Where has it gone!

[headlight]

Like this

 

[Nanniemate]

They were indeed fitted at different times by different people. The original panel which is still up there was fitted by Dave Newell about 8 years ago. The missing panel was added a couple of years later by a company that were fitting them at one of the Warner shows.
When I find a company to fit a new one I will get them to check the fixing of the other panel. As I mentioned in my original post everything seemed fine at Easter when a friend cleaned the roof for me!
Yes it was across the front of the roof.
What is the consensus of opinion regarding fitting a flexi panel instead - would it be more secure as the profile would be a lot thinner?

Maybe pop back and see Dave again you never know he may even give you a smile ,
I was at my first show , not part of a Fun rally and was considering panels and was pulled away from a stand by a friendly by passer who was listening to the conversation and told me not to do it , due to quality and cost.
I took his advice and then paid Dave a visit not good it they do take a fly.
But looking at it the connector seemed to be unplugged rather than ripped off but lets hope you get it sorted quickly and cheaply , is your solar still working ?

 

[Lenny HB]

But looking at it the connector seemed to be unplugged rather than ripped off but lets hope you get it sorted quickly and cheaply , is your solar still working

It's your eyes gov, on one the cable has been pulled out of the plug and the other one the cable has been ripped in half.
Panel defiantly went AWOL on the move.

 

[Cal54]

I’m afraid getting Dave to do it isn’t really an option Nanniemate as it is a bit far (he fit it at a show when he use to go to them).
I’ll make a couple of phone calls this morning and see what I can sort.

 

[Nanniemate]

It's your eyes gov, on one the cable has been pulled out of the plug and the other one the cable has been ripped in half.
Panel defiantly went AWOL on the move.

according to Specsavers my eyes are fine maybe the quality of my screen as I cant zoom in so I can see a plug thingy on the end of the one cable I'm not wrong but will stand corrected and bow to your greater knowledge photos on screens I dont seem to be able to see the detail other can

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[autorouter]

t is at the front.I'm amazed that it has missed both roof lights & the aerial?

Aerodynamics is definitely very weird and by no means intuitive. Most of the lift of an aeroplane wing is because of the curved upper surface, not the push from the tilted lower surface. There will have been a very strong uplift force due to the pressure difference between the air above and below the panel. Google Bernoulli Effect for further details.

Paradoxically, any turbulence or wind buffeting doesn't increase the upward force, it actually reduces it. The position at the front of the MH, as the air curves up from the front, is about the worst position for this pressure uplift effect.

A full width support across the front of the panel, acting as a spoiler, doesn't actually reduce the pressure uplift force either. But at least it provides more surface area for the adhesive. Adhesive strength depends on the total area of adhesive.

 

[Morning Major]

Looking at this from an engineers point of view I would only fit these panels longitudinally like the remaining one as the design of the brackets, and the fact they are on the shorter sides, allows for air to flow over the top and not underneath.

You could fit the new one like the one you have left beside it.

 

[RedFrame]

Aerodynamics is definitely very weird and by no means intuitive. Most of the lift of an aeroplane wing is because of the curved upper surface, not the push from the tilted lower surface. There will have been a very strong uplift force due to the pressure difference between the air above and below the panel. Google Bernoulli Effect for further details.

Paradoxically, any turbulence or wind buffeting doesn't increase the upward force, it actually reduces it. The position at the front of the MH, as the air curves up from the front, is about the worst position for this pressure uplift effect.

A full width support across the front of the panel, acting as a spoiler, doesn't actually reduce the pressure uplift force either. But at least it provides more surface area for the adhesive. Adhesive strength depends on the total area of adhesive.

Sorry, have to disagree with a couple of points.

In its most basic translation Lift is dependant on the speed differential of a fluid between the upper surface and lower surface of an object. Therefore the position at the front of the van is irrelevant in terms of lift, it just changes the angle of attack, probably past stall angle. Also putting a full width support across the front would have an effect as it would reduce the flow underneath the panel.

Cheers
Red.

 

[autorouter]

In its most basic translation Lift is dependant on the speed differential of a fluid between the upper surface and lower surface of an object. Therefore the position at the front of the van is irrelevant in terms of lift, it just changes the angle of attack, probably past stall angle. Also putting a full width support across the front would have an effect as it would reduce the flow underneath the panel.

If the full width support reduces the flow underneath, then isn't that increasing the speed differential, and therefore increasing the lift force? As I said, not very intuitive, which is why they do so much wind tunnel testing to check the hand-waving arguments.

