[Al Posts: 1008 Status: Offline WWW]

It's probably something I'm doing  .  While I have it in the air I'm going to paint glue on the contact area of the skirt.  Only thing I have found so far is a tiny little tear less than 2" long at the top of the divider skirt, where it goes into the metal strip that clamps it to the hull, so that's not going to affect it.  I'm going to put a wee patch on it to stop it getting any worse.  I haven't checked the rear skirt yet, but walking around it on the beach when Becky was at the helm, the skirt looked ok on the outside & the hover seemed to sit pretty level, so it 's probably going to be OK.

[Ronnie L Posts: 531 Status: Offline]

Al.
I’ve ripped the skirt before now, it was at Loch Fyne.
We went across from the camp site to Creggans.
There was a fair rip in the skirt, two of us in the craft and big dog.
It felt a bit odd. Woolly was the feeling but it didn’t show any signs of plough in.
If you haven’t got a rip anywhere and you don’t fancy going down to Johns.
Give Steve some diesel money and ask him to come to you.
Something has happened since your first flight.
You should know this more than anyone…….Sevs just don’t do this.
That craft has looked after this very inexperienced hovernaught and never ever scared me……although I’ve done some really daft stuff that beginners do……ask any of the spectators…….no ask John.
Get some expert advice. Don’t get frustrated.

[Al Posts: 1008 Status: Offline WWW]

Why would it dip its nose in pretty much ideal weather conditions?  Rpm was around 3000.  Speed reached a little over 25 mph.

[Ian Brooks Posts: 3598 Status: Offline]

A plough in is a violent event. The driver is unseated and likely to be up against the windscreen holding the broken off steering wheel, meanwhile the passenger has gone right over the top. You and your passenger appeared   to remain in your seats and continued to take video. If that was a plough in, the camera would have been on the floor as your passenger grabbed for anything to hold on to!

The Sev design can dip its nose at high speed under some conditions and that results in a sharp speed reduction, but it can’t be described as ploughing in. All that is required is to maintain lift hold course and wait until the nose comes back up.

Seriously, a plough in would have you thrown out of the craft taking the windscreen with you.

[Al Posts: 1008 Status: Offline WWW]

This one is on the water when plough occurs


https://youtube.com/shorts/VL-RIJL9Z04?feature=shared

[Al Posts: 1008 Status: Offline WWW]

https://youtu.be/FSjOIOvlJlw

[Al Posts: 1008 Status: Offline WWW]

I took the Surveyor out again this afternoon.  According to XC, wind speed approximately 6mph, there were a few ripples on the water.  Anyway started heading downwind, 3000 rpm and 25.4 mph I touched the brake slightly and it ploughed in again.  As it started to plough I increased the RPM to 3400 and released the brake.  Brake. works, no spray over the front. 


What I did notice on the beach today, that it was striking some smallish rocks that were only 4 or 5 inches high.  This craft has a hover height of 11.25 inches, so it should be missing small rocks.



If it's not the divider skirt, could there maybe a rip on the inside of the skirt?  Just wondering if its losing air into the rear compartment, maybe the cushion pressure / skirt pressure is not enough?


I'll try and upload a video of it on the beach later showing how its sits and brake working.


The first time I flew it, there was no wind, and it flew fine in both directions on the loch.


Something has obviously happened, I've now ruled out pilot error, as I made sure that I kept the RPM above 2800.

[John Robertson Posts: 5277 Status: Offline WWW]

The brake "not working" means it doesn't dip/drag the nose as it should.  It will vent the now all-one cushion resulting in the rear dropping instead.  As the front is the the same pressure as the rear (due to the ineffective divider) the craft will ride nose- high all the time - hence the spray.  I've had a damaged divider three times in all over the years and it's pretty obvious there is something badly wrong!

[Ronnie L Posts: 531 Status: Offline]

I didn’t realise the lift fan would be able to produce enough air with divider damaged and the brake open.
Hence why I thought it would be more  savage dip with divider damaged.
Good to get the proper explanation.

