This is a base level conversion kit to make your DragonFlight 95 into a class legal US1M. This boat conversion is sometimes known as the Dragonstein. https://www.rcgroups.com/forums/showthread.php?2964063-DragonStein-DF95-to-US1M-conversion

The main part needed is the tailpiece. It extends the hull length to meet the class minimum. I have been calling mine the “stinger”.

The second part extends the keel fin. When used with the stock DF95 ballast bulb, it extends the full depth to just under the class minimum. It is optional and not required to be class legal, but you should use it!

-These min. and max. measurements are based on US1M 2017 class rules.

There are FDM and SLA versions of each part.

US1MstingerFDM.stl - The FDM tailpiece was my original design. It is bulkier than the other version, but prints well on a filament printer. It will print directly on the bed with no supports needed.

US1MstingerSLA.stl - The SLA tailpiece is my 2nd version. It is lighter and sleeker. I had some folks ask if this scoop holds water. It does not. It self bails just as any boat does. I have not tried to print this with an FDM printer.

US1MstingerSLAsupp.stl - This is the pre-supported SLA model as well. It works for me. If it doesn’t for you, then use it as a guide to do your own.

keelspacer.stl - This is the basic heel spacer file.

keelspacerFDMx2.stl - There is the FDM specific file that is actually 2 spacers placed so that they allow cooling time on each layer as the head moves from one to the other. Their thin ends are placed so that any stringing happens there. This will make a nicer print than just printing the single spacer alone. No supports needed. Print on the bed.

keelspacerSLAsupp.stl - This is the SLA pre-supported keel spacer version.

Print Settings

Rafts:

No

Supports:

Notes:

FDM notes -PLA+ or PETG .40 nozzle, .20mm layers, 4 walls, 15% infill to start. You may need changes to achieve your best print

SLA - Epax soy-based or water-washable resins. 05mm layers.

All STL files are oriented to be ready to drop on the build plate.

Post-Printing

Assembly

You will need the following extra parts or their equivalent:

One M3 X 50mm stainless steel socket cap screw (Amazon) to bolt the fin on with the keel spacer installed.

Two DF65/95 backstay hook screws (SKU:881551 @ radiosailing.net) to attach the tailpiece.

1/4 to 1/2” double sided tape of good quality.

Tailpiece:

1. Print and finish your tailpiece as desired. I just sand the bottom a bit and use the print as is. You may want to make it slick. You may want to permanently attach it and fair it into the DF95 hull.
2. I use 1/4" double-sided sailmaking tape to attach the tailpiece.
3. The tailpiece should align on the tabs and be centered side to side. It does not fit flush. There is a small step in at the rear radius of the DF95 and it sits just inside that. Once i am happy with the mounting location. I drilled two small holes in through the hull.
4. Carefully install your screws.
5. I use a small piece of line to attach the tailpiece to boat, just in case.

Keel Spacer:

1. Make sure the spacer drops in easily into your keel box. Make sure your new bolt drops easily through the hole. You may need to file, sand, or drill to get a fit with good clearance, but mine drop right in off the printer. This slightly loose fit will help the parts all mate easily when assembled.
2. Insert the spacer, keel fin through the bottom and the bolt from from the top. Tighten as needed. Be careful about over tightening this bolt.

Sail: You are own your own for now, but you can make a DF95 A+ sized rig using the DF95 rig hardware kit, plus a carbon mast tube extension. Look at plans for US1M B-rig measurements, these work well with the DF95 stock ballast as a light air rig. The blend of these will make a good sail, as pictured above.