81 GCAT 5.0 Rebuild :: Catamaran Sailboats at TheBeachcats.com

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81 GCAT 5.0 Rebuild

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rockypointbob

Rank: Lubber

Registered: Jul 13, 2017

Last visit: Sep 28, 2020

Posts: 30
Posted: Sep 06, 2017 - 12:29 AM

Finally got the hulls back from repair and repaint...they look great.

So now I'm into the next phase of this project, which is to reattach the cross beams to the hulls. As I rebuild the boat, I want to replace all the hardware. I have the original assembly manual, which provides me the bolt lengths but it doesn't provide the diameter(s) or strength/type. Anyone know what I need to attach the three cross beams and best source to purchase? I do have all the back-up bars and beam inserts.

One other point...in the assembly manual it talks about "compression tubes"; what are these and should they be replaced and if yes, are they obtainable?

Any other considerations I should be aware of regarding installing the beams?

Thanks!

Edited by rockypointbob on Sep 05, 2017 - 11:23 PM.
jsb4g

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Registered: Oct 11, 2016

Last visit: Jun 19, 2018

Posts: 42
Posted: Sep 06, 2017 - 08:12 AM

Hi Bob, I sent you a reply email regarding your other questions. What page of the manual are you referring to? I will answer the rest of your questions with precise measurements in a week or so, including the stainless crossbeam bolts.
MN3

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Posted: Sep 06, 2017 - 08:21 AM

QuoteOne other point...in the assembly manual it talks about "compression tubes"; what are these and should they be replaced and if yes, are they obtainable?

These are tubes that surround the beam bolts
they fit snug (top to bottom) and prevent you from over torquing down your beam bolts and sqwashing the beam down. they also can help to add rigidity/stiffness to your boat - and the stiffer the better.

Optimally they are made out of alum to avoid any corrosion with the beam
i have seen gcats with pvc... hardly optimal but better than nothing (i guess)
MN3

Rank: Master Chief

Registered: Jun 20, 2006

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Posted: Sep 06, 2017 - 08:21 AM

QuoteFinally got the hulls back from repair and repaint...they look great.

Pics or it never happened! :)
rockypointbob

Rank: Lubber

Registered: Jul 13, 2017

Last visit: Sep 28, 2020

Posts: 30
Posted: Sep 06, 2017 - 09:17 AM

It happened....finally.

https://www.thebeachcats.…ictures?g2_itemId=128943

Edited by rockypointbob on Sep 06, 2017 - 07:18 AM.
rockypointbob

Rank: Lubber

Registered: Jul 13, 2017

Last visit: Sep 28, 2020

Posts: 30
Posted: Sep 06, 2017 - 09:22 AM

jsb4gHi Bob, I sent you a reply email regarding your other questions. What page of the manual are you referring to? I will answer the rest of your questions with precise measurements in a week or so, including the stainless crossbeam bolts.

My copy of the manual doesn't have page numbers......it's the "Assembly Manual and Parts List".

I received your email with the other information, gracias!
rockypointbob

Rank: Lubber

Registered: Jul 13, 2017

Last visit: Sep 28, 2020

Posts: 30
Posted: Sep 06, 2017 - 09:24 AM

MN3
QuoteOne other point...in the assembly manual it talks about "compression tubes"; what are these and should they be replaced and if yes, are they obtainable?

These are tubes that surround the beam bolts
they fit snug (top to bottom) and prevent you from over torquing down your beam bolts and sqwashing the beam down. they also can help to add rigidity/stiffness to your boat - and the stiffer the better.

Optimally they are made out of alum to avoid any corrosion with the beam
i have seen gcats with pvc... hardly optimal but better than nothing (i guess)

Ok, so if I bought some stock to fit the bolt diameter I could cut it down to size as needed?
MN3

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Posted: Sep 06, 2017 - 09:41 AM

QuoteOk, so if I bought some stock to fit the bolt diameter I could cut it down to size as needed?

Yes! that's what i have - some regular stock cut to size
rockypointbob

Rank: Lubber

Registered: Jul 13, 2017

Last visit: Sep 28, 2020

Posts: 30
Posted: Sep 11, 2017 - 09:18 AM

So from everything I could find on the subject, seems the proper bolt diameter/type for the cross beams is 1/4"x20 316 stainless steel. Sound about right?

I'm also needing to replace the screws for the rudder mounts through which the rudder pin passes, top and bottom. They look like a type of self-tapping metal screw. Are these specifically for fiberglass?

Here's a pic

Edited by rockypointbob on Sep 11, 2017 - 07:23 AM.
rockypointbob

Rank: Lubber

Registered: Jul 13, 2017

Last visit: Sep 28, 2020

Posts: 30
Posted: Sep 11, 2017 - 09:29 AM

The other thing I was wondering about regarding the rudder system...

As I was looking at pics on Hans' facebook site, I stumbled across one of a rudder system on what could be a 5.0. I noticed something that was way different than on my system. Here's the pic from Hans site..

