Tug Forum

Model Builder's Den => Hulls => : des March 08, 2016, 18:51:43

: Scratchbuilt hull material
: des March 08, 2016, 18:51:43
Has anyone tried to build a hull using the frame and plank method, using styrene strips and sheets?  Any ideas how such a hull would compare with a similar hull made in fibreglass from a mould - weight, quality of finish, amount of work involved, durability of the finished hull, etc

Or is this such a dumb idea that I should forget it now before I spend too much time and effort on it?

Des
: Re: Scratchbuilt hull material
: 2tugboats March 26, 2016, 19:44:25
Hello Des,

I am surprised that there are no replies, 70 readers, to your important question here.
I personally would like to know which approach, frame and plank or fiberglass has,
in the opinions of the many experienced here, the most favorable attributes towards
less work and energy put out and finished product looks and strength.

Personally, I have always avoided fiberglass but the fact is, fiberglass hulls look
"knock-out" beautiful, are strong, and light weight.  And I would love to get
involved the the fiberglass tugboat "mold" world. . .or would I?

Part of what I would like to hear about is if I am right in that a "fiberglasser" has to build
their tugboat with a frame and plank anyhow to have the form to fiberglass. I don't
even know if I have that right because I have never worked with the glass. With out
some input here, which would be quite simple for many to give, I only know what
I don't know.

One of my friends sent me this picture of their fiberglass start on their tugboat. Is it
really that simple?

(http://twotugboats.com/images/635438d8d50093604a29178ef3004156.jpg)

And below here is one of my approaches. . .ambient it rough, very rough, but it worked
out alright. A lot of work, wood filler, and I never did achieve the "right" tugboat hull look.

(http://twotugboats.com/images/4985ed1c1fc84f644e1c61a68d28525e.jpg)

Again, a perfect and strong question Des, thank you very much,
Michael
: Re: Scratchbuilt hull material
: Tiny69 March 27, 2016, 00:46:59
The point of the original question is the use of plastic strip and sheet a viable use of materials to build a plank on frame hull compared to a fibre glass hull.  In my own experience I have only built plank on frame hulls using plywood for the frames and limewood for the planks.  I have not come across anyone building a plank on frame hull using plastic so I guess this is why there have been no replies to the question.  To build a fibre glass hull a mold has to be constructed first to lay the fibre glass matting into and apply the fibre glass resin.  This is time consuming and probably not the best way to construct a one off hull, but if more than one is required then more copies can be made form the one mold.

: Re: Scratchbuilt hull material
: NickelBelter April 06, 2016, 23:58:49
The fibreglass hull would be superior in all aspects except ease of construction.  Moulding a skillful and time-consuming practice which is why so few people make moulds of hulls that aren't going to go into mass production. 

Styrene won't take fibreglass as nicely as wood planks will and the fibreglass is a key component to keep the planks from separating along the edges.  It's also softer than a wooden hull with resin and 'glass applied.  Vac-forming is a better method to produce a styrene hull, but the equipment needed to vacform a bigger hull is beyond what most model builders can justify. 
: Re: Scratchbuilt hull material
: des April 07, 2016, 15:37:40
Thanks for that, NickelBelter.

Firstly, I have no intention of mass producing a hull, which is the main reason I am reluctant to build a hull as a plug, then make a mould, finally to get ONE fibreglass hull.  It's a lot of effort.  And vac-forming is out of the question (I had never considered it).

It seems to me that if I have to make a plug (in effect, a hull in itself) in order to then make a mould and then finally lay up a fibreglass hull, then why not simply eliminate the second and third steps?

From building an AZIZ kit using a fibreglass hull, one of the things I found is that there are NO reference points anywhere on a plain fibreglass hull;  and it is difficult to measure anything accurately either around curves or in tight spaces.  A lot has to done by eye alone.

On the other hand a frame and plank hull has references everywhere - you have a keel running full length, from which you can accurately measure side to side;  and you have a number of frames and / or bulkheads from which you can measure fore and aft.  Hence why this time I am considering a frame and plank hull.

