Longitudinal engine bed stringers

[Kastally80]

Does the middle one correct or not ?
thank you

[Willallison]

If these are your engine bed stringers, then where do the engines go?
I'm assuming that you have a twin engine boat - the centreline stringer clearly can't go under the engine....
If it's a twin engine boat, you haven't left sufficient space betwen the engines to allow access for anything, and most engines are wider than their mounts.

[Kastally80]

Thank you Willallison for your help
It's effectively a twin engine boat .The engine mount will not be bolted directly to the beds but to a flange projecting out from the side. That's because i want to install different kind of propulsions :Z-drive, V-drive, AS-drive, Zeus or IPS with a large choice of engines : Volvo, Mercruiser, Fiat (370hp) ...The recommanded shaft spacing is 950 mm who gives a mount spacing of approximatively 378 mm, it will be difficult to place two longitudinal bed stringer of 120 mm wide and 370 mm high each one (difficult to laminate between the beds). that's why i choose to place à center line bed stringer, of 120 mm wide, who will be divided without interruption after the engine room in two longitudinal stringers with the same wide 120mm as you can see in the picture. Do you think that's possible ?

[Willallison]

Without doing any numbers it's difficult to say, but I've certainly never seen the sort of set-up that you've shown, and there are some very closely spaced engines out there....
If you're talking about only 378mm between the two mounts then that's simply not enough room for a person to get between them for servicing.
The mounts will have to be very heavily built in order to cope with that spacing. Also you probably can't use the same sized stringers if they're having to cope with twice the engine size.
But back to your question, engine beds are often irregular in their shape. Personally, I'd suggest at least running through the fwd bulkhead before you split them and maintain your minimum required height and width at least that far forward. As always, it's impossible to be certain without doing the necessary calculations

[lazeyjack]

Bonjout, ca va?
for inboards you need 600mm, between c/l girdars, they are not known as stringers
your boat is a wee bit small and that is not a good way to terminate a bed(girdar)
may I suggest you go into a manufacturers website and download pdf,s of the engine, thsi will let you arrive at your bed height, your crank c/l and in case of sterndrive your cutout in relationship to the bottom,
if you email your dwg in rhino or something I will draw in the beds as they should be
bon chance

[Kastally80]

Ca va trés bien merci Lazeyjack.

The problem will be resolved if i place the engines at 1200 mm shaft to shaft then i put two beds with enough spacing to make lamination easier between them. But a friend told me that the boat will handles badly with 1200 mm and that i shouldn't have more than 950 mm spacing. What do you think about that ?

Thank you all for your help

[lazeyjack]

now you have it right, but let the girdars run right throught he boat
the spacing you show is common on outboards, but what will you achieve with twins over single?

[Kastally80]

The first reason is to strengthen the hull because the boat will be used for patrol, fishing...
the center line overlap is considered as a stringer itself. By putting two stringers i will reduce the dimensions of pannels so i reduce the constraint on it and the laminate thickness will be reduced too.
The last reason is to save place.

The picture shows another structure with girders that deviate slightly outward after the second bhd. What's your opinion?

Merci

[fcfc]

You can clearly see there www.barracudatec.com.br/pdf/RE_Paper.pdf no straight stringer system on picture 7 and 16. Stringers lateral position is narrowed to match engine location.

Et le pire, c'est d'écrire en anglais.

(The worst is to write in english)

[Kastally80]

You are rigth fcfc
Merci pour ton aide, je vais voir ça tt de suite.

[lazeyjack]

pire(ecrire)??