WIP Ford GPA

[matto_mati]

Hi Forum,
The Ford GPA was an amphibious jeep during WW2. It saw action on the west and east fronts and I thought it will be a nice addition to VSF. More history here. And some awesome art here.
I am almost done with the body and I wanted to see how it handles in VSF.

But the amphibious action is a disaster. The GPA lifts it nose way too high even at minimal power:

And it won't turn:

Here are the elements:
body [element]
1830 [mass]
5984.6 [i_xx]
6238.24 [i_yy]
1560.85 [i_zz]
0 [dx]
-0.4 [dy]
-0.05 [dz]

wheel [element]
-0.75 [x]
-0.555639 [y]
-1.09039 [z]
45750 [kt]
9150 [kd]
1.5 [kf]
0.01 [kw]
4575 [wkt]
915 [wkd]
0.1 [wkf]
0.1 [wkw]
45750 [max_thrust]
9150 [max_float]
0.5 [max_land]
0.1 [radius]
brake [control]

wheel [element]
0.75 [x]
-0.555639 [y]
-1.09039 [z]
45750 [kt]
9150 [kd]
1.5 [kf]
0.01 [kw]
4575 [wkt]
915 [wkd]
0.1 [wkf]
0.1 [wkw]
45750 [max_thrust]
9150 [max_float]
0.5 [max_land]
0.1 [radius]
brake [control]

wheel [element]
-0.75 [x]
-0.555639 [y]
1.01761 [z]
45750 [kt]
9150 [kd]
1.5 [kf]
0.01 [kw]
4575 [wkt]
915 [wkd]
0.1 [wkf]
0.1 [wkw]
45750 [max_thrust]
9150 [max_float]
0.5 [max_land]
0.1 [radius]
steer [control]

wheel [element]
0.75 [x]
-0.555639 [y]
1.01761 [z]
45750 [kt]
9150 [kd]
1.5 [kf]
0.01 [kw]
4575 [wkt]
915 [wkd]
0.1 [wkf]
0.1 [wkw]
45750 [max_thrust]
9150 [max_float]
0.5 [max_land]
0.1 [radius]
steer [control]

point [element]
-0.5625 [x]
0.766964 [y]
-1.09039 [z]
45750 [kt]
9150 [kd]
1.5 [kf]
0.01 [kw]
4575 [wkt]
915 [wkd]
0.1 [wkf]
0.1 [wkw]
45750 [max_thrust]
9150 [max_float]
0.5 [max_land]
0.1 [radius]

point [element]
0.5625 [x]
0.766964 [y]
-1.09039 [z]
45750 [kt]
9150 [kd]
1.5 [kf]
0.01 [kw]
4575 [wkt]
915 [wkd]
0.1 [wkf]
0.1 [wkw]
45750 [max_thrust]
9150 [max_float]
0.5 [max_land]
0.1 [radius]

point [element]
-0.5625 [x]
0.766964 [y]
1.01761 [z]
45750 [kt]
9150 [kd]
1.5 [kf]
0.01 [kw]
4575 [wkt]
915 [wkd]
0.1 [wkf]
0.1 [wkw]
45750 [max_thrust]
9150 [max_float]
0.5 [max_land]
0.1 [radius]

point [element]
0.5625 [x]
0.766964 [y]
1.01761 [z]
45750 [kt]
9150 [kd]
1.5 [kf]
0.01 [kw]
4575 [wkt]
915 [wkd]
0.1 [wkf]
0.1 [wkw]
45750 [max_thrust]
9150 [max_float]
0.5 [max_land]
0.1 [radius]

bumper [element]
0 [x]
0 [y]
2.32765 [z]
1 [full_bumper]
45750 [max_thrust]
0.5 [max_land]

bumper [element]
-0.83265 [x]
0 [y]
1.74574 [z]
-0.7 [beta]
45750 [max_thrust]
0.5 [max_land]

bumper [element]
0.83265 [x]
0 [y]
1.74574 [z]
0.7 [beta]
45750 [max_thrust]
0.5 [max_land]

wing [element]
0 [x]
0 [y]
0 [z]
1.5708 [gama]
1 [is_hydro]
1.6 [wing_sur]
5.5 [wing_cla]
10 [wing_cd0]
0.05 [wing_cdi]
0 [wing_al0]
0.25 [wing_alm]

wing [element]
0 [x]
0 [y]
-2.40287 [z]
1.5708 [gama]
1 [is_hydro]
0.16 [wing_sur]
5.5 [wing_cla]
0.05 [wing_cd0]
0.05 [wing_cdi]
0 [wing_al0]
0.25 [wing_alm]
rudder [control]

motor [element]
amphib [motor_type]
0 [x]
-0.555639 [y]
-1.09039 [z]
36000 [fuel_time]
2500 [rpm_max]
500 [rpm_min]
60 [motor_hp]
0.6 [prop_diam]
17952.3 [max_thrust]
1 [num_props]
engine [control]

cable [element]
0 [x]
0 [y]
1.74574 [z]

hook [element]
0 [x]
0 [y]
-1.80215 [z]



Could any one help me get some control of this seep (seep = sea going jeep) in the water?

