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trebuchet03 02-24-2008 11:56 PM

Building an HPV Fairing
 
It's that time of year again! It's time to make our fairing for this year's competition. We've been designing for the better part of 6 months, now it's crunch time and time to manufacture. I'll keep updating this post as progress is made.

I'll put a better into here eventually... For now, here's some history...
2006 Model
http://www.primitiveengineering.com/...g/06ucfhpv.jpg

2007 Model
http://www.primitiveengineering.com/...8/fairing1.jpg

The 2008 Model shares characteristics of both previous models (moreso the 2007).

If you ever want to make a fiberglass or CF or Kevlar etc. fairing for your car - the process will be very similar


2/24 - Foam Cross Sections
Today we sketched out cross sections of our fairing onto 1" 4x8' sheets of foam.
http://www.primitiveengineering.com/.../truckfoam.jpg

This section looks squid like : D
http://www.primitiveengineering.com/.../squidfoam.jpg

Here's a bunch of the top sections on one sheet of foam.
http://www.primitiveengineering.com/.../crossfoam.jpg

What does done do with foam cross sections? You cut them out, glue them together and make a male plug. More on that later.

Careful Details: There's 2 or 3 keys. A quarter inch PVC pipe will be put through these holes with align the entire thing. The rectangle thing you see is a 5" by 24" index rectangle extruded through the entire model. We used this to make sure the projector was calibrated to 100% scale. How did we get sections? We just used the cross section view in Solidworks directly off our 3D model and projected it on a wall.

2/28 ish - Vendors and Models
Timing is critical. Ideally, we would be much further than we are. But predictably, we’re right where I thought I would be.

Composites Order In? Check - Pickup Friday March 7 from S. Florida
Home Depot Supplies? Check - Got the last (for now) items today and delivered to workshop
Frame Team? On Track - manufacturing begins Saturday

Rose, from UCF’s ASF budget office has been really great this year (ALL of our order must be signed by three people, the approved by someone in Rose’s office, then Rose has a PO made and she submits the order to the vendor). She was out, sick, for the past two days and the pile up of paperwork was obvious - a lot of people depend on her (and she does a great job). I visited her today to follow up on some budget requests, and she moved us to the front of the line - I had a phone call from one of our vendors within 30 minutes to work out a pick-up date (it’s a really big and fairly complicated order).

Tomorrow, I will start around noon on cutting foam and gluing together. Hopefully, the plug foam can be finished (glued).
Saturday, I am going on Catrike’s annual ‘bent rally. I don’t own a Catrike (I wish) but I’ll be riding my Challenge Distance.
Sunday, I hope to have the plug sanded and an initial coat of joint compound applied (so it can have a nice long/slow cure). To save on Bondo costs and sanding time, we’ll be using wall joint compound. I currently have a few samples curing at the moment to test for dry times/conditions. It’s cold right now, so hopefully that doesn’t cause problems.

So right now, I’ve got some compound curing on a rough scale model (testing surface finish of this stuff). This model will need a lot of compound to reach the proper shape… Oh, and because I’m hinting on shape here - material hint: think graphite and bullet proof material - no paint and light weight : D

http://www.primitiveengineering.com/...roughmodel.jpg

3/02 - Plugging Away!
Friday, here's what we look like....
http://www.primitiveengineering.com/...8/foamglue.jpg
Foam sections were cut, then glued together.

The next step is sanding... To speed the process up, a cheese grater did the bulk of the material removal. We then followed up with sand paper and drywall screens.
http://primitiveengineering.com/blog...8/sandfoam.jpg

http://primitiveengineering.com/blog...sandedfoam.jpg

Once we finished sanding.... Joint compound was applied. While it takes longer to cure - two 5 gallon buckets cost the same as 1 gallon of Bondo. Additionally, if we used Bondo - we would have needed to apply a layer of epoxied fiberglass as Bondo will melt styrene foams. Lastly, we can wet sponge sand joint compound and get super smooth finishes.
http://primitiveengineering.com/blog...08/fairmud.jpg

Details - be sure to apply enough joint compound as not to expose any foam. Polyester resin + styrene foam is a very bad combo.

