Bedding non-through bolted hatches with Butyl?

[Swift Drift]

So I've removed and rebuilt the old alluminum framed Bomar hatches on my 1988 Catalina 34 (new acrylic, new hatch dogs, new seals). I'm now going to be reinstalling on the boat in the next day or two and have gone back and forth on how to bed the frames to my fiberglass deck. I would very much like to bed with butyl tape as I've had tremendous results using butyl to rebed all of my stanchions.
My hesitation stems from the fact that my hatch frames are screwed down to my deck rather than through bolted like my stanchions are. I will end up moving forward with one of the following three options:

1) Bed with butyl tape only

2) Bed with Butyl tape and caulk the exterior seam with 3m 4000 uv once overflowing butyl has been removed.

3) Bed and also caulk exterior seam using 3m 4000 uv for the entire job.

If at all possible, I would like to stay away from option 3 given that it will be messier, more difficult to undo, inconsistent with my exisiting deck hardware bedding methods, etc. However, I want to do the job right.

Therefore, I humbly submit my dilemma to the collective. What say you?

P.S. I have the same scenario/dilemma with plastic framed Beckson ports that mount inside the cock pit and provide light to my aft cabin. I would assume that the same logic would apply in this application with the understanding that there are two main differences: a) Plastic vs. alluminum frames b) vertical mouting orientation vs. horizontal (flat)... any input is appreciated.

[Beersmith]

Option 3 except use Sikaflex 295 UV instead of the 4200

[belizesailor]

Glad to see you are not using the almost universally over, and incorrectly, used 5200. 4000UV is great stuff. I would tend to stick w just that rather than a mix of materials...although I do have some windows bedded w 4000UV and butyl and that has worked out fine.

[Swift Drift]

Thanks for the input guys. So basically stay away from butyl unless I'm dealing with through bolted (not screwed in) items....bummer! I love using butyl tape.

So moving on to the the sikaflex 295 uv compared to 3m 4000 uv conversation; both are polyurethane based and seem very similar. Are they essentially the same product with different manufacturers? Does it really matter which one I use? Or am I just opening up a "chevy vs. ford / which kind of anchor is best" can of worms?

[roverhi]

Butyl will work just fine. If you use enough, no need to mess with a second tiype of caulk. Only thing to be careful of is butyl around the fastener glomming onto the butyl on the frame and pulling it into a big glob around the fastener. When you install the hatch, run the fasteners relatively tight but not locked up. Go back the following day or even a couple times thereafter and tighten the fasteners. The butyl will continue to ooze out till you've got the hatch pullled down tight. If you don't pull it down completely, no big thing as the butyl will not shrink and will continue to seal.

When I installed new ports on my boat, the cabin sides had too much curvature for them to draw in flush. Didn't want to distort the frames by trying to bend them to the curvature of the cabin. They wouldn't have sealed if I'd done that. tightened the center fasteners and then pushed butyl into the gaps at the ends. Worked a treat and the butyl filled gap isn't noticeable, that is for everyone but me.

[belizesailor]

Originally Posted by Swift Drift

Thanks for the input guys. So basically stay away from butyl unless I'm dealing with through bolted (not screwed in) items....bummer! I love using butyl tape.

So moving on to the the sikaflex 295 uv compared to 3m 4000 uv conversation; both are polyurethane based and seem very similar. Are they essentially the same product with different manufacturers? Does it really matter which one I use? Or am I just opening up a "chevy vs. ford / which kind of anchor is best" can of worms?

I have not used the Sika product and BeerSmiths post referenced "4200"...not sure whether that was a typo or not.

@BeerSmith....also the name of a great piece of brewing software...do you brew?

[belizesailor]

Re Rovers suggested technique to wait a bit before you fully tighten the fastners...this works well regardless of which option you choose.

If you crank down on sealant too soon then you tend to squish more of it out of the joint resulting in a less effective seal...let it cure for a short time and then tension the fastners.

[Charlie]

I recommend Dow Corning 795. It is used in high rises to glue in windows and has very good elasticity. Pretty inexpensive as well McMaster-Carr

[s/v Jedi]

Originally Posted by Charlie

I recommend Dow Corning 795. It is used in high rises to glue in windows and has very good elasticity. Pretty inexpensive as well McMaster-Carr

That is silicone!? Who uses silicone as hatch frame bedding compound? Obviously some do... hope you never have to paint around the hatch...

[sww914]

I've put about 30 windshields in with only butyl tape and thin aluminum trim retaining the glass. It's good for 20 years like that. That's how all Porsche 914 windshields and rear windows were installed, all Ford Explorer and Taurus quarter glass, and many many others.
Butyl tape between a flange and something solid is good for longer than 20 years.