 

[Minxy]

You're all making me paranoid! Our panel at the front is mounted widest side to the front although it does have the longer full width mounts on the shorter sides. It's been on for 3.5 years and when I cleaned it earlier this week it showed no sign of any movement or deterioration of the sealant so hopefully won't go for a fly!

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[Nanniemate]

Blinking heck this is getting very technical , I don think my van will go fast enough to take off and I thought Bernoulli was pasta

 

[Sandancers]

Looking at the OPs picture.

The adhesive, possibly Sika 522, but who knows, has held onto the bodywork OK, either when the panel flew off or when it was prised off.

Now having talked to the Sika technical services before fixing ours onto the roof, Sika 522 needs to be applied with certain conditions met.

It should only be applied when the temperature is above 13c. It needs a bead size of 2mm / 3mm between each mating surface.

And crucially, the corner mounts need to be wiped down with a solvent to remove the release agent which may still be present.

After that, the mounting surfaces should be abraded to give a roughened finish.

Sika also recommend that their activator is used within a specific time period before using the adhesive.

The technical services also recommended leaving the vehicle to stand for several days before use after fitting the panel as Sika 522 dries at a rate of 2mm per 24 hours in ideal temperature / humidity conditions.

Now if the OP didn't do the job himself or indeed witnessed that the above steps had been taken (if he was aware of them) it could be that the people who fitted the missing panel did a duff job. And the customer would not know the difference.

 

[Cal54]

I can confirm I didn’t do the job myself and didn’t watch the work being done!
It is now booked in to my ‘go to’ guy at Kendal but it will be end of July. He is supplying and fixing with both adhesive and screws and is going to move the wiring so less is exposed on the roof. He will clean everything up and check the other panel, but he confirms everything looks in order with that one as it is screwed down! Good price and it will be a 120 wt panel.
Happy it will be sorted properly

 

[RedFrame]

If the full width support reduces the flow underneath, then isn't that increasing the speed differential, and therefore increasing the lift force?

Put simply, No it will not increase lift.

You're all making me paranoid! Our panel at the front is mounted widest side to the front although it does have the longer full width mounts on the shorter sides. It's been on for 3.5 years and when I cleaned it earlier this week it showed no sign of any movement or deterioration of the sealant so hopefully won't go for a fly!

No need to worry Minxy, a solar panel has the aerodynamic properties of a brick, ignore the tech chatter, if you're checking the panel when you clean the roof it'll be fine.

Cheers
Red.

 

[Gromett]

In its most basic translation Lift is dependant on the speed differential of a fluid between the upper surface and lower surface of an object.

If the full width support reduces the flow underneath, then isn't that increasing the speed differential, and therefore increasing the lift force?

Put simply, No it will not increase lift.

I have questions

RedFrame your first quote above seemed correct to me.

autorouter the same thought occurred to me, although I would rather have the blocker.

RedFrame your last quote directly contradicts your first quote and contradicts what I understand to be true?

If the front of the panel is blocked there is still lift as I understand it.

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[TUCANO]

Blinking heck this is getting very technical , I don think my van will go fast enough to take off and I thought Bernoulli was pasta

Cal54, her panel went pasta also.

 

[Bessy765]

Trick is to make sure there is a decent bed of adhesive and to drill hole through the feet so the adhesive comes up through the holes to give a better bond, and to make sure you key the rook where you are placing the feet. In over 30 years of repairing caravans and motorhome at least 4 or five customers have asked me to check why their panels are not charging to find one or more missing.

 

[RedFrame]

I have questions

RedFrame your first quote above seemed correct to me.

autorouter the same thought occurred to me, although I would rather have the blocker.

RedFrame your last quote directly contradicts your first quote and contradicts what I understand to be true?

If the front of the panel is blocked there is still lift as I understand it.

I can't explain 5 years education in one post, but in order to create lift the flow needs to be laminar. Imagine two molecules at the leading edge of a wing, one goes over it, the other under it. The two molecules must meet at the trailing edge of the wing and to do this they need laminar flow, simply reducing flow won't increase lift.

Cheers
Red

 

[Gromett]

I can't explain 5 years education in one post, but in order to create lift the flow needs to be laminar. Imagine two molecules at the leading edge of a wing, one goes over it, the other under it. The two molecules must meet at the trailing edge of the wing and to do this they need laminar flow, simply reducing flow won't increase lift.

Cheers
Red

I am not an expert in this, but did do basic physics. My understanding is that laminar flow is not required for lift only a difference in pressure. Laminar flow is an advantage as it reduces drag and therefore increases efficiency. But it is not required.
I also don't believe the 2 molecules must meet at the trailing edge. an equivalent number of molecules are more likely to meet at a point after the trailing edge but not necessarily at the trailing edge and not necessarily the same ones?

