Towing stability studies

..

Do you have any photos of this installation? I'm wondering if it'll
help settle down my Komet.

Jeremy

All my photos are of the gliders not the trailer !

I taped a couple of pieces piece of angle, parallel to the leading
edge of the finbox, 4 inches or so behind the L/E and about 75% of the
height of the fin box.
I pop-riveted them on once I was convinced it all worked.

I'll sketch something if you want and mail it

On Jan 31, 12:15*am, nimbusgb wrote:
On 27 Jan, 19:20, John Galloway wrote:

At 17:48 27 January 2008, Nimbusgb wrote:

Have you noticed how the boxes on new trailers are
now square

If we're talking Cobra, isn't it just metal top - square,
grp top - curvy?

The latest square finbox I saw was on a GRP top.

I have a trailer that happily tows at 80mph and has behind a number of
tow vehicles. I am currently towing with a short wheelbase Volvo
SUV. This trailer is uniquely low, but seems to self damp when a semi
passes or the wind gusts and has an aerodynamic fin. I have always
suspected it has something to do with the fin to trailer wheel moment
vs trailer wheel to hitch moment. I have never had to play with
weights etc. The wheel placement is different than the Cobras which
seem to be more centered.

Picture at http://www.illunis.com/Files/trailer.jpg

Scott

On Jan 31, 3:45*pm, scooter wrote:
On Jan 31, 12:15*am, nimbusgb wrote:

On 27 Jan, 19:20, John Galloway wrote:

At 17:48 27 January 2008, Nimbusgb wrote:

Have you noticed how the boxes on new trailers are
now square

If we're talking Cobra, isn't it just metal top - square,
grp top - curvy?

The latest square finbox I saw was on a GRP top.

I have a trailer that happily tows at 80mph and has behind a number of
tow vehicles. *I am currently towing with a short wheelbase Volvo
SUV. *This trailer is uniquely low, but seems to self damp when a semi
passes or the wind gusts and has an aerodynamic fin. *I have always
suspected it has something to do with the fin to trailer wheel moment
vs trailer wheel to hitch moment. *I have never had to play with
weights etc. *The wheel placement is different than the Cobras which
seem to be more centered.

Picture athttp://www.illunis.com/Files/trailer.jpg

Scott

Link should be Picture at http://www.illunis.com/Files/Trailer.jpg

Sorry

Scott

scooter wrote:

I have a trailer that happily tows at 80mph and has behind a number of
tow vehicles. I am currently towing with a short wheelbase Volvo
SUV. This trailer is uniquely low, but seems to self damp when a semi
passes or the wind gusts and has an aerodynamic fin. I have always
suspected it has something to do with the fin to trailer wheel moment
vs trailer wheel to hitch moment. I have never had to play with
weights etc. The wheel placement is different than the Cobras which
seem to be more centered.

Picture athttp://www.illunis.com/Files/trailer.jpg

Scott

Link should be Picture at http://www.illunis.com/Files/Trailer.jpg

How much does the trailer and glider weigh? I suspect it's quite light,
as the forward wheel placement generally works against stability. I'm
reminded of a couple trailers Roger Frank built years ago.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

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* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Jan 31, 1:45*pm, scooter wrote:
On Jan 31, 12:15*am, nimbusgb wrote:

On 27 Jan, 19:20, John Galloway wrote:

At 17:48 27 January 2008, Nimbusgb wrote:

Have you noticed how the boxes on new trailers are
now square

If we're talking Cobra, isn't it just metal top - square,
grp top - curvy?

The latest square finbox I saw was on a GRP top.

I have a trailer that happily tows at 80mph and has behind a number of
tow vehicles. *I am currently towing with a short wheelbase Volvo
SUV. *This trailer is uniquely low, but seems to self damp when a semi
passes or the wind gusts and has an aerodynamic fin. *I have always
suspected it has something to do with the fin to trailer wheel moment
vs trailer wheel to hitch moment. *I have never had to play with
weights etc. *The wheel placement is different than the Cobras which
seem to be more centered.

Picture athttp://www.illunis.com/Files/trailer.jpg

Scott

My expeience is the right tow vehicle makes more of a difference than
anything I've ever been able to do with loading I've not played with
aerodynamic fixes - but my instincts are that most of these have minor
effects except in special circumstances.

In my estimation the thing that causes stability problems is the
influence the trailer exerts on the yawing motion of the tow vehicle
itself. It does this by exerting lateral force at the tow ball. That
lateral force gets translated into yawing moment based on the weight
of the tow vehicle and the distance between the tow ball and the
natural "pivot point", which is the rear wheels. I would think better
tow vehicles combine adequate weight with a short distance between the
ball and the rear wheels, plus good tire contact area to resist side
loads. I also suspect having adequate weight distribution on the front
wheels helps (that is, loading up the trunk probably doesn't help).

