1978 Chrysler Sport Fury - AQ140/280 - Bilge/Foam question

[ChristopherRobin]

Hi All,

I'm rebuilding the above mentioned runabout, duplicating the original transom/stringer/sole construction. It's a 16' tri-hull with a pair of 3/4" plywood stringers 18" apart. Flotation foam filled the 2 outer cavities from stem to stern, but only filled the forward 1/3rd of the cavity between the stringers. The cavity is 5-1/2" deep at the keel.

Originally, the bulkhead that defined the forward wall of the engine compartment bilge was not tabbed to the hull, leaving the area between the stringers open to water infiltration from the bilge. There were no other passages for water to enter or exit the cavities under the sole.

My intention is to tab the new bilge bulkhead to the hull, sealing the entire area under the sole. I would then fill all 3 cavities completely with 4lb closed cell foam. The top of the sole would be finished with 2 layers of 1.5oz csm and 1 layer of 6oz cloth, tabbing the sole to the hull. Carpet will cover the glass.

My question is: Is there any reason to not fill the cavity between the stringers with foam?

Thanks in advance,
Chris

 

[Bondo]

Re: 1978 Chrysler Sport Fury - AQ140/280 - Bilge/Foam question

Hi All,

I'm rebuilding the above mentioned runabout, duplicating the original transom/stringer/sole construction. It's a 16' tri-hull with a pair of 3/4" plywood stringers 18" apart. Flotation foam filled the 2 outer cavities from stem to stern, but only filled the forward 1/3rd of the cavity between the stringers. The cavity is 5-1/2" deep at the keel.

Originally, the bulkhead that defined the forward wall of the engine compartment bilge was not tabbed to the hull, leaving the area between the stringers open to water infiltration from the bilge. There were no other passages for water to enter or exit the cavities under the sole.

My intention is to tab the new bilge bulkhead to the hull, sealing the entire area under the sole. I would then fill all 3 cavities completely with 4lb closed cell foam. The top of the sole would be finished with 2 layers of 1.5oz csm and 1 layer of 6oz cloth, tabbing the sole to the hull. Carpet will cover the glass.

My question is: Is there any reason to not fill the cavity between the stringers with foam?

Thanks in advance,
Chris

Ayuh,.... Rather than Sealin' anything, ya oughta be designin' Drainage into it...

There's no such thing as a WaterProof compartment under the sole,...
Without Drainage, it'll rot out quicker...

 

[Woodonglass]

Re: 1978 Chrysler Sport Fury - AQ140/280 - Bilge/Foam question

I Agree ^^^. Drainage for your flotation foam and the center bilge area is very important.

 

[ChristopherRobin]

Re: 1978 Chrysler Sport Fury - AQ140/280 - Bilge/Foam question

Bond-O and Wood: Thanks for your input. I've done a lot of reading here, all the information has been very helpful in helping me plan my strategy for this rebuild. I agree that it's important to give water a way out. I'm concerned that will also give water a way in. Please indulge my thought process, I tend to beat the horse until well after it's dead...I think the Admiral accuses me of being obtuse...

I plan to completely encase all the new wood in 'glass (1.5 oz CSM in addition to 1708 tabbing, poly resin): Top of the stringers, bottom of the sole, etc. I know I can't completely keep water out, it will find its way through screw penetrations no matter how well they are sealed and condensation is always an issue. I'm trying to determine which is the lesser of 2 evils: water coming in in small amounts through screw/bolt penetrations or water coming in in larger amounts through the weep holes.

Here's what I'm stuck on. The hull is very flat between the stringers. If I put in drainage from the outer cavities to the bilge I'm concerned that water has the potential to flow into these cavities from the bilge. In order to effectively drain the outside cavities the weep holes would be below the waterline that a bilge pump is capable of maintaining. This boat will be in a slip all summer and I'm confident there will always be some water in the bilge. Given this ***umption, my thought is to treat the cavities under the sole as the Boston Whaler folks do: seal them with glass and fill them with foam. There would still be a bilge in the lowest part of the hull, it just wouldn't extend forward of the engine compartment.

I suppose I could put weep holes in the proper places and put plugs in them while the boat is in the water. Then water would not back up into the foam from the bilge, but I could still open the holes to drain water when I pull the boat after the season and can get the bow high enough to drain the bilge. I would seal the bulkhead to the hull and put in 4 weep holes as close to the hull as possible: One through the bulkhead on each side of the keel to drain the center cavity and one in each stringer where they meet the transom.

Here's a pic, you can see the gap between the bulkhead and the keel (which happens to be off-center: I'm thinking the boat was made after lunch on a Friday...



Thoughts?