Reducing an Air Draft

[Mr Proach]

I'm looking at the possibility of using the French waterways to reach the Med later this year. sadly the Sealine 450 has an air draft of 4.5m so I'm currently looking to see if the radar and the ancillaries are readily removed and then replaced. I would place the radar reflectors as low as possible to try and reach the 3.5m limit that is in place on most waterways but my questions to the more experienced are;

is there any reason why radar would be required transiting waterways, and;

has anyone successfully reduced the air draft in order to complete the transit to the Med?

many thanks for any advice and/or opinions

 

[Whitelighter]

Later boats had a hinged mast.

You could get your mast cut and then hinged. Longer cables will allow you to keep the antennas in place.

You'll have to measure to see if this reduces it enough

 

[Jegs]

I'd want 3.4 metres air draft.

John G

 

[Mr Proach]

Thanks for the replies, I've got a nasty feeling the flybridge is at around 3.9m by itself. So now looking for alternatives, I cant see a route through France that will accept that much of an air draft so I think its either find a boat already in the Med or consider the long way around (not appealing)

 

[jimmy_the_builder]

Thanks for the replies, I've got a nasty feeling the flybridge is at around 3.9m by itself. So now looking for alternatives, I cant see a route through France that will accept that much of an air draft so I think its either find a boat already in the Med or consider the long way around (not appealing)

Stick it on a truck. (There isn't a waterways route through France at that height).

 

[Avalon]

You'd be fine getting to Paris, and on the Rhone south of Lyon. So maybe get it trucked Paris-Lyon. But you might have to drop the radar arch for that anyway.

 

[Bertramdriver]

My sympathy. Our plans took a radical overhaul when no road shipper would take us with a keel to helm airdraft of 4.85m. We're now taking a long slow cruise from Greece to SOF. Want to swap?

 

[Jegs]

You'd be fine getting to Paris, and on the Rhone south of Lyon. So maybe get it trucked Paris-Lyon. But you might have to drop the radar arch for
that anyway.

St Jean de Losne [near Dijon] into the river might be cheaper than Lyon.

John G

 

[Mr Proach]

No thanks. I had considered trucking it and that option is looking more and more attractive. I don't really want to rely on a survey on a boat I will barely know in a foreign port. Shame because the plan to use the French waterways was really appealing.

 

[Mr Proach]

Jegs, so am I right in thinking the whole of the Rhone is a 6m minimum air draft?

RHONE and ENTRE DES MERS
> Rhone 3.00m 6.00m 11.00m
> Petit Rhone, Rhone a Sete 2.20m 5.00m 8.00m

 

[Bertramdriver]

The option we've taken is to motor up to port St Louis and then spend a month or two removing our hard top, helm station windscreens and radar/ coms mast. We'll then replace the windscreens with fold downs and the canopy with a " broom style" drop down canvass canopy. I'll remount the mast on the saloon foward. I reckon I can get down to 3.4m with a 1m draft. More problematic is running the 2x 435 hp DD's for hour after hour on tick over@5 knots. Alf ( Divemaster) reckons it's doable so we'll try it.

 

[Mr Proach]

good point on the engines, what about single engine running and trim the drift out?

 

[Bertramdriver]

good point on the engines, what about single engine running and trim the drift out?

Alf advised against it. Not enough flow over one rudder at low speed to give reliable steerage. So two motors needed. I did think of putting an extender on the rudder but that stacks up the pressure on the hydraulics
Btw we've already written off the smaller canals but will travel wider on the bigger canals and rivers including Germany etc.

 

[Mr Proach]

thanks for the tip. I think I have the foundation of a plan, truck the boat to St Jean de Losne (need to check of the nav requirements south to Lyon) and stick with the river to Port Louis.

 

[Jegs]

Jegs, so am I right in thinking the whole of the Rhone is a 6m minimum air draft?

RHONE and ENTRE DES MERS
> Rhone 3.00m 6.00m 11.00m
> Petit Rhone, Rhone a Sete 2.20m 5.00m 8.00m

The books say the Rhone is 6 metres & observation would indicate that they are correct. Rhone a Sete 5 metre clearance seems right - 100 metre craft on that as well as Rhone. The Saone from St Symph. [near St J de Losne] is given as 4.8 metres & is definitely over 4. The Saone from St Symph was upgraded to take similar vessels as the Rhone & has larger locks & greater clearances than the upper section.

If you decide to put the boat in St J de Losne Blanquarts has a crane but it is on the canal de Bourgogne above last lock - check bridge height at lock. H2O have, I believe, a tuning fork delivery system onto the basin leading to the river - again check the different bridge height .

Macon on the Saone & Valence on the Rhone would probably be fine, but check weight capacity.

ATB,

John G

 

[blueglass]

Alf advised against it. Not enough flow over one rudder at low speed to give reliable steerage. So two motors needed. I did think of putting an extender on the rudder but that stacks up the pressure on the hydraulics
.

We managed fine on one engine in our Atlantic 38, although did fire up both engines for more control in locks.
Its important to alternate the engine you use singly to avoid any problems with the trailing engine which of course still has the prop turning as you make way.

 

[Mr Proach]

The single engine running has me really interested, I found an old thread on the issue (TAMD 63P River Use ) and it seems as long as the engines are alternated and given a period at higher revolutions periodically there shouldn't be an issue. the parasite drag on the non-powered prop doesn't seem to be a major factor in either wear on a gearbox or fuel consumption.

 

[Cardo]

No one seems to have covered your radar question - No, no need for a radar on the canals. You can only travel during daylight hours, and if it gets foggy, you probably wouldn't want to be travelling anyway. AIS receive is handy if you have it, though, as most big boats on the canals tend to transmit. Useful for seeing if anything big is on the other side of the lock.

We travelled through the canals a couple of summers ago with our radar (and reflector) in our forward cabin.

 

[Mr Proach]

No one seems to have covered your radar question - No, no need for a radar on the canals. You can only travel during daylight hours, and if it gets foggy, you probably wouldn't want to be travelling anyway. AIS receive is handy if you have it, though, as most big boats on the canals tend to transmit. Useful for seeing if anything big is on the other side of the lock.

We travelled through the canals a couple of summers ago with our radar (and reflector) in our forward cabin.

Thanks Cardo, the plan now is to truck the boat to St Jean de Losne, so hopefully no need for removal of anything.

 

[Bertramdriver]

The key issue is the amount of control you can achieve with just one engine/rudder. Most planing mobo's have relatively small rudders which require a goodly water flow around them to be effective. My experiance of trying to run on one engine was not reassuring. At low revs <1000 rpm I had to put the rudders hard over to achieve a straight line which increased drag and required higher revs and so it went on constantly having to balance revs against rudder. Hence the exploration of rudder extenders. This was at sea so I guess it was all extreme but I do know the canalised rivers can have wicked currents in excess of 4/5 knots. Running down stream ( especially the Rhone) on one engine / rudder would be a challenging experience so please report when you've done it. All the advice I've taken is run on both at tick over and then give the lumps a good blast when you get into unrestricted waters to burn off the muck.