Honda Insight Under-body Smoothing Panels (custom belly pan / undertray)

[3-Wheeler]

Originally Posted by Ecocinqueboy

Hello,Three Wheeler,

I am very impressed by all the work you have done on your undertray.

1. I was wondering how you allow all the heat from the cooling system,the engine and the exhaust to escape ,especially the cats which run really hot.
2. Is the heat not trapped between the underpan and the underside of the car body?
3 In winter I suppose that it warms the car interior more easily but in summer ,is there not a fire risk?

Ecocinqueboy.

There is only one cat under the hood, and I had to cover this with fiberglass batting to keep underhood temperatures down to a reasonable level in the summer.

The heat is not trapped, because just as basjoos has mentioned, the heat travels through the radiator, through the engine compartment, and out the wheel wells. The heat can also exhaust through the slots next to the windshield wipers.

In my case, it can also exit just in front of the second catcon underneath the car.

In the winter, the engine heat is so low that I have a hard time keeping heat in the radiator, even with an almost full radiator block.

Jim.

[3-Wheeler]

After two full years of being mounted on the car, the panels had to come off for a tire alignment.

Getting the fasteners out proved difficult, as many were rusted in and simply broke off when trying to be eased out with the screw driver.

The car went in for alignment, and after it came back, I had to drill out several of the broken fasteners.

Most of the panels looked pretty good, but several had some severe water damage and needed to be fixed.

The panel shown below is from the location right under the engine, and the section affected is right in front of the front tire, and gets quite a bit of water/snow flung from the front tire.

There are cut wood dowels that fasten to the underside of the grill fascia and hold the panel in that location. These wood dowels were complete saturated with water and had to be removed, and new one's embedded back into the foam in the same location.

This time, epoxy/micro balloons were mixed to form a slurry, that will hold and seal the wood dowels and not break down chemically from the water.



The same thing for the other front tire.



This part of the spat got hit with some debris on snow covered roads, and knocked out a chunk of foam, and was re-fiberglassed with several more layers to strengthen it up.



This tab was reinforced with the micro-slurry, since it had sustained water intrusion.



This portion of the panel has, what else, Bondo, and notice that it is simply flaking off.



The same thing again for this spot on the panel. It's pretty obvious that Bondo is not an item that should be used on epoxy/fiberglass composites. It just does not stick well enough long term.



Jim.

[jime57]

I used coroplast in the center and aluminum panels at the front and back. I think that might be more rugged. I also used a lot of the automotive grade plastic "pop" fastners, which cannot rust. I'm thinking of removing the few bolts I used and coating them with anti-seeze grease.

The aluminum cannot be shaped into complex shapes, and that is a slight negative, but this can be compensated by using multiple panels. Not as smooth as 3-wheeler, but looking at production panels like the Audi A8, I think it is probably adequate.

[3-Wheeler]

Originally Posted by jimepting

I used coroplast in the center and aluminum panels at the front and back. I think that might be more rugged. I also used a lot of the automotive grade plastic "pop" fastners, which cannot rust. I'm thinking of removing the few bolts I used and coating them with anti-seeze grease.

The aluminum cannot be shaped into complex shapes, and that is a slight negative, but this can be compensated by using multiple panels. Not as smooth as 3-wheeler, but looking at production panels like the Audi A8, I think it is probably adequate.

Actually Jim, I am using Anti-Sieze compound on all metal fasteners as well. I found out about this from the body shop that did the repairs on the car.

Will report back on how well it works after another winter.

Jim.

[rvpps2rocks]

Props on your attention to detail. Looks amazing, great job

[ECONORAM]

Originally Posted by 3-Wheeler

After two full years of being mounted on the car, the panels had to come off for a tire alignment.

Getting the fasteners out proved difficult, as many were rusted in and simply broke off when trying to be eased out with the screw driver.

The car went in for alignment, and after it came back, I had to drill out several of the broken fasteners.

Most of the panels looked pretty good, but several had some severe water damage and needed to be fixed.

The panel shown below is from the location right under the engine, and the section affected is right in front of the front tire, and gets quite a bit of water/snow flung from the front tire.

There are cut wood dowels that fasten to the underside of the grill fascia and hold the panel in that location. These wood dowels were complete saturated with water and had to be removed, and new one's embedded back into the foam in the same location.

This time, epoxy/micro balloons were mixed to form a slurry, that will hold and seal the wood dowels and not break down chemically from the water.


Jim.

Pretty remarkable for your first undertray project and 2 years of use. Just pointers to help you (and us) make better aero parts down the road. Well done. I took some pointers from your construction and material choices. might have to follow suit on my wife's Avenger. With the truck I went the route jime57 did; 0.050" aluminum sheet down the center, with corroplast on the sides and plastic automotive fasteners and 1/4" bolts (had to start somewhere). I might have to incorporate some of your foam building in the engine bay. Thanks for sharing!

[brucepick]

This project shows amazing craftsmanship. Thank you.

How did you attach the panels along the sides - at the rocker panels?

[3-Wheeler]

Originally Posted by brucepick

This project shows amazing craftsmanship. Thank you.

How did you attach the panels along the sides - at the rocker panels?

Hi Bruce,

I originally used mild steel fasteners in all locations, and they work fine, until driven in the winter with salt on the road.

Since then, I switched to stainless fasteners where possible.

The rocker panels still have mild steel plaster board screws. Each year, I have to pull these out, and either replace with new, or coat them with anti-seize paste.

Fastener rust is the biggest issue I have with the underbody panels and tail.

Speaking of rust, part of tail is held on with 1/4-20 x 4in bolts, and some of these rusted enough over the years, to break off when attempting to tighten slightly. I had to remove the tail to replace all the mild steel bolts with stainless.

Hopefully this summer I will get the chance to completely sand down the tail to get all the lumps out and then repaint it with a color that matches the car. The lumps came from using light-weight spackling as filler, and expanded when the sun heated up the surface in the summer.

Jim.

[brucepick]

Thanks.

How about stainless steel sheet metal screws for the rocker panels? I think the Insight rockers are aluminum; if that's correct then electrolysis between this two metals is not as bad as with other combinations. Is thread pitch too shallow on sheet metal screws?

[3-Wheeler]

Originally Posted by brucepick

Thanks.

How about stainless steel sheet metal screws for the rocker panels? I think the Insight rockers are aluminum; if that's correct then electrolysis between this two metals is not as bad as with other combinations. Is thread pitch too shallow on sheet metal screws?

Regarding stainless screws for panels under the driver area, I tried some stainless ones from Menards but the threads do run all the way to the head, and so they don't work. Might have to find some online and order them.

Yes, the frame structure is aluminum there, so the chemical reaction between steel and aluminum occurs quickly.

The thread pitch is "course" on the sheet metal screws, and these are now stainless, so not really an issue.

Jim.