Wednesday, June 24, 2015

Grumman SP145 - Part 2: Choosing new floor material

I researched a lot of options for new floor material which I will list along with pros and cons and maybe this will be of interest to someone facing the same decision.

When dealing with aluminum boats you should beware galvanic reactions which can occur with dissimilar metals + an electrolyte. Examples would be steel screws into aluminum + salt water, or pressure treated wood (copper + salt) against aluminum.

Plywood - The original manufacturer used plywood, stainless steel screws and carpet. Occasional moisture or splashes will not hurt the plywood but my boat lives outside. Carpet would only make things worse by trapping moisture.

Painted Plywood - Painting is a good option, looks pretty good and lasts for years. The painted plywood the previous owner used held up for over six years with no sign of deterioration.

Epoxy over plywood - A excellent option that is expensive and time consuming but very long lasting.

Pressure treated plywood or decking - Pressure treated wood in contact with aluminum will cause galvanic corrosion because of the copper and salts used to treat the wood. The best advice is to allow the wood to dry well, preferably for some months, before installing. This is because pressure treated lumber has fairly high moisture content when you buy it and that additional moisture will only accelerate the galvanic corrosion. On top of that, you either have to seal the plywood or seal the aluminum so they can never come into contact.

There are new treated plywoods rated for aluminum contact but if you read the fine print that is only under dry conditions. They still contain copper and salts and will cause galvanic corrosion if they get wet.

Marine grade plywood is just pressure treated plywood that costs twice as much. There are other options such as MDO which is very heavy and very expensive.

Composite decking - Seems like an ideal floor material as it doesn't corrode aluminum and often comes with 15-20 year warranty. But it's also very heavy, gets very hot in direct sun, expands and contracts more than wood, and is relatively expensive.

Cedar/redwood/cypress or other rot resistant wood - Unfortunately the same oils that provide rot resistance also tend to corrode aluminum. But the plus side is that nothing beats real wood in appearance.

There are serious pros and cons to every flooring option. In the end I chose Eastern red cedar because it's extremely rot resistant, beautiful, plentiful and inexpensive in my area. I tried to use nothing but red heartwood (white sapwood is not rot resistant). A shot of spray paint over the aluminum will hopefully be enough to prevent corrosion. For fasteners I stuck with stainless steel. I figure if the manufacturer chose stainless who am I to second guess them.

Freshly planed ERC. I wish it stayed this color.

Monday, June 22, 2015

Grumman SP145 - Part 1: Nasty old floor

My aluminum boat is in dire need of a new floor. The original floor was carpeted plywood which the previous owner covered with painted plywood. The painted ply held up well but the original floor was turning to dust so it all needed to come out.

The above pic is after I removed the painted plywood, what you see is the original carpeted floor or what remains of it.

The hull bracing and bait well were fastened with aluminum blind rivets so removal was just a matter of drilling out the center and punching them through.

Clean and ready for a new floor. 

Thursday, May 7, 2015

Swing Arm Task Lamp

Swing Arm Lamp

Months back I made this articulated arm lamp but the arms were too narrow and didn't develop enough friction to hold the lamp without drooping over time.

I made this swing arm lamp as an improvement. It reuses parts of the original hinge with a longer central pivot.

The bottom arm has a dowel that engages one of three notches in the upper arm. The notches are only about 3/8" apart but allow approximately 20" vertical movement.

Lowest position
Middle position
High position
When swung left it lights up my drill press table. When swung right it sets above my lathe's headstock.

Here is a free plan. You will need to adapt it to whatever lamp you have. 

Friday, May 1, 2015

Rockwell Delta 46-111 Lathe, Part 3.1: Variable Speed

This will be my 2nd lathe converted to variable speed.

This is the lathe, a Rockwell 46-111, circa 1974. Which I have finished repainting. You can read more about the lathe in previous blog posts.

