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Deep draft motor boat

Posted by Max green 
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Deep draft motor boat
24 September, 2018 20:40
Is Lough Derg suitable for 4ft 9 draft Motor boat?

Edited 1 time(s). Last edit at 24/09/2018 20:43 by Max green.
Re: Deep draft motor boat
25 September, 2018 09:00
Hi Max,

4'9" exceeds the official draft figures for Lough Derg of 1.35m (about 4'5") but you would probably be OK on the main navigation channels.

You would however have difficulty coming alongside in a few places and would be severely restricted in going "off-piste". Harbours like Terryglass can be quite shallow. Even with a 4ft draft we have grounded coming alongside the inner wall in Dromineer.

Bear in mind that despite appearances the level of Lough Derg does vary quite a bit and can go down a lot in a dry summer. (Though perversely, it didn't seem that badly affected this year)

I think you would find going off Lough Derg quite challenging, specially north of Athlone but even some of the river sections between Derg and Athlone can be quite shallow. At this time of year the powers that be deliberately lower the upper Shannon to provide capacity for winter rains. We were alongside the Strand Quay in Athlone last week and the boat sat on the bottom when they opened the sluices in the weir.

A lot would depend on the underwater profile of the vessel. If it's a single screw with the prop and rudder well protected behind the hull structure (like Chang Sha) you might not mind the odd bump and scrape on the bottom (assuming you have a sound hull!). If you have twin screws suspended on shafts and P-brackets under the hull with spade type rudders, then any contact with the ground is likely to be expensive - and we had a report of significant damage in the marked channel between Banagher and Shannonbridge earlier this year to a vessel that draws only 1 metre.

There are lot's of sailboats on Lough Derg that draw 1.5 metres or even more but they are restricted to the deeper areas and of course can't go upstream without lowering their masts - but again, anything they hit is likely to be with the keel which is generally pretty substantial.

Another factor to consider is squat. When you apply power in a boat, the stern digs down as the prop sucks water out from under the boat. The amount of squat varies with the level of power, the hull form and the profile of the channel you are in. It tends to be worse in smaller channels. (It's actually possible to ground a boat completely in a canal by applying too much power). Chang Sha has a fine entry a counter stern and a basic bathtub shape underneath. She squats at least six inches at the cruising speed of 5 knots.

I would say 4'9" in a motor cruiser is too much for Lough Derg and way too much for the rest of the Shannon. But that said, if all you want to do is travel between harbours that you know have plenty of water then you would probably be OK but in my opinion you would be restricting yourself unnecessarily. You would also want to check that whichever marina you planned to keep the boat in had enough draft at the lowest possible summer level - I've heard of some that do not.

Hope this helps,

Best Wishes,

Colin Becker
Re: Deep draft motor boat
25 September, 2018 20:54
Hi colm,cheers for advice,may go for plan b,boat with less draft ????
Re: Deep draft motor boat
27 September, 2018 21:49
[quote Max green]Hi colm,cheers for advice,may go for plan b,boat with less draft ????[/quote]

3ft or 3ft 6in draft and you should be able to cruise anywhere on the Shannon, Erne and SEW navigations.
Re: Deep draft motor boat
30 September, 2018 13:14
I agree whole heatedly with all the previous points made, but Another point might be worth mentioning, is resale possibilities you may be happy to Buy this Boat and love it, but try reselling it when you tell possible purchasers that she is 4 foot 9 inches in draft, Most of the Sailing boats on Ree and Derg dont have this Draft
Re: Deep draft motor boat
02 October, 2018 20:43
Are you sure you have got the draught measurement correct. It is either a very large cruiser or carrying a "lot" of ballust which could possibly be removed. My ex barge weighed in at 63 Ton and drew 3foot 8 inches. Drew
Re: Deep draft motor boat
29 January, 2019 16:25
Hi Colm,could you recommend anyone to change A cutlees bearing on a p.bracket the boat is in banagher.regards max
Re: Deep draft motor boat
30 January, 2019 13:50
Hi Max,

I would have thought that Morgan Smyth and the boys in Silver Line would be able to do that.
Chatterton's in Portaneena would be able to do it as well.

There are a few other people around who could do it but as the boat has to be out of the water to do the work it may make sense to go to a boatyard who can do the whole thing.

GMY Chang Sha
Re: Deep draft motor boat
30 January, 2019 16:18
Hi Max Morgan and the lads in silverline did mine, all well since regards, Ian
Re: Deep draft motor boat
31 January, 2019 21:54
Hi,thanks for the information regarding cutlass bearing,the boat is out of water at the moment! Regards max

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