builds. If I can help you out, just holler! ;)

Hey thanks people for the feedback and ideas. (And thanks for moving this thread)

Ha, cheers elhigh, i am pretty happy with it so far. Not much to report here, as deep winter makes it hard to do any large projects. But, i have been looking for two gas struts just the right specs to lift her up... cant wait! Also drew some pics on the tablet of side skirts/rear treatment (massive diffuser!) Will try to upload for a laugh.
I did score some cedar strips at work this week, which may turn into side skirt structure.

Thanks aerohead, i gotta say your yota is part of the inspiration for this build.
Hmmn i do have some JB weld... and it sure would be nice to get a handle on how much the topper helps. It will be a spring project for sure. Minus 30C here today ouch!
I have been doing a lot more neutral coasting up to intersections, learning my route, and the truck sure coasts nice!

Another round or prob just tweak this topper until i have to get another truck. I will be restretching the rubber onto the frame when its warm out, which may be a good time to soften the transition. Really i dont loose any useable space, and it should help the flow along the side which moves onto the back, and crosswind flow. My buddy suggested trying rubber cement to weld the seams. Im down. And i would like to cut the tail corners a bit.
Anyways thanks for the input freebeard. Man i need a shop!

Here is drawing of my vision! The business end!

http://ecomodder.com/forum/attachmen...9&d=1425102997

Me, too. There are seams in the rubber sheet? Where are they. I could see rubber cement to hold the rubber sheet against the stringers, but I suspect there would be some minimum overlap needed to resist shear.

Four posts in less than an hour? If no-one has replied you can just edit the initial post.

Tying everything together in flat black would help visually. It sounds like a job for 6-8 coats of Plastidip S. It would 'similarize' various materials and probably match the rubber sheet on the cap.

vision
 

The rendering looks real good! I can't see it scaring anyone off.
Plenty of testosterone!:D

Yea freebeard theres a seam running down each side, where top meets side. It is stapled right now. I do have about 2 inches overlap, think it would be plenty of area to bond. More if i smooth it out!
Plastidip S . Noted! And needed. does that help with rust?

[QUOTE]vision

The rendering looks real good! I can't see it scaring anyone off.
Plenty of testosterone!

/QUOTE]

ha can you tell i like F1! im not looking for downforce but to increase the pressure behind the truck. In reallity i had chains on the truck this week, so i picture the rear wheel skirts opening like a bus cargo door. And the skirts/macho diffuser may not be as low as one would like.

The quote looks like it does because there's a missing '[' on the closing tag.

2 inches of overlap might be enough. Plastidip is a rubberized coating that encapsulates the surface

https://www.youtube.com/user/DipYourCarcom

Here's a picture I made to show a 4-bar link for a front fenderskirt.

http://ecomodder.com/forum/member-fr...2-11-13-05.png

If the lower bars are longer, then it would 'clamshell' open.

Yea exactly! Just longer arms so it lifts higher, for full wheel access... i will get the kids lego out to play with the 4 bar when the time comes. And thanks for the forum tips freebeard, i need em!

Legos
 

Cereal box chipboard links,cork board base,push-pin anchor pivots,and tacks (upside down with points up) flying pivots are great for proofing out mechanisms on a tabletop.
If something is going to bind up,you'll know in a moment.:)

Maybe it's worth pointing out that the thing to take away from that fender-skirt model is that the two top bars are connected in torsion so any tendency for the pivots on the ends of the bars (and hence the skirt itself) to rock is thwarted.

Very nice! Thanks for sharing that.

wheel skirts carpenter style
 

So its finally warm enough to work outside without it hurting... time for some wheel skirts!
I cut out most of the rust with a zipdisk, then made a wood brace by gluing two strips of oak together and clamped them in a curved mold. Made a template out of cardboard, transfered it to the coroplast political signs, which were sprayed black and screwed them on with sharp metal screws and washers. BOOM!
It took about 3 hours and ten bucks. Stoaked!

side photos with trailer
 

Took some pics today of the rust bucket for the template test... should be interesting.
And took some with the trailer on and topper up, to show potential highway position... need to bolt topper to bed more first. ...just dont want any trouble from semi wash in a crosswind.
I did install two gas struts a while back which i scored in los angeles in car park, thank you lazy roadside mechanic! They are a shade weak ~22 lbs each, but do help lift the topper, and now i know what i need for length and force.
I need to make it open slightly higher to push the air over the front of the trailer smoother, and some lightweight sides would be nice.
Pulling the trailer around 90 km/h seems to be the best for staying in OD and locked. Revs are low round 1750.
Just for fun i propped the trailer ramp up to round 5 degrees to imagine a trailer boat tail! Thats right! Out.

