Adding cleats to a foam filled rigid tender

I have a 11.5’ rigid bullfrog tender (https://www.bullfrogboats.com/) that came with the boat I recently purchased. I like the ruggedness and durability of this tender but there are no cleats for tying lines to. I purchased some cleats to add but when I went to install learned the rigid shell is foam filled so there is no easy way to get to the underside of the pvc shell. I inquired of the manufacturer and their response is the rails on the boat are designed to handle the load of lines. I could use screws into the pvc to hold the cleats but that’s unlikely to provide sufficient holding.

Anyone else have a similar type tender and figure out a way to add proper cleats? I obviously could remove the foam filli g to get to the underside and then add new foam but this isn’t an optional choice. I thought about some sort of fastener that expands like you use for drywall hanging but not sure anything will expand with the foam filling. All inputs appreciated.

Im not an expert, but i have been bolting things in boats, a dinghies a lot, and i think there is not product like the one you were describing

If there is, I look forward to reading the thread.

Might be other types of opportunities such as the transom, or some area up front you could through bolt

We had a couple of Triumphs that were rotocast and foam filled. I drilled for a 4” removable plate and then cleaned out the foam. I used a flexible drill extension and used the drill bit like a router to clean out the foam. Then through bolted with a backing plate. Worked fine. But it was a PITA to get the foam out until I thought about using the extension on the drill.

Comodave, thanks, I have several access panels on each side of the rotocast from the original manufacturing. Before removing I thought these were to allow access to the inside but upon learning it was foam filled figure they were used to get the foam inside during the build. I was trying to avoid removing the foam but believe this might be the only practical solution.

How thick is your bridge deck? I am in the midst of a very similar project and my bridge deck is a foam core about 2" thick. My solution was to drill significantly oversized holes (¾" in my case) clear through the foam core deck and fill them with thickened epoxy, then drill the appropriate size hole through that and use a backing plate on the bottom side of those "pillars" through the foam core.

HeadedToTexas said:

How thick is your bridge deck? I am in the midst of a very similar project and my bridge deck is a foam core about 2" thick. My solution was to drill significantly oversized holes (¾" in my case) clear through the foam core deck and fill them with thickened epoxy, then drill the appropriate size hole through that and use a backing plate on the bottom side of those "pillars" through the foam core.

Click to expand...

I’m not looking at my boat deck, it’s my rotocast tender shell that I’m looking to add cleats. What you describe I’ve done when putting holes through my foam filled pilothouse roof.

Ah-hah. Sloppy reading on my part. Similar situation though. Will the forces and longevity issues on those cleat mounts dictate a similar approach?

I think you are looking to do something more like this - taken from West System...

HeadedToTexas said:

Ah-hah. Sloppy reading on my part. Similar situation though. Will the forces and longevity issues on those cleat mounts dictate a similar approach?

Click to expand...

If I can get to the underside I’ll install a backing plate to spread the load.

Roger that.

LovetoBoat said:

I think you are looking to do something more like this - taken from West System...

View attachment 121525

Click to expand...

That won’t work with a rotocast plastic boat. The only way to get the cleats attached properly is to use the existing access plate and then reef out the foam and use bolts and a backing plate. Ben there done that with 2 previous rotocast Triumph boats. They were made just like the Bullfrog dinghy in question. You can add foam back in after installing the cleats if you want to but it won’t make much difference in the flotation of the boat. I wouldn’t do it just in case you ever need to tighten up the cleat in the future.

Can you just skip the cleats and tie to the rails ??

Benthic2 said:

Can you just skip the cleats and tie to the rails ??

Click to expand...

+1

We have a 14' Rendova RIB with both cleats and rails fore and aft. Most of the time we wind up using the rails to secure the RIB, Since the rails are on top of the cleats they are actually easier to use than the cleats.

Maybe make some fancy custom soft shackles that live on the rails? Might be better than tying lines to the rails?

Comodave said:

That won’t work with a rotocast plastic boat. The only way to get the cleats attached properly is to use the existing access plate and then reef out the foam and use bolts and a backing plate. Ben there done that with 2 previous rotocast Triumph boats. They were made just like the Bullfrog dinghy in question. You can add foam back in after installing the cleats if you want to but it won’t make much difference in the flotation of the boat. I wouldn’t do it just in case you ever need to tighten up the cleat in the future.

Click to expand...

Thanks for confirming. I spent the afternoon reaming out the foam and have added the cleats. It wasn't too bad getting the foam out as there was some air holes on the topside. I double nutted the bolts with a lock washer so hopefully they never loosen up. I guess I could have left the foam out but felt better knowing the tender was unsinkable having these rotocast tubes filled with foam.

Glad it worked out for you. Reaming out the foam can be a PITA…

Another option is Well-Nuts. Not as strong as a backing plate or large washers but probably ok for just tying up. I wouldn’t lift or tow with them. Should be ok with Hershoff style four hole cleats. I use them to install canvas snaps with #6 machine screws. They are available up to 3/8-16 threads.

https://www.albanycountyfasteners.com/blog/well-nuts-what-are-they-and-how-are-they-used/

Benthic2 said:

Can you just skip the cleats and tie to the rails ??

Click to expand...

Yes that works for short docking lines but is difficult when you have a 50 ft anchor line that you need to adjust.