Installing helm seat californian 34

[surfer919]

New to this site. Just bought a 1978 34" Californian LRC. Am new to twin diesels and come from a sailing background. When I bought the boat the helm seat had been removed and never replaced. Have purchased new helm seat. How do I attach pedestal to deck?? Don't know if I should lag bolt it or some other attachment method. Believe it is plywood and foam. Have 18" pedestal. Bought toggle bolts but am unsure if they are strong enough. Any ideas would be greatly appreciated !!

 

[Delta Riverat]

Are your floor panels removable, ie screwed down?

 

[Comodave]

New to this site. Just bought a 1978 34" Californian LRC. Am new to twin diesels and come from a sailing background. When I bought the boat the helm seat had been removed and never replaced. Have purchased new helm seat. How do I attach pedestal to deck?? Don't know if I should lag bolt it or some other attachment method. Believe it is plywood and foam. Have 18" pedestal. Bought toggle bolts but am unsure if they are strong enough. Any ideas would be greatly appreciated !!

Welcome aboard. Is the helm at the flybridge or in the salon? I much prefer through bolting a seat base. In a heavy sea the stresses on the seat can become very high and the leverage on the seat base can rip it loose if it is just lagged to the deck. But first, where will the seat be located and what type of deck is it, fiberglass or wood?

 

[surfer919]

My flybridge has no way to access beneath the floor. Fiberglass over plywood and a foam core. Appears to be 3" thick but that is mostly foam I think.

 

[surfer919]

I am new so I apologize for the double reply. The seat is on flybridge and you are right the lateral force on seat attachment bolts must be very strong. Noticed the previous seat was not through bolted. Is it possible there is a thicker piece of plywood under seat? How did they attach the original seat??

Thanks!

 

[Old Sea Dog]

What is your overhead like in the main salon. Are there panels that you can remove to access the the floor if the flybridge? Hopefully so. Then you can thru bolt the seat base. Just be sure to use a strong backing plate with substantial hardware.

 

[Comodave]

I added a second helm seat on our last boat. I don’t want to remove the headliner in the salon but I absolutely wanted to through bolt the base. I used a Todd aluminum base plate. The old ones had a large hole in the middle. Now the plate is solid. This is what Todd calls it now.

Quick Release Base Plate

This one could be used if you drill a large hole in the middle. Then select the mounting location. Use a hole saw to cut through the top fiberglass of the deck only. Then I took some 3/8” aluminum plate and cut it into some small pieces that I could slip in thru the hole in the deck. I drilled and tapped the aluminum pieces so I could bolt the Quick Release Base Plate to the deck. Then you just screw the pedestal base into the quick release base plate. Of course caulk the base plate to the deck.

 

[Pete Meisinger]

Bite the bullet and get at the underside of the flybridge floor. That seat MUST be through bolted with a solid backing plate in place.

pete

 

[surfer919]

Sounds like a good idea. If I understand correctly you use a hole saw and put tapped aluminum plates under deck. Do you tape the aluminum strips to hold in place while bolting the plate down from the top of deck??

 

[bkcorwin]

Sounds like a good idea. If I understand correctly you use a hole saw and put tapped aluminum plates under deck. Do you tape the aluminum strips to hold in place while bolting the plate down from the top of deck??

Would not use tapped aluminum plates. Clearance holes through backing plate with washers and nuts.

 

[mvweebles]

I think the question is, since the plate is placed "blind" with no access from beneath, how to hold the plate in place while the bolts are threaded into place. Sounds a bit like a moonshot to me now that OP mentions it.

Maybe glue the plate in place with a strong adhesive such as 4000 or similar., held in place with clamps while it sets. Would have to give it a day or two to set. Then be careful setting the pedestal and bolts.

Peter

 

[bkcorwin]

OOPS misunderstood.

Is the layup fiberglass -> foam core -> plywood?

OR is it fiberglass -> plywood -> foam.

 

[CharlieO.]

Guys, if you have the hole in the middle of the base you can reach inside the hole to hold the nuts while tightening the bolt/screw from the outside. Dave suggested drilling the hole in the middle of the base as well as the floor. At least that is how I am understanding it. I am paying attention because we also would like to add pedestals.

 

[Comodave]

Sounds like a good idea. If I understand correctly you use a hole saw and put tapped aluminum plates under deck. Do you tape the aluminum strips to hold in place while bolting the plate down from the top of deck??

I just held the plates in place while I screwed them in place. It worked well and I never had any problems with the installation having the seat break loose and I am a pretty big guy.

 

[mvweebles]

I just held the plates in place while I screwed them in place. It worked well and I never had any problems with the installation having the seat break loose and I am a pretty big guy.

Here's the pedestal base I'm thinking of. Is the receiver cup where the post fits closed on the bottom or open (I'm thinking closed but not sure)? The hole, if open, is fairly small and the screw-pattern fairly far from the center. Seems like it would be a bit of a challenge to hold back-plate in place while setting screws. Maybe there's a different pedestal base?

Peter

 

[Comodave]

Guys, if you have the hole in the middle of the base you can reach inside the hole to hold the nuts while tightening the bolt/screw from the outside. Dave suggested drilling the hole in the middle of the base as well as the floor. At least that is how I am understanding it. I am paying attention because we also would like to add pedestals.

Exactly. But I didn’t use nuts. I used tapped aluminum plates since I couldn’t reach in and get a fender washer and nut in place. I made the aluminum plates long enough so I could hold them in place while I screwed the bolts into them. They were long and narrow plates. The old deck plates had a large hole in the middle but I can’t find them online anymore so I would go with the one in my first post and drill the hold in the middle with a hole saw. Then position it in place on the deck and use the hole saw to cut the hole in the deck.

