(Project) Boat tail-4 Door Sedan VW Mk2 (1990 Jetta GL)
 

I started building a boat tail on my '90 VW Jetta. The plan is/was to use the Aero templates, both versions, for a true, attached flow boat tail.
http://ecomodder.com/forum/member-je...7-template.jpg
http://ecomodder.com/forum/member-je...mplate-new.jpg
Through my measurements, the cars height is 54.5" tall. Giving me a 100% tail length of 194.02" and each 10% on the second template of 19.4" from Max roof camber. So, at 19.4 inches( or 10%), there should be 3.5degree down turn from level. At 38.8"( or 20%) it should be 7.5 degrees, and so on. I had planned on going out to 60% for length/space reasons, and that put me out to 45" from the end of the bumper.
I measured out the elevation drops on the template, and for my height vehicle, the drops are as follows;

10%= .76"
20%= 2.3"
30%= 5.37"
40%= 9.98"
50%= 16.12"
60%= 23.8"
70%= 31.48"
80%= 39.15"
90%= 46.82"
100%=54.5"

The original lights will be moved to the rear and the third brake light will be mounted as I get the rear window put in. There will be a trunk opening and the old trunk lid and window are removed.

This is not intended as a one time project, to be completely finished when simply fully enclosed. It will be an ongoing project that probably won't end until the car is completely destroyed. It also, probably, will show what NOT to do as much as what to do:o:D.

Criticisms and ideas are always welcome.

I did want to note here, as there has been some discussion about finding Max roof camber, that I did it on the car, not the computer. Using a level gauge, I traced from the front of the roof toward the back until the gauge read equal to the floor reading between the front and rear tires. I then did the same thing starting at the rear of the roof and moved toward the front. I took the middle of those two marks as the max roof camber or starting point for the rest of my measurements.

Post two will have updated pics and building material used.

Here is the link to the pics in this thread with a lot more thrown in.

Pictures by JethroBodineEM - Photobucket

Picture of car with template overlay as of 08-11-2012;

http://i1201.photobucket.com/albums/...g?t=1344742328

After getting the measurements, I planned on making a solid base for the extension out of round steel tubing( free) and supports our of thin steel flat bar and and round stock( cheap or free). I was going to use cardboard and fiberglass resin for the skin, but further reading of MetroMPGs thread said that he was having issues with moisture bubbling before he removed his. A friend at work had used cloth fabric, chicken wire( for shaping) and resin for builds, followed by body filler( Bondo, if you will) for final smoothing. Sounded like a plan to me. I grabbed the welder and set to work.
http://i1201.photobucket.com/albums/...M/HPIM1578.jpg

Rear window and trunk removed( sorry for the blurry pics, it was dark in the shop, flash only lit near objects, and when I turned off the flash to lighten the pics, I couldn't hold the camera steady enough, which I couldn't tell viewing them on the camera, found out while downloading them:o).
http://i1201.photobucket.com/albums/...M/HPIM1579.jpg

Wiring harness already extended and run through( temporarily) the old light opening.

http://i1201.photobucket.com/albums/...M/HPIM1581.jpg

First loop welded to the body of the car.( Sorry, again)

http://i1201.photobucket.com/albums/...M/HPIM1583.jpg

The full frame welded in place. The rod down the center is just a place marker for measuring angles at different percentages of template.

awesome work. cant wait to see more pics

Here are a couple pics of the lights on the end of the frame. I don't have any pics of the chicken wire/frame assembly, but pics of the fabric on the framework will show what's happening.
http://i1201.photobucket.com/albums/...M/HPIM1584.jpg

and blurry,
http://i1201.photobucket.com/albums/...M/HPIM1585.jpg

More to come.

Here's the cloth stretched over the framework.

http://i1201.photobucket.com/albums/...M/HPIM1587.jpg

Gaffer tape is holding it in place. I didn't sand the body where it meets the tail as I'm going to do the final attachment with screws and body sealer to allow for flexing( hopefully).

http://i1201.photobucket.com/albums/...M/HPIM1589.jpg

Here is the first coat of resin. The fabric did sag a bit, but I pulled it tighter after this pic and before the next coat. Took a whole gallon of resin to saturate the fabric. And for those who are wondering, that is a queen sized sheet with little snowmen on it:D.

http://i1201.photobucket.com/albums/...M/HPIM1592.jpg

I put more fabric around the edges, both as a sealer for now and to give me something to cut/fit as I need. The edges of the sheet, also, started to pull away in places and this seemed to help.

http://i1201.photobucket.com/albums/...M/HPIM1593.jpg

I had to extend beyond the sheet on the end, so now it covers the whole top side, bottom belly pan will be aluminum sheeting, and I haven't decided on the end, yet.

