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Replace saildrive gasket with foam


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I have heard of some people who replace the outside sail drive gasket with a foam insert and then glass over it leaving a gap which is filled with a sikaflex. 

Has anyone had experience with this? Type of foam? Size of gap? 

I had to remove my gasket and I am contemplating a new volvo gasket or the foam/glass option... 

Thanks 

 

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Why would you do that? The fairing cover on the hull side is easy to do. A Saildrive is engineered to be able to move significantly via the engine mount flex, some in use, more in an impact. This movement is extended at the base of the saildrive where it protrudes through the hull. Filling the void will load the SD in a manner for which it was not designed. It will also make removal of the drive for any service work much more difficult.

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I have a Volvo SD and I agree with IT,  also I'm sure you will transmit vibration to the hull negating one of the benefits of an SD. The fairing boots are not particularly expensive so I'm curious as to why you would contemplate this ?

 

 

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The decision/investigation stemmed from three independent conversations.

Yesterday my antifoul painter said that a lot of times he is finding the boot is replaced with foam. 

Independently, last week my engine installer, when I told him I was replacing the boot, said he'd just done an new SD installation and the owner had a builder cut foam inserts claiming it was superior to the boot and he's been doing that for years.

And when I told someone else about the boot in the a conversation about inspecting the rudder bearings, he said 'well hell, if you've got a builder coming down, get him to replace the saildrive boot with foam. 

There is a limited number of posts on the Internet about doing this. It seems that alot of people have issues with the boot falling off personally I have never had that. But I do find that the boot becomes very chunky and lumpy and is not a smooth surface anymore. 

This is the most detailed I have found, this post was from 2014 and the op had the foam in since 2006.

https://www.myhanse.com/sail-drive-diaphragm_topic8671_page2.html

 

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Boatright at Pier 21 said that they are doing this frequently. Quote: "Lots of race boats are having it done and we're seeing more and more cruisers asking for it."

They use a construction foam to fill the gap to about 20mm and fill the rest with sealant. If you need to take it out for any reason "stick a wire hook up there and yank."

With the lockdown I wasn't able to be around to watch, get in the way and be an annoying customer. But I got a couple of photos in the evening.

I believe the foam is about 2.5cm thick.

I will post another photo when she's next out at the Floating Dock. 

 

20200814_180840.jpg

20200813_160831.jpg

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This sounds like you’re on the receiving end of some dubious tech advice. A bit like the wide boys who think they can do a better job of redesigning their car suspension in their driveway than the manufacturers with their $millions R&D budgets.

I was always a bit unsure on the strength of a SD boot until one day - to my horror - the haulout crew accidentally lifted one of my previous boats out of the water with the rear lifting strop positioned under the bottom of the SD leg (skeg). It was inspected and found to be fine even after lifting half the weight of the boat. That convinced me the standard manufacturer’s design is OK.

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11 minutes ago, Aleana said:

I was always a bit unsure on the strength of a SD boot until one day - to my horror - the haulout crew accidentally lifted one of my previous boats out of the water with the rear lifting strop positioned under the bottom of the SD leg (skeg). It was inspected and found to be fine even after lifting half the weight of the boat. That convinced me the standard manufacturer’s design is OK.

I suspect that would be the inside gasket and more importantly the engine mounts. Unless your engine was wobbling around with no mounts attaching it to the boat? I would not have expected any load on the inside gasket at all, unless a mount gave way? 

The outside boot slips down easily over the saildrive, so a sail drive going up into the boat (with no engine mounts to stop it) would just rise out of it.

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True. Although there was undoubtedly a decent load delivered to both the boot and gasket as the mounts moved to their extreme positions to absorb a few tons load.

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8 hours ago, Island Time said:

I had the same issue, but it broke a mount, and tore the seal. Also distorted the SD leg. Had to change the whole unit....

Blimey ! hopefully an insurance job IT ?

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Yep. Last time I’ve lifted the boat without me being there. There are sling markers on the gunnel, but the lift operator “didn’t see them” .  Imo did not look, and did not last as a lift driver....

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4 hours ago, w44vi said:

How well does the prop speed work on the sail drive ?

We have run the prop speed program in the past. Works a treat, only thing I would say is that we reapplied yearly do an over night on the Floating Dock sorted us between 2 yearly hull antifoul.

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On 14/08/2020 at 8:34 PM, CarpeDiem said:

Boatright at Pier 21 said that they are doing this frequently. Quote: "Lots of race boats are having it done and we're seeing more and more cruisers asking for it."

They use a construction foam to fill the gap to about 20mm and fill the rest with sealant. If you need to take it out for any reason "stick a wire hook up there and yank."

With the lockdown I wasn't able to be around to watch, get in the way and be an annoying customer. But I got a couple of photos in the evening.

I believe the foam is about 2.5cm thick.

I will post another photo when she's next out at the Floating Dock. 

 

20200814_180840.jpg

20200813_160831.jpg

19 months later. And first time out of the water. 

Still looking good and intact. Has lasted way better than the boot. 

20220324_082636.thumb.jpg.9cbd0fe21d4dd0eabd2f90c210a7eef7.jpg

 

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I have the foam / sika setup on my Y88 with an SD20/2YM15 setup.  Was like that when I brought it  - had never had a sail drive before and got a bit of a fright when i pulled the boat out of the water the first time to find no boot. Has been like that since the engine was installed in '05.   Got some advise, and used Sikaflex 291 as the sealant when I re did it.  Seems to be fine, although getting a smooth finish was a bit challenging (but that's just me...).  just antifouled over the top and seems OK 14 months later.

We also have propspeed on the SD leg and its still in great nic after 14 months, prop a different story though....

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1 hour ago, Black Panther said:

I'm curious what's happening to these boots. I had one for 8 years, never a problem. 

I have heard of the boots slowly peeling back around the edges when surfing down waves and becoming a bit of a flappy drag.

Personally I had not had a problem with them, although I have had past boots become pretty rough and lumpy and no longer being a smooth surface.

I had to cut the boot off 19months ago, for a reason that I now cannot remember... and rather than replace the boot this was the alternative option I went with.

I don't think there's anything wrong with boots, this is just an alternative option and not necessarily better.

 

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My SD20 boot was installed 9 years ago, used 5200 , not lifting any where, I get 2 years with prop speed, prop is a kiwi prop, boat is used regularly and kept on a berth at HMB marina, not happy with the black trilux 33 used on and around leg tho, gets alot of growth , must be something better out there 

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