Underskin advice

[Kitchen363]

So I've see a few boats that have underskin installed on them. Really like the idea of not having the wake, beat the heck out the bottom of the boat. Water will even splash through the table pole hole in the floor.
Anybody ever done this themselves? What thickness aluminum was used? Where can you buy large sheets of aluminum (in the Cincinnati area)?
Do you have to break the edges of the sheeting down toward the logs or just install a flat piece.
My first thoughts are to overlap the sheets back to front, drill a 1/4" hole in the sheeting and drill and tap the frame of the pontoon and attach the underskin with a 10-32 stainless steel truss head screw. I'm thinking I want the underskin to be removable if I ever need to access the decking bolts underneth to tighten them in the future.
Also I use a up-down lift type trailer of haul the boat dose this pose any unknown risk?

2006 Bentley 200 cruise
90 hp Mercury 4 stroke

 

[5150abf]

Re: Underskin advice

You need some pretty beefy aluminum to stand up to the beating, we use .080 in the front and .100 at the back by the motor pan and you want to go from back to front so the water doesn't grab any of the sheets.

We use stainless rivets to hold ours on and they are pretty big rivets and the edges are broke with a strip(we use extrusion) that goes along the tube.

The sheets set directly on the cross members so a scissor trailer shouldn't be a problem.

Don't know where you can get the sheet though, they are gonna be fairly big and prepare yourself, aluminum is way pricey, a single sheet 10'x78'' is @ $240.

Maybe try calling a builder, you may be able to get a wave tamer for one of there boats and make it work on yours, Bently is out of buisness so you can't call them.

 

[Kitchen363]

Re: Underskin advice

Anybody ever done this and bought the aluminum off the internet, (where)??? Just would like to price compare vs. some local fab shop.

 

[Kitchen363]

Re: Underskin advice

Well my Aluminum sheet should be in tomorrow. I purchased it from a local shop (Riverfront Steel) here in Cincinnati

Here's my next question. Aluminum rivets or Stainless steel?? I'm thinking Stainless would be the right choice?
How many should I use?? How should they be spaced?
What size rivets? I'm thinking 1/8"dia. X 1/4"

Also thinking of using a mastic tape (Rubbery, sticky, tape) to place in between the deck and the underskin aluminum. Its less than 1/16" thick. Good idea??

What do you guys think???
How has every one else done it

 

[rogerwa]

Re: Underskin advice

What price did you get on the aluminum..

 

[Kitchen363]

Re: Underskin advice

What price did you get on the aluminum..

3003 48" X 120" .05 thickness (size between 3/64 and 1/16) $77 dollars
I work for the local electric utlity company that dose a ton of business with Riverfront steel. Price should be the same if your off the street???

3003 48" X 96" (1/16") was $92

 

[Boss Hawg]

Re: Underskin advice

Keep us posted on your progress- I'd be interested in doing my 20' Sun Tracker
Also how do you like launching/loading with the center lift?
I have one under mine too but have'nt quite got my boat ready to use yet

 

[Kitchen363]

Re: Underskin advice

Keep us posted on your progress- I'd be interested in doing my 20' Sun Tracker
Also how do you like launching/loading with the center lift?
I have one under mine too but have'nt quite got my boat ready to use yet

It's not too bad. The only bad part is that the Hooiser trailer has no bunks to hit and stop. You just got to make sure you don't back the trailer in the water too far or you could over shoot and smash into you truck. Some day I'll get around to adding some.
After a few launches it's a piece of cake

I will try and take some pictures of the progess of the underskinning
And report how the 3003 0.05 thickness stuff holds up over time, I know some guys have used up to 1/8" thick aluminum
But the Bentley has a ton of braces in the rear So it should work out ok..

Any thoughts on the size and amount of rivets I'll need??

 

[lmuss53]

Re: Underskin advice

I used 1/8 inch thick fiberglass sheet from a local company that makes f-glass extrusions. These were slightly imperfect and I got them for $40 for two 4'X10' sheets and $15 for a 4'X8' sheet. There is nothing in them but resin and glass so I think they'll hold up. They look like shower stall material only lots thicker. I put them up in with #8X3/4" self drilling zinc coated screws. I would have sprung for the stainless screws but they didn't have enough in stock, I would recommend the stainless. We also slipped a piece of pink foam used to isolate wood framing from concrete blocks in between the sheet and the cross member. The sheets weigh about 15 pounds for the big ones and 13 pounds for the small. We used one whole big sheet and the small one, along with a 15"X24" piece off the last 4X10. I used most of a box of 100 screws to cover the 24" wide sections between my 3 logs and the area in the stern. I doubt if you can get this type of material at this price anywhere except where it is made. I bought it from a cash and carry lot one of the maintenance guys from the company has in town.

I can get 6 inch wide by .060 aluminum strips from a friend's work that I will bend 45* at the 1" mark to put along the edges. I'll use the same screws on the edge pieces. I have enough of the strips to finish the starboard side now, it needs it since the 3 logs now push a lot of water up through the hole under the helm and soak the deck.

