Christian Ed and Hobby info - Beavertail Stealth 2000 Keel Repair

Overview

Materials and Tools

Welder Setup

Welding Thin Stuff

Welding Practice on 1/4" HDPE

LDPE on HDPE

Fixing my Wheelbarrow

Keel Buildup and Repair

Summary

Long-term Update

Overview

I originally thought of making a generic page on plastic welding. But there are plenty of excellent articles and videos covering the subject, so I decided to focus on plastic welding as it applies to maintaining my boat - the Beavertail Stealth 2000.

When this page is fleshed out, it will cover:

- Keel buildup and repair
- Hole and gouge filling
- Modifications and accessory mounting.

The Stealth 2000 (and all of the Beavertail boats) are made from roto-molded High Density PolyEthylene (HDPE). HDPE welding requires a air or tool temp of about 580*F and HDPE or LDPE filler material.

One problem is that I don't know how thick the plastic is on the keel - that's important to keep from burning through when welding. I suspect that the keel plastic is about 1/4" thick when new.

Materials and Tools

The price of tools follows the axiom - "you get what you pay for". If you want a plastic welder that runs like a nice MIG - you're gonna pay some serious money. On the opposite end of the spectrum you can get an 80 watt soldering iron with a spreader tip for $16 at Harbor Freight. Or if you already have a shop compressor, you can get an 800watt hot air welder for ~$50. My garage is chock full of Harbor Freight junk, er I mean tools.

You can use either LDPE or HDPE as filler material for HDPE welding (but not the other way around). HF doesn't sell either LDPE or HDPE filler rod, but there are online retailers who do, and offer it in different colors and shapes. You can also make your own filler rod if you have some scrap HDPE cutting boards lying around, and you can scavenge LDPE material from squeeze bottles, etc. Basically you just need to learn the triangular recycle symbols with 2 or 4.

Welder Setup

You don't need much pressure (5psi), but you do need a continuous supply of air for a long period of time. My 4.5 gallon 150psi compressor would run a 50% duty-cycle supplying the air (and I needed a moisture trap). I realized that I didn't need that much air so I looked to two other sources I have on hand. One is a portable HVLP paint sprayer that could provide 100x more low-pressure dry air than what I needed (but it is noisy). The other is an airbrush compressor. I went with the airbrush compressor.

Note: The Harbor Freight welder I am using must always have a continuous air supply or you will burn it out. Anytime the unit is plugged in, the air must be flowing. Don't believe the temperature control knob, (Chinese quality), it is best to unplug it when not in use. You must keep the air flowing for at least 5 minutes after unplugging the unit so that it will cool down. It has a rather high thermal mass and does not cool down quickly. But this is not a treatise on tool care, so burn it up if you want to.

Welder heating element temperature and air volume are interrelated so I chose to fix the air volume and adjust the temperature. I have an air-flow valve that I use for reducing the flow to air tools, so I could've varied both airflow and welder temperature. But I discovered through practice that I could get close enough varying one variable - so I left air-flow fixed.

If there is one thing I would add to this welder, it would be tip air temperature readout. I really don't like the bobbing in and out method of temperature management.

Air Brush Compressor

Welding Thin Stuff

The problem with the Harbor Freight welder #96464 is that it doesn't come with different size tips. The stock tip simply delivers too much heat to be usable for welding thin stock. So I modified the setup as follows:

1. I'm using an airbrush compressor - designed to run for long periods. 20 psi max at 0.5CFM, so it doesn't create moisture. If I didn't already have the air brush compressor, I would use an inline filter and regulator. Note: the real CFM increases as the pressure is reduced, so the LFM (the important metric) is very similar to having my shop compressor hooked up and set at 5psi. But I don't have an LFM flow gauge, so I'm going on how the flow feels to touch.
2. I used a short piece of 1/8" copper refrigeration tubing as a reducer. Shaved the end down a touch and tapped it into the mouth of the stock tip. Note: A shorter piece would allow you to easily drill out the opening to open it up a little - make your own tips.
3. Set heat adjustment between 6 and 8

Harbor Freight Plastic welder with modified tip

Copper Tubing Reducer in stock tip for welding thin stock

Welds on 1/8" cutting board using scraps for filler

Welds on 0.030" cutting board using scraps for filler

Welding Practice on 1/4" HDPE

I have 1/8" and 3/16" HDPE welding rod. I got both sizes because I had no clue about which to use. So I practiced with both on some scraps of 1/4" HDPE. A big part of the practice was to discover the correct heat setting based on weld results.

