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Old 04-09-2007, 08:26 PM   #31
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Originally Posted by MetroMPG View Post
FYI, I practically wore out YouTube watching this tadpole video: http://youtube.com/watch?v=qiv4aDolVaI
If I ever ride the MS150, I need something cool like that... So how much would a velomobile set me back?

Edit: Oh, wait, I see that velomobile is a generic term rather than a brand name. Anyway, a recumbent would be cool.
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Old 04-12-2007, 11:48 AM   #32
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Hey, I was thinking of something from my days of building racing sailboats.

If you want to make the shell lighter and stiffer, you could try this:
Make the molds for the shell as negative molds (like bathtubs)
When you build up the layers, put in a layer of something like this:
Klegecell
and then use a vacuum pump to apply pressure. You do this after your outer couple of layers have been applied and have set.

To do this, after the outer shell is set up, you have to put in all the following and get the vac pump going before the resin starts to set.
1- a layer of mat or cloth
2- apply resin, roll out the bubbles
3- lay in pieces of klegecell (they won't fit perfectly - that is what the vacuum is for.)
4- lay a big sheet of plastic in the mold. Seal its edges to the edges of the mold, except...
5- in one spot, put the hose from a vacuum pump under the plastic sheet, and seal all around the hose.
6- turn on the pump.
7- watch as the plastic sheet is sucked down on to the surface of the shell, klegecell, and mat
8- smile a satisfied smile as you look for leaks
9- let it run until the resin is fully set, probably overnight

Different stuff to note:
The adhesive that you use to seal the edges needs to be pretty good. We used some kind of 3M product that we called "monkey poop". Helpful, I know. It was kind of like high-tech modeling clay. It came on rolls with a wax paper backing. It did not dry out and was super sticky.
Nothing sticks to wet resin, so when you apply the layer of mat and resin, be careful not to get it on the edges of the mold.
The vacuum pump hose may ingest resin, so think about a trap of some kind, or use hose that you don't care too much about.
Put a little scrap of klegecell in front of the end of the vacuum hose to keep from sucking the plastic sheet in.

Of course, experiment with it first since it is a little hectic trying to get everything in the mold and sealed up before the resin kicks.

The advantage of this method is that even if you only get something like 36"H2O vacuum, you are applying 190 lbs of force per square foot, which gets everything nice and smashed together.

Here's a video:
Vacuum Bagging video

The klegecell will make the structure stiffer and is a way to give the shell some three-dimensionality to reduce flex, oil-canning, and all that. Plus, it's fun to say "Klegecell" and "vacuum bagging"

It occurs to me now that you guys probably already knew all this, but in case you didn't, I hope it was helpful.
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Old 04-12-2007, 12:05 PM   #33
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Hehe - Last year we used Divinymat (I've been referencing it as Kmat) and vacuum bagged :P For some reason, we went with coremat this year (which is just a fiber bulking mat) instead of the foam core. All of our testing showed that Kmat + glass is VERY strong and better strength/density ratio

Quote:
The adhesive that you use to seal the edges needs to be pretty good. We used some kind of 3M product that we called "monkey poop". Helpful, I know. It was kind of like high-tech modeling clay. It came on rolls with a wax paper backing.
Haha, that's that stuff we used :P

Quote:
The vacuum pump hose may ingest resin, so think about a trap of some kind, or use hose that you don't care too much about.
Put a little scrap of klegecell in front of the end of the vacuum hose to keep from sucking the plastic sheet in.
We had a perforated film release and breather mat with extra breather at the vacuum port (which was not directly above the tool)

Quote:
It occurs to me now that you guys probably already knew all this, but in case you didn't, I hope it was helpful.
No worries I'm sure if someone else is going to tackle a project like this, it's great to have more than one version I'm actually working on the tool making/vac bagging video right now We pulled our part last week and it came out great -- the entire thing is a tad over 20 pounds (on account that core mat is pretty much thick paper towels drenched in resin :P). But that's better than last year with a larger surface area


-----
I forgot to mention....
Here is where we ordered from.

