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Old 03-18-2008, 12:27 AM   #21 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
Well, happy belated.

Interesting method of getting the foam out, for sure!
Thanks 22 is no milestone (kinda weird)...

In any case - I've been busy talking with people today, getting special permissions, having doors unlocked, adjusting models and getting a little anxious as it takes awhile to finish (9 hours and 18 minutes!)... Update in the original post....

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Old 03-18-2008, 08:45 PM   #22 (permalink)
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Updates.... Look at the cool yellow model
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Old 03-18-2008, 09:17 PM   #23 (permalink)
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Cool. 3-D printing. Great thread.
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Old 03-18-2008, 10:17 PM   #24 (permalink)
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Awesome stuff, can't believe I just caught the thread now. Reading this makes me wish my school had a HPV contest...

What are the rules for this competition? A practical HPV for the average person or an extremely efficient design?

I'm sure you've seen this site before.

I think next year you should knock off the sexiest HPV ever created: Rob English's Mango.

Mango Side


Mango Top


Ristroretto


- LostCause
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Old 03-19-2008, 03:33 AM   #25 (permalink)
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is this pink foam your using the insulation type from Home Depot?
What did you use to glue the sheets together?

I'm thinking this mite be the method for me to
make my own wheel skirts for your project..

Have you tried the gasoline method of foam melting? I know it works on styra..
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Old 03-19-2008, 10:46 AM   #26 (permalink)
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Gasoline would melt it... But the clean up really sucks...

Yes, it's the same foam. We used 3M Super77 spray adhesive to glue it together. Don't use Super90 as it well melt the foam on contact (77 will melt the foam if you spray too much).

We didn't buy from home depot though... HD sells 3/4" boards - we are using 1". The foam works well for car fairing type projects
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Old 03-21-2008, 12:08 AM   #27 (permalink)
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Check out the groovy cad....
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Old 03-23-2008, 01:12 AM   #28 (permalink)
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Well, apparently there's a 45 image max.... So I continue here....

3/22 - Sigh of Relief!
Report was submitted today! Woo! That's done! But the work is still on : )

Today we got a largish list of stuff done
  • Cleaned Shop
  • Built Support Frame #2
  • Sanded First Plug (up to 800 grit)
  • Made a jig and cut foam ribs
  • Sanded said ribs
  • developed hatch cut lines
  • developed rib layout
  • developed coremat placement
  • cut coremat
  • cut glass tape to cover foam ribs
  • cut Kevlar (for extra abraision resistance)
  • cut peel ply
  • cut breather
  • made vacuum bag
  • fixed tool holes and dry spot with homemade epoxy putty paste

So here's our tools


And here's everyone (minus me) making ribs. They're 1/8" foam strips (1" wide) with a hand sanded chamfer so the vacuum bag pulls a fiberglass cover over the edges without air gaps.


Here's the ribs


Laying out ribs


Coremat is really strong... but a lot heavier than foam when impregnated with resin. So only thin strips are used where needed for super support. That door is hinged at one point - so that point needs some beefy support to hold that load.


Peel Ply and breather laid out


Be organized... All of those pieces are labeled as is the actual tool. Even the fiberglass backing has a matching label. This will speed us up while laying everything up so we can get under vacuum faster.


Peel ply (back) - breather and Kevlar (middle) - custom vacuum bag (front)


Tomorrow (sunday)
  • sand tools (from epoxy)
  • wax
  • dry lay up
  • cut carbon
  • spray PVA
  • lay up first part!


3/23 - First Part Lay Up
Finally!
So yesterday, that paste epoxy was applied to cover up some goofs... Now all that had to be sanded off.... Check this out...


The tool was then sanded again up to 800 grit.

Then, we draped...

It looks a lot better in person (my camera didn't pick up the fine detail) : )

Here I am cutting! To help find a cutting line, remove a few strands (just tug o them) and you'll get a perfect line : )


So, we got all the lay up stuff organized, tested the vacuum pump, and started the lay up (oh, we waxed and sprayed PVA again). I want emphasis, tested - that is, I turned it on, held my finger over the input, pulled full vacuum, then turned it off....

So we started lay up. First, a gel coat like layer... Then some thin resin - then the carbon was draped, coremat was placed, ribs were placed, glass tape was placed, Kevlar was draped. Placed the peel ply, draped the breather and then got it in the bag, sealed the bag and added a vacuum port...

We used a shop vacuum to pull the bulk of the bag... Then, switched over to the vacuum pump... Switched it on - NOTHING. Switched it off - and a flash of light came up under the switch. First, I thought it seized like the last time, so I began tear down while the rest of the team worked on adapting a fridge compressor to fit.

I took off the vac manifold - and the vanes still spin.... Tried turning it on, nothing... Took off the electrical service panel - the insulation was cracked and rotted away... The pump was shorting out :/ By that time, a hacked solution came together, so I abandoned the pump....

So, no one was working on the bag - getting wrinkles out, so I attempted to get some of that out.... Then the vacuum came full on.


You can see some of the rib structure...

So, now, time for a beer. Celebratory beer followed by flipping the whole thing, throwing a space heater in and bringing the temperature way up to get the process started : )



Woo!