You seem to be implying that a wooden frame & plank hull should be sheathed with fibreglass, presumably for water sealing and strength, and that a styrene hull would probably need the same treatment but would not "take" the fibreglass as well as the wooden hull.

I know next to nothing about fibreglass at all.  And I have limited experience in working with wood.  So it never occurred to me that sheathing a hull would be necessary.  I had thought that styrene itself is water resistant, so sheathing would not be necessary.  Wood also swells and shrinks, which styrene doesn't, so expansion or shrinkage at joints probably should not occur.  I would expect that joints in a styrene hull would be permanent and watertight, without swelling or shrinkage.

I accept that styrene would result in a softer hull material - but I don't intend to drop the hull, or run it onto rocks.  But even if I did, I would expect it to be easier to repair.  Also, the softer material makes it easier to work, which is one reason I am considering styrene as a hull building material.  But I am concerned about the ability of a styrene hull to support 10 - 12 kg total displacement without bending or hogging.

I am not rejecting your advice - nor have I settled on styrene as a hull material.  I'd certainly like to continue this discussion with other members to get more opinions and ideas.

Des.
: Re: Scratchbuilt hull material
: sea monkey April 07, 2016, 20:40:42
Not sure about costs in Aus but styrene is much more expensive that plywood here so cancels itself out for hull construction. I have seen some German models made with styrene hulls but they were hard chine so easier to make from panels. Styrene also warps very quickly in sunlight.
I've used ply ribs and balsa strips before and that was quick and easy. Wood is very forgiving and easy to sand and fill. A coat of epoxy or polyester resin makes the hull much stronger and resistant to minor knocks. Usually best to coat the inside as well.
: Re: Scratchbuilt hull material
: 2tugboats April 07, 2016, 22:29:15
Well Des, you received lots of ideas and thoughts about making your tugboat hull
and for me, I also now have my eyes much more open with new ideas and approaches.
Styrene strips didn't get much support here. Using them in my mind's building mode,
I can't see the strips working out very well. Wood strips are the way to go if I am
planking a hull. Tiny recommends "Limewood".

I will confess that I quickly learned that plastic or vinal window bind strips don't
work at all. I still throw used blinds in the dumpster and sense that there is a tugboat
part there somewhere.

For my first tug several years ago, I took the time to fill all the spaces between the
frames with Styrofoam. The foam was just for flotation, however, looking at the filled
and flush "hull", I did think about the mysterious fiber glass. I quickly figured that
because of the cost of fiberglass, the mess and glass particles, my inexperience
and the smell. . .I would pass.

One main point that I learned from several of the replies here is that I can now see
how to make a production mold. Just thinking. . .maybe I will have to get us't to
the smell.

A pleasure to be here on the Forum and thank you to all who have shared. For sure,
now I know what I don't know about fiber glassing and all.

Michael



: Re: Scratchbuilt hull material
: des April 07, 2016, 22:57:48
I had thought to make a plug by shaping polyurethane foam, then coating it with plaster, then make a mould from that.  I still haven't completely discarded that idea.  At least it's fairly easy to free-form the hull shape.

Sea Monkey - what type of plywood?  Can I get it at Bunnings?  Also, what type of epoxy or polyester resin would be suitable?  What about polyurethane (Estapol)?  Do you put it on before painting, or after?

I'm considering a hull approximately 1100 - 1200 mm length, by around 250 - 300 mm beam;  guessing a total displacement around 10 - 12 kg.  One reason I am considering styrene is its light weight, so I don't have to worry unduly about how heavy individual components and sub-assemblies are likely to be.  Has anyone any idea how heavy a hull this size would be if built in wood?  (For American readers, these dimensions are 43 - 47 inches length, 9.5 - 11.5 inches beam, 22 - 27 lbs.)

Des.
: Re: Scratchbuilt hull material
: NickelBelter April 17, 2016, 21:45:01
If you're going to use foam, you can just fibreglass over it once you've carved it to shape.  Here is a build log from RCGroups showing just that method of construction.

http://www.rcgroups.com/forums/showthread.php?t=1337980 (http://www.rcgroups.com/forums/showthread.php?t=1337980)

Easier still is to build a conventional keel and frames hull but fill the spaces between with foam and sand them all down to the frames. 

