Mounting HDPE...through bolt with sealant

[Tin Man]

I am preparing to install my new Lowrance HDS PRO 10 with 3 in 1 HD Active Imaging transducer.

I have mounted HDPE blocks on the transoms of several boats. All were epoxies using flame treatment and West System G-Flex. The were all still attached after 2-3 years. However, this new transducer is larger, expensive, and heavier so I am considering through bolting the HDPE black using sealant between block an hull.

Questions:

1. Are there are any drawbacks to through bolting? I was planning on two (one upper, one lower) #10 SS bolts with flat and lock washers and nuts.

2. What adhesive is preferred between HDPE and painted alum hull? I am using a 5"x 7" x 1" HDPE block.

3. Ond of the attached pics show my inner transom access. The orange pencil (bottom) shows where I placed a bolt through existing transom hole (from previously mounted transducer that was screwed) and the second hole will be drilled 4" directly above it . As you can see, there is a 3"x 3" alum tube (part of transom reinforcement)....I would use the current hole (bottom) and one additional hole above the tube. Bolt holes would be 4" apart (as show on blue tape placed on HDPE block.

NOTE: There is not a lot of room to work with inside transom and the bolt on bottom would require me to use "feel" only when attaching the washer., sealant, washers, and nut.

Thoughts?

Thanks!

 

[airshot]

If it were me.........I would add a bigfer, longer block just in case any future add-ons might be needed. One never knows what the future has in store. This way once you have two good bolts holding it in place, you won't have to do this again !! If it were me.......bigger block and a couple bigger bolts then add-on whatever the future brings !

 

[Tin Man]

If it were me.........I would add a bigfer, longer block just in case any future add-ons might be needed. One never knows what the future has in store. This way once you have two good bolts holding it in place, you won't have to do this again !! If it were me.......bigger block and a couple bigger bolts then add-on whatever the future brings !

when you say, "bigger," what does bigger mean....taller, wider, ? It is 1" thick which is plenty for this application. I do not have much width....to the right is the hull's chine, to the left is the live well intake. I was considering a taller block....to encompass the upper hole seen in pic (this upper hole is used for a cable clamp).....it would make new block about 9" tall. This would mean I would be reusing current existing holes for this project....NO new holes would need to be drilled. However, I do not believe I would ever need to mount transducers "higher" as most, if not all, transducers mount within 1"-2" of variance of suggested height.

 

[airshot]

Just expressing an opinion, if it were me....I would put as large a piece as I could make fit as a just in case....been there, done that....never have I been sorry for going bigger, but many times have I been sorry for not making it bigger! Your call, your boat....with all the work and difficulty of getting a piece mounted, I would use that effort to go as large as I could. If you never need it, so what...but if you do ??

 

[guyg]

I wouldn’t trust glue on hpde at all. In industrial applications, it’s always heat welded. Through bolting should work well, but seal the holes well with 3m 5200 or similar. Good luck!