Breakfast with Phil Knox

[miket]

http://www.evworld.com/images/pknox_bellypan.jpg
I can't really see what you did around the axles and wheels.

I would love to have an inflatable airplane.

Document sans titre

Woopy-Fly Inflatable Wing Aircraft

Im imagining some sort of shape memory alloy springs that when heated shrinks the inflatable truck tail like accordion or roll up the tail like a sleeping bag. Or a rope that pulls the tail up and over the vehicle. Realistically i would probably get out and fold it up on the street before i entered a parking lot lol.

The current cap is a foot taller than the cab, im going to try and buy a used utility cap, i would like to have the flip up sides and not have the equipment so visible though big glass windows. Some of those utilty caps dont have a radius on the rear and top corners. Sharp edges are bad right? A shorter cap level with the cab would reduce rear area by 4sq feet.

a 2"f/4"r lowering kit would be very pricey but i could lower the rear 2" with a $60 pair of drop shackles if that would be a good idea. I'd probably have the clearance above the diffuser to do it.

I wish the truck had one of those engines that shuts off half of the 8 cylinders while cruising.

Yes i could attach the tail to the trailer hitch or flip up cap door, roof racks etc. I wonder how much a 5ft long tail would reduce cd and improve mpg at 65mph?

[aerohead]

Originally Posted by miket

http://www.evworld.com/images/pknox_bellypan.jpg
I can't really see what you did around the axles and wheels.

I would love to have an inflatable airplane.

Document sans titre

Woopy-Fly Inflatable Wing Aircraft

Im imagining some sort of shape memory alloy springs that when heated shrinks the inflatable truck tail like accordion or roll up the tail like a sleeping bag. Or a rope that pulls the tail up and over the vehicle. Realistically i would probably get out and fold it up on the street before i entered a parking lot lol.

The current cap is a foot taller than the cab, im going to try and buy a used utility cap, i would like to have the flip up sides and not have the equipment so visible though big glass windows. Some of those utilty caps dont have a radius on the rear and top corners. Sharp edges are bad right? A shorter cap level with the cab would reduce rear area by 4sq feet.

a 2"f/4"r lowering kit would be very pricey but i could lower the rear 2" with a $60 pair of drop shackles if that would be a good idea. I'd probably have the clearance above the diffuser to do it.

I wish the truck had one of those engines that shuts off half of the 8 cylinders while cruising.

Yes i could attach the tail to the trailer hitch or flip up cap door, roof racks etc. I wonder how much a 5ft long tail would reduce cd and improve mpg at 65mph?

miket,the area around the front wheels is just open for all the area of wheel flop.I've made no effort to dial in all the little nuances.
The area at the rear axle is open allowing full extension of the axle.There's nothing remarkable about any of it.
My tail rolled up like a sleeping bag with a couple cinch straps to hold when stowed.
Next phase has a hinged,rigid 2-pc bottom which folds down,exposing the envelope which inflates also with fan.
A mechanical reversing valve switches action to evacuate the bag and a simple cable/pulley system folds the bottom panels and draws it to the stowed and locked position.
With respect to your cap,my friend switched a 10-inch taller than cab height box for a cab height box and picked up 3.6 mpg hwy.
Jeeps have a swing-away spare tire holder which might serve you for a tail mount.Parked at the curb you just unlatch and swing to access the utility bed.A 12-VDC umbilical 'hinges' with it to power the tail.
I would recommend you not drop the rear unless you can match it at the front.A negative rake,I believe,would work against you.
18-inches of structure worked out to about 24-inches of tail on my VW Bus,due to the radius at the back of VW's body.That got me 4-mpg.5-feet would be pretty remarkable considering what 44-inches did on the Chrysler Airflow.

[miket]

I love that idea!!!

All the 1gen tundra drops i've seen are lowered 2" more in the back than the front. I've seen 1" rear drops sold as leveling kits. IF i find a budget way to drop the front 2" or maybe 3" Then im looking at droping the rear 2"-5" for about $55parts.

Why would a neutral or negative rake work against me???

If the inflated tail could work with the tailgate extender out then i wouldnt have to worry about rain or snow on the tailgate outside of loading/unloading. I wish my father bought a truck with an extended cab + long bed. Doubt 2' makes much of a driving difference on an 18' truck, heck we will be carrying a 20' long ladders sometimes. But he didnt. Im hoping with bedslides and a shelf we'll be able to cram everything under the cap most of the time and that we''ll need the tailgate extender rarely.

What would i do about the taillights? some sort of trailer light setup?

[aerohead]

Originally Posted by miket

I love that idea!!!

All the 1gen tundra drops i've seen are lowered 2" more in the back than the front. I've seen 1" rear drops sold as leveling kits. IF i find a budget way to drop the front 2" or maybe 3" Then im looking at droping the rear 2"-5" for about $55parts.

Why would a neutral or negative rake work against me???

If the inflated tail could work with the tailgate extender out then i wouldnt have to worry about rain or snow on the tailgate outside of loading/unloading. I wish my father bought a truck with an extended cab + long bed. Doubt 2' makes much of a driving difference on an 18' truck, heck we will be carrying a 20' long ladders sometimes. But he didnt. Im hoping with bedslides and a shelf we'll be able to cram everything under the cap most of the time and that we''ll need the tailgate extender rarely.