3/7 - Materials Pick Up
http://primitiveengineering.com/blog...uffinmycar.jpg

I drove to West Palm Beach to pick up some materials…. 10 gallons of polyester resin, a mess of epoxy and a whole bunch of other materials : D Here’s some stuff in my car - there’s four more boxes that you can’t see : D

3/10 - Bottom Job
http://primitiveengineering.com/blog.../bottomjob.jpg

The interesting thing about wall mud… Apply a thick coat, and it’s difficult to get bubbles out. So much so that we spent about a day of labor filling bubble holes, re-sanding - then discovering more holes….

Oh, we made some samples today... This is a preliminary first test...
http://primitiveengineering.com/blog...samplecure.jpg

Combos include base fabric alone. Base, coremat (1.5"), fiberglass (3" wide). Base, Foam (1"x.125"), glass. Base, Foam (1"x1"), glass. Base, Kevlar.


3/11 - Bondo Epiphany
http://primitiveengineering.com/blog.../bondocoat.jpg

To fix all those air bubble holes... Bondo! And the surface finish is very very smooth (ideal). So a thin coat for the entire plug! Sanding comes soon...

And we did more sample testing....
http://primitiveengineering.com/blog.../samplevac.jpg
Foam is much lighter than the coremat as it doesn't soak up much/any resin. It's also much stiffer (or seems to be). I cut cross grain and with the grain of the foam (2 samples each) using a jig on a band saw (for uniformity). They're currently on my patio under vacuum....

The plan is to get into the materials lab tomorrow and do some testing... Thus far, I've worked out an Izod impact test - tensile testing and potentially a bending test. I'm designing an abrasion experiment now.

3/14 - Woo Glass!
In the past three days -
First round of material testing
Finished Plug
Third round of sample making
Built a plug frame/table
Cut table and sealed plug to table with Bondo
Applied mold releases (wax and PVA)
Laid up a tool (1 of 2)

Tool Table
http://primitiveengineering.com/blog.../tooltable.jpg

Cut Table
http://primitiveengineering.com/blog...8/tablecut.jpg

Edge of Plug bondo'd to table surface
http://primitiveengineering.com/blog...tablebondo.jpg

Wax applied - then PVA sprayed (which is why it has a green tint)
http://primitiveengineering.com/blog...08/toolpva.jpg

First Tool as we left it today
http://primitiveengineering.com/blog...08/tooling.jpg

So - materials testing - we did Izod impact testing with some surprising results. We had some samples with a layer of glass, 1/8" foam, layer of carbon/Kevlar. We impacted the carbon/Kevlar side and a curious thing happened. The foam/glass broke and the carbon/Kevlar just bent out of the way. In one case, the carbon/Kevlar de-laminated from the foam. I'll have more info on this later.

We prepared some samples for tensile testing. To do this, we made our normal samples but laminated a metal plate on each end between the layer of carbon/Kevlar and a layer of fiberglass. This metal plate allows metal gripper jaws to clamp down while a machine pulls the sample apart. Oh, the vacuum pump seized up while making these samples. I tore it down today (3/14), applied some oil to the bearing and vanes and the thing spins again! I think the heat got to it as the oil level is correct...


The plug was placed in that table to make a perfect 1/2 waterline plane in which 1 of the 2 tools could be laid up. Bondo sealed the edges (to keep resin from leaking down) - the plug was waxed at the waterline so the bondo can be separated later.

The plug is prepped with paste wax #2 (by hand) and PVA #10 sprayed on with an HVLP gun.

So FIBERGLASS!!!!!
We only had three people today, so it was a scramble. The tool structure isn't perfect (should work though), but we applied a gel coat like layer of resin first to ensure a good surface finish. To make this gel coat substitute, mix cab-o-sil (aka aerosil aka fumed silica) into polyester resin until you can remove the mixing stick and nothing drips off (and it holds peaks). Then add a little more as the MEKP catalyst will thin it out a little. Mix in your hardener (MEKP) then apply the resin to the surface with a brush (careful not to tear the PVA). It's thixotropic - this means when you apply a force to it, it becomes thinner - but only while applying a force (this is why hitting the ketchup jar makes it come out). Smooth out the entire surface with long strokes. You may have to work the same area with several brush strokes so the resin thins out and flows enough to coat smoothly (when you let it sit, it will gel up until moved again).