Spools of welding rod

What I discovered pretty fast is that too high heat will oxidize the plastic (see the brown). 1/8" HDPE rod and #7 heat setting

And if you continue to raise the temperature, the weld will oxidize and become very weak. The following picture shows a double pass on both sides using 3/16" HDPE rod and a heat setting of #8. Although it looked strong, I broke this apart with my fingers. I did this deliberately to see what would happen.

For what I was doing, given the LFM of the air-brush compressor, using the stock tip, 1/8" welding HDPE rod and a heat setting of #6 gave the best results.

I cross sectioned some of my welds to better understand what was happening

Good adhesion on both the left and right sides. 1/8" HDPE rod and #6 heat setting

Good top and bottom adhesion. 1/8" HDPE rod and #6 heat setting

And the following picture shows a weld that didn't adhere on the right side. 1/8" HDPE rod and #6 heat setting

So what did I learn from this?

1. Air temperature, air volume and rod diameter are intricately interrelated. This is as tricky as welding with Oxy-Acetylene. I understand why they use a shield gas when welding thick stuff.
2. Visual inspection of the weld process needs to be done in the 1st inch or so. I know stopping a weld is icky-pooh for a number of reasons, but so is laying down a worthless bead.
3. Visual inspection is hard to do. I'm not an expert. Cross-sectioning one of my welds showed poor adhesion - visually I thought it a good weld. There is a shiny edge that forms just past the bead edge on a good weld.
4. I watched a number of YouTube videos on how to apply the heat and add the rod. It is not the same as metal welding. I would say it is closer to hot-gluing. In any case, a person should take advantage of the online training available.
5. I thought that watching the bow-wave of the rod melting was the best way to judge the weld quality. Now I'm thinking I should pay more attention to what is happening behind the rod. I think I need to see that shiny edge forming.
6. Practice, practice, practice with the materials you are going to use before starting in on the final work.

LDPE on HDPE

LDPE welding rod melts at a lower temperature than HDPE. The advantage here is that the rod lays into the joint easier, so it is less likely for the operator (me) to overheat and start oxidizing. I cross sectioned a T-weld and you can clearly see the difference in material densities. It first appears that the adhesion was poor, but I couldn't pick and peel the fill material nor could I break the pieces apart - so I was faked out by the density difference. I did overheat one weld and got some brown oxidation - that weld was very weak. So no magic with LDPE but it is interesting.

LDPE filler rod on HDPE base - a lot stronger than it looks. The densities are deceiving.

I like the ease with which 1/8" LDPE rod lays down. But it is just as susceptible to oxidation as the higher melting point HDPE - perhaps more so given the lower melting point. But I understand why people like using it.

Fixing my Wheelbarrow

I'm sure anybody who's ever owned a plastic wheelbarrow has destroyed it by dropping a 24" round of Douglass fir into it. Well at least thats what I did. I wasn't looking for an excuse to play with my welder - it just happened.

In the past I would've thrown the wheelbarrow away, (they're cheap), but I decided to fix this one. The recycle symbol said it was HDPE and I'm guessing it is 3/16" thick.

Drilled the ends, sanded the edges, and welded a single pass of LDPE rod.

Reinforced the underside with a strip of 1/4" HDPE. The white weld on right is HDPE rod. The clearish on the left is LDPE.

So I'm sure this looks like another way to justify buying a plastic welder, and it is. The more I weld, the more confident I am about tackling repair jobs.

Keel Buildup and Repair

The above picture shows the typical road rash that accumulates on the keels from dragging the boat on concrete and asphalt. This picture shows the wear from 10 months of use, loading and unloading at public boat launches, my driveway, etc. Now the keel hasn't worn through yet, but I want to head it off now so that I don't have to deal with leaks later.

