Boat design consultancy - one year later

[MapisM]

Perhaps I could fold down the frame of the sunroof while it is fold together, And or fixing a pole on the helm seat
Any advice on this ?

Tricky question, Bart. If you want a cover capable to withstand the winter, not only you must think of rain, but also of wind.
Wind was the main reason why I decided to make my top foldable.
I've recently been onboard during a F8 storm which lasted for one and half a day, and I was very pleased to have gone that route.
I don't think the side enclosures would have withstood such wind, if they would have been high enough to reach the fully raised top.
If you use the existing frames and the radar arch, you're bound to have a huge wind exposure.

With rain, in a sense it's the other way round. A higher top allows for steeper side covers, which might not require any support. But as we just said, a low cover is much better to reduce wind problems.
I had to deal with that in my boat, because the F/B is huge (vs. the boat size), particularly in length: almost 8m overall. I don't think yours can be longer, even if your boat is quite bigger than mine.
Anyway, "my" solution was on one hand to make the top cover as long as feasible (4.5m), and on the other hand to design the folding geometry in such way that the top is as centered as possible, when lowered.
In spite of all that, the stern cover was still not steep enough to avoid the risk of collecting rain and ultimately tear apart under the weight of water.
No big deal, though. One wooden pole under the centerline of the stern cover was enough to avoid that.
I'm attaching below a few pics to show how it looks when lowered, also from the inside.

I'm afraid that to evaluate what could be the best solution for your boat, it's really necessary to see her in flesh. Even if the ideas discussed here when I first thought of this project were indeed useful, I don't think I would have been able to design a practicable solution just looking at some pics.

 

[BartW]

I don't think the side enclosures would have withstood such wind, if they would have been high enough to reach the fully raised top.
If you use the existing frames and the radar arch, you're bound to have a huge wind exposure.

I agree with your concern, but I believe you didn't understand my plan quite right,
my plan was to make a cover just going over the FB front windscreen, and the side walls (tube) left and right, so that I just have to raise the cover in the middle to avoid collecting rain on top.

folding down the existing canopy/sunroof, so that it is at the hight of the FB side tube gard rails, could give a strong support for the new cover from left to right,
the cover would then go over the table and over the sofa, but under the radar arch.
yes I know all difficult to explain in words. (might make a small drawing)

will go to the boat in a few weeks with the cover maker, a Belgium guy who made a canopy for 3 previous boats, and has lots of experience,
so we shall see what he say's

by the way, I measured the FB surface, from windscreen to the back behind the tender it is 8.8m length and 3.7m wide.
I'm wondering if the cover should also go over the tender or not,
then that part will be the highest, and the most exposed to the wind, and prone to wind damage,
The existing tender cover has already been blown off partially on a few occasions.

 

[Deleted User YDKXO]

Very nice, Mapism but I must admit I would not have chosen that navy blue canvas colour but a cream/off white colour which IMHO would have gone better with the varnished wood but thats just my opinion. Its a hell of a strong structure and I'm surprised that one person can lift/lower the weight but then all that pasta must make you Italians much stronger than we Brits

 

[MapisM]

yes I know all difficult to explain in words. (might make a small drawing)

Yep, that would help.
But based on your latest explanations, maybe I undertood what you have in mind.
Of course, by keeping the cover very low, you will reduce the wind resistance.
But it might be more difficult to avoid the formation of water pockets anywhere over the whole surface.
You've got more than 30 square meters to deal with, securing the cover in such way that it won't be blown off and it will self drain also under heavy showers. And without an almost rigid top above the center, as the one I've got...
I would keep an eye to accessibility, too. You want to be able to access anything on the F/B also while it'll be covered, just in case.
I'm curious to hear what your expert will suggest, keep us posted!

 

[MapisM]

I would not have chosen that navy blue canvas colour but a cream/off white colour

LOL, we actually debated that at length with SWMBO.
The Sunbrella fabric which we choose also allows a different colour on either side, and till the last minute we considered the alternative of beige below and blue above. Btw, IIRC that's what jfm went for on Match, albeit with black above, rather than blue.
It's one of those things where you'll never know if the alternative would have been better. But overall we're very pleased with the result, when seen in flesh it's actually better than in pics.