4 layers of 1.5oz chopped fiberglass mat was applied. The edges were also glassed to make ~2" flange for use later.

http://primitiveengineering.com/blog...08/tooling.jpg

The temperature swings today were quite insane - it was really cold, followed by pretty warm. Enough to totally screw up my hardener measurements which caused some areas to start smoking : eek : I'll use less hardener tomorrow (but it's supposed to be warmer anyway : D).

3/15 - Glass Take Two
Today we popped the plug/half tool out of the grips of the table
Cut the flange down to size (somewhere between 2 and 3 inches)
Cleared the table of excess bondo
Put the plug back into the table
Fixed the gashes in the foam from cutting the table
Covered any exposed foam (packing tape - it works awesome as a barrier)
Waxed
Sprayed PVA
Applied resin/glass - four people today : thumbup :

http://primitiveengineering.com/blog...v08/popped.jpg
To pop it out - scrape around the flange with a putty knife. Then, shake the table. Lift the plug with a jack (throw some foam under to protect it) - bang on the table a little more... Enough banging will get it to pop out. You don't want to separate the tool from the plug just yet...

http://primitiveengineering.com/blog...08/trimmed.jpg
Flange trimmed with a jigsaw.

http://primitiveengineering.com/blog...secondtool.jpg
By the end of the day - the result... The fourth person really helped. We had one person dedicated to cutting glass, one person dedicated to mixing and pouring resin and two people dedicated to wetting out (and they always worked the same areas so they know exactly how to handle challenges of those particular curves).

Oh, the wind wasn't with us today - so we didn't have as good of ventilation. We got a little stoned by the end of it - I made sure everyone sat outside in fresh air for awhile before we went back in to clean up... Yesterday, the wind wasn't giving us problems - and there were no side effects from the styrene...

3/16 - Birthday Problems : (
Today is my birthday! I'm 22 : eek : Today was clean up and mold separation day. So the entire plug+tools weighs somewhere in the realm of 300+ pounds. It was only two people today, and lifting was quite a task. The workshop was cleaned up, organized, swept, etc.

Then came mold release time... Mixing sticks were used as wedges to split the tool flanges apart. One tool came off in 30-45 minutes of labor. The other half (the first one we laid up) didn't go so easily. Eventually, we drilled 7 or 8 small holes to hit it with compressed air - and that didn't even work. We then dumped water in there - to try and liquefy the PVA release agent and soften the joint compound. That didn't work. We tried several other methods over a period of 3-4 hours....

Sadly, here was the scene....
http://primitiveengineering.com/blog...8/chainsaw.jpg

http://primitiveengineering.com/blog...08/crowbar.jpg

A Chainsaw and crowabar... The mold release failed - in epic fashion. This plug is officially done... But, the good news is - the tooling surface is good! I love how well that cheap gel coat alternative works : D

So comes to an end the spring break work week. Hours tallied - 76 by me alone... I gotta see how many everyone else did (I think it's somewhere around 200-250 this week alone)...

3/17 - This... Is a Tease

It's not done... It still has another hour or so until it's finished... And then it needs some post processing... But here it is.

http://primitiveengineering.com/blog...pv08/rpmid.jpg

I'll show you what it is when it's done and cleaned up : D


3/18 - Here It is!

After several meetings and model revisions (to save on material) - this came out of a machine... Rapid prototyped in 9 hours - the material is ABS and the process was fused deposition : thumbup :

http://primitiveengineering.com/blog...freshprint.jpg

http://primitiveengineering.com/blog...pv08/model.jpg

So we spoke wit another professor who controlled the measurements lab - which has a water tunnel.... Basically, he said go do it - do it now, just figure it out and get it done... My kind of attitude!

