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Feb 23, 2018, 12:19 PM
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excellent advice jerry......
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Feb 27, 2018, 03:54 PM
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Thread OP
I have the first coat of filler on and sanded. I am using the light Spackle as Jerry suggested. It will need a second, maybe a third application? I have the stem (Beakhead ?) cut out and epoxied on. The keel and sternpost are almost ready. I plan to make the center section of the keel a bit thicker and drill through it, using my drill press, with pilot holes for the keel fin and ballast tube mounts. I just have to figure out the optimum location near the center of gravity without interfering with the radio mounting pad and mast locations,

It is looking pretty good, to my untrained eye, but I have a concern about the railings. The balsa I used to plank is only 1/16" and seems to have a lot of flex and will be very fragile. I also have to go back and verify the rail top height. Right now it is deliberately too high. Maybe I should have planned that better?

I would like to take this mock-up hull to the resin and fiber glass stage and then start over with the pine planked more carefully built final version. I learned a lot so far that I hope will serve me well.

Rod
Feb 27, 2018, 04:38 PM
Actual Model Aviator.
pitviper51's Avatar
looking good and more seaworthy every step of the way. Im assuming having to fill like that insures youll have to paint the hull instead of having wood finish look.
Feb 27, 2018, 06:17 PM
SCALE Sailor
JerryTodd's Avatar
Use the filler till it's fair and smooth to YOUR satisfaction.
When you're ready to glass, trial fit the cloth dry first, give it a coat of resin and lay the cloth onto the wet resin. If it's not right lift it off where you need to and set it again. Then give it a covering coat. This is where you'll see, and regret, any corners you cut in the bare wood sanding and filling.
Feb 28, 2018, 03:46 PM
Registered User
Thread OP
Jerry Todd, what is your source for glass cloth and resin? I'm guessing that the automotive stuff is too heavy for this application.

Rod
Mar 01, 2018, 02:46 AM
Balsa Lover
gupi's Avatar
There are also special balsa fillers available that are very light and sand like balsa, used for building RC aircraft.
Mar 01, 2018, 08:48 AM
SCALE Sailor
JerryTodd's Avatar
I get 4oz cloth from Duckworks. They'll sell it in small quantities. I get poly resin from Home Despot or someplace like that, a gallon was around $40 last time. They didn't have smaller sizes there any more when I looked last.

Poly's used to build real boats and is fine for models. It's softer and easier to sand than epoxy, but it's not as strong, nor is it an adhesive like epoxy. It's also not truly waterproof, water can get into it by osmosis over time, causing blister problems in real boats - unless you're keeping your model in a tub of water for months at a time, that won't be an issue for you.

To get a smooth surface you have to fill the cloth's weave with resin, the heavier 6oz cloth with the thicker weave requires more resin to fill it or your boat will look like a basket. The resin is what's sealing your hull. The cloth is like re-bar in concrete, and acts a little like shrink wrap. You could use any sort of cloth, even bed sheets, but that wouldn't hold up like glass cloth and could rot where glass won't. On a model it's probably not a big deal.

The trick with plastic encased wood, which is what you're building here, is not to let water get to the wood at all. I painted some automotive anti-freeze inside my hulls before coating them in resin. The glycol permeates the wood displacing moisture without shrinkage. They use glycol to conserve wood artifacts from shipwrecks. (If you do that, wear gloves and protection, glycol can permeate you too and crystallizes in your brain.)

If you make a hole in the hull, for prop shafts or anything else, make the hole oversized and fill it with epoxy. Then cut or drill it to the proper size. That way the hole is entirely through epoxy and there's no wood exposed to water. The plate that holds the heel of my rudders is done that way or water would get into the plywood, cause it to swell, rot, and basically destroy the models. I coat the inside for the same reason. Water that gets into the hull can't get out, soaks into the wood, and in that dark enclosed space promotes mold and rot. Coating the inside won't prevent mold, but it will prevent rot. You need to wipe out what water you can and leave the hatches open so the hull can air out to prevent mold.
Mar 01, 2018, 04:55 PM
Registered User
Thread OP
OK, thanks again Jerry, 4 oz cloth is on order.
Mar 03, 2018, 06:06 PM
Registered User
Thread OP
My fiberglass cloth arrived today, pretty fast delivery!