I think your .050 aluminum sheets will do just fine, and I would put them up with stainless screws. I've seen other forums where guys used screws without any issues... so far. I would also put some sort of closed foam isolator between the sheet and the crossmembers to keep the rattling down.

I had a hoosier drop trailer with my first pontoon and I liked it just fine. A piece of 2X4 and a couple of U-bolts to hold it to the frame make a fine stop and keep those little steel bumps from tearing up the front of your boat. I never cranked the trailer up and down to launch or recover. I just ran the boat up on until it bumped the stop, or backed it down in far enough to drift the boat off. Be careful doing these things if you are inexperienced and especially if you have no stop on the front of your trailer

 

[Kitchen363]

Re: Underskin advice

town.



I think your .050 aluminum sheets will do just fine, and I would put them up with stainless screws. I've seen other forums where guys used screws without any issues... so far. I would also put some sort of closed foam isolator between the sheet and the crossmembers to keep the rattling down.

I'll have to look into that self tapper screw idea. I'm thinking I'll need around 400 to do my 20' Bentley. Poping that many S.S. rivets would kill your hands It seem to my like the guys at the boat dealers are all using rivets though.


As far as an isolator between the sheets. I got a 4" wide stripe of the mastic tape stuff that builder's use to seal up the outside of a house. It's about a 1/16" thick.

 

[fyrfightr]

Re: Underskin advice

I'll have to look into that self tapper screw idea. I'm thinking I'll need around 400 to do my 20' Bentley. Poping that many S.S. rivets would kill your hands It seem to my like the guys at the boat dealers are all using rivets though.


As far as an isolator between the sheets. I got a 4" wide stripe of the mastic tape stuff that builder's use to seal up the outside of a house. It's about a 1/16" thick.

You can buy an air riveter to install the pop rivets. Here is one place to get them http://www.harborfreight.com/air-tools/riveters.html

 

[Kitchen363]

Re: Underskin advice

Well, I decided to use rivets, Got a box of 1/8 X 1/4 Stainless steel with a stainless mandel. Got 500 of them at Fastenal for $37

Hopefully I'll get some buddies over this weekend to pop all those rivets.

This is going to cost me a lot of beer

 

[jetwrnch]

Re: Underskin advice

I just picked up some 48" x 50" sheets of 6061 aluminum at a scrap yard for $10 each. They're fairly thin @ .036, but I can't imagine with 6061 on an inland lake I would need more. I can get thicker sheets if needed. I installed them with zinc platted tek screws. I'll go back and replace them with stainless now that the holes are there. Total cost for materials is about $40 not including bug spray.

 

[VaGent]

Re: Underskin advice

Can .063 5051 be used for unskinning or does it have be thicker than .063?

 

[rickdb1boat]

Re: Underskin advice

.063 5052 is what I used Les. I preferred to use screws just in case I need to drop a sheet in the future. Have had no problem with the metal and no screws have come loose in 3 years of boating in rough water. Used about 400 and ran them in with a hammer drill..

 

[Kitchen363]

Re: Underskin advice

Can .063 5051 be used for unskinning or does it have be thicker than .063?

I just got my done yesterday!!!!!

I used 0.050 3003 which is not as stout as 5051. A few things to consider are how far apart are your floor braces?? My are just a few inches apart on last 6 feet of the boat. The rest of the braces are on two foot centers.
I also used a ton of rivets

 

[Kitchen363]

Re: Underskin advice

Got the underskinning done yesterday and got to do a test run

First impressions are SMOOTHER Quiet ride. I would compare it to driving your car on the interstate with the windows up (underskinned) vs windows down (not underskinned)

Picked up a good 2-3 mph

Water/wake off the back of the boat is much smoother.
I skied yesterday too, shot right up, that extra couple of mph made it soooo much fun

I'm going to try and upload some photos of my work. Maybe throw out some ideas how to do it better. And a list of material and prices.

 

[rickdb1boat]

Re: Underskin advice

Hi Kitch. I'd like to see the pics of your work. I have the same boat and motor, only mines a 2007.

 

[Kitchen363]

Re: Underskin advice


Here is what I attached to my frame under the boat. Just cut to size, peel the tape and stick. Window seal tape.

All Done!!!

[/ATTACH][/ATTACH]

Here's some tips, try to overlap every seam.
I added some 3 1/2" strips down the sides. If I had to do it again I would have got the strips bent in a 90 degree angle. This would help the edge of the big sheet to be stiff between the braces near the sides.

The rivets were not bad at all, it went quick after it was held in place with a few rivets. Hands were fine after the job.

I used three 4 x 10 sheets of 0.050 3003 aluminum $250
Window tape $free from my Dad
Box of 500 1/8 x 1/4 Stainless rivets $37
Less than $300 For a much improved ride

 

[rickdb1boat]

Re: Underskin advice

Looks just about like mine. Nice job...