S.M. U-1 (a new RC project)

[DrSchmidt]

The backside of the hull molds are done. Next will be the mold for the conning tower. As the deck is curved, a flat underside of the tower won't do. So the first step is to pull a decks section from the hull mold that will act as base for the sail mold. To make the interior of the sail mold accessible, I wanted to make an opening in the base, a slightly smaller that the sail contour. Therefore I designed and 3D-printed a plug. I adjusted the hight of the plug using polyester filler and then inserted two threaded insets in the base of the plug. Then I positioned the plug in the center of the deck using a cross made of 2 mm GRP sheet. The cross ws screwed to the pug and fixed to the mold using clamps. I used PVA as parting medium. Then I printed two bulkheads and secured and sealed them using putty. Again the plastic was coated with PVA. Then I applied a first layer pf surface resin and cotton flakes as coupling layer. After curing, I filled laminated the remaining voids using glass and carbon fibers and filled the remaining voids using resin soaked glass shreds .

[DrSchmidt]

Pulled the modified deck section from the mold....no problems this time...and cleaned the seams. Tomorrow the backside will get a layer pf GRP so that the piece gets a nice surface on the backside, And thn I can proceed to get the master of the coning tower fit to the deck and prepped for making its mold....

[DrSchmidt]

I applied a GRP backside to get an even and clean surface. The excess GRP was then removed using an angle grinder, my Dremel and some files and sandpaper. Nasty busyness, but now I have a nice tool and can start prepping the conning tower.

[He Who Shall Not Be Named]

This is primo, graduate-level tool making. Laying up a portion from the hull tool to create a fixture/extension to a sail tool, eliminating any indexing issues between eventual GRP sail and hull parts. Sick!

(furiously taking notes... can't have this German taking ME back to school!).

Wow.

David
A Bit Humbled

[DrSchmidt]

Thanks David. It's a method I was taught when building molds for RC planes. To get a seamless transition between the airfoil and the fuselage you'd first make the wing mold and then pull a center section from it that would then go onto fuselage master. Same here. For flat decks it's not worth the effort, but with the bend deck of the U1, it will make things much more easy.

[He Who Shall Not Be Named]

Thanks David. It's a method I was taught when building molds for RC planes. To get a seamless transition between the airfoil and the fuselage you'd first make the wing mold and then pull a center section from it that would then go onto fuselage master. Same here. For flat decks it's not worth the effort, but with the bend deck of the U1, it will make things much more easy.

Now I have a better idea of what you're doing. I'll file this trick away. Thanks.

[DrSchmidt]

Started working on the master for the conning tower.To be able to position the tower in a fixed position, I glued two threaded inserts into the bottom of the master. Now one can easily mount and fix it on the deck section using two M5 screws. Next step is to fill the remaining gap between tower and deck using 2K polyester putty (Bondo basically). Next job will to sand the master and then some filler....

[DrSchmidt]

I sanded the excess putty flat and gave the master a final sanding with 800 grid paper. Then I mounted the tower again on the deck section, inserted two 2,5 mm diameter steel rods in the holes for the periscope and then everything was coated with 2K primer. Due to the heat here in Germany the primer started to cure just before the third layer resulting in a very rough surface. But that will son go when the master gets its final sanding.

[DrSchmidt]

Sanding down of the conning tower didn't really work out as well as I'd like to....so the thing went into the bin and I started printing a new one. No half-assed things....

[He Who Shall Not Be Named]

Keep plugging away... this is going to be a beaut!

[DrSchmidt]

So...I printed a new master. I altered and improved a bit on the printing strategy, too. Looks good for a second try.

[DrSchmidt]

Hitory repeating....again a threaded inset into the base to screw the conning tower to the deck section. Then bondo on the interface, conning tower onto the deck, and after curing...sanding, Voila: Any gap is gone.

[JHapprich]

Nice! Your build rate is absolutely impressive! Always looking forward to your U-1 Updates! Will the appendages be 3D-print masters,too?

Jörg

[DrSchmidt]

This time applying the epoxy filler and the consequent sanding worked well. So I'm currently setting up the parting plane for the first halve of the mold. Good thing: I have the conning tower design in the CAD. So it was easy to print the silhouette, glue it onto the parting plane, and cut it out using a padsaw. The two grooves for the periscopes were ct using a bench saw. Then I set up the plane, leveling it with stacks of printing paper, and finally gluing it into place using hot glue. Finally I closed the gap between plane and master using candle wax. Alignment pins and box walls next and we are good to go....

[DrSchmidt]

Finished the box and set the alignment bolts (10 mm steel rods). Then I applied the surface resin and covered everything with cotton flakes as a coupling layer.