Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Spray on Inside of Windscreen

The Aero chassis Plus 8 seems to have one aerodynamic curiosity in that when driving on a damp/wet road and hood down moisture is deposited on the inside of the screen, dash and interior mirror. This is irritating and something the Roadster didn't do.

Although the Plus 8 looks like a trad the body has a couple of significant differences:
1. It is wider by 4.5 inches across the cockpit behind the seats.
2. It is rectangular, not trapezoid, in that the front and rear track are the same.

There could be other differences, but without a tape measure comparison it is hard to be certain.

I've tried fitting the wind deflector that Williams offer: it helps but doesn't fully solve the problem. Possibly because it isn't as wide as the cockpit.

It seems that the spray is coming from the back, although this isn't proven. So the next step is to fit rear mud-flaps behind the rear wheels, as described by DW. But instead of neoprene on the circuit board I'll use this:

Spray Control

Not expensive, about £25 for 0.25 sq m.

At the front the wheel arches have backs to them, so there is no obvious place for a mud flap, but I think lining the inner wing with this stuff might be worth while. But I'll leave this until I've explored the rear wheel arch route.

It has been suggested that the problem isn't limited to the new Plus 8, but might be associated with the presence/absence of a spare, in that the spare changes the airflow over the rear. Does anyone have any thoughts on this?

Peter

How bizarre!

I don't know enough about aerodynamics but find it hard to comprehend how spray can come back so far over the back of the body from the wheels under such a large rear wing but I suppose it is the answer

Unless it is wet spinning off the side of the tyre or flicked up from the front and then getting caught in some airflow around the cockpit

Don't think the footprint is relevant Peter. My '76 was near rectangular, not the very trapezoid shape of later cars and I didn't have a problem with the inside of the screen, nor with the '93 which is 1" wider at the rear than the '76...
Of course, both are much narrower overall than the new generation +8

It's a problem for me too. My first Morgan, 2002 4/4 with stud hood later converted to Simmonds hood was comfortable to drive on wet roads. Rain really did go over the top and the inside of the screen remained dry. Current car, 2011 plus 4 with easy up hood is a pain in wet weather. Rain still goes over the top, above a certain speed, but the inside of the screen and the mirror rapidly get covered with mizzle. Both cars have spare wheels and are usually driven with side-screens if the roads are wet. The difference in shape/size of the screen appears to be the problem.

My experience on this is that when driving on A/B roads, my plus 8 interior fills up with all manor of road dust and debris. I have not experienced this in any other Morgan.

I imagine is it a n eddy of wind caused by the windscreen. The air cime back round into the car. A wind break at the back might help.

I wonder if Mr Morgan did wind tunnel tests.

Out of interest what's the issue with so called Trapezoid Trads? Never quite understood what all the fuss is about....I've had quite a few cars over the years with differing front and rear tracks.

Rant over..back on topic! Both my 4/4 and Roadster suffer from rain misting the inside of the screen at speed. Put It down to to bluff screen causing cockpit turbulence. Handy at times. Twice I've had baseball caps fly off on the motorway only to have them blow back into the car!
You should stick some wool strands on your top screen rail and dash top Peter and see how they behave.

Peter, I had this on my +8, and have it on the Roadster. I noticed that when I fiited inner wing liners to the +8 the problem became less. I fitted the wing liners to protect the wings from stones flying up and causing dents/paint starring due to the poor roads especially where we live. The other benefit from the liners was everything kept much cleaner underneath. I think the spray issue diminished as the water from the rear tyres was more limited to how it escaped the rear end of the car. It did not totally eradicate it but helped.

The liners I made using black corian sheet 4mm, and marked the edge of the wing with masking tape and the measured to the inner side of the wing and then transferred to the sheet, joined the dots and cut out the liner. Initially cut oversize and then trim down before final fit. Ther rears are easy to fix, for each side cut 4 stainless flat bars to clamp around the rear wing stays, 2 clamps each side, drill a holes at the lower point of the bar to bolt through the liner and use penny washers, the front edge of the liner can be fixed using the front wing to rear wing bolts. The fronts are a bit trickier, you need simpler supports for the rear edge to wing stay and these need to be bent to the appropriate angles, to fix the top and front you need a long s/s bar, from top of the king pin area, which can be bolted to the upper wing stay, this is bent into the shape of the wing and stops below the headlight with a T piece on the end bolted or welded in place, the front of the liners is then secured using 2 bolts and penny washers to the T bar.

It will take about a 4-8 hours depending on competency and tools to hand for cutting and drilling stainless. None of the above requires any holes to be drilled on the Morgan. It's well worth the effort and relatively cheap.

I have to to mine for the Roadster, have all I need but have not had time yet, but hope to do other the next few weeks, when I will post pics etc. as I promised for others on ™.

Peter,
you mentioned before that your Plus 8 produces spray inside the car. I have a roadster and I have seen the same, maybe to a smaller extend. I my opinion this I not caused by the rear or the shape of the body but from the windshield itself. Normal windshields are installed in a rather flat angle these days to reduce the drag by allowing the air to flow along the surface. Whenever the airflow cant follow the surface, it leads to turbulence. Since our windshield is installed upright, no laminar airflow is possible. If you position such a plate I an airflow, it will result in massive turbulences behind it and you will even find areas with backflowing air. This backflow will guide dirt and spray to the back of the shield and on the dash.
It's about the same effect that you have with modern cars, the rear end is always dirty because of the turbulences there.
The only solution for a Morgan is to remove the screen or adjust the angle.

Regards

Thinking about it there is another solution:
Brooklands or Speedster.