Re. handling the structure manually, actually it's borderline for just one folk. I always asked a hand to someone else in the marina to lift or lower it. It's jusy a matter of half a minute, anyway. Much better safe than sorry!

 

[BartW]

You've got more than 30 square meters to deal with, securing the cover in such way that it won't be blown off and it will self drain also under heavy showers. And without an almost rigid top above the center, as the one I've got...
I would keep an eye to accessibility, too. You want to be able to access anything on the F/B also while it'll be covered, just in case.
I'm curious to hear what your expert will suggest, keep us posted!

this morning I had a first conversation with the cover maker, (I did send him some pictures of the FB last night)
first he suggested to fix the fly bridge cover on the radar arch, (highest point) but I don't like that, as I believe this will catch lots of wind, and it looks ugly.

second option he proposed and we principally agreed on,
is to make 3 or 4 curved and removable beam bars (between port and SB side hand guard rails on the flybridge) spaced app 2m between each bar,
and having 3 belts or straps, going from the FB front window, over these beam bars, over the tender, fixed and tightened at the rear border of the FB.
The cover will then be supported by these beam bars and these belts.
It will have many straps on the sides, and on the rear for tightening
We would have acces to move under the cover (0.7….1.2m high inside)
we would make a few “doors” with zippers in this cover, at least one in front of the helm, for occasional helming / manouvring the boat from there, while the cover is on.

He has 3 options for the cover tissue:
- PVC, but disadvantage is condensation on the underside, and mould where the PVC touches the side walls
- New sort of fabric, synthetic upperlayer, and cloth under layer, disadv, this material seems to stretch a little, and remains stretched, not elastic
- Canvas, we believe this is the best, but it is 50% more weight, difficult to handle when placing the cover or when taking that off.

Any sugestions ?

 

[jfm]

Tricky question, Bart. If you want a cover capable to withstand the winter, not only you must think of rain, but also of wind.

Agreed, and also 150mm of snow, which is very heavy

 

[MapisM]

Agreed, and also 150mm of snow, which is very heavy

Doh! I'm obviously spoilt by some years of southern Sardinia weather... I must admit that I didn't think of that.
Actually, I'm sure that my top could withstand some snow, anyway.
Dunno about the bow and stern side sections, though.
Its's good to be reasonably sure that it won't matter, anyway!

In reply to Bart's last question, I'd stick to good quality canvas.
The weight will make a tad of difference in handling, but nothing critical, even with the large surface you're talking about.
I would make it in separate sections anyway, at least 3, if not 4 or even 5.

 

[BartW]

Agreed, and also 150mm of snow, which is very heavy

Doh! I'm obviously spoilt by some years of southern Sardinia weather... I must admit that I didn't think of that.

Ok that leaves me only one solution when it snows in SOF;
bring the boat to Sardinia

 

[DAKA]

Really well proportioned, looks great


If snow/heavy rain is an issue you could add Velcro valves.

2 ft vents on the seams that open under stress to allow the water to fall in, just push them back when next on the flybridge.

 

[MapisM]

Really well proportioned, looks great

If snow/heavy rain is an issue you could add Velcro valves.

Thanks for the appreciation.
The suggestion makes sense, but luckily around here snow is not an issue at all.
Not till this statement of mine, that is...
...now, where's my horseshoe when I need it?

 

[BartW]

here is a principle drawing of what we have in mind,
comments or or opinions are welcome

 

[MapisM]

Sounds like the most efficient solution for a storage-only cover.
Btw, I wouldn't bother to find a solution for opening the helm area, to allow helming the boat from the F/B also when she's covered.
That's easily feasible with the cover I made on my boat, also when it's lowered, but I don't think I'll ever use her that way. Much easier and convenient to just use the main helm station inside.
The only thing I would consider, looking at your drawing, is to separate the 4 sections of the cover along the beam bars, rather than longitudinally.

 

[AndieMac]

here is a principle drawing of what we have in mind,
comments or or opinions are welcome

Those SS transverse bows are going to be quite long and will need good support to stay in place (for and aft movement) under the weight of the large covers Bart.
Also wondering about the longitudinal straps going over the top of an inflatable dinghy which is subject to deflating in colder weather, and loosing your strap/support tension, causing sag and pooling in the covers.

