Boat design consultancy

[MapisM]

Ok guys, I'm looking for opinions and ideas on a boat design issue, which in turn also affects functionality.

In the two pics below is shown firstly the existing boat, with a s/s boxed radar arch which is the one the boat was built with.
Arguably not the nicest choice for a wooden boat, but it's already there and does its job.

Below is a rough drawing of an hard top job which is being evaluated.
The obvious advantage, aside from getting rid of the arch, would be having some shade on the FB, still leaving a wide aft space for sunbathing, and the possibility to enclose the FB with front and side canvas, and also cover it completely when the boat is not used, with some further canvas astern.

BUT, it's much easier to draw it than make it.
The cover structure has to be roughly 10'x 13', thus requiring quite some strength (hence also weight).
The idea is to use 4mm alu for the cover, slightly curved along the beam, with some alu tubes underneath, all around the cover and along its beam, at 2' distance each, to strenghten the whole surface. The pillars on the aft side, which should appear as a sort of prolongation of the main deck pillars below, would also be made of alu (boxed), and the whole structure should be painted in white.
The front supports would be 40mm polished s/s tubes.

Wadduthink?
Any view/proposal/idea will be highly appreciated, because before going ahead with a job which is neither trivial nor inexpensive I'd really like to evaluate all pros and cons.
Many thanks in advance!

 

[jfm]

Ooh, interesting stuff. Gorgeous boat by the way. A few initial (ie subject to further reflection) thoughts:

1. remember, you're not designing this for strength. you're desigining it for stiffness
2. There are alternatives like a Ft Lauderdale-stlye frame and canvas top, but I'm ignoring those and sticking with the "hard top" brief
3. I like the sketch, and would go with rectangular aluminium box (painted white) for the aft legs and s/s 40-50mm thick-walled tube for the front legs
4. I don't like the aluminium sheet for the top. It dents easily. It's hard to get paint to stick long term. Will have joints. You cant compound-curve it. It has plenty of strength but virtually zero stiffness so you are totally dependent on a chunky frame (= ugly) to get stiffness.
5. I'd prefer to get some 18mm MDF cut into "frames" as if you were building a hull mould, then fit slightly-curved 4mm MDF sheet onto those frames, so making a mould. (A possible additional feature, tho maybe not necessary, is to design in two curves with axis 90deg to the other curves, so as to create a quasi compound-curve). And then add a lip/flange around the edge of course. Apply the special release agent/surface for MDF and then you could then have a curved white GRP hard top moulded, which can be bolted to the metal supports. You could make it Airex/Divinycell cored, to give you instant stiffness. You could then line this on the inside just for aesthetic reasons - eg big flexi sheets of GRP moulded against a flat suface, and thin enough to bend - but it may not be necessary. Though, a liner would allow neat install of recessed lighting, etc

You could make the rear legs thicker, and match up to the boat by making the white bit of the boat thicker, just by painting it white and adjusting the teak trim, like pic below

I know of another pic that will inspire you - will go look for it and post it if I can find it

 

[jfm]

Here's the pic i was looking for. Obviously you dont want an exact copy (!) but it serves as inspiration as to what GRP artisans can make, bespoke. This is a lovely job technically (let's not drift this thread by getting into whether it is beautiful or ugly!). There are compound curves all over it and possibly an internal gelcoat roof liner

 

[jfm]

These guys do a lot of them so have a selection of moulds. Might be worth the cost of having them build a plywood box and ship it to you over the pond, becuase of the cost saving if they have a mould that is already the right size?

http://www.boatersdiscountcenter.com/hardtops.htm and click the "more pictures" link

 

[PowerYachtBlog]

I like your picture 2 and JFM's picture. But I would do it lower if possible, and if not would increase a bit the height of the flybridge sides and would also make them complete once you are at it. The second option would hide the height you have and leave less space.
I suggest a height between the upper wind shield part of the flybridge to the hard top, similar to that of the lower screens.

 

[Nick_H]

Well I agree it's a good idea to do it, useful shade, and the radar stanchion looks a bit out of place on an otherwise lovely boat.

How about making a sandwich construction for the roof by glueing either flat GRP, or 2mm aluminium, to each side of some 1" rigid foam, cut to the required size and shape, then having the edge detail made in teak, and either left to match the other teak detailing, or painted white and faired in?

 

[MapisM]

Wow J, great food for thought here, many thanks.