[Swift Drift]

OK, I thought things might go this way, several different opinions from several different people..... Perhaps I should have asked "which boat is the best?" and watched everyone harmonize in agreement

I truly believe that there is merit in everyone's suggestion and like many things on a boat (and pretty much anything else for that matter) there are lots of wrong ways and lots of right ways to approach a task.

That said, I have two examples above from people that have used butyl in similar real world application and have had success (ports and windshields).

The Butyl neigh-sayers recommend an alternative product (4000uv, 295uv, Dow 795) that woudl likely get the job done, but do not provide any reason why butyl is not a good product for this applciation.

I am inclined to start out with 100% butyl and see how it goes. if I have issues, my next step will be to caulk the outer endge of the frame with 4000uv. If I still have issues, I'll uninstall and start completley over and go with 100% 4000uv.

A few reason for this approach:
1) 100% butyl will be the easiest method to reversve in the event it doesn't work
2) Butyl is my preferred method from the start if feasible.
3) As mentioned, I have real world applications from posts above that give me confidence that butyl is worth a shot.

I'll be doing the job tomorrow and will report back with my results. Feel free to throw in some last minute advice.

[s/v Jedi]

Originally Posted by Swift Drift

OK, I thought things might go this way, several different opinions from several different people..... Perhaps I should have asked "which boat is the best?" and watched everyone harmonize in agreement

I truly believe that there is merit in everyone's suggestion and like many things on a boat (and pretty much anything else for that matter) there are lots of wrong ways and lots of right ways to approach a task.

That said, I have two examples above from people that have used butyl in similar real world application and have had success (ports and windshields).

The Butyl neigh-sayers recommend an alternative product (4000uv, 295uv, Dow 795) that woudl likely get the job done, but do not provide any reason why butyl is not a good product for this applciation.

I am inclined to start out with 100% butyl and see how it goes. if I have issues, my next step will be to caulk the outer endge of the frame with 4000uv. If I still have issues, I'll uninstall and start completley over and go with 100% 4000uv.

A few reason for this approach:
1) 100% butyl will be the easiest method to reversve in the event it doesn't work
2) Butyl is my preferred method from the start if feasible.
3) As mentioned, I have real world applications from posts above that give me confidence that butyl is worth a shot.

I'll be doing the job tomorrow and will report back with my results. Feel free to throw in some last minute advice.

I completely agree with your choice. In fact, yesterday and today we've been rebedding our cast Bomar hatch, which is screwed, not bolted, with just Butyl tape.

I think the butyl tape is fine, but I had a problem with the screws turning loose. You better check that before applying butyl

Also, while I love 4000UV for visible seams, I use a polycarbonate sealant for bedding. 3M has stopped selling it (too cheap?) but BoatLife still sells it under the LifeCaulk name IIRC. I would use that because for using it, you can just think of it as the paste form of butyl tape. After 19 years it still had uncured parts under the flange, easy to remove.

[Swift Drift]

Originally Posted by s/v Jedi

I completely agree with your choice. In fact, yesterday and today we've been rebedding our cast Bomar hatch, which is screwed, not bolted, with just Butyl tape.

I think the butyl tape is fine, but I had a problem with the screws turning loose. You better check that before applying butyl

Also, while I love 4000UV for visible seams, I use a polycarbonate sealant for bedding. 3M has stopped selling it (too cheap?) but BoatLife still sells it under the LifeCaulk name IIRC. I would use that because for using it, you can just think of it as the paste form of butyl tape. After 19 years it still had uncured parts under the flange, easy to remove.

Thanks for the feedback. regarding the screws turning loose (backing out).... how are you going to solve? Locktite? Filler in screw holes? Curious to know.

[GordMay]

Butyl, similar to Silicone (but less contamination problems) has little adhesive strength; so works best as a type of Gasketing material, where it’s installed under compression; such as when through-bolted.

3M “5200" & “4200" both have strong adhesive qualities, which will enhance their watertightness under less compressive installations.

[sailvayu]

I do not recommend 5200 or 4200 for anything that has to seal. It is a great adhesive but a poor sealant. When it starts to leak, which it will, it become very difficult to remove the part. It also does not adhere well to aluminum.

I like using the Dow 795 this is a very hight quality product and works well. Silicone adheres very well to both aluminum and fiberglass. If you are worried about painting a hybrid like 3M 4000 UV works well

Butyl is good too if you get the right stuff, the problem is that is not so easy as there is a lot of cheap stuff out there. Also it never hardens and has poor heat resistance (ever take the temp a a metal deck fitting on a hot day? ) It can creep and ooze. Also a mess to clean off it you have to remove the part and lastly it has poor chemical resistance particularly petroleum products. That said I know some have had success with it.