J/46 construction

34 views
Skip to first unread message

Chris Campbell

unread,
Oct 24, 2025, 8:17:58 AMOct 24
to J/4X Owner's Group
Hi J/46 owners,

Do any of you know if the hull coring of the 46 is like the 44 in that it ends about 6-8" from the centreline on each side, and is thus solid down the middle of the boat? I'm assuming that it would, but want to check with the experts since I can't check for myself.

Thanks,

Chris

York.richardw

unread,
Oct 24, 2025, 9:14:51 AMOct 24
to j4x-owne...@googlegroups.com, j4x-owne...@googlegroups.com
The hull of the J/46 is all SCRIMP, and thus unlike the 44s.  
The hull is, to the best of my knowledge, cored all over (except where fastened to keels, etc.).  

I have had two events by which I know this.   You will be happy to know that, in a SCRIMP hull, a small hole drilled through the outer skin does not allow water migration.  In my case, an expert fiberglass man drilled out a 2 to 3 inch circle of core where the hole was, put it in a vise, and was unable to squeeze any water out!

One of the big reasons J/Boats built the 46 instead of just re-activating the 44 series is that TPI had converted over to SCRIMP, so new 44s would be lighter than old ones.  I was told the 46 hull comes out of the mold at 3000 lbs., vs 4000 lbs. for the 44 hulls.  
…. Dick York J/46 #9 ARAGORN

On Oct 24, 2025, at 08:18, Chris Campbell <camp...@ramoak.com> wrote:

Hi J/46 owners,

Do any of you know if the hull coring of the 46 is like the 44 in that it ends about 6-8" from the centreline on each side, and is thus solid down the middle of the boat? I'm assuming that it would, but want to check with the experts since I can't check for myself.

Thanks,

Chris

--
You received this message because you are subscribed to the Google Groups "J/4X Owner's Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email to j4x-owners-gro...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/j4x-owners-group/35191e4b-199f-4327-a0e4-5260e00abe86n%40googlegroups.com.

D. Scott Miller

unread,
Oct 24, 2025, 9:39:03 AMOct 24
to j4x-owne...@googlegroups.com

I have a different experience with hull #17.

The centerline of the hull is solid fiberglass from (I believe) roughly the area of the companionway steps up into the V-berth. You can tell where it becomes cored because there is a distinctive rounded “step” visible, I’m going to guess 8” from the edge of the bilge/keel sump (so, maybe 10-12” from centerline.

 

I’ve done an ultrasound analysis performed on the hull to identify any voids in the vicinity of the keel sump (and fore and aft of it); that shows the solid depth of the fiberglass…so it’s obvious where the cored portion begins—the “depths-to-non-solid-matter” become much shallower.

 

I can curate and send some photos over the weekend—I have plenty.

Chris Campbell

unread,
Oct 24, 2025, 10:20:22 AMOct 24
to J/4X Owner's Group
Agreed that SCRIMP is a substantially different way of laying up - but glad to hear that there is an uncored section down the centreline. On the J/44 this uncored section runs right from bow to transom - so the rudder post goes through solid glass, and the forestay attaches to solid glass and you hit submerged objects with solid glass. The rest of the hull is cored, and the core ramp you reference, Scott, is easily visible.

Thanks,

Chris

Dick York

unread,
Oct 24, 2025, 12:15:08 PMOct 24
to j4x-owne...@googlegroups.com
Scott-
I do not disagree.  I thought I said they had solid glass where high loads are.  If not, please excuse my omission.  Certainly the "deadwood" part of the hull you mention would be high load. 
The other item I may not have mentioned is the stringers, grids, and other support in the J/46 hull.  Apparently that design was re-done from the 44, and may be significantly different.  
Thank You ...Dick 

David Jade

unread,
Oct 24, 2025, 1:05:57 PMOct 24
to j4x-owne...@googlegroups.com

FYI, I was told that the J/46 stringers/grid was laid up as a separate piece and then filled with expanding foam (just to hold its shape – i.e. not structural). Then it gets inverted onto the hull and infused all in one shot along with the hull. So the stringers/grid are essentially hollow except for that lightweight expanding foam.

 

Also, most of the limber holes in the stringers are were the infusion lines ran. Unfortunately, those limber holes were made of PVC, which breaks down and then you can get leaking into those hollow areas. If you ever see brown stains anywhere around the bilge, it’s likely that foam that got wet and is breaking down and oozing out.

 

I was also told that the aft part of the keel stub around the keel bolt tubes is filled (likely with glass filler – packed with cloth scraps maybe) and essentially solid after infusion.

 

David             _/)

~~~~~~~~~~~~~~~~~~~~~

Dick York

unread,
Oct 24, 2025, 1:48:47 PMOct 24
to j4x-owne...@googlegroups.com
David-

I never saw the detailed layup schedule.  (I may not have understood it if I had.)
If you need it, I am sure J/Boats can provide it to you.

........Dick

David Jade

unread,
Oct 24, 2025, 1:54:34 PMOct 24
to j4x-owne...@googlegroups.com

Dick,

 

I did speak with J/Boats at the time of our keel bolt resealing last spring and this comes from Al’s memory (they have no written records anymore for the J/46 build, btw) and from Stephen Burke, who was the Naval Architect who oversaw the build of the J/46’s at TPI.

Reply all
Reply to author
Forward
0 new messages