Following your inputs:
1) yep, 100% agreed and understood, wrong wording from my part
2) actually that's an alternative I considered, but the cost estimation my yard gave me was not much lower, hence I ruled it out. I couldn't see any real advantage of frame+canvas over the hard top, or am I missing something?
3) sorry, I did use the term 'boxed', but the aft legs were supposed to be rectangular also in my sketch. Anyway, making them larger and match the main deck accordingly is a great idea, looking at the overall proportions! Only problem is that the frame surrounding the window is made of rounded wood nicely matching the rest of the boat style. So, it's not just a matter of painting in white one part of it to make it look larger.
I don't have a better pic, but the one below should give an idea of what I mean.
4+5) precisely my initial thought! I mean, making the top in grp instead of alu. I didn't think of the build process in as much detail as you did, though.
I will definitely discuss that with the yard. I reckon that the main reason why they preferred alu was weight, but I don't think they considered to make it cored, thus needing less resin/weight for a given stiffness.

Thanks again for the moment - also for the boat appreciation, btw!

 

[MapisM]

Thanks jfm, PY and N_H for your additional contributions, I read them after typing my previous reply.
PY: I agree that a lower top could be nicer, but that's already tight as it is (195 cm height).
Luckily, neither myself nor my friends are NBA players!...
Otoh, raising all the FB sides would be really tricky. Besides, I think that "filling" the lower parts would rather look bulkier than nicer. But I'll give it a try on the picture.

 

[jfm]

MapisM, check out this site, click "custom hardtops" then see the picture gallery, about 7th picture onwards. It shows them making a male mould, in a single axis curve but then they nicely created a compound curve at the front edge (so creating good stiffness) then they moulded a nice hard top. This is perhaps what you should do, and you can include the aft legs as part of the same moulding (and install s/s poles to take the actual hardtop, with the side GRP "legs" merely acting as styling covers for the stainless steel poles

http://www.insitedesigns.org/portfolio/sites/northside/gallery/index.php

 

[MapisM]

you can include the aft legs as part of the same moulding (and install s/s poles to take the actual hardtop, with the side GRP "legs" merely acting as styling covers for the stainless steel poles

Very interesting!
By aft legs as part of the same moulding, you mean made in such way to smoothly connect to the top I guess, not really one single moulding?

PS: re. the frame+canvas alternative, did you mention it because you saw any advantage vs. the hard top?

 

[BartW]

allow me to add me apreciation for a beautifull ship;

jfm"s discription of the roof constructions is perfect, nothing to add,
but in stead of the rear support;
I think it looks also nice with side supports, angled in the other direction like this Fleming;

 

[jfm]

Very interesting!
By aft legs as part of the same moulding, you mean made in such way to smoothly connect to the top I guess, not really one single moulding?

PS: re. the frame+canvas alternative, did you mention it because you saw any advantage vs. the hard top?

Well, you could make it a single moulding (HT+legs) but I think better to put a sikaflexed joint there

No, I dont think a Ft Lauderdale T top is better. Hard top is better imho. I was just being 100% clear that I was commmenting on your actual HT proposal, not getting into a discussion on alternatives to a HT!

Thinking about this some more, I really think (a) male plug, (b) female mould, (c) finished product is the way to go, like the pictures in my link above. Reasons are:

1. Getting some compound curving is quite easy, like the pics in above link
2. You can make it wonderfully professional. Eg once you have the basic male plug made with a curved top you could at this point make the internal liner. The gelcoat would be the right way round if you think about it. Then, you can add to the male plug flat plinths for the radar, sat dome, etc. And you could add D section timbers to create "spray rails" along the top if you wanted them, or some similar pattern. Getting all these shapes in one piece of GRP would look fantastic, and adds stiffness
3. This thing needs to be capable of being walked on by you. To service the radar, clean off bird shiit, clean off red-rain. You might even fit a small ladder. By making a male plug, you can add toe rails at the edges and patches of non slip, then make all of that in one piece of GRP
4. You need to manage water flow for heavy rain. It will be rubbish if all the rain gets dumped on the flybr deck just aft of the HT. If you make a male plug, you can add a lip (like a car boot spoiler) along the aft edge to direct the rain to each side for example

I wouldn't worry about weight. This thing might be an extra 350kg at 6m radius above the roll centre but on a boat as big as yours I don't think that matters. It will lengthen slightly the resonant roll frequency but it doesn't matter.