This shows the stagnation point at the front of the model...
http://primitiveengineering.com/blog...stagnation.jpg


Flow over the model - sticky all the way...
http://primitiveengineering.com/blog...8/flowover.jpg


Iso view... Some turbulence due to surface finish (ridges that haven't been fully sanded down)
http://primitiveengineering.com/blog...08/flowiso.jpg

Smoke screen - basically, pump the dye tank pressure up and open the valve all the way....
http://primitiveengineering.com/blog.../screendye.jpg

More sticky flow
http://primitiveengineering.com/blog...stickyflow.jpg


So we also did some sample testing... These were tensile tests - ripped apart until destroyed...
http://primitiveengineering.com/blog...sampletest.jpg
I'll tell you the forces later : thumbup :

And... At the end of the day, my friend on the swirl burner design project was doing some cold flow tests with compressed air and a fog machine... Here's some CFD (compressor fluid dynamics) with smoke...
http://primitiveengineering.com/blog/img/hpv08/cfda.jpg

That's all for today - we've also been working on our design report... All engineering type stuff, not so much with the actual build... But the extra cure time for the tools is a good thing...


3/20 - Doors!

http://primitiveengineering.com/blog...plodedview.JPG

http://primitiveengineering.com/blog...atchclosed.JPG

http://primitiveengineering.com/blog...hopen_side.JPG

http://primitiveengineering.com/blog...open_front.JPG


And that's all I have to say at this time....

Christopher Jordan 02-25-2008 11:45 AM

EXCELLENT! This event was carefully followed by a velomobile blog, then the competitors just vanished. A similar competition was held in Cal Poly- San Luis Obispo in 2006; and those vehicles also seemed to vanish.

Thanks for providing this info here- I do not have to leave my desk!

countersTrike

MetroMPG 02-25-2008 07:49 PM

Nice - looking forward to following the progress.

Gone4 02-26-2008 04:08 PM

This looks very cool. I can't wait to see how it comes out.

Are you on the team making the fairing?
We just hit the crunch time for our senior projects. I'm more of a design weenie and hate this phase so I step back and watch others massacre my hard work until it functions :D.

Christopher Jordan 02-26-2008 10:53 PM

This project is very similar to how my fairing was made. The plan was to mass produce fairings... but in 2004, two had sold, so the program was dropped. (good for me to be one of the two customers since I got two trikes used as model dimensions and 4 trimmed and cut fiberglass/kevlar fairing parts).

Over 3 years later- still smiling; yet every once in a while this HPV design invention is tried.

countersTrike

trebuchet03 02-26-2008 10:58 PM

Quote:

Originally Posted by GenKreton (Post 11473)
This looks very cool. I can't wait to see how it comes out.

Are you on the team making the fairing?
We just hit the crunch time for our senior projects. I'm more of a design weenie and hate this phase so I step back and watch others massacre my hard work until it functions :D.

Yes, I'm one of 5 people on this fairing team :) We're in crunch time - While our event is in mid/late April - we need to have our design report done by march 22 :eek: And, they want photos, descriptions, testing etc :)

I love making things - so this is right up my ally :D But like the saying goes...
Quote:

If it ain't broke, fix it until it is.
:thumbup:

trebuchet03 02-28-2008 03:41 PM

2/28 Update - nothing too special, expect more awesome fun type stuff this weekend ;)

Whoops 02-28-2008 04:37 PM

Making and breaking things is the fun part. That reporting, pictures and other stuff is the bureaucratic side of things. It isn't much fun, at least I don't enjoy it, but it is necessary for other people to have some idea of what's going on. Good Luck

trebuchet03 03-02-2008 08:09 PM

3/2 update!

Oh, forgot to mention that yesterday I went on the Catrike rally and factory tour... There will be another thread on that shortly...

trebuchet03 03-11-2008 11:15 PM

3/11 updates :)

MetroMPG 03-12-2008 12:00 AM

So to clarify... Joint compound is the same as wall mud, correct?

And you abandoned it in favour of bondo for smoothing out the plug because of the bubbles?

EDIT: I can see the attraction of using wall mud - it would be really easy to sand & shape, compared to bondo.

trebuchet03 03-12-2008 12:46 AM

Quote:

Originally Posted by MetroMPG (Post 13819)
So to clarify... Joint compound is the same as wall mud, correct?

And you abandoned it in favour of bondo for smoothing out the plug because of the bubbles?

EDIT: I can see the attraction of using wall mud - it would be really easy to sand & shape, compared to bondo.

