I embarked on sharing my CWMouse Iambic Paddle with others a year ago. I finalized the design, manufactured 100 units and sold all of them during 2025. The reviews on ebay, eham and amazon are overwhelmingly positive. I had only two “warranty” repairs - both due to exceeding PLA storage temperatures (both in locked vehicles in summer heat).
Lessons
Material Science
The biggest lesson is that I should have used PETG instead of PLA from the beginning. Having temperature warnings is not enough and I suspect a few more units have “melted”1, but their owners didn’t contact me for a replacement.
After calibrating my 3d printer for PETG, I made a few special-order units in PETG. I learned that despite using same printer and optimal settings, there were dimensional changes making PLA-designed, but PETG-printed, paddles in need of tweaks to assemble correctly. Parameterizing the model for different materials, or maintaining a PETG fork, is more overhead than just switching all production to PETG.
A surprising finding was that while PETG does print slowly, it is much less significant impact on overall print time than that suggested by extrusion speed. A lot of time during a large bulk print is spent traveling between pieces and with Delta Printers it is very fast.
Mechanical strength, temperature resistance and (in my opinion) nicer surface finish are some of the PETG advantages over PLA.
Commerce
Different stores have very different reach and costs.
Ebay is very popular with Ham Radio Amateurs and provides not only a store, but also a search/advertising service. They have the best international shipping logistics and prices. I sold many CWMouse units to hams around the world! Ebay services are reflected by their high fees. The down side of Ebay is that they are very protective of their position and punish sellers for sharing their web site or email address - they want ebay exclusive lock-in.
Etsy sold only two units. It has lower fees, but does not appear to have many Hams frequenting it.
Amazon is painful. First I tried FBM2 which had a few downsides and later switched to FBA3 which had ever more downsides.
FBM cannot offer prime shipping, as I’m responsible for packaging, dropping off at USPS and logistics. Amazon very aggressively nags about shipping within 24h and keeps a scoreboard. Even when shipment is delivered late due to USPS, they count it against the seller.
FBA requires sending bulk package of a dozen+ units, which is a lot of work at-once, but no more per-unit effort than when I make small batches on-demand.
Disappointingly, all of my FBA bulk shipments were delayed in warehouses for well over A MONTH, before Amazon started selling them. Offering Prime is convenient for customers, but all of this is reflected in high fees to Sellers.
My last FBA shipment was lost. This was extremely disappointing, as a large part of my motivation is knowing Hams are using my paddles. To add salt to the wound, Amazon offered to reimburse me for only a THIRD of my price for the units they lost. There is still a small chance that after the holiday rush, 12 units of CWMouse will be found and offered for sale. Suffice to say, once this situation runs its course, I’m stopping sales via Amazon.
Stripe is the best experience for a small operation like me. They are an online payment processor with a small fixed fee per transaction and very easy to integrate with web sites.
CWMouse is already “out there” and I rely on search engines and word of mouth for sales via Stripe from my web page. All prices reflect middle-man fees, as cost of my time is fixed. If customers find CWMouse via search engines and purchase using Stripe link on cwmouse.com, they’ll save as much as $10 per unit compared to other stores.
New Products
In 2025 I built a QRP-Labs QCX-mini and bought an assembled QMX. I designed a protective magnetic cover that works with both. The cover doubles as an angled stand during operation which improves screen readability. I added this product to my web page and priced it competitively.
The production of the original CWMouse is coming to an end. I have enough components to build at most half a dozen more units in PETG. Separately, if Amazon finds my bulk shipment, a dozen more PLA units will be made available. After that, I’m switching to uCWMouse4.
uCWMouse is the outcome of my CWMouse experience. It is designed to be printed in PETG only. It is based on the same switches and the same paddle geometry as CWMouse. It has the same finger-feel as CWMouse. What is different, is that I further reduced parts count, optimized it for easier+faster assembly and it is even smaller and lighter than the original. It will be available in 2026.
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melted: PLA deforms at 140F which is easily reached in a locked car on a summer day - see post ↩︎
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FBM: Fulfilment by Merchant - stock is managed, packaged and mailed by the Merchant -> me. ↩︎
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FBA: Fulfilment by Amazon - prepackaged and pre-labeled units are sent in bulk to Amazon which ships them on-demand from their warehouses. ↩︎
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u: micro: as in - an even smaller CWMouse :) ↩︎