Underpinning question (or underskinning, underskirting)

[teecro]

40 mill = 1/24

So thinner than 1/16" right? Pretty much a thick film?

[OK Toon]

I plan to use something just about as thick (.040). There's a local steel place that has aluminum blank sign material -- in various colors. I can get the flat black for $58 for a 4'x10' piece. The crazy part is to get Bright Clear (shiny), it runs $115 for the same size of material.

http://www.wheelermetals.com/catalog/pr ... 8/aluminum

[sunedog]

I plan to use something just about as thick (.040).

I could be wrong, but I think .040 is exactly the same as saying 40 mil. Either one converts to 1/25" in fractional inches.

So thinner than 1/16" right? Pretty much a thick film?

Yes, it is between 1/16" and 1/32" in thickness.

I would think something that thin would vibrate a lot and be annoying and it would not be very durable. I'm anxious to hear your results.

[guardian667]

I use this HDPE .040 all this summer no vibration no sound this underskinning receive water just over 15 miles /hr

[OK Toon]

I plan to use something just about as thick (.040).

I could be wrong, but I think .040 is exactly the same as saying 40 mil. Either one converts to 1/25" in fractional inches.
I would think something that thin would vibrate a lot and be annoying and it would not be very durable. I'm anxious to hear your results.

I'll have to update you next year since I plan to make this my project over the winter. We keep our boat on a lift at our dock so we won't be pulling it out till after the season. Maybe just using more rivets will keep it from vibrating. But even a little vibrating should seem better than the feel of hitting the brakes over every wave. But also about 20-21mph is our top speed so hopefully that will also help on durability.

[TDJ2591]

if you have underskinning, how far apart are the rivets/screws spaced? I put mine 8" OC but am wondering if I should add more. That's the spacing the factory used on the rear of the boat so I assume that will be enough. It seems like enough but it will be much easier to add more rivets while it's in the driveway than to have to bring it back later (2 hr drive) if more are needed.

I'm very pleased with how it came out and will post pics later. Tackling this project in the driveway in 100+ degree heat index weather was brutal for this 62 year old. Luckily, my sweet co-pilot got under the boat with me and helped align the templates and aluminum panels. This is NOT a one-person project, especially if the boat has bolts extending thru the cross members like mine. It took way more time than I expected, but I had to take frequent cool-down breaks in front of a fan!

[BoatCop]

Just thought of one thing that may have slipped our minds on a project like this.

Be sure to run a feeder line of stainless wire rope between the deck and the underskin for any future wires you may want to fish through to the helm later. Engine controls, depth transducer, speaker/lighting, accessory, etc.

I would think 1/16" or even 1/32" would fit the bill, as long as it's run loose and not pinched between the skin and the frames.

A lot easier than pulling the skin.

[curtiscapk]

Great freaking idea!

[TDJ2591]

I had the same thought so I ran nylon line from inside the console to each corner of the toon. I ran 2 nylon lines to the rear on starboard side. Since I had to replace a missing transducer, I left the old transducer cable in place to be used as a pull wire. In the supports at the end of each log I added stick-on hooks and tied the string and cable to them so I could easily find them if I needed to pull wires later. I also added and ran the string thru nylon cable supports from one side of the toon to the other to make it easier to pull wires across the width and to keep the lines/wires from getting hung up on the brackets..

I attached aluminum side panels above each log with self-tapping 10-24 screws instead of rivets to make them easily removable, just in case. I also made a note of which color speaker wires went to each speaker in case I need to trace a short, as I now have to do. I believe the marina may have damaged one of my brand new speakers while pressure washing the carpet (not requested, just done to make up for damage they did to the toon).

[TDJ2591]

Finished at last! The underskinning looks great but I am unable to upload the pics. I get an error message each time I try. I'll post pics as soon as the system will let me.

Had a plan change. The borrowed 10.5' sheet metal brake would not bend the long pieces of .063 aluminum for the side panels. It was Friday and too late to try and find a fabricator who could bend it, so I cut each 8"x96" piece into 2 4"x96" pieces for the side panels. These were attached with #10x24 type F self-tapping SS screws with SS bonded washers to make them removable. The corner seam between these 2 pieces was sealed with 3M 5200 to eliminate possible metal-on-metal rattles and squeaks. The contact surfaces were sanded and then cleaned with acetone so the 5200 would adhere better. The underskinning was attached using existing C-channel bolts and 3/16" truss head aluminum structural rivets as suggested on this forum. The Harbor Freight pneumatic riveter that I picked up for about $35 worked great.

Will find out his weekend what benefit I got from underskinning. Maybe the fish will like it because they are the only ones who will see it. I just hope the goons at the marina who are beating up my logs with the fork lifts don't destroy my nice new underskinning.

[TDJ2591]

I tried posting pics from my iPhone which has not been upgraded to IOS 8 instead of the iPad using 8.0, which would not upload. Hopefully it works, the pics are sized correctly and are in correct order.