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This is the motor: 1.5hp at 90 VDC. Big improvement over the 1/2hp original motor. It's from a popular brand of treadmill. Originally it had a digital control panel and extra boards but I eliminated all that and attached a 5k linear taper potentiometer from Radio Shack. The treadmill cost me $30. I listed the control panel on ebay and it sold within hours for $35, plus $25 for the scrap metal and I came out ahead.

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Two things left to do.
  1. Make a new motor mount or modify the original. Shouldn't be difficult.
  2. The DC motor has a flat pulley but the lathe has V pulleys.

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The most common solution is removing the flywheel and attaching a V pulley. I could do that but then I lose the torque benefit of the flywheel and extra torque is always welcome on a lathe. 

This chap had a great solution. Unfortunately I do not have a metal lathe and at 1-1/8" dia the flat pulley on mine is too small to accommodate a V belt. 

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So I'm thinking I will make a 2nd pulley that will slide over the flat pulley. A 2" pulley would put me in the range of 3500 RPM at the spindle. I'll soon let you know how well it works.

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Wednesday, April 29, 2015

Rockwell Delta 46-111 Lathe, Part 2: Paint

Indexing pin and tail stock levers that originally were bare metal but I painted them black to protect against rust and improve appearance.
Anything I could fit in a toaster oven was baked at approximately 150 degrees Fahrenheit for two hours. Not sure of the exact temperature but you could touch the parts with only mild discomfort. The paint instructions said not to exceed 190 degrees.

Freshly repainted tool rest and banjo. The color darkens when dry.

Repainted bed. Same color as tool rest but the paint has dried for a few days, and shop lighting is less intense.
Better than a new dog. That logo pops!
Tail stock back together with nice new paint, looks better than 1974.

Next steps are reassembly and conversion to variable speed.

Sunday, April 26, 2015

Goodell Pratt bench lathe, Part 4: reproduction knob

My first try at a reproducing the missing tool rest knob. I goofed and made the diameter a bit too small but otherwise it looks pretty good. I'll make another but this was good for getting for the dimensions and general shape. We'll call it proof of concept.

I started by gluing up scraps of maple and beech. Beech is on the outside right.

I always forget to take pictures but I measured the original with calipers, transferred that measurement to the wood blank using the same calipers and a parting tool, then blended the curves.

Before cutting to final size, I drilled a 3/8" hole through the center and installed a 1/4-20 threaded insert. I also marked off 12 equal divisions around the perimeter using the indexing wheel of my lathe then ground 12 grooves using a Dremel. I didn't bother sanding out the burn marks because this will be painted black eventually.

After friction polish (shellac/oil). Not shown here but I also seated the threaded insert a little deeper.

Comparison with original:

Friday, April 24, 2015

Rockwell Delta 46-111 Lathe, Part 1: Overview

Picked up a 1974 Rockwell Delta 46-111 wood lathe. This was a light duty lathe sold by Delta for over three decades, from the 50's - 80's. It is a "gap bed" lathe. The theory being you can turn a larger piece near the head stock but the gap is so short that it would only be useful for turning plates or platters. Besides a little surface rust, the lathe is in excellent condition and included the original 1/2 hp motor and sheet metal stand.


  • 11"/14" swing
  • 36" between centers
  • 1"-8 spindle threads
  • #2 Morse tapers
  • 4 speeds (990, 1475, 2220, 3250)

In the late 60's or early 70's, Rockwell wanted to reduce cost so did away with the cast iron stand in favor of sheet metal which rattles like a meth head on a thunder machine if not braced and fastened to the floor. They also changed the tailstock from cast iron to cast aluminum. At least they upgraded it to a fast lever locking system instead needing a wrench.

The 46-111 indexing wheel has two rows. An inner row with 60 holes and an outer row with 8 holes. The manual includes a chart to tell you the #holes for common divisions.

Next step will be a good scrubbing, repainting, reassembly, then converting to variable speed.