Centre Hull Floating Stern-Down

parkhouse · Post by **parkhouse** » Wed 28 Apr 10, 8:51

I'm about to anti-foul the centre hull and I find barnacles and weed growing up to 40mm above the colour line at the stern while the bow's colour line must have been well out of the water. The only change to the centre of gravity was the fitting of a 10Kg radar scanner on the targa, not enough to have any major effect. If I shorten the aft waterstays and, possibly, lengthen the forward ones, I'm wondering if that will solve the problem. Any ideas?
Mike Paterson, Df1000 Champus

Oscar · Post by **Oscar** » Wed 28 Apr 10, 15:42

I think it's more a matter of the amount of time that the stern spends "wet" as the waves meet the relatively flat surface. The bow is vertical, and also in the sun more..... Are you sure the boat is actually not sitting on it's lines?

If that is in fact the case, the easiest way to move substantial weight around is moving water tanks. A 15 gallon tank in the vbirth is 120 pounds....

I would NOT mess with the geometry of the floats.

parkhouse · Post by **parkhouse** » Wed 28 Apr 10, 17:06

Funnily enough, filling the water tank drops the bow slightly (and slows the boat down) but doesn't raise the stern which is why I thought that the waterstays were out of adjustment.
And it's not an illusion - it is apparent when the boat is berthed.
Mike Paterson, Df1000 Champus

Steve B. · Post by **Steve B.** » Thu 29 Apr 10, 16:01

Pictures would help.

Don't mess with the geometry of the waterstays, the hinges will bind for sure.

My 1000 (#15) is slightly down in the stern also, but I have an arch as well.
The stern isn't very wide, so it probably doesn't take too much to drop it.

I recently added a 120 watt solar panel to the arch and am in the middle of moving the radar to the mast just above the first set of spreaders.
The main reason for pulling the mast was to replace the wire conduit.
It was loose and clanging around.

I try to keep the boat light, but on the other hand, I keep an aluminum danforth type stern hook in the aft lazarette.

My stern floats normally with the water covering about 1/4 of the rudder pull down hole.

Steve B.

parkhouse · Post by **parkhouse** » Thu 29 Apr 10, 22:23

I've requested Bo to add three photos.
The Centre Hull Bow photo clearly shows the water level rising the further back you go: the centre hull stern masking tape indicates the water level - as you will see, it is getting quite near the engine exhaust.
Finally, the port ama is obviously high in the water, as is the starboard one. The four large hinge pins around which the akas swivel are all in good condition and the holes show no sign of becoming oval.
Mike Paterson, Df1000 Champus

Please click on any of the photos to see them enlarged!

Oscar · Post by **Oscar** » Sat 01 May 10, 16:29

Has Quorning seen these pictures?

parkhouse · Post by **parkhouse** » Sat 01 May 10, 19:07

Yes and I await the reply.
Mke Paterson, Df1000 Champus

Steve B. · Post by **Steve B.** » Sat 01 May 10, 20:26

parkhouse wrote:The Centre Hull Bow photo clearly shows the water level rising the further back you go: the centre hull stern masking tape indicates the water level - as you will see, it is getting quite near the engine exhaust.
Finally, the port ama is obviously high in the water, as is the starboard one.

Compared to my boat, your floats and bow are at least 2" lower in the water. Your main hull stern is at least 3" lower than mine.
From what I see in your photos, I don't see anything which suggests geometrical anomalies with the amas or waterstays.

How much stuff do you have aboard? Have you checked all the access covers in the amas and stern area for water? Your bilge should be dry.
If not, is it fresh water? I've been fighting several rain leaks, and have almost all of them fixed.

Which engine do you have? Maybe a supercharged 7 litre V8?

I have a Volvo MD2020 The MD2030 weighs more, but not THAT much.

Steve B.

tpaliwoda · Post by **tpaliwoda** » Sat 01 May 10, 22:08

You are definety sitting low in the stern. Compared to my 1000, the stern tube is about 1/2 in the water and not even close to the exhaust.

Did you try re-sealing the stern tube? They are known to leak (just re-sealed mine last week). The aft water compartment can be filling with water adding weight directly to the stern?

It is a real crap job, any time you have to crawl into the stern locker it is a crap job.

Keep us posted

Ted

Oscar · Post by **Oscar** » Sat 01 May 10, 23:30

Yea, I'd be looking for water....

Or stuff.....

You'd be amazed. The short version of the story is that I took EVERYTHING off a 25' mono and weighed it..... over 650 pounds..... it adds up.

Just for giggles, take everything off the boat and see what happens.

After that, start looking for water. 40 gallons is not a lot, and equivalent to two people standing back there.

And, look in the floats too, not just the center hull.

Mika Harju · Post by **Mika Harju** » Wed 05 May 10, 8:19

[/quote]
Compared to my boat, your floats and bow are at least 2" lower in the water. Your main hull stern is at least 3" lower than mine.
From what I see in your photos, I don't see anything which suggests geometrical anomalies with the amas or waterstays.
Steve B.[/quote]

My DF1000R also floats much higher, it´s similar to Steve´s one.

I made some estimated calculations of this situation and foud out you´re looking after about 1000 kg of extra weight.
Sounds impossible! You need to have that V8 somewhere!