3/26 - Multi-Day Update - Failure and Recovery
The past few days have been quite the roller coaster...

So we got the part out...


Easy way to release the vacuum bag - add a little pressure from a shop vac

And it was terrible! It couldn't hold it's own weight and just folded over.... Just too weak. The solution? T ribs.

Why? Moment of Inertia. We can't change the material properties - but we can change the material dimensions. This is why plate steel can hold some load while plate aluminum won't hold crap (instead, Aluminum is shaped into a channel or box).


This is where we apply engineering - on the table. We had a few different geometries to work with, the one with a wide base and high Moment of inertia (MoI) wins. For those interested, MoI increases cubically with respect to height changes and linearly with changes in base width. That means, an increase in height is more significant than an increase in width.

That's how we came up with the T rib idea...


So foam ribs were spay glued on the inside of the part. Laid up some glass over them and put it back in the bag.


So here's the other problem....

Those hazy areas are resin rich regions... Because the vacuum wasn't applied fast enough, the layer of resin cured before the vacuum could pull it through the cloth :/

It's dead weight and looks like crap :/


We brought it to the senior design lab for an ASME presentation we had yesterday (3/22). That picture shows the extent of the resin rich zones.

I spoke with our adviser - had him walk to the lab to take a look. He's generally pretty stoic with his emotions, but he seemed very happy with our mold quality (which doubles as a transportation device) as it has a very very smooth finish. He agreed that the part isn't optimal. I told him we have enough material and I personally want to have the part redone. He agreed and we now have both the time and material to do so.

By the way - the color in that picture is all wrong - we didn't remove the mold release so there's a green tint : )

Did you know you can sew fiberglass?

You can! So, we can't do T ribs as it's a manufacturing problem (we can't spray glue on wet resin and the ribs want to spring to straight). So we're changing to one piece "L" ribs. We're making them by cutting foam with rectangular cross sections and then using a router make the section. It's an "L" with a rounded inner corner to help the glass get over it....

So, back to sewing... These new ribs are too big for our 3" fiberglass tape... We have to double up to get proper coverage. Laying up two lengths of tape over these curves is a PITA. So to make the job easier, I've sewn double wide sections of fiberglass tape (no budget or time to order wider tape right now). I'm glad I ordered the extra roll of glass tape


3/31 - Another Multi Day Update

So we laid up both sides.... Cut the flanges - did some trimming... And here it is held together with a few pieces of packing tape...



Today, we started with some glass tape to permanently combine the halves



As for weight.... Well, I'm keeping some things to myself. I'll tell you, eventually, but right now - it's a secret (but an awesome secret). I'll just say that the two halves weigh a few ounces more than the first half that got messed up I'll show you the crazy awesome rib structure later too

4/13 - So Much Progress!
It's been awhile since I've updated this
  1. Both Halves Combined
  2. Service hatch has been cut
  3. "Special" Rods have been made for mounting
  4. Custom Aluminum Set Screw Collets have been laminated to the fairing
  5. Door design has been modified
  6. Door design was scapped
  7. Door design was modified - again
  8. Door design was scrapped - uber hinge idea to lift the entire service hatch
  9. Uber NACA was laid up, mounted and hole was cut
  10. windshield was cut


Check out this awesome carbon/kevlar rod... I know it's not as pretty as the weave, but it's very functional, very light and strong enough That rod isn't even an ounce


Surprisingly, I don't have a picture of my beautiful hinge arm We're lifting half of the fairing up - reverse funny car style. This hinge arm makes it clear the seam - much like several designs for a car's hood hinge. I laminated 4 aluminum plates in there with two layers of glass tape that was spiral wrapped and spray glued into place (one layer in one direction and the second in the opposite direction). Then, I wrapped it with an outer layer of carbon. This was vacuum bagged. Weight: 7.5 ounces. A little heavy, but the Aluminum weighed 4-5 ounces


A little sneak of the incomplete frame... As pictured it's missing its side roll bars.

Last week, we cut this

Windscreen! The blue is the color of the protective film. The thing is actually clear


It looks angry to me I like. And, it's very functional - I have great visibility, I even have some peripheral vision

If I didn't mention it before... We'll be painting the thing white. Ya, it adds weight (a few pounds), but you won't bake. We intend on using this in Florida - and it gets freaking hot in there. In the sun, you can't touch the surface because it gets so hot. We're going to build a hot room to help the paint flow out - the stuff we got will have a smoother finish if you heat it to 150 for 30 minutes.
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Last edited by trebuchet03; 05-03-2008 at 01:01 AM..
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Old 03-23-2008, 08:55 AM   #29 (permalink)
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What is the projected .Cd for the design in FlowWorks ?
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Old 03-23-2008, 09:36 PM   #30 (permalink)
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What is the projected .Cd for the design in FlowWorks ?
FloWorks says .09

FLUENT (we've since meshed a model for FLUENT) says .086

Both at 30mph (or maybe it was 20 - I'll have to double check).

It sounds freaking low, but - max Reynolds number = 184. Not 184 thousand, just 184. We'll get scale wind tunnel testing soon

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