 

[MapisM]

allow me to add me apreciation for a beautifull ship;

jfm"s discription of the roof constructions is perfect, nothing to add, but in stead of the rear support;
I think it looks also nice with side supports, angled in the other direction like this Fleming;

Thanks Bart, btw there are some really nice diving spots in the area where she's based.
If and when you'll fancy a trip down there, don't forget to send me a PM!

I did try to draw it also with the reverse legs, but it looked weird - to my eyes, at least.

 

[MapisM]

Blimey jfm, aren't you tired to deal with boring legal & tax stuff?
These days, there are shipyards around which could be bought for close to nothing, ready for a good turnaround which could become a great investment in a reasonable timeframe...!
Thanks again, I'll definitely discuss all your suggestions with my yard.

I wouldn't worry about weight. This thing might be an extra 350kg at 6m radius above the roll centre but on a boat as big as yours I don't think that matters. It will lengthen slightly the resonant roll frequency but it doesn't matter.

Agreed, actually the effect on rolling could even be a slight improvement in terms of comfort - particularly at anchor, 'cause under way the stabs take care of that.
But the weight-related concerns were mainly linked to the possibilities to attach the whole structure to the FB, which is obviously all wooden with no single structurally stronger points. And of course, on top of the weight, there's the dynamic load for wind, rain, etc.
That's the only reason why I also thought (aside from the yard) that the lighter the better.

 

[jfm]

Blimey jfm, aren't you tired to deal with boring legal & tax stuff?
These days, there are shipyards around which could be bought for close to nothing, ready for a good turnaround which could become a great investment in a reasonable timeframe...!
Thanks again, I'll definitely discuss all your suggestions with my yard.

Agreed, actually the effect on rolling could even be a slight improvement in terms of comfort - particularly at anchor, 'cause under way the stabs take care of that.
But the weight-related concerns were mainly linked to the possibilities to attach the whole structure to the FB, which is obviously all wooden with no single structurally stronger points. And of course, on top of the weight, there's the dynamic load for wind, rain, etc.
That's the only reason why I also thought (aside from the yard) that the lighter the better.

Yup, I might give up the legals and buy a boatyard and do bespoking! Would be quite fun actually! Gimme 3 years... no, 2

Hmm yes you will have to get a good understnading of the strong points to attach this to. Not much I can say, without knowing your boat. At the base of the legs, you could make big fore-aft s/s strips, so the legs are upside-down T. This would allow you to attach to multiple strong points.

Regarding wind etc, one thing to remember is this design does not easily have inherent stiffness laterally. I mean, if you push the whole HT port-starboard, it will flex because you have no diagonals. It is very hard to include diagonals without spoiling the looks (though you could attach an "X" of diagonal wires with bottlescrew tensioners in winter lay up period if you get strong winds then). To help with this you will need quite chunky metalwork where the legs join to the HT. This might be able to be hidden inside GRP mouldings, or made from nicely curved s/s tube. Also if you fit a ladder (for cleaning access) that can become a disguised corner brace to provide stiffness to the corner joint at one side.

Indeed, you are also at risk of flexing fore-aft due to no diagonals in that direction, but that should be curable by having hopefully ~250mm of fore-aft dimension in the 2 main HT legs. And you could have small diagonal s/s tube corner braces where the 40mm s/s tube joins to the forward flybr deck or dashboard. So it's only the lateral port-starboard flexing you need to worry about, I think

Remember the trouble Sealine had with flexing of the GRP lid on their SC38 or whatever model they first did it with, 6 years ago?

I think the forward-facing legs look better

Ref iPlayer thing on other thread, I dont know but I do see your IP point. I'll try again this weekend...

Logging off. 5am alarm clock in the morning - 7am Squeezyjet to Nice, whereit's sunny ish

 

[hlb]

Ok guys, I'm looking for opinions and ideas on a boat design issue, which in turn also affects functionality.

In the two pics below is shown firstly the existing boat, with a s/s boxed radar arch which is the one the boat was built with.
Arguably not the nicest choice for a wooden boat, but it's already there and does its job.

Below is a rough drawing of an hard top job which is being evaluated.
The obvious advantage, aside from getting rid of the arch, would be having some shade on the FB, still leaving a wide aft space for sunbathing, and the possibility to enclose the FB with front and side canvas, and also cover it completely when the boat is not used, with some further canvas astern.