I am debating with myself about the tube ballast mounting. I need to figure that out so I can drill pilot holes in the keel before attaching it to the hull. Looking at the examples I've found on line it appears that the PVC tube is usually just about equal in length to the hull . ( Jerry's Constellation is a good example and the one I am referencing ). So locating the position of the mounting holes on the keel would seem to be about 1/3 to 1/4 of the keel length from the stem and the stern posts. I also assume that two mounting points for the threaded rods is enough. The primary concerns would appear to be leaving room for the radio gear and where and how to hide the upper bolt on the deck, or maybe under a hatch. I'll need to consult the deck arrangement plan to work that out.

Is there anything else that I need to consider?

Thanks
Rod
Mar 04, 2018, 08:46 AM
Registered User
Gammon Iron's Avatar
"Is there anything else that I need to consider?"

Maybe a third hole for another tube in the keel. This is not for mounting the ballast keel/tube. But, to run wires for the potential of a power pod that is necessary to run sailing model indoors with no wind.

Mar 04, 2018, 12:40 PM
SCALE Sailor
JerryTodd's Avatar
The problem with PVC is the steps in diameter are enormous. I used 2" i.d. I think the next step down is 1" i.d. which is a big difference in volume. Iron pipe, I think, is more incremental in sizes and obviously contributes more of itself toward being ballast than PVC does.

You might look at electrical conduit also, it may offer more sizes for you.

Another option is to glass over cardboard tubing. You can actually make the cardboard tube yourself, to the size you want, cover it with glossy packing tape, spiral glass tape around it and pull out the tube leaving a custom sized fiberglass tube. How much weight in lead you get from a given volume and what the volume of a tube is at various lengths is easy enough to calculate.

The bottom line is to cast a lead bar much like the SC&H kits had. There's a few videos on Youtube about pouring lead from yacht ballast of several tons right down to one pound drafting weights. I'm hoping to pour a split bulb for Pride of Baltimore this spring and will certainly post about that adventure, but I don't think it'll be in time to help you.
Last edited by JerryTodd; Mar 05, 2018 at 08:16 AM.
Mar 05, 2018, 07:43 AM
Registered User
Gammon Iron's Avatar
You could make your own wooden ballast keel that you can customize to any amount of ballast you need. I used thin plywood for the shape. Plus the more fin-like you can make it, the quicker turning your model will be.
Last edited by Gammon Iron; Mar 07, 2018 at 07:51 AM.
Mar 08, 2018, 12:57 PM
Registered User
Thread OP
Some good ideas for the ballast, I will have to think about that a while.

I've been kind of busy, just getting back to the Brig.

I have it pretty well ready for glass and resin, it just needs a little more sanding. I have the stem, keel and stern post installed. I briefly removed it from the building board and quickly found out how fragile the balsa planking is. I am afraid to remove the forms at this time, so I put it back on the board. I will apply the glass cloth and resin on the outside before I do anything else. Hopefully that will strengthen it enough.

I didn't layout the rail height very well either. Another lesson learned. I will have to do some careful measuring and trim the high side down to where it belongs. Not sure how I am going to do that yet. Maybe use my Dremel with a cutting wheel?

Rod
Mar 09, 2018, 03:46 PM
Registered User
You might consider doing more than one layer of glass cloth. I usually put two layers at a time (probably not the best practice), sand, and than laminate two more layers. Makes a much stronger hull.
Mar 12, 2018, 02:41 PM
Registered User
Thread OP
Yalex, Excellent suggestion on 2nd layer of glass cloth, I will give it a try.

So far I haven't gotten much done this week. It seems that there is no poly resin available in town, so I had to mail order some. It should get here late this week.

I did correct the rail height so it's even now, and did some work around the transom.. I also just slapped together a quick and dirty stand for it so I will have it when I need it.

Rod


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