Designing a tail extension for the first-gen Insight

[3-Wheeler]

Originally Posted by jimepting

...Question: I did some experimental sanding today on a piece of packing type styrofoam. I used 80 grit and I noticed that I had to get the pressure just right to avoid ripping the little balls away whole. Of course that made the surface very rough. Does the construction grade white and pink sand better?...

Yes, the pink/blue Styrofoam is MUCH better than the white packing foam.

The white stuff has a lower density, and will allow it to get crushed very easily, even with a layer or two of fiberglass cloth over the outside.

The pink/blue Styrofoam is better, since it has a higher density.

While being picky when I say this, but for best results you would want to find industrial foams that are two to five times more dense than Styrofoam.

IndyCar and F1 race cars use Hexcel aluminum honeycomb for really high quality and really expensive carbon composite structures.

I stick with Styrofoam for ease of purchase and it's workability.

Speaking of which, I use the following tools almost exclusively for shaping/working with foam:

1) Hand saw (for cutting wood, to make long foam cuts)
2) Hack saw blade
3) 1/2 round rasp file
4) 60 grit sand paper glued to 4 inch square foam block
5) 120 grit (ditto)
6) Elmers Wood Glue for gluing foam blocks together
7) 1.5 inch long wood screws for holding blocks together until dry

Jim.

[RobertSmalls]

I was on Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc. , and I noticed epoxy resin is $100/gal, whereas polyester resin is $35/gal at the auto parts store. I'm tempted to just use the polyester because I read on the internet it's easier for a beginner to work with. Downsides of polyester are that it eats styrofoam, it's heavier and thicker than an epoxy composite of the same strength, and it gives off more VOC's during curing.

[3-Wheeler]

Robert,

Now that you've had your rear bumper guard off the car, have you had a chance to estimate how much flow area each of those rear vents has?

I'd like to start cutting foam for the transom that contains the license plate and lights, and would like to have a rough estimate on how much of a vent to hole to place behind the plate.

Did a little shopping today!



Thanks, Jim.

[3-Wheeler]

Originally Posted by RobertSmalls

I was on Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc. , and I noticed epoxy resin is $100/gal, whereas polyester resin is $35/gal at the auto parts store. I'm tempted to just use the polyester because I read on the internet it's easier for a beginner to work with. Downsides of polyester are that it eats styrofoam, it's heavier and thicker than an epoxy composite of the same strength, and it gives off more VOC's during curing.

Robert,

You won't have any trouble with the epoxy resin. I've used both over the years, and West System makes a very good product.

I bought the mixing plungers with my order. The epoxy has it's own plunger/dispenser, and so does the hardener.

One pump from each container into a Glad-Wrap plastic cup, mix up for a minute, and you are set to go. I purposely mix bubbles into the mixing operation, and then smooth out to remove them when I wet out the cloth.

Make sure to wear a protective glove when handling, so as to make clean up much easier. Although the epoxy is easier to clean up.

The West System epoxy will burn your eyes very slightly if you get too close, but certainly much less so than polyester.

Over the years, I've had way more trouble mixing polyester, because I can easily lose count of how many drops of hardener I put in when interrupted for some reason. To me it's much more tedious. Some of my mixes have turned out, well, let's just say, not too good!! Either it goes too quickly or takes days to set up properly.

The epoxy is a little thinner, and but wets out the cloth fine, and really is very easy to work with. Plus like you said, the smell is much better with epoxy.

I'm going to be putting in an order for another gallon of West System this week some time. I use the 105 epoxy with 206 hardener.

At room temperature it sets up over night. If you want it go to faster then heat to about 120F or so, and it will get hard in about two hours or so. Maybe faster. I run as high as 150F in the oven. The foam starts to get affected above this temperature, so be careful with the heat lamps.

Too much heat and the epoxy will start to blister on the surface. And then too much heat beyond that and the foam will start to get soft are distort in shape. Sometimes the foam shape will come back after it cools down a little and other times, not.

I have noticed on sharp corners, the epoxy does not hold the cloth tightly around the bend like polyester does, or even Elmers Wood Glue for that matter, and that's where vacuum bagging comes in. But if I'm going to vacuum bag, I try to keep the vacuum down to just enough to hold the material tight. Too much vacuum can distort the shape of the part, especially if it's relatively weak foam. Then a heat lamp comes out to accelerate the setup time.

I don't mind paying extra for the better quality product. And with the mixing plungers, every batch sets up just like it should. Very consistent in my experience, and much better than my trials with polyester.