What I want to do is attach a thick piece of sacrificial HDPE on the points on the keels that suffer most from dragging. I don't want to go overboard on the thickness as the Stealth hull already has a lot of drag, and also because trying to heat & shape a 1/2" thick piece of HDPE isn't trivial.

I went to my local hobby plastics store and picked up 1/4" HDPE scrap. Turns out that 1/4" is about the thinnest they typically work with. The 1st 5 pounds are free, but I didn't really need a bunch, so I took a single piece.

HDPE sheet cuts easily on the table saw. My keels are ~1" wide, so I cut four 3/4" strips and then chamfered the weld side on the table saw as well.

The 1/4" thick material is thick enough to provide some protection, and thin enough to conform to the gentle curve of the keel.

Took me over 4 hours to do this. Good thing I don't do it for a living. Most my time was spent:

- Experimenting with 1/8" HDPE and LDPE rods to see which gave better results (LDPE did)
- Tacking and forming the 1st piece (after I discovered duct tape, things went faster)

LDPE rod was much easier to weld with - time will tell if it was strong enough for the job. The Stealth Hull is HDPE according to the manufacturer, but there must be a difference between the HDPE strips I was using and the hull material because the hull definitely seemed to melt faster. And this made welding with HDPE filler rod more difficult and slower. I did put down some long beads with the HDPE rod, so it does adhere, but I found the 1/8" LDPE rod faster and easier.

I don't know why it took me so long to remember duct tape, but once I taped the pieces in position for short beads (tacking), things went faster. It is still a bit of a challenge to form 1/4" HDPE over curves, but I figured out how to heat-bend-repeat and get it done.

I used the welder without the reducer - just the stock tip. Setup just like practice. The hull material was about 47*F and the welding was done outside. Given that HDPE is not a great thermal conductor, I don't think the ambient temperature mattered that much.

Initial tacking and dinner

Heating the bend with the welder and tacking with LDPE rod.

Full weld using 1/8" LDPE rod

I thought that heating up a piece in the oven might be the trick to easier forming over curves. And it might be for really complex shapes. But it was overkill for my job. And I over-heated the material which is why it went clear. Once it cooled a little I was able to use it. And my El-Cheapo die grinder allowed me to shape it "good enough".

280*F in the oven was too much. I was trying to soften it to make forming easier.

But I held it down with duck tape and formed it.

And welded it up with mostly LDPE filler rod.

My $10 Harbor Freight die grinder with a shaping bit was handy

And when I was done, I had reinforced the areas that grind when dragging and loading/unloading.

The rear of the hull - notice the grinders by the handle

The front of the hull

Summary

Time will tell if this repair job of mine will hold up. If it doesn't, I'll swallow my pride and update this blog with the results. It worked fine with my grandson and I - no leaks, no funny pulling to one side or another and the weld job is holding. I drug it around a fair amount on concrete and gravel.

For now, I feel I have a handle on welding stuff to the Beavertail Stealth 2000. I have $120 invested in the Welder and a large supply of different filler rod ($50 for the welder, $65 for a lot of rod for a lot of different materials). I plan on tacking a Ford Explorer bumper/grill repair next. And I like the fact that I can fix plastic stuff now in the cases where JB Weld just doesn't cut it.

I'm already thinking about modifications I can make to the boat before next duck season. And I think some mortar-tube rod holders would be nice for this fishing season. Being able to weld opens up a lot of possibilities.

I might have bought the self-contained air-supply welder had I not had multiple air sources on hand. But a fellow can always use the outlet of a vacuum cleaner, or an old hair-dryer with the heating element disconnected - my point is that there are options.

I hope you find this write-up helpful.

Long-term Update

So the original grind strips have done their job well - no complaints from me. But I thought I'd share some observations, after a lot of use.

- The rear of the boat is what needs protecting, the front of mine looks untouched.
- More sacrificial material needs to be added by the rear handle. The two "grinders" I added should've been taller to last longer.
- I'm seriously considering using steel to augment the HDPE runners I put on the rear keels. My thought is that a steel layer over the HDPE would reduce the friction when dragging and last longer. But I dont know how to attach a metal strip.

I'm quite happy with the job I did - I saved myself a lot of grief. I've heard horror stories from "Dave in AZ" ( ) as he worked through patching the keels in his boat that had worn completely through.