1:72 Los Angeles

[spankey]

Here are a few more photos of the tail feathers.

I have to point out that the quality of the prop from PropShopUK is amazing. I did not expect that the taper of the hull would so closely match the taper of the screw hub. This was an awesome surprise.

You should be able to see the prop shaft (5/16" stainless steel). I necked it down to 5mm, then threaded it with M5 x 0.8mm threads. On the end of the shaft, I turned off the threads (inside the prop hub, the threads do not continue all the way out to the end of the hub). Anyhow, there is room to have a small nut on the shaft, which I will use to lock the prop on there in addition to the red loctite. This is necessary when you are dealing with a 2.8" diameter prop that cost like $95. Crazyness!

I have a question....I soldered up a 'U harness' to operate the top and bottom rudders, BUT I'm not completely confident that its going to be stiff enough. Does anyone have any ideas about what else I could use to operate the stern planes and the rudders that might be stronger?



Daniel-

[spankey]

Just a few more of the planes. First set of molds was a sorry operation. The silicone mold release stuff I had that was aerosol did not allow the two halves of the mold to separate, so I had to cut them apart. In the process of cutting them, I wasnt able to get the hinge point to go into any of the castings, so I had to make do with brass, which I attached to the plane. See pics. I know, I know, its not pretty, but they are the right shape (after copious amounts of Evercoat), and they work....i.e. the stern planes work on their hinge.





Next batch of pics I have to take are of the tailshaft again. I modified it a little bit, shortening the threaded section, and getting a couple of M5 x 0.8 nuts, which I will use in addition to the red loctite to keep the nice propshopuk screw from spinning off into the dark oblivion of the depths...

Daniel-

[spankey]

Next batch of pics. I am working on the second bearing for this tailshaft. You can see the plexiglass shaft support. Trick here is making sure that the (Large) 5/16" oilite bearings don't bind the shaft, since there will be two of them. I fiber-glassed the plexiglass shaft support into the tail of the boat. I will be inlet-ing the extreme tail of the boat to allow for an M5 nut (going to find a thin nut, or shave it down on the lathe) to be tightened onto the prop, in addition to the red loctite that I'm going to use to make sure this excellent prop doesnt wander off when I call bells for a 'crash astern'.

also a picture of the newly wet-sanded sail. I did it with 400 grit. Going to be working on getting some primer that will stick. I'll be referring back to your posts Joel. Thanks.

Getting ready for a subdriver. I'll use Plexiglass to make supports for pressure hull when the kit comes out for the dual 545 motors in the 3.5" model.

More to follow in a few days.

[He Who Shall Not Be Named]

Good, sound engineering; you're comfortable around machine tools; and you are a bit of a Model Builder too. This is going to work!

David

[spankey]

Part 2....

I'm working on positives for the stern planes. I haven't made rudder positives yet. These have been shapes, but they havent been sealed yet.



Next thing I'll be doing is reading David's cabal reports on how to make molds with silicone!

Yeah, I've got my work cut out for me...

[spankey]

So the followup thats been needing to get posted for a few days now....

Indexing tabs shown below...



Now some prop shots... I've got a 5/16" Stainless steel shaft. Yes, you'll say this is too big, but this is a big boat. Also is a piece of 3/4" thick polycarbonate (its actually bullet-proof). It has an angle that matches the internal angle in the boat's stern. I will use it as a support for the 5/16" Oilite bearings that are coming from McMaster...

[spankey]

Well, there are alot of folks on this forum who at the very least get close to that title. They might not be "The Master", but either way, I appreciate all the help!

Different coefficients of thermal expansion....I thought I left that behind when I left school....NOT SO. I will mind that, since here in the Pacific Northwest, we can still drive boats in the winter, the water is just bloody cold.

When I was out there tonight, sanding the filler on the sonar dome. I noticed that the bottom hull half, while it meets the top hull half OK, the sides/corners of the bottom half seem to stick out past the sonar dome, and into what will be oncoming water flow. Might not be describing this well, but either way, I need to restrain those corners where the bottom meets the sonar dome with something... I superglued a couple of extra chunks of indexing lip up there, and that 'sort of helps', but I am considering cutting a former of 1/2" thick plastic to fiberglass up there, just aft of the joint between the top and bottom halves at the sonar dome, and have two small machine screws on the P/S sides, going into the plastic to keep those edges in the right spot.

Anyone have thoughts on this?

I should have the camera tomorrow, so I'll have more to show then.

[ManOwaR]

Thanks Daniel! In terms of 'master' though, I indeed have to defer to Dave for that title!

Another point on priming, is that fillers, especially the one part red lacquer types, are designed to adhere to primers, not really so much to the substrate itself. Always lay down a coat of primer on that bare surface before filling. This will pay dividends down the line when your submerging your model in cold water and you have all those different materials expanding and shrinking at different rates...you'll get less cracks etc because things are bonded together better.

[spankey]

Joel, Thanks for the input. I'm getting help from a master now! I'll check into those primers. I've heard DuPont Nason mentioned before. I'm looking forward to your marketing of the 1:72 Seawolf. I'm going to be getting a copy to accompany this LA boat.