The weight of a hull that size built in wood will be a minor consideration.  My current build is 36 x 11 x 5 inches and weighs perhaps seven pounds, but takes nearly three times that much to float at the correct waterline.  Build a hull too light and it will be stressed by all the ballast you have to dump into it. 
: Re: Scratchbuilt hull material
: des April 28, 2016, 03:22:21
Okay - so it looks like everyone recommends NOT using styrene for hull building.

I've just been made aware of aircraft plywood, available in thickness from 0.4 mm to 6 mm;  hoop pine, with high strength waterproof bond, and high strength to weight ratio, with fine grained blemish-free surfaces both sides.

I just read an old thread on the forum which suggests that ordinary PVA white glue is adequate for hull building, but it seems that many modellers apply an epoxy to the hull for improved water resistance;  is this applied to the outer surfaces as well, or just to the interior?  If it is not applied externally then I assume that the paint covering provides adequate moisture resistance to joints in the hull sheeting which are immersed in water.  What type of epoxy is recommended?  Is applied only to the hull, or also to bulwarks, gunwales, superstructure, etc as well?

Des.
: Re: Scratchbuilt hull material
: sea monkey April 29, 2016, 02:24:14
Des: I use modellers/aviation ply that comes in thicknesses from 0.4mm up to 3.6mm. Usually available from hobby stores that specialise in aviation. Best glue to use is superglue (CA). I give the completed hull a coat of resin inside and out to make it water and bullet-proof. You can use either epoxy or polyester resin (available from boating stores or Bunnings) but only use one type. Don't put one on top of the other Ė they don't mix or bond.
: Re: Scratchbuilt hull material
: tug-arlyn-nelson April 30, 2016, 19:20:55
Oddly enough, epoxy will bond to cured polyester but not the reverse. You see it in boatyards all the time where especially in blister repairs, the blister is ground out, then layers of glass cloth are laid in with epoxy.
: Re: Scratchbuilt hull material
: des September 05, 2018, 20:05:42
Okay - I know this is an old thread, but ...

I've decided to go ahead and build a hull using styrene.  Hull will be based on a Burness-Corlett designed hydroconic tug of the 1970's era, twin screw with kort nozzles, built in 1:35 scale.

I've finally made this decision (2 + 1/2 years!) to use styrene because of the reasons set out earlier - little or no experience with fibreglass or wood, vs confidence in my ability to get a clean finish with styrene.  Also, I've always gained more enjoyment out of building the model rather than operating it on the lake - so I'm not going to be broken hearted if it isn't a complete success (unless of course, it completely breaks in half).

I'll start a build thread shortly, but progress will be slow as I have to finish the one currently on the slips - another kit-bashed AZIZ.

Des.
: Re: Scratchbuilt hull material
: des August 27, 2019, 18:36:20
UPDATE

I've now commenced building the hull for a twin-screw 105 ft harbour / berthing tug based on a 1970's Burness-Corlett hydroconic design, at 1:50 scale.  As indicated previously I am using styrene for both framing and sheathing.  I have had some problems, mainly arising from my lack of experience in building a hull at all, but in general I am happy with progress.

The model I am building will have a total displacement of only 4.5 kg, of which approx. 1 kg will be the hull itself - I expect that I will need around 1 kg ballast.  So strength of the model should not be a major issue.  But even so, I have been surprised by the strength and rigidity of the framework that I have completed so far.

I am glad though that I chose styrene for my first scratchbuilt hull, due to the amount of rework I have had to do, including complete disassembly of the stern section to fix a twist that had developed.  Also, as I was forming up the framing for the bow I found that the bow shape was not developing as I had intended, so a re-design and re-build of this area was needed;  use of styrene made reworking much easier for those frames that had already been installed, without the need to remove and rebuild those frames.

I have decided though that this hull will be a "training exercise" in order to develop the techniques that are required to build a straight hull, and that styrene will not necessarily be the material of choice for the next one.