[Sharpy]

Aloha matto_mati,
I have not looked into the detail of your element files. (Hurts my head).

But you may want to add this into Vehicle.cfg.
// engine

1 [has_engine]
amphib [engine_type]
? [fuel_time]
? [rpm_max]
? [rpm_min]
? [motor_hp]

I honestly don't know if this will help, but just at a glance, it might.

Also you need to reshape your tp_1.dds file to fix the wake.
If you don't have that file in VSF, try importing vessel the from the boats folder. VSF will build more .dds files than a direct build. If that makes any sense.

Oh, and the rudder can be added in elements, with all parameters.
But I think you may want to add an invisible/transparent rudder in the model for VSF to find and use.
Again not to sure about that.

So, all in all I have been of no help.

[matto_mati]

Hi Sharpy,
In my vehicle.cfg file I have:
1 [has_engine]
amphib [engine_type]
36000 [fuel_time]
2500 [rpm_max]
500 [rpm_min]
60 [motor_hp]

I also have
1.2 [boat_alt]

But as far as I know the elements.cfg overrides the vehicle.cfg file.
VSF did not make a tp_1.dds file and other amphibian vehicles (that work) don't have it so I might not need it.

I'll try to add a rudder. And you have been a lot of help.

[Thor2]

Hi,

for me It looks like your car is not at the correct position, z-axes. At the first Pic it looks like the bow wave is to far in front of your car/boat. You can test the position in your 3d programm.

I dont no how it works by a amphicar, but for a boat 10 points is the minimum what you need.

Four at the Top of your vehicle, to mark the higest point.

two at the Bow, left and right side
and two at Stern, left and right.

Then you also need Points at the deepest point of your boat to make the boat stable.

Example:

Stern at the Top

point [element]
-1.7 [x]
2 [y]
-2 [z]

point [element]
1.7 [x]
2 [y]
-2 [z]

Bow at the Top
point [element]
-1.7 [x]
2 [y]
2 [z]

point [element]
1.7 [x]
2 [y]
2 [z]

Next the basic for the deepest point.

Bow:

point [element]
1.7 [x]
0 [y]
2 [z]

point [element]
-1.7 [x]
0 [y]
2 [z]

Stern:

point [element]
-1.7 [x]
0 [y]
-1.5 [z]

point [element]
1.7 [x]
0 [y]
-1.5 [z]

keel axe of the boat

point [element]
1.7 [x]
-0.50 [y]
1.5 [z]


point [element]
0 [x]
-0.5 [y]
-1.5 [z]


At last one in the middle at the bow and stern

point [element]
0 [x]
1 [y]
2 [z]

point [element]
0 [x]
1 [y]
-2 [z]


This is only a short example for a very smal boat, but normaly VSF creates the elements file automatically. So you only must optimized this file.

Hope it helps a bit, good luck.

Thor

[matto_mati]

Thanks Thor,
I will redesign the points and bumpers I did see Jason's HMAS Yarra and you might have something there but I am not sure it will work for amphibious vehicles. I'll post the results later tonight.
BTW I was able to get the vehicle to turn in the water you have to change the wing used as a rudder to an eleron (elevonl or elevonr) I don't know why maybe it's a bug Ilan needs to fix.
Wish me luck.

[matto_mati]

Hi all,
I followed what Thor said and added 8 points 4 at the highest and 4 ate the lowest ends of the GPA but that did not help.
I moved the motor from where the propeller is to the center (x=0.0 y=0.0 z=0.0) and that fixed the problem, kinda:

Now the GPA is leaning forward not as much as before but still not looking natural. I thought "Easy I'll just move the motor back" WRONG. Moving the motor now has not effect. Aren't elements fun?

I also want to lower the craft in the water:


The water line should be where the arrow is but I can't seem to do it. Not with the modeling program and not with moving the points up and down.

[Dom]

Then, two essencial parameters to correctly set are the [max_float] and [radius] of your points.

Dom.

[matto_mati]

Hi all,
Actually as you can see form this site the water level is fine. I am going forward with the modeling. The element seem to be fine and the vehicle is behaving how I want it to. Thanks for your help everybody.

Edit: I forgot to tell you I was able to fix the tilting forward issue.

[matto_mati]

Modelling is almost done I really stepped it up this past week. I added a steering wheel and more detail.




So far I have made it with a smooth hull I plan to add the ridges next week. I'll add the side ridges only the ones on top of the vehicle will be in the texture. I promise this time not to let myself slide and make better textures than my other models. The plan is to release it with 2 paint jobs one Russian and one American ether Army or Marines not sure witch yet.
Also I plan to use some features that VSF allows like a simple model and a damaged model.

[matto_mati]

Hi all,
I am having problems with the panel specially with the speedometer. It seems to respond to the wind (when there is wind it shows speed despite the fact the vehicle is standing still). And only when the vehicle is facing the wind. Is this a bug in VSF or do I need to build the instrument differently.