I've been towing for 4 years now with a VW Touareg and find it is rock
steady at any speed under any wind or passing traffic condition. The
vehicle weighs in excess of 4,000 lbs and has maybe 2.5-3 feet between
the ball and the center of the rear wheels. In a sort of ad hoc
stability test on a very straight and smooth 100 mile stretch of
Nevada highway I've towed at speeds up to 100 mph with no swaying.
Needless to say I didn't stay there long out of concern over trailer
tire ratings and a desire to stay out of jail.

9B

On Feb 21, 10:29*am, wrote:
On Jan 31, 1:45*pm, scooter wrote:





On Jan 31, 12:15*am, nimbusgb wrote:

On 27 Jan, 19:20, John Galloway wrote:

At 17:48 27 January 2008, Nimbusgb wrote:

Have you noticed how the boxes on new trailers are
now square

If we're talking Cobra, isn't it just metal top - square,
grp top - curvy?

The latest square finbox I saw was on a GRP top.

I have a trailer that happily tows at 80mph and has behind a number of
tow vehicles. *I am currently towing with a short wheelbase Volvo
SUV. *This trailer is uniquely low, but seems to self damp when a semi
passes or the wind gusts and has an aerodynamic fin. *I have always
suspected it has something to do with the fin to trailer wheel moment
vs trailer wheel to hitch moment. *I have never had to play with
weights etc. *The wheel placement is different than the Cobras which
seem to be more centered.

Picture athttp://www.illunis.com/Files/trailer.jpg

Scott

My expeience is the right tow vehicle makes more of a difference than
anything I've ever been able to do with loading I've not played with
aerodynamic fixes - but my instincts are that most of these have minor
effects except in special circumstances.

In my estimation the thing that causes stability problems is the
influence the trailer exerts on the yawing motion of the tow vehicle
itself. It does this by exerting lateral force at the tow ball. That
lateral force gets translated into yawing moment based on the weight
of the tow vehicle and the distance between the tow ball and the
natural "pivot point", which is the rear wheels. I would think better
tow vehicles combine adequate weight with a short distance between the
ball and the rear wheels, plus good tire contact area to resist side
loads. I also suspect having adequate weight distribution on the front
wheels helps (that is, loading up the trunk probably doesn't help).

I've been towing for 4 years now with a VW Touareg and find it is rock
steady at any speed under any wind or passing traffic condition. The
vehicle weighs in excess of 4,000 lbs and has maybe 2.5-3 feet between
the ball and the center of the rear wheels. In a sort of ad hoc
stability test on a very straight and smooth 100 mile stretch of
Nevada highway I've towed at speeds up to 100 mph with no swaying.
Needless to say I didn't stay there long out of concern over trailer
tire ratings and a desire to stay out of jail.

9B- Hide quoted text -

- Show quoted text -

Replacing the tires on the tow vehicle with stiffer sidewalls does an
amazing job of stabilizing the rig. The trade-off is a bit harsher
ride, but much, much safer.

On Feb 21, 11:29*am, wrote:
On Jan 31, 1:45*pm, scooter wrote:





On Jan 31, 12:15*am, nimbusgb wrote:

On 27 Jan, 19:20, John Galloway wrote:

At 17:48 27 January 2008, Nimbusgb wrote:

Have you noticed how the boxes on new trailers are
now square

If we're talking Cobra, isn't it just metal top - square,
grp top - curvy?

The latest square finbox I saw was on a GRP top.

I have a trailer that happily tows at 80mph and has behind a number of
tow vehicles. *I am currently towing with a short wheelbase Volvo
SUV. *This trailer is uniquely low, but seems to self damp when a semi
passes or the wind gusts and has an aerodynamic fin. *I have always
suspected it has something to do with the fin to trailer wheel moment
vs trailer wheel to hitch moment. *I have never had to play with
weights etc. *The wheel placement is different than the Cobras which
seem to be more centered.

Picture athttp://www.illunis.com/Files/trailer.jpg

Scott

My expeience is the right tow vehicle makes more of a difference than
anything I've ever been able to do with loading I've not played with
aerodynamic fixes - but my instincts are that most of these have minor
effects except in special circumstances.

In my estimation the thing that causes stability problems is the
influence the trailer exerts on the yawing motion of the tow vehicle
itself. It does this by exerting lateral force at the tow ball. That
lateral force gets translated into yawing moment based on the weight
of the tow vehicle and the distance between the tow ball and the
natural "pivot point", which is the rear wheels. I would think better
tow vehicles combine adequate weight with a short distance between the
ball and the rear wheels, plus good tire contact area to resist side
loads. I also suspect having adequate weight distribution on the front
wheels helps (that is, loading up the trunk probably doesn't help).

