Hi all,
I would like to install 6in inspection ports (deck plates) 9" or so in front of the forward cross bar on each hull (evenly inside the textured deck insert) on my Prindle 19. I would like to have access there for many reasons (repairs from inside, electrical wiring for permanent nav lights,...)
The holes would be cut inside the bonded deck insert that has the non-skid texture. At that point, the deck is 14.50" wide and the hole for the ports (Beckson) would be 6.625" in diameter.
Here are my questions:
Is this a high stressed area to be avoided? The tension on the forestay and shrouds, and compression under the mast is all in this area. On the other hand, The hulls are largest and tallest in this area and the hole is in the middle of the deck (stress is generally runs along the edges, the guwhales)
I can reinforce with alternating layers of mat and woven roving around this hole from the inside if ever that is required (probably not).
I am sure others have done this, because dry storage is hard to come by on a cat. I prefer asking because I would hate to have the front end of a hull break off because I did not do my homework prior to hack/moding my cat. I do like going out in the very rough weather, enough to bend the cross bar bolts which I am changing as well.

Many thanks in advance.

Paul, aka LePirateVert
(The Green Pirate, not to be taken mildly nor seriously, arrrrghhh)



Edited by lepiratevert on Jun 03, 2014 - 01:45 PM.

Paul, I would think twice about putting ports in the hulls forward of the front cross bar. I had to pull the starboard hull forward top deck off of my P-19 after the bridle wire tang broke off flush with the hull. I was shocked at how flimsy the entire hull was after the top deck was removed. It's amazing at how much structural integrity the top deck generates once it's attached.

I remember reading somewhere in a forum that you should not put inspection ports forward of the front cross bar. There must be a reason as I suspect if it were okay to place them there, the original manufacturer would have placed them there for additional storage/repairs. I know people do it but I suspect if you were to have a failure, that is where it would be. There is a tremendous amount of stress in that area. That is why there's a dolphin striker in that area. I suppose if you only sail in smooth waters it might be okay, but once in heavy chop, there will be significant stress on those hulls.

I'm no marine architect by any means so these are just my thoughts.

I had a P19 that broke in half just forward of the front beam, it did have inspection ports installed. I would not do it if I was you.

--
Greenville SC

Offering sails and other go fast parts for A-class catamarans
--

That is a very high stress area on a cat, and the top cover is structural. Any other location on the boat would be better than that . There are structural bulkheads and stringers right there to maintain the shape of the hull and thus the strength of the hull. That is a weak point on many cats even if no compromising mods are made.

Why not put them in the factory spot just behind the forward cross beam?
I suppose you would need to get your tramp modified to suit...
I am thinking of doing the same thing on my P16, thanks for the question.

--
1975 P16 "Spring Rain"Sail # 642
Home Built 2004 Optimist-Delta "Unity"
So old it has Dino hide for a sail Chrysler "Pirateer"
Steve
Oyama BC
Lat 50.1167 N
Long 119.3667 W
1700 ft
--

deleted



Edited by beachsailor on Jun 04, 2014 - 07:03 AM.

I have also installed 6" ports there and didn't have any structural problems. You have the front beam bulkhead and then another bulkhead forward of beam. Just don't stand directly on port after installation.

--
Doug Klem
Pensacola , Fl.
Blade F16
Prindle 18-2 w/spin
Prindle 18-2 x 3
Prindle 19 MX
--

Wow! Such an active forum. Thanks all for your generous feedback.

"I have also installed 6" ports there and didn't have any structural problems" Reassuring, but...
...then again...there are situations that may overload, we may lose FOS (factors of security)

"Why not put them in the factory spot just behind the forward cross beam?" On the P19, the centreboard is directly behind the forward beam.

KILLER FEEDBACK:
"That is a very high stress area on a cat, and the top cover is structural." Agreed! High compression and lateral load in waves
"I had a P19 that broke in half just forward of the front beam, it did have inspection ports installed. I would not do it if I was you." Yikes! That did it.

I was looking at the curved deck (over 3/8" on both sides of the port) and considering the delicate gelcoat repair work to build up and finish off nice with the deck texture... Reinforcing around the hole from the inside, the added weight...too much trouble and now, risk.

THIS PART OF THE PROJECT IS CANNED! Thanks folks! Great sailing to you all.

Kind regards,
Paul, aka The Green Pirate.

my cat came with 4, 6" port installed - I removed one an cut away even more to add a 8x12" hatch in my port hull just forward of the beam.

If properly installed a closed hatch should be about as strong as the sounding area

and heck, maybe a drop of preventative measure (like adding a strip or 2 of cloth/epoxy around any bulkheads or deck that looks/feels worn).

I wouldn't do it unless you need access, but if you need to i wouldn't worry about it if (if done correctly)