Do you notice anything different from the rudder pic from my boat?

Here's a better pic of mine

The rudder mounting flanges (or tabs) through which the rudder pins pass are not mounted WITHIN the rudder mounts but rather OUTSIDE the rudder mounts. The top flange is below the mount and the bottom flange is resting on the top of the lower mount. This doesn't seem right to me. I'm thinking an owner from way back must have taken the rudder system apart to repair hull damage and then screwed up when they reassembled it.

Thoughts?
MN3

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Posted: Sep 11, 2017 - 02:07 PM

I THINK they should be bolted
self tapping screws wouldn't be my choice
without access ports - i wouldn't know exactly how to address this

rockypointbobSo from everything I could find on the subject, seems the proper bolt diameter/type for the cross beams is 1/4"x20 316 stainless steel. Sound about right?

I'm also needing to replace the screws for the rudder mounts through which the rudder pin passes, top and bottom. They look like a type of self-tapping metal screw. Are these specifically for fiberglass?I

Here's a pic

Edited by rockypointbob on Sep 11, 2017 - 07:23 AM.
MN3

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Posted: Sep 11, 2017 - 02:21 PM

The current setup defiantly not optimal and i highly doubt "stock"

my GUESS would be there was damage to the transom and they felt it was easier / better to move the gudgeons vs fixing it correctly/optimally.

IF there are self tapping screws, that adds to my belief of damage... as through bolting and backing plates would be a MUCH stronger solution but without access (i.e. during actual production or ports) it would be a much larger job to gain access.

QuoteThe rudder mounting flanges (or tabs) through which the rudder pins pass are not mounted WITHIN the rudder mounts but rather OUTSIDE the rudder mounts. The top flange is below the mount and the bottom flange is resting on the top of the lower mount. This doesn't seem right to me. I'm thinking an owner from way back must have taken the rudder system apart to repair hull damage and then screwed up when they reassembled it.
jsb4g

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Registered: Oct 11, 2016

Last visit: Jun 19, 2018

Posts: 42
Posted: Sep 12, 2017 - 11:55 AM

Agreed. I have seen this numerous times...transom damage followed by remounting like this because the original spot is destroyed. It is a quick fix in lieu of a proper repair. My boat had a transom job and the way it was done is to cut inspection ports in the rear deck, rebuild transoms, place against the interior of the transom a piece of water treated/sealed 2x4 cut to the shape of the transom and predrilled to match the holes in the transom for the rudder mount (though you could use a stainless plate- custom made- for the same purpose), then secure rudder mounts with bolts, washers, and stop nuts. The wood (or stainless) plate distributes the weight across the entire transom, thereby reducing pressure on the spots where the mounts attach. My wooden plates are starting to get old and weakened by water, so I will soon be replacing them with stainless plates. I have a metal fabricator in town that will make me plates using the wood as a template.

The first of your two photos is the correct way to mount the rudders. I would NOT use self-tapping screws. Stainless bolts/washers/stop nuts.

MN3The current setup defiantly not optimal and i highly doubt "stock"

my GUESS would be there was damage to the transom and they felt it was easier / better to move the gudgeons vs fixing it correctly/optimally.

IF there are self tapping screws, that adds to my belief of damage... as through bolting and backing plates would be a MUCH stronger solution but without access (i.e. during actual production or ports) it would be a much larger job to gain access.

QuoteThe rudder mounting flanges (or tabs) through which the rudder pins pass are not mounted WITHIN the rudder mounts but rather OUTSIDE the rudder mounts. The top flange is below the mount and the bottom flange is resting on the top of the lower mount. This doesn't seem right to me. I'm thinking an owner from way back must have taken the rudder system apart to repair hull damage and then screwed up when they reassembled it.

Edited by jsb4g on Sep 12, 2017 - 11:59 AM.
rockypointbob

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Registered: Jul 13, 2017

Last visit: Sep 28, 2020

Posts: 30
Posted: Sep 13, 2017 - 12:07 AM

When I had the hulls refinished, I had the body guy build up the transoms so they should be pretty sturdy now. Looking at the pic (which I got from Hans FB site) I posted of the correct mounting of the gudgeons, it appears they also used SS sheet metal screws for the brackets.

I have inspection ports on both hulls but they are too far forward to reach the transom. I've had the boat out with the rudders mounted incorrectly (I had no idea at the time) and it worked great, but what do I know, it was my first time solo on a boat! So I guess the answer is to have two more ports installed such that we can do backing plates. Bummer.

