My whits end, a nose cone and a periscope.
I was literally ready to throw in the towel yesterday. It is times like this when I start to question what the hell I think I am trying to do. Basically I suck. Well yesterday I sucked - today I suck less.
I made a 12 foot long sheet of 1/16" thick PETG plastic, placed it over a neoprene gasket on the MDF mold and proceeded to vacuum form a 'trial' fairing. To do a proper job with vacuum forming, you need more than one single vacuum hole, so what I wanted to do was to let gravity and a single hole pull the hot plastic down so I could see where the mold required extra holes.
The first formed fairing was really a beauty - It ended up touching the mold near the back and was about 6 inches away from the mold surface at the nose. Forming a fairing this way is the very best method to get a near perfect surface finish - heat the plastic up and let gravity pull it into a bubble. Perfectly smooth and crystal clear. Unfortunately, it wouldn't fit onto the frame properly and it would be far to small inside to fit legs, knees, etc.
After sitting back and thinking about the whole process I started to question my vacuum approach. Here were the issues:
1. It would require a lot more holes - especially near the nose, the square tail section and all around the perimeter to suck in the edges for mounting properly on the frame. Drilling holes in that wood block is hell! Especially 3 foot long holes. I didn't even want to think about that hassle and the new problems that would materialize.
2. I would need the plastic to touch the mold surface to get the exact right shape to fit on the frame. It was my original idea to try to stop the hot plastic shortly before it touches the mold surface, but I can see now that won't work. Where it touches, it picks up the general mold surface quality which isn't exactly glass like - thus, you end up with a surface you can't see through thereby kind of defeating the whole purpose of the vacuum form process.
3. My vacuum SUCKED big time - no where near enough to pull the plastic down completely into the mold. The problem is the MDF is porous - There would be a few ways I could seal up the mold, but all of them would be way time consuming and more hassle.
4. Any surface imperfections in the plastic would be there to stay - You cannot sand down PETG to clean up any little bumps (or my nice little glue lines).
5. Trial and error could eventually produce a decent fairing shell, but I'd be going through dozens of 12' sheets of plastic - mucho moola and VERY time consuming!! I am under the gun right now, so I need to NOT be experimenting!!!!
So it was then that I figured I should probably use the mold to lay-up a carbon fairing because I can sand down the glue line waveys on a composite shell. Both Thom and Eric, my trusty advisors both agreed. I decided to pull a test part out to confirm that my process was good, and that I could sand the surface down to a finish that I would be happy with. It's a good thing I did a test because I would have totally wasted hundreds of dollars worth of carbon and a day of my time.
The 'test nose cone' was a disaster. I laid in 2 5 oz layers of fiberglass, then two 5 oz layers of carbon - the idea was to use the fiberglass to sand through to smoothen the outside finish. When I went to vacuum bag it, my freaking vacuum wouldn't hold worth a sh*t. After two brand new bags and a resin beginning to kick I threw in the towel.
This morning I ripped the useless bag off and the two outside layers of carbon bubbled up all over the place. The thing was a mess. Then I couldn't get it out of the mold! Argh!! One of the tests had been a new mold release - Teflon car polish. I did a test before the test and compared 3 different Teflon coatings - a spray on Teflon protector, spray on Teflon tire polish and a rub on Teflon car wax. The car wax worked very well on the test, so that is what I coated the mold with before laying down my glass.
And this is about the time when I streak of bad luck ended and the universe started being a bit sympathetic to my stress.
I eventually got the nose cone out of the mold by heating the thing up with my overhead infrared lamps. When you do this, the resin gets very soft and flexible. The part easily peeled out of the mold. Then I turned the lamp off and pressed it back down into the mold to make sure that it retained it's shape. It rehardened within minutes and the part just fell out of the mold. I'm not sure if this is a valid method of mold release, but it sure worked well.
When I flipped the nose cone over, I saw that the initial two layers of fiberglass had stuck down to the mold surface (mostly). The nose cone was salvageable! I cut the edge off and experimented with a few various sanding techniques to see how difficult it would be to sand out the waveys. I also experimented with some glazing putty which is like bondo without the catalyst. It hardens to an easily sandable surface within 20 minutes. I filled in some of the resin bubbles (due to the non-vacuum) with this putty and sanded them smooth. I found that a run up and down with the belt sander, then a hand block did the trick - the waveys were gone.
To make sure, I spray painted the nose cone with a gloss black and it looked pretty good under the circumstances (dents from bubbles, cracks from tearing it out of the mold, etc, etc)
The other contributor to my stress yesterday was the realization that if I went with a composite fairing rather than a clear plastic one, I would have to deal with splicing in windows into the nose so I could see out. I didn't want to have to deal with this because I know how important having a very clean and smooth surface is for the first 30% or so of the fairing. Adding a window with seams would certainly destroy any laminar flow at the nose.
Give and take - with a clear plastic fairing shell, I would have clean windows any shape and any size. But with windows comes interior heating - definitely an issue. But, I would not have enough control over the quality of the shape and fit with a plastic fairing and could be a loss of efficiency due to that. With a composite fairing I would have much better control of the shape and surface finish, AND no windows to minimize the green houses effect, but I can't rely only on the video camera to see out because of the lag and lack of resolution.
As a test, I did a drive the other day under the hood - where I wear a hood to simulate being in the fairing and viewing ONLY using the video monitor. Very, very difficult! I can't imagine using only the video monitor for a long race - impossible.
Solution - and many of you have suggested this to me before. A periscope. A periscope would essentially get my eyes up above the fairing without having to actually having to move my head up there.
This works great - way better than the video camera and it never runs out of battery power. I tried running with this 'under the hood' and I had no problems at all - very easy to see and control and balance.
I will need to provide a fairing for this somehow - not sure what the best way would be - a clear PETG bubble over it all, or - I don't know. Any suggestions? I should probably work at lowering it a bit for a smaller faired area.
Here are some other various shots:
Still to do:
1. Add a rear caliper brake
2. Trace the real perimeter outline using an actual fairing half shell (when I get one!), and cut out the perimeter
3. Edge laminate the perimeter
4. Thicken the frame to avoid using the spacers on the brackets
5. Bond in the bottom brackets
6. Make new remote steering out of carbon and UHMW
7. Bond on the right hand rear wheel dome.
8. Bond fasteners to frame for the left hand wheel dome9. Add a thin coat of epoxy to the left hand wheel disc because it is not air tight (and fill holes in the dome)
10. New carbon fork?
11. Carbon wheel disc and wheel dome for from t wheel
13. Wheel fairing
14. Seat (wait until you know exactly where you want it)
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