Des.
: Re: Scratchbuilt hull material
: sea monkey August 29, 2019, 02:32:08
Keep us posted with your progress photos.
Using styrene is a bold move - good luck. Iíve never got past using ply. Itís very easy to correct any mistakes, and I usually make plenty of them.
: Re: Scratchbuilt hull material
: des August 29, 2019, 04:04:07
Steve - photos coming soon, I hope.  Every time so far that I thought it was ready to photograph I found some issue that has required almost complete dis-assembly again;  all due to my own inexperience as a hull-builder, not due to the material.

I thought of you this afternoon - see my later post ref Kort nozzles.  I was hoping you might be able to give me some tips ref 3D design & printing.
: Re: Scratchbuilt hull material
: Capt.Towline August 29, 2019, 12:13:20
Itíll be good to see some photos Des. Iíve often wandered about using that method but three possible issues always held me back. The first being accurate placement of pieces the second being twisting and the third finding a good way of glueing whilst avoiding 1 and 2.

Iíll be watching your progress with a keen eye.
: Re: Scratchbuilt hull material
: Capt.Towline August 29, 2019, 12:14:47
But I really like the idea of building frames and shell plating as ship builders would with steel!
: Re: Scratchbuilt hull material
: des August 29, 2019, 13:51:17
Surprisingly, accurate placing is not really much of an issue, as long as you use at least three "3rd hand" tools to hold a frame in position whill you measure it all up and make adjustments (which WILL be necessary).

But I made two mistakes before I even got to that stage.

Firstly, I cut all of the notches in each frame for the stringers - located at the top outboard corners, and at the chines.  (I had thought that placing the stringers at these locations would stiffen the hull, as well as giving me somewhere solid to cement the "plating" in place later, and provide a watertight seam.)  So I lost these corner setout points even before I started.

Secondly, a lot of the frames are "open top" - they are roughly U-shaped in order to leave the deck openings clear.  So I lost the top centre marks as well.

Good thing it's easy to fill and file styrene without causing distortion.
: Re: Scratchbuilt hull material
: sea monkey August 30, 2019, 07:09:22
If you make the frames with closed tops the whole thing will be much stronger and more rigid when you put the plates on. Itís easy enough to cut the Ďtopsí off when finished and the hull is nice and true.
I usually attach the deck (with access holes already cut) before I start plating/planking. Really stiffens up the keel and ribs.
Warped hulls can be very difficult to fix.
: Re: Scratchbuilt hull material
: des August 30, 2019, 14:34:28
Yeah - thanks.  I already worked that out.

I had to dis-assemble the whole lot.  I put some masking tape over the tops of the open frames and marked out the top centres.  Then I put the keel into a jig to hold  it straight (there's another lesson there, too), then used some milliners elastic thread to stretch a top centreline fore-and-aft, and re-assembled the whole lot again.  When it was all lined up I glued it all together again.

Then, when I tried to line up the next frame I couldn't get it right, so I measured everything, and found that one side of everything was 3 mm higher than the other, even though it was all lined up correctly along the centres top and bottom.  It took a while to work out that I had to ease the slots in the bottoms of the frames where they engage with the keel, in order that the frames could be "rotated" a bit to get each shoulder height right.  Then set it all up, measure it several times, then glue it all again.

I am now uncertain about whether or not the frames are still symmetrical, so I have made templates for each frame so I can ensure both sides are the same.  I have had to ease one side of several frames, and fill the other sides of those frames, to get them right again.

So, many lessons learned.  Whether or not my original reasons for using styrene were correct, I am still glad I used it,  due to ease with which I can carry out the reworks needed, at only the cost of another bottle of styrene cement.

Des.
: Re: Scratchbuilt hull material
: des October 01, 2019, 19:48:04
I've had a couple of weeks off from working on this project, so not much progress has been made beyond rectifying mistakes made earlier.  But here are a couple of photos as it stands right now.

The first photo is clearly a "top down" view, showing the framing and partially clad bottom.