What would i do about the taillights? some sort of trailer light setup?

miket,the nose down rake ensures that the fore-body of the truck is in a positive pressure regime,especially the roof.
If you drop the rear only,you run the risk of moving the separation point forwards,at a point of larger cross-section,resulting in a larger wake of lower base pressure ( higher delta-P,bad,never good ).
If you plan to run with a tailgate extender you'll have to configure the tail to capture that extra volume.
Reflector/taillight kits for a utility trailer are perfect for these applications however require some rigid structure,not necessarily a problem,but extra imagineering and fabrication.
Refective material as highway workers employ with their safety vests can also be sewn to the envelope.Biking/jogging gear ditto.

[miket]

Im confused by that because i thought the roof sloping down was a good thing??? The top of the cap is flat. edit1: and the cab is close to flat.

I dont think the nose would raise noticably and the undertray angle could deal with lift.

Hmm your right i would have to make the inflatable tail hollow to do that and that would be more complicated.edit1: Maybe the second version lol.edit2: Id ither need alot of strings inside to make the tail a hollow cone or use a series of connected poles on the inside that unfold to make a tent of sorts around the tailgate.

[miket]

If the bottom is going to be rigid folding panel i could make the sides top and back rigid folding panels too and not mess with the inflationary stuff??. If i connect a rope and pulleys to the ends of the panels they'll pull together and unfold/extend. How advantageous is it to have 5 of the sides smoothly curved from inflation instead of more flat?(cap has 2 sides too) Of course theres the hybrid version with folding panels inside the base of the tail and an inflatable piece for the tip. That could give me the tailgate storage space if i desire it.

[aerohead]

Originally Posted by miket

If the bottom is going to be rigid folding panel i could make the sides top and back rigid folding panels too and not mess with the inflationary stuff??. If i connect a rope and pulleys to the ends of the panels they'll pull together and unfold/extend. How advantageous is it to have 5 of the sides smoothly curved from inflation instead of more flat?(cap has 2 sides too) Of course theres the hybrid version with folding panels inside the base of the tail and an inflatable piece for the tip. That could give me the tailgate storage space if i desire it.

miket,the panels could be flat and just perform with less efficiency than a perfect organic form.
Flow might separate and re-attach creating locked vortices which are known to provide some drag mitigation.Even "bad" boat-tails appear to provide some benefit through a process I call 'stuffing the wake,'whereas the act of filling the turbulent wake with 'anything' seems to displace some of the physical void,pushing the 'base' out closer towards the more energetic flow field.
There is no hard and fast rule as to 'how' to do the tail but it should be air-tight,and they work best with a back on them.
I think of mine like a segmented ironing-board which drops out of a wall,hinged at half-length,with an additional section which flips up to form the 'end.'
Everything else is the envelope which is inflated during deployment,and evacuated during the stowing operation,triggered by a cruise-control,automatic ,speed-sensor/logic/enable-dis-enable-slaved servo-motor,fan set,and reversing valve.
Normally-open/normally-closed momentary micro-switches provide 'proof' to system.

[miket]

The truck/cap is 6 flat sides so i'd have to transition from flat to round some how.

Again why would it be back to have the flat roof slope down slightly, i would think that would be a positive benifit of slightly negative rake.

[aerohead]

Originally Posted by miket

The truck/cap is 6 flat sides so i'd have to transition from flat to round some how.

Again why would it be back to have the flat roof slope down slightly, i would think that would be a positive benifit of slightly negative rake.

miket,if the roof is raked backwards,so too will be the grille/bumper (maybe not so bad a thing),the hood ( maybe not a good thing ),windshield ( not bad ),how the airstream is divided at the nose/windshield ( potentially harmful ),also,how the undercarriage is 'presented' to the air.
During development of the truck,it's Cd may be totally dependent upon the factory rake and could be degraded if tilted back as this would impact flow penetration.In addition,the weight bias can be altered which will affect braking and handling.
Concept cars and supercars with active suspension typically drop the nose for better performance,I've never seen an instance where the tail was dropped,unless the nose went with it.
The forward rake maximizes the amount of car within a positive pressure regime,maximizes the available energy aft of the point of max cross-section,providing the most energetic boundary layer from which further streamlining can benefit.

[miket]

Given the vehicle lengths dropping the rear bumper 2" would raise the front bumper 0.4" and change the rake less than a single degree. Honestly a 4" drop would make it easier to load/unload the bed and definitely the ladder racks and a 2" drop is really all I can get out of the front. The hood would stay in positive pressure, might have to check the wipers. Its hard to tell if the roof of the cab peaks in the front or middle, its relatively flat. I think the undercarriage would be presented with the undertray. I think even with the body dropped the axles are still the lowest point.

I just realized that the back is always sagging down bad from the constant load lol. Its already lowered. I think i should add a leaf or a helper spring, especially since i plan on adding a few hundred more pounds. I think supercars are raked for downforce more than anything.

Do you ever have problems with snow or dirt flying up through the gaps around the wheel wells or in front of the axles and filling up the cavity above and weighing down on the undertray? Ever have any problem with vertical undertray components when they'r pushing through deepish snow either driving forward reverse or turning?