 

[vas]

Bart,

from an engineering perspective, what you're trying to achieve is difficult.
I mean it's too long to be able to get a reasonably tight and stretched cover in there. The typical solution in these cases that also automaticaly sorts out water puddles and to a large extend snow stresses is to go for double curvature solutions as in (saddle shaped forms).
That means that the support/ending points for the cover are not in the same plane and some are considerably higher.

Doubt you can do it properly as it will look bad, but on microscale if you follow MM and AM suggestion and split the cover into 3-4 pieces, it would be possible to produce self stressing, loadbearing framed covers that clip one to another. It's not easy to show what I mean, if you do have a 3/4 top view of your fb I'd had a go in pshop to draw the basic lines I'm thinking. Else I'll try to knock a wireframe model in acad when I have some time in the evening after I put the kids to bed...
Everything would work under tension, the curved members will have the fabric fixed to them, the bow-stern oriented members will be straight and effectively introducing the forces (working under compressiong) that hold it together and most important you'll be able to easily store it flat packed for next winter, once you remove the compressed straight members

ah, probably post a scanned sketch first after a while...

V.

 

[BartW]

Those SS transverse bows are going to be quite long and will need good support to stay in place (for and aft movement) under the weight of the large covers Bart.
Also wondering about the longitudinal straps going over the top of an inflatable dinghy which is subject to deflating in colder weather, and loosing your strap/support tension, causing sag and pooling in the covers.

yes agree,
these straps, going over the dinghy are my biggest concern.

 

[BartW]

Bart,

That means that the support/ending points for the cover are not in the same plane and some are considerably higher.

I'm not sure if I understand this completely,
the fixings of the cover fe on the sides, are meant to be straps, vertically down along the sides, so not in the plane of the curved tubes...



fixing the cover also on the radar arch, would that be a solution with double curvature ?



I have very few pictures from the FB, if you PM your e-mail I can send you some. but perhaps a very simple scetch of your idea, would also help...


thanks a lot for your advice anyway, as you have your own, more interesting challanges to take care of, at this moment

 

[BartW]

I wouldn't bother to find a solution for opening the helm area, to allow helming the boat from the F/B also when she's covered.

Mmmmm,
After one season (120hrs) I dare to say that I’ve become quite handy in manouvring the boat, (thats what the guests say) and I love it
But the helming was always’s done from the FB.

Sometimes I don’t have experienced crew on board, then it is very handy that I have a good vieuw while manouvring. Or that I can spot a neighbour captain, or a harbour master on the quai, just giving the few small signs I need.

While manouvring In Porte Ercole, there was a small sports boat coming on my side, between me and the moored boats, I needed to stop to avoid collision,

In Cassis, the Callenque visiting boats take every gap to bypass you, even in the tight harbour,

From the inside helm, I can’t see all that….

Moreover, I need a “door” in that cover, to get at the outside (for strapping the cover)

And yes fully agree that the cover needs to be made of 4 sections, separated along the beam bars

 

[vas]

sorry for the delay, just managed to scan my small sketch and upload it:

I think it is reasonably clear what I mean with the double curvature and individual covers.
Mind you such a solution means that there must be some extra sewing and it's not a straight forward piece of material you're stretching. Easy to calculate with programs like Rhino, would be a good student exercise for next year when I'll be teaching this course tbh (but it's too late for you then)
Also note that I'm adding an extra bow-stern tube on the top of the curvature to keep things stressed and working properly.

cheers

V.

 

[MapisM]

I can see where you come from, but I'm not sure I would trust a "normal" cover maker to prepare such curved sections, because either they are EXTREMELY accurate (curvature, tension), or they're useless.
An easier alternative could be to have a (slight) curvature along the longitudinal tube on top, with the canvas going over the whole structure and forming a sort of dome.
Of course, the canvas should also be secured to the tubes below, to limit its movements with strong wind, but that's easily done with some velcro-ed pockets sewed under the canvas, aligned with the tubes.