Bertram 20 Engine Bay

I have a 66 Bertram 20, runabout. I apologize, but I don’t have drawing software, so I will try and describe what I am trying to do. Stringers run from transom to bow. Plywood stringers bedded and fiberglassed on inboard side only. Floatation foam fills all voids front to back, accept for center engine and fuel tank bay. The distance between stringers is approximately 38”. My question is when the stringers reach the engine bay, could I run them to a bulkhead and then continue them aft but further apart. Essentially, I would be building a wider box in an area where hull is thickest and foam would still be providing stiffness. Now here is the reason. I have been debating whether to replace IO with outboard. I prefer the IO for several reasons, but due to health issues I have a hard time doing service work on the motor given how tightly the Mercruisers are installed in the engine bay. Widening even by a few inches would make an important difference. I appreciate any feedback you can provide. This is my first post, if this should be in a different forum please advise. Thank you.

 

Welcome to the Forum Tom.

In lieu of a drawing, could you perhaps post some photos of your fine Bertram please?
Including (if possible) a photo or two of the Mercruiser in the engine bay?
(I presume that it is a single engine, although you mention 'Mercruisers'?).

Re converting to an O/B engine instead, I have seen a Bertram 25 here with a pod and a single O/B motor - she previously had twin inboard engines with outdrive legs.
Similarly there is another one here that was retrofitted with an inboard shaft drive diesel engine, and this seems to be fairly successful.

 

What's the reason to widen?

 

I have issues with both arms and shoulders. Which is why I would consider an OB, but a debate rages about whether this is a good idea, so I'm looking for more room in engine bay and if I can I will go with an IO as originally designed. I'm going to try and post photos as Bajansailor requested. Thanks

 

PVER

 

I was having trouble posting photos as I kept getting multiple copies. Anyway, I included as a separate reply above . In one, it shows a single mounting bracket for motor, with the starboard one already removed. I hope these help illustrate what I am inquiring about. Thanks.

 

Re your photos above, it looks as if you have taken a Sawzall to both stringers and roughly chopped the tops off?
How high were they originally?
I presume that the cockpit / cabin sole was sitting on them?
And that you will be rebuilding them to the original height?
Would it be feasible to keep the stringers in the same location, but just make the engine box / cover a bit wider (I presume that it would rest on the deck)?

 

I don't see any reason to modify the stringers. If there is access issues; modify the doghouse or access.

 

The sole will rest on new stringers. Remnant of stringers were left as reference points as I move forward.

So the walls of the engine box are formed by the stringers and because of the stringer height there is almost no access as you move aft on the engine to the exhaust, steering and starter motor. The only way to make the engine box wider is to move the stringers away from the center line. The proposal is to stop the stringers short of the transom, short of the motor and tie them into a new bulkhead instead of the transom. From that bulkhead, I would then run replacement stringers higher up on the hull bottom to the transom. This would give additional width/space around the motor.
Regarding hull stiffness, a great deal has been written about the B20 drawing most of its stiffness from the floatation foam used. My intent is to replace all of the foam except in the original area that the motor occupies and additional space picked up by widening the space between the stringers.

Additionally, I planned in filling the strakes for ease of laminating and I could add fiberglass rods to the mix for additional longitudinal support.

In total, I would be happy with an additional 3” to 4” of additional width on each side.
I hope this makes sense and I look forward to hear what you think.
Thanks
Tundratom

 

That sounds reasonable to me.
I presume that between the new bulkhead and the transom, you would grind off the remains of the existing stringers so that they are flush with the hull?

Although I don't really understand what you mean by this -

Which 'strakes' are you referring to here?

 

I plan on adding a layer of glass to the hull bottom, so everything will be ground flush before I add anything back in. Perhaps I’m using the wrong language:




The interior hollows of the strakes filled in to make laminating easier. I’ve read where people have used various rods of fiberglass to add filler and longitudinal strength embedded in the cabosil/chop strand mix.

My take away of your response is that if I execute this plan and you opened up my bilge, you would not slap your hand to your forehead and say, “ What in hell did he do?”. The transom in this boat has already been replaced and probably overbuilt (not crazy though) and I’ve kept everything neat and drawing on established practices. This is the first time I have veered off and thought to do a “small” modification, but I’m smart enough to know that it can lead to disaster if I don’t seek advice from those with the proper knowledge and experience. I will keep posting pics of slow progress from up here in the northeast and please comment at any time. Thanks
Tom

 

Sorry, but I am still baffled.
Re your photo above, it is very tiny - even if I save it to my computer and 'blow it up' I cannot see much on it.
Is it another Bertram, or a random boat you saw, or even your boat in it's current state now?

Re the 'strakes' that you mention, are these the inside 'hollow' areas of the longitudinal chines?
There appear to be two of these outboard of the (remains of) the stringers in your main photo.
Be aware that if you fill these in, this will be some extra weight - and another layer of glass over the whole interior of the hull will be more weight added.

Please do keep posting photos of your progress - everybody on here loves re-build threads.

 

This is from a Bertram 20 Bahia Mar (thank you Alex). Showing the lifting strakes (?) filled in. Essentially the same hull as mine.

 

What’s the purpose of the added layer of laminate? Is the hull weak as it is?
Most Bertrams I’ve seen have robust hulls, and do not require additional layers of laminate. The original laminate encompasses the strakes. If additional strength is needed along the strakes, I’d consider adding mini stringers along their length rather than filling them in.
Large, flat areas of fiberglass are significantly weaker than same area with corrugations.

Re the stringers, they are intended to be continuous throughout the length.
Relocating them at a bulkhead will create a weak point along the bulkhead, however, adding engine room stringers close alongside them might allow them to be cut down somewhat in the engine area to improve access.
Another approach might be to allow generous longitudinal overlap, hopefully to the next bulkhead forward.