How thick is your hull

[bbg]

In order to get the definitive answer I've just been out and cut the boat in half to find out.
This is an end-grain balsa sandwich construction so I gues the resin at each side is about 2mm

You could've just bought a longer trailer ...

As for layup thickness - on my boat it seems to be thick enough to keep the water out. Works for me.

 

[Bosun Higgs]

Wait for it, this has all the ingredients of a pi$$ing contest 99.9% of which will be based on inaccurate, irrelevant or imaginary dimensions. The only thing that is really thick here will be the thought processes and their resulting prejudices.

Of course I could be wrong....

Absolutely Robin.

Whats more, a hull that is thicker than necessary is both slower than it need be and more costly. Do people say "my Vauxhall is heavier than your Ford " implying its a better car? No they don't because weight is a statistic not a virtue.

 

[noelex]

The bottom is 10mm thick tapering to 8 6 then 5mm . All solid aluminium, but the real strength is in the web of bulkheads (which are 14 or 12mm thick aluminium) and the T shaped stringers(6mm thick alumium). There is a stringer at least every 25cm.

 

[doris]

I never intended this to become a contest as to who has the biggest willie. I was very interested in the cutouts from the through hull fittings and am curious as to other boats . The layup on the Dehler was hand done with lots of woven rovings, I watched some of it, not any of the chopped up mulch. Always nice to know what might happen when I hit something.
It would appear that we are on the heavier side of average. Not sure if that is good or not but it must be comforting!

 

[AntarcticPilot]

My hull is as thick as my skin - that is, it keeps the inside in, and the outside out!

 

[Robin]

Steel and aluminium boats will be thinner than are wooden boats and grp boats will be somewhere in between. All that tells us is that to achieve the same results, different materials need to be sized differently. Now narrow the focus onto the different laminates within the generic term of grp and the same applies that different laminates are different thicknesses to provide the same results and the choice of laminate/layup is determined by what function it has to achieve. Function may be stiffness or flexibility as well as brute strength or puncture resistance and cracks can occur in a very thick as well as a thin layup. It is far too simplistic to assume thick is strong and thin is weak. One difference between steel, aluminium and wood built boats and those made of grp is that the grp one will have different skin thickness in different places and maybe different layup specs too.

 

[AndCur]

The Achilles 24 is around 65mm were the keel bolts on tapering out to about 6mm on the topsides. Hull is layed up using woven mat not chopped stands.

 

[Lakesailor]

Oh dear. Sounds like the resin slumped during lay-up.

 

[30boat]

The Achilles 24 is around 65mm were the keel bolts on tapering out to about 6mm on the topsides. Hull is layed up using woven mat not chopped stands.

Chopped strand matts are essential in conventional polyester layups as they provide adhesion between layers of woven rovings.Without them the layup wouuld soon delaminate,so you must have CSM in your hull.

 

[jonjo]

According to some an egg shell would be a useful reference.

 

[flyingscampi]

My hull is thicker than yours

 

[Ubergeekian]

According to some an egg shell would be a useful reference.

 

[snowleopard]

Chopped strand matts are essential in conventional polyester layups as they provide adhesion between layers of woven rovings.Without them the layup wouuld soon delaminate,so you must have CSM in your hull.

Do they still use woven rovings? AFAIK most laminating has been done with bi- or tri-axial stitched fabrics these many years. As the strands are parallel they don't leave the sort of resin voids that CSM was used to fill. Remember that the best resin/glass ratio achievable with CSM is 2.5 : 1 but with biaxial, 1.1 : 1 is easily managed.

 

[JimC]

Chopped strand matts are essential in conventional polyester layups as they provide adhesion between layers of woven rovings.Without them the layup wouuld soon delaminate,so you must have CSM in your hull.

This has not been necessary for many years. The modern fabrics don't need it.

 

[DogWatch]

All the tosh about Bavarias, layups and hull thickness in the other post made me dig out the cutouts from my speed and depth transponders. On a Dehler 39, built in 2006, the thickness is about 23mm. These are at the very aft end of the forward bunk so well forward of the keel.


What about other makes? Any accurate comments?

Mine were dumped in the bin at the yard, as they should be by all normal, ordinary, mentally sound types...

to put it another way, do you store and file all your rubbish?