I decided to paint the tail so that it would be less conspicuous.

http://i1201.photobucket.com/albums/...M/HPIM1594.jpg

I...um... ran out of hide-in-plain-sight black and had to finish with a can of metallic blue(all I had:o:rolleyes:).

http://i1201.photobucket.com/albums/...M/HPIM1596.jpg


More to come.

How long did it take from start through Post #6 with the fabric stretched and painted? The posts are all dated the same afternoon but I can't believe you did it all in one day - or did you??

No matter the color, I can't see paint being the answer on this.

You need to replace/cover the bed sheet-cum-snowmen with a
Cloak of Invisibility :D

That said, I admire your initiative, your let's go get 'em approach.

Looks like a pretty good job. I'd like to see a tuft test to determine if the air is attached over those surface undulations. Any plans for testing it?

Also, what does the bottom of it look like? :)

Brucepic- the welding, rear seat and window removal, chickenwire, and lights were one day( 10:30am to 7:05pm with a half hour lunch break. Fabric/resin the next day after work. The painting was another day after work( before the rain).

Rokeby- Where can I get one? My favorite Dungeon Master passed recently and forgot to tell us where the last bag of holding that is holding our last cloak was located.:D

Sven7- No tufting 'till smooth, this is just to get the thread started while I still remember what was going on and when. I chose a more complicated path than your anal Probe( awesome job, by the way!) The bottom is open, right now, but will be worked on tomorrow after work. Going to be aluminum as is the rest of the belly pan.

I've already been questioned by 4 different people if it is an electric car:thumbup:.

Oh, sounds great! (The Probe already has attached flow, otherwise I would have made a boat tail. :cool:) I can't wait to see this in aluminum. It's gonna look sweet.

AeroJetta in the making. Sweet!

One full day's work and a couple (long?) evenings - very impressive!!

Impressive regardless, in fact.

The resin was about 3 hours and painting was less than an hour( and it shows:D).

Worked on the belly pan tonight.

http://i1201.photobucket.com/albums/...M/HPIM1599.jpg

Here is the sheet aluminum about to be put on under the frame.

One of the things I found out tonight is that a single layer of fabric will NOT stand up to this winter as I cracked what I have now fairly easily:o. More layers are in my future.

http://i1201.photobucket.com/albums/...M/HPIM1600.jpg

Left side about to be screwed on, air saw in the background. I used self drilling, hex head screws, as with the rest of the belly pan( benefits out weigh the penalties at this point).

http://i1201.photobucket.com/albums/...M/HPIM1606.jpg

Side view for now.

http://i1201.photobucket.com/albums/...M/HPIM1605.jpg

Tail fully enclosed underneath:thumbup:. I still have a couple panels to put on after the wheels and to enclose the end before I can move on to the floor I'm going to add for cargo/sleeping when camping( similar to the Anal Probe's.

Tonight was another 3 hour tour, and tomorrow night probably will be as well. I'll try to get final angle of the exiting belly pan. There is a small lip at the end to, hopefully, give good separation.

Kind of noisy, at this stage, but better than this morning. I used .23 gallons of gas on the way to work this morning which is on par with some of this summers' runs, but not a record( .2 gallons for the 20.45 mile run). I've been averaging .29 lately. The trip home( after dark) was .44 gallons and I've been seeing over .5 gallons regularly. The cooler weather is seeming to be offset by the tail:D. MUCH more testing and further finishing will tell the tale.

I started working on the rear wall for the tail on Tuesday night and a friend at work started replacing the alternator in his V6 VW Corado. Wound up helping him more than working on my own rig, so I settled for a duct tape/cardboard wall with cut outs for the lights and a hole behind the license plate for light nut access. This will act as a template for the final wall, whatever that might be.

http://i1201.photobucket.com/albums/...M/HPIM1607.jpg

Rear opening with light assembly inside.

http://i1201.photobucket.com/albums/...M/HPIM1608.jpg

You can just barely see the access hole behind the plate. Gray silicone is sealing it for now. The outside is not sealed, I figured that it would help hold the plate in place.

Still using about .23 gallons on the commute to work. Thought I was going to have a record trip this 44 degree F. morning( sub .2 gallons), but ran into traffic on the last 6 miles.

Holy cow I did not see this coming! Way to jump in with both feet Ken. Love it!

We're going to have some fun on October 16th. :thumbup:

Mike

Whew! Do NOT put a tail on your car unless you like talking to people. Almost every time I stop somewhere, someone asks about my car. I'm trying to get my answers concise and interesting, and keep their attention long enough to pique their interest. Most are interested in the mileage, as in," You REALLY gettin' 63 mpg in that because of ...that...thing?" Always answering "Yes", one young lady replied, "That's better than my Mom's Prius.":D. I'm getting to meet some really cool people.