What about the Dotan kick-up rudder system? Guess I would have the same issue with mounting?
rockypointbob

Rank: Lubber

Registered: Jul 13, 2017

Last visit: Sep 28, 2020

Posts: 30
Posted: Sep 13, 2017 - 12:09 AM

Here's another rebuild question: The finish on the cross beams and mast is pretty beat up. What's the best way to clean them up? Is painting an option....bad idea?
dmgbear55

Rank: Mate

Registered: Jun 22, 2015

Last visit: Jul 06, 2018

Posts: 258
Posted: Sep 13, 2017 - 12:22 AM

I had good success using the Awlgrip system on all of my aluminum on This End Up. Steps were to sand the anodizing, use their wash coat, next up was the 545 epoxy primer, then used the Awlgrip 2000. Paint is never going to be as durable as anodizing, but there are very few places to get a mast anodized.

I am very satisfied with the appearance and the durability of this finish system. It was a lot of work though for a DIY project. If you are using professionals they likely could work through this pretty quickly. Me not so much.

Here is the album on the aluminum work on my project:

https://www.thebeachcats.…ictures?g2_itemId=123176

--
dg
NACRA 5.2 #400
This End Up
Original owner since 1975
--
MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: May 22, 2024

Posts: 7089
Posted: Sep 13, 2017 - 09:02 AM

QuoteWhat about the Dotan kick-up rudder system? Guess I would have the same issue with mounting?

from what i have read, most people who try Dotan's on beach cats are not happy with the results

Quoteit appears they also used SS sheet metal screws for the brackets.

I still highly doubt it - that is not the correct screw for this application and i find it unlikely they are sheet metal screws - more like number ss philips heads with nylocks behind them, probably a ss backing plate of some type

this is a crazy high stress area of the boat, and when rudders hit bottom (happens more than you think) self tapping screws could rip right out of fiberglass
MN3

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Posted: Sep 13, 2017 - 09:34 AM

the more i think of this, the more i think it is ok how it is
i am no engineer but i think the sheer forces would not be changed by this set up, or if they are changed it isn't by much

i am certain self tapping is not the correct solution
adding ports is not optimal nor fun work

i think i would leave it as is

hopefully one of our engineers on here will comment too
jsb4g

Rank: Lubber

Registered: Oct 11, 2016

Last visit: Jun 19, 2018

Posts: 42
Posted: Sep 14, 2017 - 07:50 AM

rockypointbobWhen I had the hulls refinished, I had the body guy build up the transoms so they should be pretty sturdy now. Looking at the pic (which I got from Hans FB site) I posted of the correct mounting of the gudgeons, it appears they also used SS sheet metal screws for the brackets.

I have inspection ports on both hulls but they are too far forward to reach the transom. I've had the boat out with the rudders mounted incorrectly (I had no idea at the time) and it worked great, but what do I know, it was my first time solo on a boat! So I guess the answer is to have two more ports installed such that we can do backing plates. Bummer.

What about the Dotan kick-up rudder system? Guess I would have the same issue with mounting?

I don't know anything about the Dotan system. I defer to MN3 re sheet metal screws vs bolts. It makes sense that bolts would be better. As for leaving as is, since repairing it correctly is a major undertaking, you could just leave it as is, but remember this thread if you encounter issues later. Lastly, I will be going sailing this weekend, so I will be able to measure any parts you want measured. I remember you wanted the rudder pin length and diameter measured. I am using clevis pins right now, but I have the original long rudder pins too. Was there anything else?
rockypointbob

Rank: Lubber

Registered: Jul 13, 2017

Last visit: Sep 28, 2020

Posts: 30
Posted: Sep 14, 2017 - 11:27 PM

jsb4g
rockypointbobWhen I had the hulls refinished, I had the body guy build up the transoms so they should be pretty sturdy now. Looking at the pic (which I got from Hans FB site) I posted of the correct mounting of the gudgeons, it appears they also used SS sheet metal screws for the brackets.

I have inspection ports on both hulls but they are too far forward to reach the transom. I've had the boat out with the rudders mounted incorrectly (I had no idea at the time) and it worked great, but what do I know, it was my first time solo on a boat! So I guess the answer is to have two more ports installed such that we can do backing plates. Bummer.

What about the Dotan kick-up rudder system? Guess I would have the same issue with mounting?

I don't know anything about the Dotan system. I defer to MN3 re sheet metal screws vs bolts. It makes sense that bolts would be better. As for leaving as is, since repairing it correctly is a major undertaking, you could just leave it as is, but remember this thread if you encounter issues later. Lastly, I will be going sailing this weekend, so I will be able to measure any parts you want measured. I remember you wanted the rudder pin length and diameter measured. I am using clevis pins right now, but I have the original long rudder pins too. Was there anything else?

I'm actually headed down to Mexico this weekend so I'll be able to finally see all the parts, take measurements, etc. But thanks much for the info on the traveler car; got it in today. I guess I will leave the rudders as is for now and until I actually get to the point of flying a hull, which will probably not be anytime soon. Actually, there is one thing that would be most helpful...some good pics of your jib rigging. I feel pretty confident with rebuilding the mainsheet rigging but not so much with the jib. I've seen some pic of a Gcat 5.0 barber-haul set up but they weren't very clear. Thanks!