Reproducing Old Parts Using the Most Efficient Techniques

I am currently working on the restoration of a 1936 Gar Wood 18-foot Utility. This has been a long, ongoing project but unlike many, it seems to be gaining momentum. This project has had some challenges. For example, it had the original Chrysler Ace engine I intended to restore. After taking things apart, it was clear the engine had spent some time underwater years ago. The internals were rusted beyond recognition.

The original cast iron exhaust elbow on this engine had been “blown through” some time ago. Apparently this style elbow was known for having a hot spot where years of use burned through the iron. The hole was “repaired” by brazing. While this probably worked to a degree, it sure did not look pretty.

On this particular item, the most effective way to have this dealt with was to have a new elbow cast. With the help of Bud Brackett at Maine Classics, I have a new elbow in hand. The process went something like this:

  1. Send the original to Bud
  2. Bud cleaned up the original casting by grinding away all of the brazed weld. He cleaned up the original by using fillers, sanding, etc.
  3. Build a sandbox and a core to cast the new part with the void in the center
  4. Send off to the foundry to cast in iron
  5. Do the finish machine work. This included drilling the exhaust elbow mounting holes and machining the neck down slightly to perfectly fit the rubber connector between the elbow and the iron pipe.

There was a bit of a back-and-forth dance to all of this. One issue becomes the availability of the soft copper tubing to have the new exhaust pipe made (that is another challenge). Next, I had to work back from that—knowing the OD and ID of the new copper exhaust, I had to make sure the connecting rubber and exhaust elbow were a compatible fit. There were slight modifications made to the elbow to make all things work together.

The reason I named this post “Using the Most Efficient Techniques” is that casting was the most efficient way to create an accurate duplicate in this instance. I will follow this post up with another reproduction scenario that goes a different direction, using 3D printing for a plastic prototype and 3D printing an actual usable metal part. Different techniques for different challenges!

The elbow appears to be from an ace rather than a crown

I am thinking you may have misread. Yes, this is an Ace.

This is at the other end of the reproduction spectrum. The fairlead on my old Gar Wood was original, but a bit worse for the wear. Two mounting holes had been ripped out. The hole that is bored through from fore-to-aft was dramatically off center (likely off from day one) and the overall piece was losing its shape—wavy, edges were no longer straight, etc.

My son, who is CAD proficient, took accurate measurements from the original, and created a new digital 3D model for the part.

From there it was just a matter of finding an online resource for 3D printing. I first wanted a plastic part to check the fit against the bow stem, the overlap onto the cutwater, etc. This piece was a lower resolution print so there is some texture to it. Everything was perfect so now it is off to the same printer to have 3D printed in Silicon Bronze. The bronze will be printing in a much higher resolution so it texture will be minimal.

Disadvantages of this method are few:

  1. You must have the skills to create the part in CAD modeling software. I was lucky as my son has those skills and knocked this part out in about 30 minutes.
  2. Cost for 3D printed metal is still “right up there”

Advantages of this method are:

  1. Creating the 3D model is much quicker than creating an actual pattern to use for casting.
  2. Quick! Casting one of something is doable, but there is typically a decently long lead time.
  3. The large diameter hole that runs fore-to-aft can be an accurate void in the “print” making mechanically milling this unnecessary. For the record, little “positioning dimples” were included in the 3D model to create marks where this part is to be drilled. Full holes could have been included in the model and print, but I wanted the flexibility to defer the diameter until later, so I could check the hole diameter and countersink to the actual screws.
  4. The finished metal part will have very low porosity. Much lower than cast bronze.

Cost for the 3D printed plastic prototype was $90.00 with a two day turnaround. By the way, there are hundreds of online resources for having a 3D model created of your part. In most cases you need to ship an original to them. Many of these resources can scan your original part as a starting point in created the cleaned up model. Four example, if you have one cleat but you need three more, this is a great way to go.

Cost for the 3D printed plastic prototype was $90.00 By the way, there are hundreds of online resources for having a 3D model created of your part. In most cases you need to ship an original to them. Many of these resources can scan your original part as a starting point in created the cleaned up model. Four example, if you have one cleat but you need three more, this is a great way to go.