Daniel-

[ManOwaR]

Spankey,
If you have any shine on that gell coat at all your primer will have poor adhesive performance. Do an entire dry or wetsand with 400 or maybe even 320 over the whole thing to get that shine off. Make sure you clean and degrease the surface with lacquer thinner or acetone too. Second, you might want to change over to an acrylic auto body primer like Evercoat Durabuild or DuPont Nason (same stuff as Dave uses but different name). It can be airbrushed on and thinned with lacquer thinner to different consistencies depending on your task ie. thick high build priming or thin for visibility coats. The flash off time is a fraction of that Krylon stuff and also sands much better.

Regards,
Joel

[spankey]

Good news, passed the Flight Review, so I'm back to work on the boat now.

Over the weekend, I was working on cleaning up the indexing strips and adjusting the fit of the bow cone to the bottom hull half. I used some evercoat metal glaze to start blending the two halves of the bow sonor dome. This stuff wasnt completely hard last night, so I havent sanded it yet.

I also had some trouble with the cut when I removed the sonar dome from the lower hull...the saw blade drifted, and I had to add some material to the lower hull half to fill a crack between the sonar dome, and the lower half. I did this by putting tape on the bottom hull half so the tape followed the curve of the hull. Then, I mixed up some evercoat, and added some fiberglass cloth fibers...individually, so that the filler would have some meat. put that stuff on the sticky side of the tape, and let it cure. When the tape was removed, the filler followed the curvature of the hull bottom, and I just sanded off what I didnt need so that the bottom half now meets up with the top half at the sonar dome joint much better.

During this process, I've had grey krylon primer on the boat. The hull has a white gel-coat, and the paint keeps sc-raping off... it looks terrible. What can I use to get the grey primer to stick to this white gel-coat?

I'm sorry to dissapoint, but I still dont have my camera back...the other photos were on a borrered camera.

More to follow in a day or two.

[spankey]

The indexing strips worked well. The sides of the boat line up good. I am going to have to do some filling work on the seam between the bow sonar dome, and the lower hull half. After I made the cut, I sanded it, to clean it up, and it didnt look so good. Cut just wasnt up to par, so I'll have to do some sorting on that.

Otherwise, went well. I am glad you warned me about thinning the glass...I thickened it, but apparently not enough. I used 'Fiber Glast' 2000 series resin for the job. When you mix that stuff, it calls for 1 part hardener to 3 parts resin. I added more, maybe 1.25 parts hardener to 3 parts resin. The working time before it got tacky was supposed to be 120 mins....I figure I needed at least that much time. I had the indexing strips clamped with paper clamps while it was curing. Beefed it up with 2 layers glass cloth an it still ran...even with thickener. Between when I left the boat last night, and when I got to it today, it had run down into the top/bottom of the hull halves. Ohh well, I'll sand/s****e it out to lighten up the hull a bit. No hard done.

Edit...apparently cant say s c r a p e....not sure why.

Unfortunately no pics on this yet. Should have some in a couple days.

Having to study for a Biannual flight review now...

[He Who Shall Not Be Named]

Good plan on the indexing strips. You can minimize dribbling of the epoxy resin by mixing in some talc or other inert filler -- make a paste, less likely to run.

Way, way overkill on the bearing holes for the rudders and stern plane operating shafts -- keep it simple!

Looking good so far.

David

[spankey]

Yeah, that sounds like a good idea...try to kill as few brain cells as possible....I need as many as I can keep ahold of.

I just cut the AFT end of the 'Z' cut. The hull came with indexing lips, which I heard were good to alternate...more work to glass them on, but I think it might help keep things lined up. The linear distance of the hull that needed indexing lips was ~50", so the plan was to go with 5 strips. 3 of the strips will be on the top of the hull, and two will be on the bottom. I've used paper clamps to show them in position, where I intend to glass them onto the top and bottom halves of the hull.

I will mask off the whole top and bottom halves of the hull, so that through sloppy glass work (Entirely within my ability to do), I dont get any resin on the 'good' sides of the hull halves.

Before I glass the stuff together, I'm going to be working on finding some blocks of either plastic (Probably LDPE or HDPE) or possibly aluminum or brass. These will be positioned in the tail cone where the rudder and plane penetrations will occur. The intent is two-fold...first, have a thick solid surface to act as a 'bearing' / support for the planes and rudders as their control arms pass through the fiberglass hull. The second purpose will be when I extend the top piece of this support material (for the upper rudder) in the AFT section past the Z-cut. If this material is aluminum or brass, I will drill, tap, then thread this, and the top hull half will screw onto the bottom half into this material. If plastic (Polyethelene) I will glass, or in some way glue a nut on to the material, and it will also function to attach the two hull halves together. I'll attempt to draw something that show's what I'm up to later.

In any event, attached are a couple photos of the hull halves which have been cut, and the indexing lips.

Daniel-

[He Who Shall Not Be Named]

Do all your glass work (bow and stern pieces, and indexing strips) in one sitting.

David