Worked a bit this weekend. Got the rear end shaped and the light cutouts made, still need to drill the holes and weld the sucker on( no pics yet).

http://i1201.photobucket.com/albums/...PIM1609.jpg?t=

Did a bit of filling. Bought some car care, all cotton "diapers" @ $2.99 for 6. Cut one open( they are folded in thirds and stitched together) and used it to seal the remaining left side hole and smooth the transition.

http://i1201.photobucket.com/albums/...M/HPIM1610.jpg

Left another sewn up and used it to fill the tail a bit. Ocean State Job Lots had resin for $10/gallon:eek:, no glass cloth:mad:. I'm taking back the $27/gallon I bought last week:rolleyes:.

http://i1201.photobucket.com/albums/...M/HPIM1611.jpg

While they were hardening, I took a chunk of TUFF-R insulation that I had kicking around and shaped it into a filler/overhang for the tail end. I think with shaping and sealing, this will add a good separation point for the top line of the tail. Speaking of which, anyone know if this stuff is OK to use with regular resin? Maybe I'll ask in a separate thread.

http://i1201.photobucket.com/albums/...M/HPIM1613.jpg

Added a little metallic blue camo and ready to ride, again.

Nope, polyester resin will eat that stuff up. Gotta use epoxy resin.

Or paint the foam with some latex house paint first. Then you can use the polyester resin on it.

Thanks TC. Dang.

Wait... I just saw some spray latex house paint today at the discount auto/tool store, right next to the Tite-Bond glue. I love one stop shopping:D.

Water tracks
 

There was a light mist on the way to work. When I got out I saw some condensation tracks on the tail. And here they are;

http://i1201.photobucket.com/albums/...M/HPIM1621.jpg

Left side, at an angle.

http://i1201.photobucket.com/albums/...M/HPIM1622.jpg

Right side looking forward.

http://i1201.photobucket.com/albums/...M/HPIM1623.jpg

Straight forward.

I like these tracks better than the twin spirals I used to get on the trunk lid(even though the two cyclones were kinda' cool in a light snow:o).

I also made a template overlay, and all I can say is...Oops:o:o:o.

http://i1201.photobucket.com/albums/...Tailontail.jpg

In my haste to have the car runnable, I seem to have deviated a bit in my measurements. This will have to be addressed in the spring( probably) as I don't have nearly the free time available between now and snow fly.

That's so true!

When I was making the prototype tail on the Firefly, I had people stopping their cars at the end of the driveway and getting out to ask me about it.

I saw a driver stop mid-turn in an intersection to look at it.

Wow very nice! Can't wait to see the results on the run.

When you get this tested to really see what you have, I have another addition I've always thought of and thought I would throw a mock up out there.

Its horribly ugly and just a suggestion, but I have always wonder about air deflectors and recombinors (not a word) around the lower section of the exposed wheel. I would think ABA or tuft testing would show some benefit, I'm not sure how bad the air is off the wheel, but this would be a triangle or rounded shape to try to match the air off the wheel and smooth it into the tail.

I figure it should be about the same purpose as the humps on the back of old open roadster race cars, like this porsche has: http://procarmodels.com/wp-content/u...393a5baa37.jpg

Anyway just a thought for future discussion.

As another boat tail driver I agree to your lots of comments form others. I get it all the time.

your project is looking good, any plans for a window for rear view?

Weather Spotter- You are definitely one of my influences for starting this project. I really enjoyed reading( and re-reading) your build project. I was going to do a rear window, but, I cut out the rear seat support and tried lying down in the vacant rear seat/trunk area and found it more than long enough for me. I'm now leaning toward using a license plate camera instead. This would allow both a quicker and easier way to seal the passenger compartment for the winter. I have LOTS of experience driving vehicles without a rear window, so I don't really notice the loss.

MetroMPG- Obviously, also a great influence for me and this build, I almost used cardboard( I have an inexhaustible supply) sealed with resin as my media, but on the 3rd or 4th read of your thread you mentioned bubbling, I assume like 3wheelers water based problems. Thought I'd try this route. Time will tell.

itjstagame- I've got a ways to go before I get to the tire strakes, but you do bring up a good point. I'm thinking along the lines of aerohead's t-100. Might not be feasible around here as I drive on dirt roads to get home.

Yeah - I can heartily recommend NOT using cardboard for permanent mods! :D

(And the prize for most obvious statement of the day goes to...)

Unless perfectly encased in resin (which must never, ever crack), by design it will thirstily lap up water and eventually turn itself into a bloated mess.