BUT, it's much easier to draw it than make it.
The cover structure has to be roughly 10'x 13', thus requiring quite some strength (hence also weight).
The idea is to use 4mm alu for the cover, slightly curved along the beam, with some alu tubes underneath, all around the cover and along its beam, at 2' distance each, to strenghten the whole surface. The pillars on the aft side, which should appear as a sort of prolongation of the main deck pillars below, would also be made of alu (boxed), and the whole structure should be painted in white.
The front supports would be 40mm polished s/s tubes.

Wadduthink?
Any view/proposal/idea will be highly appreciated, because before going ahead with a job which is neither trivial nor inexpensive I'd really like to evaluate all pros and cons.
Many thanks in advance!

My problem with this is, your adding a new design to an old boat. I'd be more inclined to follow the boats own lines. I'd take a point above your centre fender, on the fly bridge and maybe usesing SS steel Tube, rake the arch back, same as the front?? If that makes sence. So you have one tube raked back, from the flat bit of the fly, then another from maybe nine inches down. Joining up about 3inch apart. I'd cover this, with a maybe one inch thick piece of mahogany, front face only. Or same as the other wood you have.

Dunno how much wood you have on show. The result needs to be about the same.

 

[MapisM]

My problem with this is, your adding a new design to an old boat. I'd be more inclined to follow the boats own lines.

Yup, I perfectly see what you mean.
Strictly from an aesthetic viewpoint, imho the best solution would be a wooden mast, period. Nothing else.
Btw, there is an almost sistership (though more fisherman-style) which was built with an arch similar to the one you describe - see first pic below.
But once you begin to think of the advantages of an HT, wood surely isn't the best material to play with, for such a wide and thin structure.
Besides, there isn't actually a lot of varnished wood up there - see the other two pics below.

Oh, and she ain't as old as you might expect: built in 1996, and her bulder didn't change a lot in the meantime, either!
The last two pics show one of their last single deck, which as you can see is still very similar, and the bigger double deck which is possibly more modern, but just a bit.

 

[MapisM]

Regarding wind etc, one thing to remember is this design does not easily have inherent stiffness laterally.

We gave that a thought, particularly in view of a possible usage with canvas to cover the whole FB when not used.
One idea was to make the front tubes crossed, but as you say they would spoil the look. Removable wires are a possibility, though!

Have a nice flight tomorrow morn.
You might as well grab the occasion of the trip to think further about your first statement...

Yup, I might give up the legals and buy a boatyard and do bespoking! Would be quite fun actually! Gimme 3 years... no, 2

...as you surely know, investment is all about timing!

 

[David_Jersey]

I think you are trying for something that will look good with cover and without - to be honest I think you have to settle for one or the other.

I would go for looking good without and settle for with enclosures looking like a circus tent To that end I would seperate the Radar Arch more from the cover frame design - indeed what about no arch, and simply a central pole / tripod?

Our American friends seem to be the masters at enclosures.

Not quite suitable I think - but shows some invention on prioritising the radar arch and looking to the cover as a secondary / hidden(ish!) function:-

This Hatteras I think gets away with the radar arch not following the angle of the aft pillars by reversing the angle:-

Albeit cant say I like the hard top or the extra height radar (satellite dome?).

Be a shame to ruin the lines of your boat by adding something that is permanently in place, rather than just when raining or hot.


Alternatively, just go for the radar arch, forget the full enclosure and settle on a fold away Bimini over the helm area:-

Even when in place would look deliberately unoriginal - rather than a failed attempt to integrate with the rest of the boat's design.

 

[MapisM]

I think you are trying for something that will look good with cover and without - to be honest I think you have to settle for one or the other.

Yes and no. I mean, the option of fully enclosing/covering the FB is strictly for when the boat is not used. Main reason is that it's all teak up there (as shown in previous pics), and both the wood and the seams could use some protection against sun and rain. Very different from the US way of using enclosures: in many boats (mostly fishermen) they don't even have the helm station downstair.
So, yes, I'm trying to do something that will look reasonably nice, but only with no enclosures. I know it'll be ugly when fully enclosed, but can't see any way to avoid that, and it doesn't really matter anyway.
And foldable arches would be very impractical on such a big area, not to mention that they would have a hard time to withstand strong wind etc.