(On waterline level: Amas: L7m * W0.5m * WL0.06m *2pcs and Center Hull: L8m * W1m * WL0.06m)

parkhouse · Post by **parkhouse** » Wed 05 May 10, 21:51

You are all correct regarding the geometry of the three hulls - Quorning say that it is not possible to adjust the waterstays in order to move the centre of buoyancy. The boat is just back in the water but I'm not yet in a positon to unfold the amas. With them folded, the water level at the stern is at the same level as everyone else - half way up the stern tube hole - but, of course, it will rise when the amas are opened and the buoyancy moves forward. Weight? Steve, the V8 is only firing on three, like everyone else's (it's a 2020 Penta) and there is no water in any of the main hull bilges apart from 1/2 litre below the rear locker. The stern shaft seal is a water-lubricated manecraft seal, Ted, and is always a little wet but a sponge is always enough to dry the compartment out. As for the contents of the rear locker, I've removed several miles of ropes this evening and the water level is EXACTLY THE SAME! Never mind, I'll weight them and leave them off for just now, Oscar. Next step will be to see how much water is in the amas but I doubt if there will be 1000 kg of the stuff, salt or fresh. Thanks for doing the sums, Mika.
Mike Paterson, Df1000 Champus

tpaliwoda · Post by **tpaliwoda** » Thu 06 May 10, 0:30

I think you may have miss under stood me. I want you to check the rudder hold down tube that exits the stern. The one the line runs through to the rudder. There is a compartment all the way at the stern that prevents any water from coming forward if there is a leak. I would check that compartment. That could hold a good 40 gallons of water! and it sits right at the stern. Having 300 lbs sitting right on the stern will certainly make it sit lower.

Double Horizon · Post by **Double Horizon** » Thu 06 May 10, 15:04

tpaliwoda wrote:I think you may have miss under stood me. I want you to check the rudder hold down tube that exits the stern. The one the line runs through to the rudder. There is a compartment all the way at the stern that prevents any water from coming forward if there is a leak. I would check that compartment. That could hold a good 40 gallons of water! and it sits right at the stern. Having 300 lbs sitting right on the stern will certainly make it sit lower.

I also experienced cracking (and leaking) of the stern hold-down-line tube in the 1000, and repaired it by wrapping it in resin-coated fiberglass. However -- that tube runs from the aft cockpit bulkhead to the stern just above the bolts that secure the lower rudder bracket. The entire run is visible and accessible from within the aft locker. There is another compartment that hides the steering quadrant, but that is higher up. There is also a compartment below the aft locker floor, accessible from an inspection hatch. Are you referring to one of those?

Mika Harju · Post by **Mika Harju** » Fri 07 May 10, 7:20

parkhouse wrote: The Centre Hull Bow photo clearly shows the water level rising the further back you go: the centre hull stern masking tape indicates the water level - as you will see, it is getting quite near the engine exhaust.
Mike Paterson, Df1000 Champus

Attached you will find a photo of my stern. When folded the transom and stainless steel made rudder frame of my DF are completely out of water. Both water and fuel tanks are full, otherwise I keep my boat quite empty and light.
This means about 100mm difference between our boats.

Please click on the photo to see it enlarged!

tpaliwoda · Post by **tpaliwoda** » Sat 08 May 10, 1:33

Larry,
Yep that is the area i am talking about.
I fixed mine by using a real thick mixture of West System and some filler.
Not pretty, but did the job!
I see on the 35 they changed that design completely. They are now using a bolted flange fitting attached to the hull.
Real smart system.

Ted

parkhouse · Post by **parkhouse** » Sat 08 May 10, 9:24

The stern tube for the rudder hold-down assembly is dry. I pumped about 2 litres of water from the stern section of each ama - the bilges underneath are both dry. I'm not sure if the bilge runs the full length of the ama so when I open the boat next week I'll check under the forward sections. According to the manual, the weight of boat including sails, batteries and engine should be 2.7 tons. The gauge on the crane (possibly inaccurate - it didn't quite work by steam but you know what I mean) said 3.2 tons without the mast. I listed everything fitted to the boat not included in the empty weight and came up with a total of about 250 kg. If the forward sections of the ama prove to be dry....
Mike Paterson, Df1000 Champus

Oscar · Post by **Oscar** » Sat 08 May 10, 17:32

Hmmmm the evidence is mounting for water in the aft end of the amas. FWIW in the rehab of my amas I have installed foam bulkheads to divide them into 4 sections and have access to the deepest point of every section.

Double Horizon · Post by **Double Horizon** » Sat 08 May 10, 17:54

parkhouse wrote:The stern tube for the rudder hold-down assembly is dry. I pumped about 2 litres of water from the stern section of each ama - the bilges underneath are both dry. I'm not sure if the bilge runs the full length of the ama so when I open the boat next week I'll check under the forward sections. According to the manual, the weight of boat including sails, batteries and engine should be 2.7 tons. The gauge on the crane (possibly inaccurate - it didn't quite work by steam but you know what I mean) said 3.2 tons without the mast. I listed everything fitted to the boat not included in the empty weight and came up with a total of about 250 kg. If the forward sections of the ama prove to be dry....
Mike Paterson, Df1000 Champus

If your boat is still on dry storage you should see if you can get hold of a moisture meter to check the hull cores. Just another point of information; although I'd be very skeptical that there could be enough water weight (to cause this) in the small voids between foam core blocks, even if the decks AND hulls showed high readings.

Oscar · Post by **Oscar** » Sun 09 May 10, 2:23

I'd be very skeptical that there could be enough water weight (to cause this) in the small voids between foam core blocks

Chainsaw math........

To get the stern to squat that much would take.....say 4 people in the cockpit?

4x180 pounds....= 720 pounds= (62 pounds per cubic foot) 11 cubic feet....
x 48 (assuming 1/4" core) = 528 square feet....... (PURE water mind you)

Say an average height keel to gunnel + some deck = 8 feet x (port and starboard) 16 feet..... we're talking 33 feet of boat.....

Probably not.....

Steve B. · Post by **Steve B.** » Sun 09 May 10, 16:09

Imho, the boat is low everywhere, especially in the stern.

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Centre Hull Floating Stern-Down

Centre Hull Floating Stern-Down

Stern low?