[John Robertson Posts: 5277 Status: Offline WWW]

As has been asked - what throttle/RPM?
If the divider is compromised then the brake won't work (nose won't drop much/at all) AND you'll be getting spray over the nose continuously AND you will have poor//insufficient lift volume requiring more throttle (usually indicated by lower than normal speed caused by increased drag) .  I assume it isn't compromised as you must have been using the brake downwind to control speed?  If you were using the throttle to control speed  then my money would be on that as the cause (operating below full-lift throttle when moving is guaranteed to cause handling problems/damage/etc.).  You should never operate below full lift throttle unless the craft is stationary.  Particularly when coming to a stop on land - any, even minor, dragging or scraping to a halt WILL damage the partition skirt (and possibly the rear bag and hull).

Full lift throttle is the RPM at which the craft doesn't rise any more when increasing throttle above that setting when on a smooth'ish (low leakage) surface).  This is the absolute MINIMUM RPM value - when operating over leaky surfaces (chop.waves, stony beaches, etc.) OR with a higher load then more throttle will be required. Again, as said, the throttle should only be moved below this position when the craft is stationary,

I would suggest you operate at lower speed (say 20mph or less) until you get the basic handling/feel sorted (at 30mph plus stuff can go wrong very quickly and fatally).

[Al Posts: 1008 Status: Offline WWW]

I see where you are coming from Ian, as more air / pressure in the front compartment, so when the brake applied it has little effect.
But what happens if the front curtain is pushed back and allows more air to escape from the front chamber?  Surely as the curtain pushes back, the air pressure within that chamber will drop, allowing the nose to drop pushing the front curtain back further allowing even more air to escape causing a plough in.


My first Surveyor (Yellow one) ploughed in once and that turned out to be the divider skirt was too short, which is leading me to think the divider is either ripped or more likely deformed.

[Ian Brooks Posts: 3598 Status: Offline]

[quote author=Ronnie L link=topic=8461.msg64737#msg64737 date=1750253956.


Question to Ian.
Say the divider skirt was torn a bit at the bottom but not destroyed.
In my head the brake would still work, but more savagely than normal but if the front skirt wasn’t holding air because it was disturbed. Could it appear to plough in, although not fully?
[/quote]

If the divider is damaged but still there, the brake will lose effectiveness partly or completely depending how bad the damage is.

[Al Posts: 1008 Status: Offline WWW]

I haven't looked yet, but I'm suspecting the the divider skirt is not opening up properly from sitting on the trailer for such a long time, that it has deformed it, so it is bent at 90* instead of opening up like it should.  Only a theory at present.  When I get back from holiday end of next week I'll have a look.


My way of thinking is that this would make the divider skirt way too short, so allowing too much air in to the front compartment, the front curtain gets pushed in a little from the waves, allowing the air to escape too quickly pushing the nose down pushing the front curtain back further exacerbating the air loss causing the craft to plough, because the divider is a few inches above the water from where it should be, because it is deformed effectively shortening it.


Ronnie, your suggestion of taking it to John or Steve to have a go is a good one and if I can't see anything wrong with the divider skirt, ill get in touch with them.  Because it could be pilot error on my part.

[Ronnie L Posts: 531 Status: Offline]

Al
It has never ever ploughed in during my ownership, and I’ve done a lot of mikes in it.
Sometimes in quite challenging conditions.
If the divider skirt isn’t damaged.



I would ask John or Steve ( Ian is too far away) to have a test in it. I know it’s quite a trip, but it would put your mind at ease.
Those two have more experience than probably anyone else.
I reckon it would be a worthwhile trip.


Question to Ian.
Say the divider skirt was torn a bit at the bottom but not destroyed.
In my head the brake would still work, but more savagely than normal but if the front skirt wasn’t holding air because it was disturbed. Could it appear to plough in, although not fully?

[Ian Brooks Posts: 3598 Status: Offline]

It’s supposed to make the front drop, that’s how it works.

The partition is ok if the brake is working. Or at least it’s still there.

It shouldn’t plough in - not properly like a segmented craft does. They will sometimes do the nose-down slowing down thing in a tailwind after hitting a wave peak, but not ploughing.

The auto slowing down thing can be more pronounced if the partition skirt is a little too long. It starves the front partition of air, and wave-pumping gradually drops the front compartment pressure. I would check the skirt trim per the standard instructions.