Please note the above are not statements of fact, they are questions.

My reason for stating laminar flow is not required, is that I can blow over the top of a sheet of paper and generate lift. When I blow I am not capable of generating a laminar flow and that is a fact, yet I still observe lift.

 

[Kannon Fodda]

OK so what is the difference between the lift effect of the sail, wing, aerofoil of these two split molecules compared to suction that might occurred if no splitting of molecules. Or am I simply confused. And bottom line the OP's panel wasn't stuck down properly.

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[Gromett]

And bottom line the OP's panel wasn't stuck down properly.

Correct

The rest of this is just interesting and for curiosity. I love learning new stuff

 

[VXman]

Just been out and checked the security of my panel which I fixed with Sikaflex. Seems completely stuck. I think I'll add it to my trip check list to check it every time I go away.

If just done a 3 week trip in Scotland after fitting my panel. On the first part of the trip I stopped 4 times and climbed through the skylight to give it a good tug. I also didn't go ove 50mph. It took me 2 weeks to get the courage to go over 70 mph!

Anyway, over 1000 miles later and speeds up to 75mph and it's still solid.

 

[Gromett]

I just did a quick experiment to test a hypothesis.

If there is no air under the surface and air flows above the surface you would suspect extremely high lift. But this is not the case. I wanted to test what would happen if you sealed all 4 sides of a solar panel (not advisable)

I placed a sheet of paper on my kitchen work surface and blew across it. No lift was generated.
When I bent the paper a little so that there was a gap under it, lift was generated when I blew.

So there needs to be air under and over. The air flow doesn't need to be laminar, and there doesn't need to be airflow underneath the surface.
Finally the surface does not need to be curved, although that appears to help.

 

[Gromett]

Keep forgetting I have chatGPT subscription. Asked it this; Interesting that is suggests laminar flow can actually be an undesirable thing occasionally. That I didn't know. Although it may be making that up

 

[The Wino]

I just did a quick experiment to test a hypothesis.

If there is no air under the surface and air flows above the surface you would suspect extremely high lift. But this is not the case. I wanted to test what would happen if you sealed all 4 sides of a solar panel (not advisable)

I placed a sheet of paper on my kitchen work surface and blew across it. No lift was generated.
When I bent the paper a little so that there was a gap under it, lift was generated when I blew.

So there needs to be air under and over. The air flow doesn't need to be laminar, and there doesn't need to be airflow underneath the surface.
Finally the surface does not need to be curved, although that appears to help.

I think the amount of lift will also depend on the angle of attack. I think a lot assume as it's flat on the roof there's no angle of attack but it depends on the direction of the airflow which could well not be parallel to the roof as it's just come over the windscreen. I recon if you put a flat sheet of ply on a roof rack there would be quite likely be lift although the ply is flat and as soon as the front becomes lifted there will be a huge increase as the angle of attack increases.

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[Gromett]

Ahh so it may be the coanda effect causing the lift on my paper. I just checked and no lift is created if the paper is flat and parallel to the work surface.
But now I am thinking maybe there is some vacuum being formed by the paper being lifted up when placed flat on the surface. Experiments are over for today.
If anyone else fancies joining in

 

[The Wino]

The chat bot beat me to it but sounds a similar answer

 

[Gromett]

I think the amount of lift will also depend on the angle of attack. I think a lot assume as it's flat on the roof there's no angle of attack but it depends on the direction of the airflow which could well not be parallel to the roof as it's just come over the windscreen. I recon if you put a flat sheet of ply on a roof rack there would be quite likely be lift although the ply is flat and as soon as the front becomes lifted there will be a huge increase as the angle of attack increases.

Think that may just be due to direct pressure rather than aerodynamic lift?

Anyway, Work is calling so need to go and deal with my Canadian client. Been interesting

 

[Nanniemate]

I used to check mine when it was first fitted


Just in case someone nicked it flying off if you check your mirrors at the suggested rate you'd see it in one or the other.

Many years ago I asked 2 lads to pick up a bumper on the m5 they said don't bother no-one will know who it was.

My reply was OK can you just stop and get the numberplate then please

 

[The Wino]

Ahh so it may be the coanda effect causing the lift on my paper. I just checked and no lift is created if the paper is flat and parallel to the work surface.
But now I am thinking maybe there is some vacuum being formed by the paper being lifted up when placed flat on the surface. Experiments are over for today.
If anyone else fancies joining in

A lot of glider wings make use of laminar flow and incorporate turbulator tape to control where the laminar flow detaches from the wing surface.

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