Next year, I'd love to use the nomex honeycomb. There's a lot of cool tricks for structural mounting you can do and it's super light. It just wish it wasn't triple the cost :P At the bottom of the page you can see the coremat stuff we used. It's lighter than glass - but heavier than foam core.
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Old 04-12-2007, 12:40 PM   #34
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Hehe - Last year we used Divinymat (I've been referencing it as Kmat) and vacuum bagged :P For some reason, we went with coremat this year (which is just a fiber bulking mat) instead of the foam core. All of our testing showed that Kmat + glass is VERY strong and better strength/density ratio
<snip>
We had a perforated film release and breather mat with extra breather at the vacuum port (which was not directly above the tool)
<snip>
core mat is pretty much thick paper towels drenched in resin
<snip>
Next year, I'd love to use the nomex honeycomb. There's a lot of cool tricks for structural mounting you can do and it's super light. It just wish it wasn't triple the cost :P At the bottom of the page you can see the coremat stuff we used. It's lighter than glass - but heavier than foam core.
Coremat and roving are brutally heavy. We hardly ever used roving, and never used coremat in our boats.

The perforated film release and breather is something I was not familiar with until I poked around some on the 'net. Too cool. How sweet to be able to get all that extra resin out.

I have not worked with nomex honeycomb. Sounds really cool.
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Old 04-12-2007, 12:56 PM   #35
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Coremat and roving are brutally heavy. We hardly ever used roving, and never used coremat in our boats.

The perforated film release and breather is something I was not familiar with until I poked around some on the 'net. Too cool. How sweet to be able to get all that extra resin out.

I have not worked with nomex honeycomb. Sounds really cool.
I forgot to mention.... With the part pulled and the two halves glassed together..... We can stand in the fairing with it raised off the ground It's way too strong - but extra points for roll over safety/protection.

The breather also helps get even pressure over the entire part -- no need to have a bunch of different ports to get even pressure

For reference - here's our layup.

3 Layers of Glass
Specific loading zones got coremat (including the entire bottom)
1 Layer of glass

This honeycomb is really cool -- it's just paper and glue! But it similar to a cardboard box -- really strong because of the geometry

-----
Out of curiosity, what do you do for a living? Just curious as we're always looking for the knowledge resources for different manufacturing methods and the experience we just don't have ourselves (after all - we're just college students) :P
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Old 04-15-2007, 12:17 PM   #36
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Here's the next installment

Time Lapse with captions inside

http://www.instructables.com/id/EZR0D24F05JJOYL/



She's a lot lower than last years model. It will be lifted another 3 inches or so to mount to the frame
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Old 04-21-2007, 10:49 AM   #37
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Here's an update... No video - but some progress pictures

Stiffeners Added to Frame:


Now with Windows (PETG):


Interior View:


Interior View further back (because camera has no peripheral vision :P):


Here's how the windows are attached:


Naca Duct:


EDIT: it appears my site is having some tech. difficulties... Again! Give me a few to rollback some server crap

EDIT#2: So I got hacked... but he botched it... Not sure how he got access yet because my mode settings...
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Old 04-21-2007, 05:37 PM   #38
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Out of curiosity, what do you do for a living? Just curious as we're always looking for the knowledge resources for different manufacturing methods and the experience we just don't have ourselves (after all - we're just college students) :P
Sorry, been traveling and I missed this question. I am a ChE and have mostly done environmental and project management work. But I love making stuff and seeing stuff made, and have visited a bunch of different manufacturing facilities, and worked in the sailboat shop/factory, auto parts store, and a nylon spinning plant, so I know something about a lot of different things. Any time you have a question, just PM me or e-mail me. I'll let you know whether I know anything or not. I don't know anything about any kind of welding, so I can save you from having to ask about anything along those lines. :-)

The fairing looks great. The windows are beautiful. Did you make them yourselves? I hope you guys do great on the grading/competing.
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Old 04-21-2007, 05:43 PM   #39
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Sorry, been traveling and I missed this question. I am a ChE and have mostly done environmental and project management work. ...

The fairing looks great. The windows are beautiful. Did you make them yourselves? I hope you guys do great on the grading/competing.

Very cool

The front window/windshield was Vacuu-formed off of another tool cast from our actual part The other two were cut to fit and attached. The nice thing about PETG is that you can fold the sheet in half, it it takes the bend

Alas, I wasn't there for that stage of construction - but I do agree, they came out beautifully
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Old 04-24-2007, 09:14 PM   #40
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Fabricated the wheel disks today



Made from an unknown surplus plastic -- nice and thin, very flexible and doesn't appear to be brittle. As of this instant, they will be frosted (to look nicer than that). They still need to be epoxied together (to hold shape) - but will attach with Velcro
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