Deck Thickness at Cabin Top

[SkipperDave]

I finally broke down and bought a microwave (since I like hot food on longer distance cruising) that I plan to install the way you would from underneath a kitchen cabinet. Location on my Ericson 35 MK II will be just forward of bulkhead/partition at Nav station, underneath port settee. Fortunately it is short enough, heightwise, not to interfere with headroom when sitting there. With a little help from Pythagorus I have figured out all the geometry to make it level since FB headliner in this area of cabin slopes downward about 9 degrees on headliner below windows towards teak siding against inside of hull. I want to mount the thing with four blocks and four screws each with threads on main bolt descending downward that match four holes on top of microwave with these supporting bolts inset into wooden blocks. I plan to drill thru thru headliner (which I have learned from this forum may have as much as 1/2" of empty space between it and first fiberglass laminate). Not really interested in screwing into end grain balsa sandwiched above for any additional strength, but won't mind going part way into core which I understand is about 1/2 inch think. Counting on four self tapping metal screws on each of four blocks through headliner first and then into underneath fiberglass laminate upon which balsa core sits. Soooo, since the wood blocks will be varying thickness due to the geometry of slope and points where main bolts will screw into top of microwave. How far can I drill and screw into headliner to reach first FB layer of laminate and partially into core without puncturing top of deck from below?? Again, this question boils down to how thick is headliner, any empty space, plus up though first layer of fiberglass sandwhich and, say partway into core before penetrating FB at top deck which naturally I want to avoid. Might use a few dabs of epoxy on blocks where they meet the ceiling for added strength and security. But would prefer to avoid not using any adhesive on wood blocks to headliner as whole unit may have to come out some time in future. Sorry this is so long winded and would be happy to send pictures. Just not finding reliable thickness info of part of deck described above.
THANK you all; this is marvelous Website and I have learned a lot from it. Will post some pictures of various pics of projects, I have undertaken in past few years.

 

[Christian Williams]

I wouldn't hestitate to drill holes in the cabin house or deck, which is how the tracks and winches and cleats are attached, and I'll be doing it tomorrow to install pad eyes for jacklines.

Wouldn't want a microwave falling on your head.....

 

[SkipperDave]

Reply8-31-16

Thank you Christian. Actually I am considering drilling from deck above, but still need to know how thick deck is. Because, yes, having microwave falling on my head would be very unpleasant experience.

 

[Loren Beach]

Thank you Christian. Actually I am considering drilling from deck above, but still need to know how thick deck is. Because, yes, having microwave falling on my head would be very unpleasant experience.

I have drilled thru the cabin top for installing blocks and winches on two boats from different companies. Both seemed to have a half inch of balsa coring under the surface frp and one layer of translucent cloth and resin on the bottom. This might be a sort of industry "standard". An older boat with an interior liner gives you an additional surface to contend with, and my prior boat had that, altho I never tried to hang anything heavier than an oil lamp from it.

Loren

 

[Guy Stevens]

Different aproach

I would take a different approach to this problem.

I would use some 1/2 marine ply squares, drill holes and use tee nuts, or threaded inserts in the top of the blocks. Then clean and lightly sand, and clean again and secure the blocks with west 610 to the overhead.

This will allow for removal later, and will be 4 less places to leak through the deck.

Also when you change the microwave when the one that you have quits working, with a little work with a chisel, you can remove the blocks, leaving only their top lay still attached.

t nuts look like this:

Threaded inserts using a small amount of epoxy when threaded into the plywood would work just as well to, but I have found take some practice for most people to use effectively.

Guy

 

[SkipperDave]

Solution: Tee Nuts!

Guy, Thank you very much; this sound like a genuinely excellent alternative and solution. Like you, I don't like drilling into deck of any boat unless absolutely necessary. Have no idea where to purchase Tee Nuts, but my brother in law runs a high end machine shop and am confident he could guide me, or maybe McMaster-Carr. Will need to match thread on nuts to threaded openings on top of microwave for under cabinet installation with nut. Have worked with West system extensively, so no problem there. Only other complication is that overhead headliner (and deck) slopes about 9 degrees and to level microwave will have to cut blocks at angle and mount/epoxy precisely, but have done the geometry to transfer block hole points to level plane. Many thanks again!
--Skipper Dave

 

[Guy Stevens]

Link

http://www.mcmaster.com/#tee-nut-inserts/=13zh6ik

For interior of the boat the 18-8 would be fine, and I would bet that one of those sizes is right for the Microwave.

Guy

 

[SkipperDave]

Tee Nuts

Hey Guy, Thanks very much. I used to have a McMaster-Carr catalogue, well over 2,000 pp. thick. Obviously, this is now available on line. In any event, Tee nuts mounted on angled blocks would definitely be the way to go if I decide to mount from below which also would be best way to insure that holes on top of microwave line up precisely with bolts poking down; since i likely would install microwave with blocks screwed in and then figure out a way to epoxy w/ blocks bolted and attached to microwave to underside of FB headliner. Other alternative would be to try and mark bolt holes very exactly on underside of headliner and drill right through to deck above and mount that way. No matter which alternative, if I am off more than a few thousands of an inch friggin holes on microwave will not line up as they not a square or even a parallelogram, Pythagoras no help on that dimension...but did lend me a hand on vertical plane.
Thanks Again, SkipperDave