Hull thru Bolting

potis

Active Member
Oct 15, 2006
143
San Ramon, CA
Boat Info
1998 400 DA Sundancer
"Soggy Dollar"
Engines
8.1L V-Drives
I will be installing two tow ring/eye pads on my fiberglass hull Zodiac for towing behind our 340DA. The rings will require thru bolting w/ backing plates. My question is regarding the bedding and tightening of the bolts. I'll likely be using 5200 as these will be at / near water line and subject to constant water when it use, and they will be permanently installed. I seemed to recall reading somewhere that when doing this type of installation (thru bolting) the nuts on the bolts should be just snugged down to where the caulk begins "oozing" out, but not fully tightened as this will then squeez out all or most of the caulk. Then after it cures a bit, how long I cannot remember, the nut should then be fully tightened down, compressing the caulk but not squeezing it out. Looking for particulars on this or am I off base? Thanks.
 
Keep in mind that the transoms on almost all Sea Ray boats are cored with plywood. If you tighten the bolts on the eye too much it is easy to crush the gelcoat on the outside and the FRP on the inside if you over tighten and compress the pllywood core.

I would use this type of eye where you have not only a backing plate but a plate on the exterior:


They are available in various sizes.

Run the finishing nuts all the way out on the outside then insert the eye and do all the tightening from the inside. The 2 plates will be helpful in keeping you from crushing the transom by over tightening.

3M 5200 is a good choice for this application. It can be messy, but put enough on the bolts and under the plates so it squeezes out everywhere. 5200 is pretty easy to clean upbefore it cures.....wipe off the excess with paper towels then use paper towels wet with WD-40 to clean up what you smear around.
 
fwebster - thanks for the input. Let me clarify a bit on the installation I am doing. The tow eyes I'm adding are going on the dinghy, not onto my Sea Ray. (Already have them on the Sea Ray). Here is a photo of the eyes I will be installing. I'll be putting two onto the forward quarters of the Zodiac. These will be my tow connection points using a bridle set up. Sorry about the image size. Couldn't get it quite right.

IMG_3024.JPG
 
Just curious, does your RIB not already have a tow ring on the bow? Mine came with a single tow eye pre-installed in the bow. What is the advantage of using 2 tow rings?

I always thought that the preferred method of towing was to attach a line to the bow tow ring, then to 2 points on the stern. I get that for non-RIB models the glue-on rings may not be as strong as a bolt-through ring so 2 are needed.
 
It does have a single bow eye. While it is acceptable to tow using that point of connection, due to the size/weight, it is recommended to have the additional tow eyes, especially if towing while on plane.
 
More clarifications and questions:
The dinghy I will be towing is a 14' Zodiac with 50HP OB. Total weight is around 625 lbs. I do not trust a single connection point at the bow eye (U-bolt) for towing, unless in calm water at no wake speeds. My goal is to be able to tow this boat when on plane at 25-28knts when necessary.
So, I will be using a three point bridle to connect to the Zodiac. The center will go to the U-bolt boy eye. The other two will connect with one of the following options:
1. Use the SS eye pads thru bolted into the rigid hull of the Zodiac, as previously described. Most secure method, but the idea of 8 bolt holes at or below the waterline does not excite me.
OR
2. Use the large glue on D-Ring tow eyes attached to the tubes and then either:
A. Connect directly to each of those D-rings, or
B. A method I have read and heard about but never tried, Run the 2nd and third bridle line thru the D-rings but don't connect them, simply use the D-ring as a "rigging pass thru", then run the lines all the way to the stern of the dinghy and attach to the two U-bolt tie-down tow eyes. The D-rings keep the lines aligned and help keep the bow up.

Appreciate the input from everyone.
 
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You have a floating RIB with minimal drag, why would you need all that extra attachment?? Doesn't make sense. Is the Zodiac hull that cheezy?
 
You have a floating RIB with minimal drag, why would you need all that extra attachment?? Doesn't make sense. Is the Zodiac hull that cheezy?

Wayne, Zodiac is one the best built RIBs out there IMO, this all has to do with stability and safety of towing 700-800 lbs safely, without episode, while on plane at 25-29 knots. If you look at almost all inflatables they have D-Rong tow eyes for just this purpose.
 

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