 

[SteveK]

Dave, What did you do with the hand sized hole in the center?
I saw the idea as workable to pre install bolts from bottom, a nut on topside to create studs onto which a chair base would attach. Once studs are in place, I would fill the hole watertight.

 

[Comodave]

Here's the pedestal base I'm thinking of. Is the receiver cup where the post fits closed on the bottom or open (I'm thinking closed but not sure)? The hole, if open, is fairly small and the screw-pattern fairly far from the center. Seems like it would be a bit of a challenge to hold back-plate in place while setting screws. Maybe there's a different pedestal base?

Peter
View attachment 136189

With that one the hole will be really small in the middle and it may be tough to reach the plates into place. The one in my first post goes onto the deck before you put a pedestal onto the plate. You secure the plate to the deck first and then bolt the pedestal like in your photo to the plate.

 

[Comodave]

Dave, What did you do with the hand sized hole in the center?
I saw the idea as workable to pre install bolts from bottom, a nut on topside to create studs onto which a chair base would attach. Once studs are in place, I would fill the hole watertight.

No studs. The plate in my first post gets through bolted to the deck using the tapped aluminum plates then the seat pedestal gets bolted to the plate.

 

[bkcorwin]

No studs. The plate in my first post gets through bolted to the deck using the tapped aluminum plates then the seat pedestal gets bolted to the plate.

Do you get any wobble at all in the sockets? I was thinking of using those for something but I feel like the old ones I used to use always kinda wobbled? If the new ones are better thats exciting.

 

[SteveK]

What about the access hole getting waterproof

 

[Comodave]

Do you get any wobble at all in the sockets? I was thinking of using those for something but I feel like the old ones I used to use always kinda wobbled? If the new ones are better thats exciting.

I am 260 pounds and never had any wobble at all. The fiberglass deck was about 1/4” thick on that boat.

 

[Comodave]

What about the access hole getting waterproof

I put caulk under the deck plate between it and the fiberglass deck. And then caulk between the plate and the pedestal base.

 

[surfer919]

Thank you for all the input. Ordered some base plates and will see if it is feasible to thru bolt pedestal into top of salon. Saw a You Tube video of this. It will be visible but secure. It looked OK, would prefer something that was not visible but this seems like the way to have the strongest attachment to flybridge without possibility of seat ripping out. Will use acorn nuts to attach to
thru bolts in salon or run bolts through plate into pedestal for clean appearance.
Will cut headliner and make a small x to put bolts thru. Does anyone see a problem with this approach?

 

[garbler]

Do you know for certain how the bridge deck is constructed ? If solid laminate how thick and if cored you’ll have to re-engineer the project. I would advise drilling a test hole to find out and confirm before going any further.

If cored you may find a number of revelations (1) the deck will not support the pedestal without a backing plate at min 50% larger than base, (2) core/foam removal in way of base and plate build solid (3) or utilize glass or metal pillars on each foundation bolt between base and backing plate to prevent collapse (4) think about a nice high bench type seat with storage.

Rick

 

[Comodave]

Thank you for all the input. Ordered some base plates and will see if it is feasible to thru bolt pedestal into top of salon. Saw a You Tube video of this. It will be visible but secure. It looked OK, would prefer something that was not visible but this seems like the way to have the strongest attachment to flybridge without possibility of seat ripping out. Will use acorn nuts to attach to
thru bolts in salon or run bolts through plate into pedestal for clean appearance.
Will cut headliner and make a small x to put bolts thru. Does anyone see a problem with this approach?

There may be a gap between the top of the headliner and the bottom of the deck. If you through bolt through the headliner it may crush when you tighten the bolts. On our last boat that I referred to there was about a 1/2” gap. If I had installed a backing plate on the inside of the headliner it would have crushed down the headliner and who knows what it will look like when crushed. The headliner may distort around the backing plate and look bad.

 

[surfer919]

Thanks for all the suggestions, appreciate it. Will start with drilling a test hole to see the composition of the deck. Still wonder how original helm seat was attached by the factory. My helm seat was removed by previous owner when deck was painted. The original holes were covered up. Anyone know??

 

[North]

Contrasting thought... I just replaced the helm seat post that came with my Californian 34. It was not through bolted. I can't recall if it was 6, 7 or 8 screws but it was just 'glued and screwed' to the deck. That approach held it solidly for more than 43 years. In fact, it was difficult to get off. I used the same screws and generous Sikaflex 291 to attach the nice new pedestal. You've got glass, plywood, glass for the deck by the way. Good luck!

 

[surfer919]

Thanks North. Will drill test hole and check it out. Would be nice to just glue down and screw. What size lag bolts did you use??

 

[North]

Flat head screws. 1 1/2” long. I used the old screws because I couldn’t get fat enough short stainless screws that day. The flat heads should sit flush in the tapered holes of the seat post base. I suspect these would be #14 or #12 screws. Their business ends are about 1/4 wide.

8 of those (even 6), along with the bedding compound, have a lot of holding power. Moreover, I don’t think you’d have an immediate catastrophic collapse if they let go. You’d notice some movement and some increased gap between the base and be able to use more extreme methods at that time — if you needed it.

There were 8 of them in the old base. I only have 6 with the new base (which is also a smaller diameter) so we’ll see how well I hold up. I suspect I’ll be fine.