Yes, wall mud=joint compound -- I interchange those terms at will (sorry) :p

We didn't abandon it so much as we used it as a primer/conversion coat. Wall mud cures by drying (which is why it can't get wet). Bondo chemically cures and contains styrene. Because it contains styrene, it will melt polystyrene foam (and won't actually stick). So the mud is used as the initial build up/primer and acts as a compatible layer between the foam and Bondo.

If we wanted to use bondo from the start (no mud), we would need to apply a layer of glass and epoxy resin to serve as a boundary (this is what was done last year).

And yes, wall mud is SO MUCH easier to sand and shape. But it has long cure times. Bondo is much much harder, much smoother when sanded and cures quickly (sets within minutes - or seconds if too much hardener is used :rolleyes:)



I think this will be the method used in the future - unless something better comes along :)

MetroMPG 03-12-2008 12:52 AM

OK, thanks for the clarification. Just thinking ahead to the partial Kammback construction for the Fireflea this summer. I think I'm going to shape a "plug", then glass it to make the part.

Harpo 03-12-2008 06:17 AM

Looks Good!
 
I had the privilege to consult and power a HPA in the early 80's. Unfortunately, the Warped Wing and trailing tail design had big parasite drag problems. I'd trained up to give 'er ~265watts for an hour or two, but any course adjustment made it closer to 300watts. We made our spars with kevlar tape wrapped around aluminum tubing, then ate the aluminum out with acid.

Will this be speed contest or endurance? How many watts will the occupant deliver and for what period of time? I'm a USA Cycling Coach, so I'm very in to the power training.

trebuchet03 03-15-2008 12:27 AM

Quote:

Originally Posted by Harpo (Post 13840)
I had the privilege to consult and power a HPA in the early 80's. Unfortunately, the Warped Wing and trailing tail design had big parasite drag problems. I'd trained up to give 'er ~265watts for an hour or two, but any course adjustment made it closer to 300watts. We made our spars with kevlar tape wrapped around aluminum tubing, then ate the aluminum out with acid.

Awesome!

Quote:

Originally Posted by Harpo (Post 13840)
Will this be speed contest or endurance?

Yes

Points breakdown
Design: 40%
Sprint: 30%
Endurance (relay type race): 30%


Quote:

Originally Posted by Harpo (Post 13840)
How many watts will the occupant deliver and for what period of time? I'm a USA Cycling Coach, so I'm very in to the power training.

We have a minimum of four riders - 1 of which must be female. I've personally been doing 3x5 interval training for the sprint event and then constant wattage training for the endurance.

For the endurance training - I'm trying to work up to 200 watts sustained for 60 minutes. Right now, I'm around 160 on plateau :/ I've got a little more than a month to keep working on it. For the actual endurance event, I'll only be riding for ~30 minutes. What kinda sucks - the recumbent machines that can give wattage readings are in a much more upright position compared to the seat position of the actual vehicle - but, my own 'bent is a bit closer to the actual seat position :thumbup:



Oh, and original post updated :D

Harpo 03-15-2008 06:50 AM

More info!
 
How long is the sprint in minutes?

I have some training recommendations for the endurance/tempo 30 minute effort. You can make some progress in four weeks. Assuming 160watts is your 60 minute power.

Tempo work is good, but to really get the metabolic changes, you need to be developing closer to the watts you want to meet. The bread and butter training for 30 minute efforts are 8-20 min., sustained efforts.

Week One
Tues - 3 reps x 8 minutes with 2 minute recovery (180 watts)
**Minutes 6-8 should require concentration to maintain rpm, but you should not be anaerobic and gasping for air**
Wed - 2 reps x 8 minutes with 1:30 minute recovery (180 watts)
Thur - Spin 45-60 min. in Zone 1 HR (<=120 watts)
Fri - 3 reps x 8 minutes with 2 minute recovery (180 watts)
Sat - OFF or Spin 20-30 min. in Zone 1 HR (<=120 watts)
Sun - 60-90 minute tempo (avg 150 watts)
Mon - OFF or Spin 20-30 min. in Zone 1 HR (<=120 watts)

We can possibly work up to 12's at 190 watts, but 200 watts will be a stretch with roughly 12-14 workouts.