LOVE THIS series

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I am a sucker for authenticity. It’s not for everyone, I know. But, my goal with restoration is to be faithful to the original methods. Does it improve the performance of the boat? No. Does it mean the restored items will need less attention over time? Not necessarily. But, the restoration does serve as a pretty darn faithful example of how these boats were made back in the day. To my eye, if parts are reproduced with an eye towards visual and functional accuracy, they should be very difficult to discern from the originals.

One of the things I have always favored is the look of the original galvanized, rolled and soldered fuel tanks. Most held up well for 50+ years—and that was with typical use, stored out in the elements, etc. A new tank, built with those methods, especially with a boat seeing less use, and pampered in a garage will last a long, long time.

I needed to replace old tank on several boats. I can go into more of the “why,” but these old tanks were always much worse off then meets the eye. When I set a goal to build a faithful reproduction tank, the first thing I needed was the bronze fittings—scavenged off of a donor tank, purchased off of eBay, or whatever. The tank fittings themselves have gotten harder and harder to find.

Pre war tanks used by Chris-Craft and Gar Wood were largely the same construction, ie: rolled galvanized sheet metal with a top seam (I think this is referred to as a flat lock seam). The ends were also sheet metal, with flanges that were then wrapped over the ends of the tank, and then peened tight. All of the seams were then flowed with solder. The tanks for each manufacturer were so similar that they may have been sourced from the same vendor.

Pre war fittings were generally cast bronze flanges of various sizes, that were affixed to the tanks with rivets, with their mating surfaces also flowed with solder. ) Post was tanks were a different animal). The big flange received a threaded copper pipe with a large jam nut for the fuel fill. Tank vents, (if the era dictated that) were typically NPT fittings—standard plumbing fittings of the day. The fuel pickups were another matter. Most tanks had a hexagonal fitting that threaded into a flange for the fuel pickup. Very early tanks were actually bottom (gravity) feed fittings on the tank bottom. These fell out of favor when Coast Guard regulations said so. The fuel feed fittings were move to top mount, which meant there had to be a fuel pickup tube that extended to the bottom of the tanks. What looks like a simple hex fitting at the top of the tank is actually an assembly—the hex fitting itself, which has a reduced diameter neck that accepts a straight copper pickup that is soldered in place. The length of that pickup varied depending on the tank diameter. There is also an important fitting at the top of the fuel pickup, which was an anti-siphon feature. There is another hole in the neck that is drilled and tapped to accept a carb jet with a given orifice size.

Out of all of these components you are doing well if you have a good donor tank. The tanks are worthless. The flanges are worth keeping track of.

In my case, I had some, but not all of what I needed. I watched eBay for years, and never really case arose the right fittings. So I proceeded with making them.

Unlike my previous posts which utilize 3D printing, casting etc, I decided to go a different route and have these machined on a CNC controlled mill. By using this method, I was able to get all of the geometry exactly right including the I.D. diameters, and the thread pitch. in this case all of the threads were machined.

The issue with machining these is they just did not have a cast look—which is important for them to not look like computer machined reproductions. All this took was some time with a pneumatic needle scaler. I pounded the heck out of them with the scaler, giving them an authenticate sand cast look. All of this work got painted a Gar Wood green-gray color, but even under the paint you can spot the stuff that looks too new.

The net result is a brand new fuel tank built exactly like they were in 1936. Again, this is not for every one, but it pleases me!

Original Tank

Machined Brass Fuel Pickup With Soldered Pickup Tube and Anti-Siphon Fitting

Closeup of Fuel Pickup Hex Fitting And Machined Flange (Made to Look Cast)

Detail of End of Sheetmetal Tank. The Recessed Bead is to Support the End of the Tank While the Craftsman Rolled and Peened the End Caps in Place

All in Place and Ready for Cleaning and Paint


I LOVE LOVE LOVE this series Bill.

Thanks Matt. Hopefully it is of interest to some who face similar challenges.