I've been towing for 4 years now with a VW Touareg and find it is rock
steady at any speed under any wind or passing traffic condition. The
vehicle weighs in excess of 4,000 lbs and has maybe 2.5-3 feet between
the ball and the center of the rear wheels. In a sort of ad hoc
stability test on a very straight and smooth 100 mile stretch of
Nevada highway I've towed at speeds up to 100 mph with no swaying.
Needless to say I didn't stay there long out of concern over trailer
tire ratings and a desire to stay out of jail.

9B- Hide quoted text -

- Show quoted text -

I agree,
I have been towing for the last 12 years and averaging 12000km a year.
During that time I have towed with two different Mini Vans.

If the trailers are set up right, as in weight distribution and tires,
the limitation is the indeed the vehicle when it comes max save speed.
In the first case an Aero Star, with the extended box.
The comfort limit was/is 115 km/h no wind, no truck passing.
This would drop to 100km/h with cross wind and trucks passing.
In the second case, a Honda Mini Van low C of G, short coupled to the
tow ball, plenty of power, relative good in fuel consumption, same
conditions 130km plus (tested to over 160km) out west) No drop in
speed needed below 120 in any condition, but snow ice and wet
conditions. My normal speed in the US is 125km/h on smooth 4 lane high
way when traffic and weather conditions allow. Trucks passing is a
none issue as no trucks pass.
I would think that most, if not all modern Mini Van's of that class
make good tow vehicle. In case of smaller cars like a VW Jetta
and similar cars, they do a fine job as well, just dive slower and get
an anti sway set up. My friend has a set up like that and he trailers
his glider happily anywhere with half the gas consumption, (its a
diesel)
I could Iove that too.
Udo

wrote in message
...
On Jan 31, 1:45 pm, scooter wrote:
On Jan 31, 12:15 am, nimbusgb wrote:

On 27 Jan, 19:20, John Galloway wrote:

At 17:48 27 January 2008, Nimbusgb wrote:

Have you noticed how the boxes on new trailers are
now square

If we're talking Cobra, isn't it just metal top - square,
grp top - curvy?

The latest square finbox I saw was on a GRP top.

I have a trailer that happily tows at 80mph and has behind a number of
tow vehicles. I am currently towing with a short wheelbase Volvo
SUV. This trailer is uniquely low, but seems to self damp when a semi
passes or the wind gusts and has an aerodynamic fin. I have always
suspected it has something to do with the fin to trailer wheel moment
vs trailer wheel to hitch moment. I have never had to play with
weights etc. The wheel placement is different than the Cobras which
seem to be more centered.

Picture athttp://www.illunis.com/Files/trailer.jpg

Scott

My expeience is the right tow vehicle makes more of a difference than
anything I've ever been able to do with loading I've not played with
aerodynamic fixes - but my instincts are that most of these have minor
effects except in special circumstances.

In my estimation the thing that causes stability problems is the
influence the trailer exerts on the yawing motion of the tow vehicle
itself. It does this by exerting lateral force at the tow ball. That
lateral force gets translated into yawing moment based on the weight
of the tow vehicle and the distance between the tow ball and the
natural "pivot point", which is the rear wheels. I would think better
tow vehicles combine adequate weight with a short distance between the
ball and the rear wheels, plus good tire contact area to resist side
loads. I also suspect having adequate weight distribution on the front
wheels helps (that is, loading up the trunk probably doesn't help).

I've been towing for 4 years now with a VW Touareg and find it is rock
steady at any speed under any wind or passing traffic condition. The
vehicle weighs in excess of 4,000 lbs and has maybe 2.5-3 feet between
the ball and the center of the rear wheels. In a sort of ad hoc
stability test on a very straight and smooth 100 mile stretch of
Nevada highway I've towed at speeds up to 100 mph with no swaying.
Needless to say I didn't stay there long out of concern over trailer
tire ratings and a desire to stay out of jail.

9B

Tow vehicle, definitely.

Most US made SUV's have a resonance about the vertical axis that roughly
matches the trailers sway frequency. You can demonstrate this by pushing
rythmicaly with one finger on a rear quarter panel. When you find the
resonant frequency, the vehicle will wiggle 2 - 3 inches side to side. This
is not roll , it's pure undamped yaw. If this resonance exactly matches the
trailer, you're in for an 'interesting' ride. Most of this is tire sidewall
motion.

I've actually been chased out of dealer showrooms for demonstrating this.

Most SUV's with off road pretensions have tires with high sidewalls in order
to get more ground clearance. You can replace the wheels and use low
sidewall tires but then your vehicle looks like an East LA "low rider" and
you'd have to buy the big fuzzy dice to hang from the mirror and the chrome
welded chain steering wheel so the cuffs and collars matched

Bill D