MetroMPG 03-15-2008 10:07 AM

Quote:

Originally Posted by Frank Lee (Post 14367)
When I built a foam/glass body for a SAE super-high mileage car...

I didn't know about this. Post up a thread, Frank!

I don't suppose you have any pics?

MetroMPG 03-15-2008 10:09 AM

Quote:

Originally Posted by trebuchet03 (Post 14366)
the recumbent machines that can give wattage readings are in a much more upright position compared to the seat position of the actual vehicle

Are there design restrictions on seat angle/height?

trebuchet03 03-17-2008 01:31 AM

Two day update! Today was a sad update though :(

MetroMPG 03-17-2008 10:33 AM

Well, happy belated.

Interesting method of getting the foam out, for sure!

trebuchet03 03-18-2008 12:27 AM

Quote:

Originally Posted by MetroMPG (Post 14672)
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....

trebuchet03 03-18-2008 08:45 PM

Updates.... Look at the cool yellow model :)

MetroMPG 03-18-2008 09:17 PM

Cool. 3-D printing. Great thread.

LostCause 03-18-2008 10:17 PM

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. :D

Mango Side
http://i264.photobucket.com/albums/i...Mangoside1.jpg

Mango Top
http://i264.photobucket.com/albums/i.../Mangotop1.jpg

Ristroretto
http://i264.photobucket.com/albums/i...istretto03.jpg

- LostCause

Chris D. 03-19-2008 03:33 AM

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..

trebuchet03 03-19-2008 10:46 AM

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 :D

trebuchet03 03-21-2008 12:08 AM

Check out the groovy cad....

trebuchet03 03-23-2008 01:12 AM

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
http://primitiveengineering.com/blog...pv08/tools.jpg

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.
http://primitiveengineering.com/blog...08/ribbing.jpg

Here's the ribs
http://primitiveengineering.com/blog/img/hpv08/ribs.jpg

Laying out ribs
http://primitiveengineering.com/blog.../riblayout.jpg

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.
http://primitiveengineering.com/blog...ematlayout.jpg

Peel Ply and breather laid out
http://primitiveengineering.com/blog...ndbreather.jpg

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.
http://primitiveengineering.com/blog...8/assembly.jpg

Peel ply (back) - breather and Kevlar (middle) - custom vacuum bag (front)
http://primitiveengineering.com/blog...kevlar_bag.jpg

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...
http://primitiveengineering.com/blog...frost_here.jpg
:D
The tool was then sanded again up to 800 grit.

Then, we draped...
http://primitiveengineering.com/blog...arbondrape.jpg
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 : )
http://primitiveengineering.com/blog...tingcarbon.jpg

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.

http://primitiveengineering.com/blog...v08/vacbag.jpg
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 : )

http://primitiveengineering.com/blog/img/hpv08/done.jpg

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...

http://primitiveengineering.com/blog...bagrelease.jpg
Easy way to release the vacuum bag - add a little pressure from a shop vac :D

And it was terrible! It couldn't hold it's own weight and just folded over.... Just too weak. The solution? T ribs.
http://primitiveengineering.com/blog...pv08/tbeam.jpg
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).

http://primitiveengineering.com/blog...ngineering.jpg
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...
http://primitiveengineering.com/blog...8/newbeams.jpg

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.
http://primitiveengineering.com/blog...8/secondat.jpg

So here's the other problem....
http://primitiveengineering.com/blog.../resinrich.jpg
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 :/

http://primitiveengineering.com/blog...pv08/inlab.jpg
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?
http://primitiveengineering.com/blog...8/sewglass.jpg
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...

http://primitiveengineering.com/blog...pv08/front.jpg

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

http://primitiveengineering.com/blog/img/hpv08/tape.jpg

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 :thumbup: 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

http://primitiveengineering.com/blog/img/hpv08/rod.jpg
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 :thumbup: That rod isn't even an ounce :thumbup::thumbup:

http://primitiveengineering.com/blog...8/hingearm.jpg
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 :p

http://primitiveengineering.com/blog.../integrate.jpg
A little sneak of the incomplete frame... As pictured it's missing its side roll bars.

