Thursday, June 23, 2005

Suspension Options and Weightshift for PPG

Many PG pilots are making the transition to PPG these days. One of the most frequent discussions with those making the transition is the harness setup and weighshift. Here are my thoughts on the different harness suspension types and their ability to initiate a weight shift turn.

I was a PG pilot first, and the majority of my PPG flying is of the launch, climb,shutdown, thermal variety. For a PG pilot that is hoping to move to PPG as a means of getting air timeand soaring, there are two main things to consider.

The first is obviously weight shift, but the second (and more important) is the ability to feel the wing. As PG pilots, we get lots of input from the wing transferred to our hips via the harness. This input is more important than you would think, andits something that most motor harness can't provide, regardless of weighshift ability.

A third issue is how the weight shift is engaged. In a PG harness, a quick roll of the hips will initiate a turn, that is not the case with most motor harnesses and takes some getting used to.

First, there is the common misconception that a low attachment point on a PPG means better weight-shift. Low attachment points have ABSOLUTELY nothing to do with weight shift. It just happens that a couple of motors with good weight shift have lower attachment points. To get good weight shift, you need to separate the pilots weight from the motor, and have the risers as close to vertically aligned with the hips as possible. Lower attachment points are often associated with increased ability to weight-shift turn (though not always the case) because several brands that have low attachment points are also good weigh-shifters. Good weight-shift can also be found in mid-level and higher attachment points (depends on the manufacturer).

Good weight-shift is observed when the suspension allows differential movement of the left/right riser attachments relative to pilots center of gravity.

Ok, here's the run-down. There are 4 types of harness suspensions out there that are known to give good weight shift. This may not be an all inclusive list, but these are the ones that I am familiar with and have personally flown. So, in no particular order:

1) PAP/Airfer/Bowles System
The PAP style system, also used by Airfer and on modified Fresh-Breeze units by Chris Bowles. This was one of the first harness suspensions to give good weight shift. It consists of low mounted distance bars that pivot up/down independent of each other. The bars attach to the harness where the normal biner connection would be and the glider is clipped into a shackle or biner on the distance bar (where depends on the pilot weight).

This system allows a standard PG harness to be used, assuming it has been modified to provide points on the back to hang the motor. The best advantage of the Pap style system is that it closely mimics the feel of a PG harness and does a good job of transferring input from the wing to the pilot. PG pilots are used to a certain about of feedback, and its not just feedback from the brakes and this system delivers that. It also allows more natural PG style weight shift, initiated by a quick roll of the hips. This is the system that Will Gadd used on his XC across America.

This system gives the best combination of weight shift and feeling that a PG pilot would be used to and does a moderate job of reducing motor torque. Launches are sometimes tricky due to the torque twisting the motor around since this is a relatively loose harness setup.
Available on PAP, Airfer units standard, and an upgrade to a Fresh-Breeze unit (Chris custom machines the parts for his mod)

2) Fresh-Breeze Floating Suspension (soft j-bars)
The standard suspension on all Fresh-Breeze units. It consists of an aluminum boomerang that you attach a biner to clip the wing into, along with a short webbing connection to the motor and a longer webbing connection to a biner in the normal hook-in position on the harness. Just about any PG harness can be used, but back protection and airbags could hang down and restrict airflow over motor (needed for cooling). A Thin Red Line harness, or any other harness without a seat board, should NOT be used. The results are not pretty, not comfortable, and not kind on the family jewels.

I feel that this over shoulder suspension gives the best weight shift of any suspension out there. Torque is moderate on this suspension, and can be lessened by loosening the shoulder straps after takeoff and with weight shift. This system gives a good 'feel' from the wing also. The method of initiating the weight-shift for this suspension (and the rest of the list)is quite different than the PAP system or a PG for that matter. Instead of rolling the hips, you have to push down with your thigh, and then roll your hips. Takes a bit of getting used to.

Another benefit is that this suspension allows the pilot to ditch the motor if necessary but remain connected to the glider. The main disadvantage is that it is a relatively high hook in point and most pilots lower their brakes to give a more comfortable hand position. Pain in the butt if you fly the same glider PG and PPG and move between the two often. This is also a very comfortable harness that allows you to recline more than most.

Available on FB motors stock, and can be retrofitted on just about anymotor.

3) Movable Distance Bars
Moveable distance bars are similar to the Pap system, but instead of the glider hooking in into the distance bar, it hooks into the harness at a point along the hypotenuse of the triangle formed bythe distance bar and the upper frame of the harness. Decent weight shift and really good torque reduction. Another good compromise, and its comfortable.

One down side is you can't ditch the motor. Another is that you are sitting very upright, something that PG guys have a hard time adjusting to, and probably sours as many on motors as the weight and the noise. Paralite (out of business now) developed a version of this system that has a mechanism that physically forces the distance bars to move opposite each other, rather than being independent. So, if the right side goes down, the left side is forced up. This gives incredible weight shift and great response to WS inputs. This mod is availalbe from ParaCruiser and can be adapted to call Paralite, Paracruiser or FB units.

4) Ridged, Low Attachment Points. (ie. Walkerjet)
Even though it has a ridged attachment point, the WalkerJet motor has such low attachment points and a wide seat board that it actually does allow some weight shift. I've only got 2 flights on a WJ, and I didn't observe as much WS as the other systems, but I was able to get around 3 inches of riser differential. Another pilot I trust says he can get about 4. Others claim more, but due to its low hook-ins, it a more natural system for PG pilots and its a comfortable harness setup.

Available only on WalkerJet units (that I know of)

In Summary:
  • Best Weight Shift: #2 FB Suspension
  • Best 'PG Feel': #1 PAP Style

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