building tips needed - tips

[wayne57]

I would like to ask some of you guys that have done alot of scratchbuilding a few questions.
When covering a frame work of a early sub such as a holland type that is cylindrical in shape is it better to plank the frame with small strips or try and sheet it with bigger strips.
also when finished what is a good sealer to use?
Can i use fiberglass resin to seal it up with, then lightly sand it?


thanks

wayne

[JWLaRue]

Hi Wayne,

If practical, I'd use

Hi Wayne,

If practical, I'd use strips that were the same (scale) width as used on the prototype...especially if the final hull shape is not smooth, but obviously made up of flat plates. Otherwise, it doesn't make a lot of difference....just make sure that the strips are not too wide so as to require so much sanding that you mkae the edges too thin.

When you speak of sealing it with fiberglass resin I get the impression that you are talking about using wood for the hull. This would not be the first choice that most would make for a sub hull unless we're talking a master upon which molds are made. It's very, very difficult to make sure that no water gets into the wood....and wet wood will expand and cause all sorts of problems.

-hope this helps,

Jeff

[tmsmalley]

The Holland being more streamlined

The Holland being more streamlined than cylindrical, will take a lot of gore shaped pieces (like the pieces in a hot air balloon) doing it by the plank-on-frame method.

If you want a working model (not a mantlepiece) the "Lost foam" fiberglass method might be easier for you, unless you are a very experienced planker. And then you will wind up with a 100 percent fiberglass hull not subject to warping and the other water problems common to wood plank subs Jeff mentioned.

The advantage of lost foam method is that it is easy - at least easier than the plug and mold method. Of course with a mold you can make multi hulls (few guys I know have actually done made more than one copy of the hull - other than the pros like Matt Thor, Dave Merriman and the few others who do it commercially.)

With the lost foam method, you make the shape of the hull you want out of foam in two halves, coat the foam halves with several layers of fiberglass cloth and catalized epoxy resin- after it has cured you throw away the foam and are left with fiberglass shells - the two hull halves! "Easy as cake."

You make the hull shape in two halves (Port and Starboard) out of blue or pink contractors' foam from a good set of plans. Since the foam comes in 1" and 2" thicknesses - if you use those dimensions as your frames, it makes it go really easily!
Blow up the plans to the size of model you want to build, then transfer the "frame" dimensions to the foam with a Sharpie from the plans. Make them a little bigger than the final size so you have room for the foam you lose during the final sanding.

Glue your rough cut pieces with water soluable glue -I use Elmers school gel glue - to pieces of that slick white shelf material you can get at Lowes, Menards, Lamperts - builders super store (you can get the foam there too.)

Sand and fill (dents, goofs) each foam half with wall spackle

NOTE _ before you fasten the 2" thick pieces of foam to the shelving material, you have cut it so it is the same shape as the flat side of the foam - the shape for the Holland would look kind of like you cut a solid football from end to end.

Layer several (I use 3 or so) layers of 4 oz epoxy fiberglass cloth/resin over the foam and let it hang down off the edge of the shelving so it is easier to cut with the Dremel wheel after it has fully cured.

Be sure to follow the epoxy instructions EXACTLY. Otherwise it won't cure properly and be too squishy or brittle.

Use a lighter weight cloth - say 1 oz as your last layer to give a smoother finish to the outside of hull.

After both halves have cured on the shelf board, scribe the edge of the hull with a thin point Sharpie pen and cut around each with a heavy duty cutoff wheel/Dremel tool.

Pry the halves off the shelving board (its easy since the gel glue doesn't form that strong of a bond) and gouge out the foam with the claw end of a hammer. You can melt out the last little bit with some solvent - rubbing alcohol etc. It makes a heck of a toxic gooey mess so dispose of properly.

Stick the halves together with strips of fiberglass cloth around the outside - you sand these flat later. After you have the finished hull shape, you need to cut around where you want your opening to be. Make sure it is big enough for WTC or any working parts you'll need to get at.

Once the opening is cut, take more strips of fiberglass cloth staturated with epoxy resin and this time put it around the hull half seams on the INSIDE. Once these have cured, you can sand the outside strips flat.

Make some lips for the hull opening to sit on - just as Dave Merriman is shown doing on the Eckloss' Vanguard build thread that is running right now. Viola! You have your hull.

I kind of show how I did this on my H.L. Hunley model on my website. RC-Submarines.com Once you are in the site - click on "My Projects".

Good luck!!!