Looks like you're having fun.

Any advance on the measuring your actual fuel use, or are you still using the force? :D

Given what you're hauling, maybe you don't really want to know!

leaky fuel tank
 

Ha funny you ask, i scored a fuel tank tuesday night, and going to try swapping it tonight with the knowledgeable father inlaw. If it works i will see how bad the mpg really is! I am interested in the bluetooth ebd2 dongles, but from research i dont think it will work with my 95 gmc... anybody try here?
instant feedback would be nice.
I think there are some sore necks in town as people are just about twisting there heads off as i roll by!

Haha! I know the feeling. (Seen my CivicTail thread?) :D

You'll probably have to go with the MPGuino if your truck is pre-OBD-II.

But even if you have to stick with pen & paper & fill-ups, it's better than nothing.

mpguino for pre obd2
 

Ok MPGuino eh, thanks a lot.
Yea i like your cardboard grid structure on your back window... i have no rear widow vision with this cap, no problem with these huge mirrors!
while lying under the fuel tank tonight working the bolts half way out i couldn't help but check out the rustbuckets dirty underbelly. You know aero dirty. I would like to find/score a stock air dam if possible. Easier than a bellypan and who knows how much life the old truck has left. 595 K kms on her! I want to make 600
The fuel tank bolts are soaking overnight... Like four rusty inches long!
Next day...
okay got the tank switched and tested. Will fill it tomorrow, and start a fuel log. Turns out the old tank was patched once before, and looks like thats where it was leaking again. Man my shoulders are sore! Out.

numbers
 

The rustbuckets Fuel log...
now keep in mind this is a working truck, i haul a 6x12 enclosed trailer and a bunch of tools round the countryside.

16.8 l/100km or 14 mpg - mix 10 trailerhwy, 50% hwy, 40%town

21.3l/100km or 11 mpg - mix 20% trailer, 40% hwy, 40% town

14.1l/100km or 16.7 mpg - mix no trailer , 90% hwy, 10% town

was a little bummed at the results with out the trailer, but the truck was loaded with tools and the side winds were intense today, maximum gust 69km/hr! At 90 degrees too.
Nice to finally see some numbers. From the Saskatchewan windtunnel... out.

I like the shell. Pre-Tacoma, for a couple months I was daily driving my Chevy 1991 K2500LD 4x4 with the 350 TBI. I managed to get it up around 18 MPG, mainly thanks to a 4L60 automatic to NV4500 manual transmission swap I did a while back. From your photos, it doesn't look like you have a factory air dam installed. I saw a 0.5 to 1 MPG improvement from installing one on my truck.

Thanks aardvarcus, you have a good eye... no airdam, yet. But watch this space! And running without a grill block right now, after pulling the trailer in some warm weather. It would be interesting to test mpg unloaded on a calm summer day, if there is such a thing!

wow, i just caught this thread too.
where in Saskatchewan you at? will be going to Saskatoon in July and camping at Bright Sand with the in-laws.
topper looks great.

lift
 

Thanks deejaaa it looks good at 100km/h! I live near North Battleford, which is 140 kms west of saskatoon.
I forgot to clamp one side of the cap down yesterday and it started lifting off the bed as i was driving. So i gently slow the truck down until 85km/h where it sits back down.
So the lift force at 85km/h is about the weight of the rear of the cap (cause its hinged).* I figured i was getting a little lift. Not too worried... with a max speed of 105 im not taking off anytime soon.

trailer fairing
 

So it was calm enough today to try the topper in the up position, while hauling the trailer... (see earlier photos). Results: wow. Increased drivability... i now have from 80 to 100 +km/h in OD and locked, where normally it 85 to 95. To me this says more aerodynamic, less drag. It sure makes it easier to pull. Should be even more slippery with the triangle sides and a higher position. Stoaked!
a guy at the dump asked me how much for a cap and wheel skirts... hmmmmn?!