 

[stav]

Well if you want thick you have me, well Jandavina: Hull skin is not that thick aft port quarter about 9mm, fwd where I removed a skin fitting to one side between the berths perhaps 12mm. I did try and put a couple of additional bolts in the stem fitting and could not penetrate the GRP with a 4mm drill so at least 3inches thick, and from a cross section drawing of the hull where the keel bolts come through it is 6 inches thick. Then there are the aluminium frames glassed in but I expect they are powder in the bottom of the glassed in skin by now. Interestingly I expected her to be just CSM but there is evidence inside of woven roving.

I happen to agree that thick does not necessarily equal good but believe a product such as a boat should be able to survive a bit of abuse. I think I have been aground 3 times but only one was with a bump as the previous times I knew I was pushing my luck. But the hard bump was in the Morbhian on rocks with some tide, another small graze to the lead keel along with the others from previous owners but we did get straight off and find the necessary passage.

A better question might be how thick does a hull need to be to take some knocks and survive for 50 to 80 years, because a hull should be able to be refurbished a number of times before it is obsolete because lets face it GRP as a material for our environmentally friendly world simply does not fit: it cannot be burnt and cannot be made in to anything else useful, unless you consider grinding in to road fill or sinking all the knackered boats together to make reefs for the fishes, may be studland would be a good site..... Think I will go now.

 

[MapisM]

Steel and aluminium boats will be thinner than are wooden boats and grp boats will be somewhere in between.

Correct. My wooden boat has 40mm planks and 80mm frames.
Since the empty space between frames is slightly less than the width of the frames themselves, it means that more than half of the hull has a 120mm thickness. In spite of that, she's surely not stronger than much thinner steel hulls, for instance.

 

[TradewindSailor]

.....
A better question might be how thick does a hull need to be to take some knocks and survive for 50 to 80 years, because a hull should be able to be refurbished a number of times before it is obsolete because lets face it GRP as a material for our environmentally friendly world simply does not fit: it cannot be burnt and cannot be made in to anything else useful, unless you consider grinding in to road fill or sinking all the knackered boats together to make reefs for the fishes, may be studland would be a good site..... Think I will go now.

I tend to agree. All yachts should be able to go aground at 5 knots in a decent swell on sand withought the keel coming through the bottom. They should also not sink after a collision at that that speed. Obviously racing yachts have more lighter construction .... they are built to win after all, but they shouldn't be disposable either.

I watched a J24 get broken up on a reef in a F2 but with 2 swell in less than 6 minutes. The whole of the port side was taken away and the keel was pushed up through the bottom. It was recovered the same afternoon .... and then chopped up. A reef or rocks with swell is probably more than most grp boats can stand for long ..... but some do survive.

The question is how far towards indestructibility do you go? If a builder builds his hulls strong can he sell them at a profit? Can he sell enough to make tools or a production run worthwhile ..... or is he just going to sell a couple a year?

I would suggest that in the current market production boats are always going to be at the lighter end of the scale with the hulls being designed for service conditions that don't include being impervious to groundings and collisions. Provided they can survive in the average charter fleet for 5 years without expensive repairs, they've done their job. If a few have perished along the way because they have been operated beyond their limits .... should the builder worry?

 

[Woodlouse]

I have witnessed a boat that was built to take a few knocks and scrapes. I can only however supply the hull thickness at the waterline.

Here it goes...
Outer planking three planks deep as follows;
Outermost planking: 6 inches.
Middle planking: 4 inches.
Inner planking: 3 inches.
Frames: 12 inches thick, 21 inches wide. Spaced 1 inch apart.
Internal planking: Between 4 and 8 inches.

Which makes a grand total of up 32 inches thick. Or 812 mm for those who like metric.

I think Fridtjof Nansen wins this 'size matters' contest.

 

[TradewindSailor]

One problem with thin hulls, especially cored, that is not normally highlighted is osmosis.

The structural strength of a thick hull with osmotic blistering will be much less compromised than that of a thin hull due to the redundancy within the laminate. In addition, the thicker hull will be much less effected by the remedial work of peeling.

By the way, most yacht builders today only give guarantees against visible osmosic blistering for the first five years. It is generally excepted that if you get visible blisters within 5 years there is something seriously wrong with the layup. It's strange though that I can't find their guarantees/warrantees on the internet though.