The second photo shows the hull set up within the assembly jig in preparation for installing the next frame.  The three "3rd hand" tools enable me to set the frame  to the correct height, and adjust each top corner separately to achieve the required spacing from the previous frame;  and to achieve the required "shoulder" height.  The bottom tool holds the frame in the keel and prevent unwanted rotation of the frame relative to the rest of the hull.

One of the things I have found is that everything must be assembled without applying any force at all.  Using plywood, if a joint is tight then you would just give it a tap with a hammer until it fitted;  not so with styrene, as styrene does not have sufficient internal strength to resist any such force, and so some distortion WILL occur.

Des
: Re: Scratchbuilt hull material
: Capt.Towline October 07, 2019, 01:50:50
Great progress Des and thanks for posting. So much to take in from the pictures and makes it even more evident that accuracy is key! Using your ďhelping handsĒ to keep everything in place...I imagine a lot of cross checking.

I see youíve doubled up on some of your transverse frames which I assume gives a bit more rigidity. I wandered whether starting out with some sort of deck plate jig would have made it all easier but as you have different deck angles and heights, even getting this right would be a task in itself.

Good luck going forward and keep us up o date!

CT
: Re: Scratchbuilt hull material
: des October 07, 2019, 13:05:40
Hi CT - thanks for the comments.

I doubled up on those frames where I thought they'd be subject to some extra load - eg at the rudder post, where the prop shafts penetrate the hull, and where some gear will be mounted (motors, electronics, etc).  But once I started actually assembling the bits I found also that these doubled frames were also easier to work.  I'm thinking that if I do this again I'd double them all.

I did form up the aft deck area upside down over some graph paper, starting from the deck hatch edge beams and working outwards;  then adding the frames to the deck support structure, then finally adding the keel into the frame notches.  This gave me a solid assembly that I knew  to be "right";  so when I rolled it over and set it into the assembly jig I could use this section as a reference point to set up the other "loose" frames into position prior to cementing them in place to the keel and stringers.  But it took me 4 or 5 "wrong" attempts before I worked out the "right" way to do it all.  All very time consuming, and lots of rework.

Des.
: Re: Scratchbuilt hull material
: Capt.Towline October 08, 2019, 09:33:50
Aye, we all live and learn Des....youíve obviously got a practical mind which will always find a way.

Keep up the good work....and the pictures!

CT
: Re: Scratchbuilt hull material
: des October 28, 2019, 17:36:39
I've now got the hull framing completed, and about half of the hull sheathing added.

After I had initially completed the framing I found there was excessive flex in the region where the keel sweeps up to form the stem post, even after the stringers had been fixed in place, and even with the keel still held in the build jig.  This is because the stringer material doesn't have sufficient rigidity to resist this movement, partially due to the material itself, and partially because there is insufficient spacing from side to side in this region.  To overcome this flexing I installed a shelf spanning 4 frames up to and including the final frame right at the bow.  (I know that I could have achieved the same result by installing the foredeck, but I wanted to the keep the area clear until after I have completed cladding the bow area.)

Here are some photos.

: Re: Scratchbuilt hull material
: des October 28, 2019, 17:40:56
More photos
: Re: Scratchbuilt hull material
: mike_victoriabc October 29, 2019, 05:33:25
Interesting build - looks very tidy!
: Re: Scratchbuilt hull material
: sea monkey October 30, 2019, 16:45:44
Good work Des.
Will you give it an internal coat of resin to water tighten everything. That should also help with removing any flex.
: Re: Scratchbuilt hull material
: des October 30, 2019, 17:18:29
Hi Steve

No, I hadn't planned on epoxying the hull, either internally or externally.

I was intending to rely on getting an adequate water seal along the seams between cladding sheets by using a "putty" made up by dissolving styrene scraps in liquid solvent / cement.  All of the seams are slightly filleted so that they leave a partial gap along the seam, while still fitting snuggly together;  the putty flows along and into these seams and fills and seals them.  When the solvent evaporates it deposits the dissolved styrene into the joints, and filling the fillets and seals them.  Then later I will rub back and fill any blemishes (and there are plenty) with a commercial putty prior to painting.