Last week, we cut this :D
http://primitiveengineering.com/blog...rofilewind.jpg
Windscreen! The blue is the color of the protective film. The thing is actually clear ;)

http://primitiveengineering.com/blog...windscreen.jpg
It looks angry to me :D I like. And, it's very functional - I have great visibility, I even have some peripheral vision :thumbup:

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.

Cd 03-23-2008 08:55 AM

What is the projected .Cd for the design in FlowWorks ?

trebuchet03 03-23-2008 09:36 PM

Quote:

Originally Posted by .Cd (Post 15694)
What is the projected .Cd for the design in FlowWorks ?

FloWorks says .09

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

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 :)

trebuchet03 03-23-2008 10:56 PM

Update above (this page)

Direct Link

trebuchet03 03-27-2008 12:36 AM

Updates in post above... Good and Bad.... We're on the good side of things now :)
Direct Link

Cd 03-28-2008 01:28 PM

Quote:

Originally Posted by trebuchet03 (Post 15795)
FloWorks says .09

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

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 :)


How does FLUENT compare to FloWorks in ease of use ?

Point zero eighty six. Slick !

I wonder how that this would translate to a full size car if the shapes were identical. I know that the frontal area would change, but how is the .Cd value changed when a shape such as yours is scaled up ?

trebuchet03 03-28-2008 01:45 PM

Quote:

Originally Posted by .Cd (Post 16688)
How does FLUENT compare to FloWorks in ease of use ?

Point zero eighty six. Slick !

I wonder how that this would translate to a full size car if the shapes were identical. I know that the frontal area would change, but how is the .Cd value changed when a shape such as yours is scaled up ?

Fluent is considered to be more robust and more accurate - but, it's not as user friendly. You need to use Gambit (another piece of software) to create the fluid mesh which, if you don't know what you're doing, will fail.

Floworks is much faster to setup - there's a nice GUI and it automatically makes the wind tunnel and creates the mesh.

If you don't know what a mesh is.... A mesh creates discrete points in space for the solver to use. Otherwise, it would have to solve an infinite matrix of equations. If you ever see CFD with nice smooth lines/color gradients - that's interpolated data to connect the dots on the mesh ;)

As for scale up... I can do a run tonight and tell you :p All one would have to do is run the test at a higher velocity (as if you modeled scaled down). What overall dimensions do you want? Just give me a width and I'll scale everything up proportionally. Theoretically, cD shouldn't change very much - but Reynolds number will (which could mean some of the flow goes turbulent)...

AndrewJ 03-28-2008 09:11 PM

A quick question for clarity's sake.

If I remember correctly you previously said that your CFD program doesn't compute the Cd in ground effect, right?

So what will the Cd be with the ground effect?

Christopher Jordan 03-29-2008 01:16 PM

How very labor intensive! Congrats! I am in awe- mine went through similar forming, but I had no idea of how much time and labor went into it- when I got it in 2005 I slaapped the Pod together in 2 months maximum.

trebuchet03 03-30-2008 11:29 AM

Quote:

Originally Posted by AndrewJ (Post 16769)
A quick question for clarity's sake.

If I remember correctly you previously said that your CFD program doesn't compute the Cd in ground effect, right?

So what will the Cd be with the ground effect?

No clue :/ I'd love to know how to make a rolling wind tunnel for CFD - but I don't know how :( If anyone knows (and I know it's possible) - please let me know :thumbup:

trebuchet03 03-30-2008 11:33 AM

Quote:

Originally Posted by Christopher Jordan (Post 16826)
How very labor intensive! Congrats! I am in awe- mine went through similar forming, but I had no idea of how much time and labor went into it- when I got it in 2005 I slaapped the Pod together in 2 months maximum.

We just passed to one month date for actual construction :D I'll have an update later after we pull the second attempt of the first part out :thumbup:

trebuchet03 03-31-2008 08:36 PM

Another update above :) Go check it out :)

pawilkes 03-31-2008 09:18 PM

I was at competition last year, mostly as a spectator. my grad school research was on designing a hand-powered cycle that the HPV team from Wisconsin based their design on last year. anyhow, i was amazed at the fairing UCF put together last year and i guess you're just building on that. good luck at competition and enjoy Wisconsin's spring conditions.


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