Hope this helps.

Jim.

[Christ]

Originally Posted by 3-Wheeler

Hi Aerohead,

Actually Elmers Wood Glue does get affected by moisture later on.

It will soften and come back off, even after a year. It just takes a while.

I found this out first hand with another motorcycle fairing. The fairing got a crack in it, and the spring time rain kept working it's way into the small opening.

Eventually the delamination was enough for me to perform surgery on the fairing and fix the bad section.

I keep close tabs on the current fairing, looking for cracks, which are really obvious and small chips of paint that get knocked off by pea-gravel hitting the front of the fairing.

And the main reason I started using Elmers Wood Glue, is that at the time I had no way to isolate the Polyester resin from attacking the foam underneath. I never heard of Epoxy resin, and with two young kids growing up, probably could not have paid the steep price for it either.

Like you mentioned previously, now we have Elmers Glue, Latex paint, and/or Epoxy resin to allow the usage of Styrofoam in our composites.

As mentioned, Elmers Glue is pretty robust overall. I would have no qualms about using it on the tail extension.

Jim.

Is Elmer's wood or white (paper) glue water soluble while it's wet?

I'd need a way to thin it out to allow it to soak my fabric material (usually either canvas or polyester sheet fabric) completely without too much intense rubbing labor.

I'm kinda considering making a few things with some of the left over fabric I have later on.

Also, can Elmer's be cured with heat outside of the presence of open air? (Can I vacuum bag it and toss it in the oven?)

[Christ]

Originally Posted by 3-Wheeler

Yes, the pink/blue Styrofoam is MUCH better than the white packing foam.

The white stuff has a lower density, and will allow it to get crushed very easily, even with a layer or two of fiberglass cloth over the outside.

The pink/blue Styrofoam is better, since it has a higher density.

While being picky when I say this, but for best results you would want to find industrial foams that are two to five times more dense than Styrofoam.

IndyCar and F1 race cars use Hexcel aluminum honeycomb for really high quality and really expensive carbon composite structures.

I stick with Styrofoam for ease of purchase and it's workability.

Speaking of which, I use the following tools almost exclusively for shaping/working with foam:

1) Hand saw (for cutting wood, to make long foam cuts)
2) Hack saw blade
3) 1/2 round rasp file
4) 60 grit sand paper glued to 4 inch square foam block
5) 120 grit (ditto)
6) Elmers Wood Glue for gluing foam blocks together
7) 1.5 inch long wood screws for holding blocks together until dry

Jim.

Florist's foam (green, medium density) works perfectly for forms. It breaks into smaller pieces fairly easily, and it's dense enough that you can sand/cut it cleanly, but you can also just push shapes into it (like if you wanted a certain ball shape, you could just push the face of the ball into the foam) which saves alot of work on custom/complex contours.

You can get it in blocks at hobby shops and art/craft stores (Michael's comes to mind, locally).

IIRC, it doesn't glue very well except with hot glues, which actually allow you to glue two pieces flush because the glue melts the foam enough to allow both pieces to face off on each other. You might be able to get away with a brushed layer of Elmer's though.

[jime57]

Originally Posted by 3-Wheeler

Robert,

Now that you've had your rear bumper guard off the car, have you had a chance to estimate how much flow area each of those rear vents has?

(snip)

Did a little shopping today!


Thanks, Jim.

I know I'm way out on a limb with this crazy question, but is there any merit in the idea of "bleeding" air into the underside of the boattail from these vents? The air might help reduce the negative pressure and smooth the overall flow. It is just a thought, and an uneducated one at that. If there were any merit, the discharge vents would have to be handled very carefully I'm sure.

Nice load of material. Where did you buy?

[orange4boy]

There is also a commercial product used in boat building for compound curves. It's a foam sheet with a fibreglass backing on one side. The foam has been sliced into 1/2" cubes so it's flexible. Glass the other side and you have a very rigid sandwich in no time. Can be used with polyester resin or epoxy. No idea on price.

There are also many new waterproof glues in the same family as Elmers glue which would probably work. Check out woodworking stores or hardware stores.

[orange4boy]

And with the mixing plungers, every batch sets up just like it should.

Super important to mix well and fully. no shortcuts here or all your work will be ruined.

MIX MIX MIX! Especially with epoxy which is thicker and harder to mix.

Is Elmer's wood or white (paper) glue water soluble while it's wet?

Yes.

[orange4boy]

Titebond III waterproof "ultimate wood glue"

Betcha that'll do the trick.