This is the first time I've used this cheap form of putty.  It's also very useful for sealing the gaps between butchered joint halves.

As for stiffening the hull, I am expecting the external hull sheathing and deck will do this adequately - it's already quite rigid except just behind the forward bulkhead where there is still some minor flex due to the local geometry, but I expect this will  go away once the deck is laid.
: Re: Scratchbuilt hull material
: des November 19, 2019, 16:38:21
More progress - I've got the upper bow cladding on.

The hull is sheathed with 1.5 mm styrene sheet, but I thought that I might have a problem bending this material to get the tight bend at the bottom of the piece.  Nevertheless I thought I'd have a try.  The result is as I thought - a total disaster.  So instead I layered it up using 3 layers of 0.5 mm sheet;  this has given an acceptable result, although I will need to fill teeth marks from clamps used while the cement was setting.

Des
: Re: Scratchbuilt hull material
: des November 19, 2019, 16:44:02
One thing I've found with using styrene as a building material, and using sheet-on-frame construction, is that you can be as rough as guts in the construction of the framework, but the cladding will still take on smooth lines.

Also, you can be fairly rough with the cladding as well, with cleanup using a dremel sanding drum or a mini file;  or by using filler where the sheeting doesn't match up properly.

The photo below shows how I got my original Lines Plan wrong.  I didn't recognise the error on the Plan, nor when I assembled the framework, nor even when I added the cladding to the sides, undersides and transom.  It wasn't until I added the chine cladding that the error became apparent.  But - filler to the rescue.

Des.
: Re: Scratchbuilt hull material
: sea monkey November 20, 2019, 11:25:05
That's every tidy. You're making the styrene bit look easy. Nice work.
: Re: Scratchbuilt hull material
: des December 10, 2019, 17:13:22
The basic hull is now mostly complete - still no decks or running gear, and still to have anchor pockets cut in.  But the hull itself is done.  So, yes, it is feasible to build a hull using styrene with a frame and sheathing method.

The hull is quite rigid, and surprisingly strong, despite weighing in at only 910 grams - about 2 lbs.  So I am still on target for the hull with decks to be around 1 kg, and for the completed model (with battery, but without ballast) to be less than the calculated 4.7 kg total displacement.

Did I get the chines right for a Burness Corlett hull?  Not quite - but if I build another one I now know where to make the changes needed to get closer to that target.

: Re: Scratchbuilt hull material
: des December 10, 2019, 17:17:44
More photos.

The hull has been sprayed with several coats of high-build automotive primer / putty to fill minor imperfections, and to highlight any that needed attention - and there were several.

The slots at the bow are simply locators so I can cut out the openings for the anchor pockets in the right places relative to the internal frames.
: Re: Scratchbuilt hull material
: sea monkey December 14, 2019, 16:45:58
You made that look surprisingly easy.
I'm tempted to give it a go on my next hard chine hull.
What are you using to glue the 0.5mm layers together to get them so flat and bubble free?
: Re: Scratchbuilt hull material
: des December 14, 2019, 17:05:33
Mostly I use a Tamiya super-fine, clear liquid styrene cement.  This is actually a solvent, so a thin layer of each piece "dissolves" and migrates into the adjacent piece, giving a weld joint which is claimed to be as strong as the parent material.  I use this when I am looking for a quick result.

When I want more working time I use a Humbrol liquid poly cement.  This works in a similar manner, but takes longer to go off.

For those layered pieces I used the Humbrol to fix the first layer to the framework.  I applied the glue to the frame edges, stringers, etc, then applied the sheet styrene and clamped it in place with about 10 - 12 mini spring clamps.  The result was rather bumpy as the thin sheet material was not stiff enough to take on a smooth shape.

The second layer was applied using the same Humbrol liquid poly, applied over the whole surface area of the first panel and spread around between the two layers.  The second layer took on a smoother finish, and the third better still.

There are some cavities between each layer, but these are minor.  In a couple of places I've drilled through the first layer and injected some of the Tamiya cement to get a better fix between panels, and then filled the holes.