If you add the rear window you can remove the side mirror. on my car that was worth 1.6 MPG. Even with a window you can still lay down back there. I have done it in mine. You might want to add a wooden frame and mount a cheep set of blinds or a curtain :)

It looks like you will need to redo the angle of the top anyway so that would be a good time to do it.

Do you ever get over to Michigan? I would be interested in comparing our tails :)

Is there anything you want more pictures of or user data on my car?

I'm not sure, but with the template overlay it looks like there might not be a good location for a window. I will be keeping an open mind until I actually get to that stage.

How's yours holding up? Any new developments? Any observations?

A few testing updates on mine, so far;

on my calibrated test hill, I have been coasting from 45 mph to a +5mph over what I was getting before the tail( as an example, if I had accelerated to 76 previously, I would have gotten 81, and of course that would be an average),

P&G now works better than DWL+EOC for my commute to work. Every time I tried P&G over the summer, I used .03 to .05 gallons more going to work. After the tail, I'm now getting about .02 gallons better out of P&G.
20.45 mile trip,
summer record of .20 gallons(102.25 mpg),
recently( before tail) around .29 gallons(70.52 mpg),
after tail DWL/EOC at .23 gallons(88.91 mpg),
and after tail P&G .21 gallons(97.38 mpg).

As for a window, right in the middle of the back looks like a good spot for a small one.

Mine is holding up good. One guy rear ended me but his hood crumpled, I had to do some touch up fiberglass but no big deal. My seal on the top leaks a bit of water during heavy rains but that is not a beg deal. it puddles then evaporated.

My best idea is about 5-7 MPG gain. I know my coating distance has gone way up. I regular coast .75 to .9 of a mile to a stop. with a tail wind I go a mile.

I get lots of comments on it and lots of looks but I like it.

Welded the end plate on the tail today and smoothed out some of the clumps on the right side.

http://i1201.photobucket.com/albums/...M/HPIM1629.jpg

I cut the shapes with a plasma cutter and smoothed/final fit with 90 degree die grinder with a 2 inch 36 grit roloc pad( don't look too close at the left one:o). The center hole is just big enough to fit my arm in for plugging in the lights and tightening the nuts on the light assemblies.

http://i1201.photobucket.com/albums/...g?t=1318719620

All together and now I can start smoothing/shaping from rear to front. Hopefully doing some tomorrow between raindrops:D.

Nice to see the progress. Love the dedication!

Mike

Thanks, Mike. The next week will, hopefully, see a smoother, quieter( and maybe even one color) tail. Tire noise gets pretty bad above 60mph as the rear is still open in places underneath. Besides, I've got a certain someone to try to beat this coming weekend.

JethroBodine
I'm impresed! :thumbup: I'm looking forward to the mpg outcome when it is all finished. :eek:As to the gathering of crawds to talk about boat tails, the same happens to me on my motorcycle which has a boat tail also. They are impressed when I tell them that I get 2.9L/100km [81 mpg US] I have gotten as good as 87mpg on one tank that had lots of tail wind.
Keep up the good work.:cool:

Thanks Redyaris.

The recent cooler weather had me down into the low 50s mpg before the tail. So far, according to MPGuino, this tank is around 59. 500 miles, so far and just below the half-tank mark. I'll be filling up on Thursday or Friday before my trip to Fonda, NY to meet up with blownb310 on the field of (mpg) battle.

Is this "mpg battle" an organized event or a personal "grudge match" between you and blownb310? :confused:

No grudge here:). He's putting on a small rally before winter and invited me( or I invited myself... not really sure:D). I've always loved racing, and this is a great opportunity to get more experience for next summer( If I don't have to have any more surgeries:mad:).

you know as much as i am on here i just now seen this.... so this is your trick to stay ahead. you evil B@#%!$D!!!! your cheating

LOL j/k man looks good. your going way more than i am willing to go.

BWA-HA-HA!!!:p I mean... Oh no! You found my SECRET weapon:p.

It is a bit too weathery to work on the tail outside and I promised my son we would only spend one day at the shop( he chose Saturday). I see a few long days ahead( after work) this week.

Did a little "living with it" work tonight. As the rear window and trunk were eliminated, the openings in the tail were generating a lot of noise in the car. Tonight I added a vertical partition out of 1/4" plywood. Cut WAY down on the road noise.

http://i1201.photobucket.com/albums/...M/HPIM1634.jpg

View from the front seats. I would have done more, but my last can of expanding foam decided to not work... at all... except around the seal on top of the can, not through the tip. There is a hole cut in the left side( right side of the pic) for tail light wiring and the wall had to be installed in two pieces( there is a back strap down the center).

Tomorrow night... well, every time I try to plan something, it goes awry. Will update as I go:D.