Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Yachts and Sail => Topic started by: CJ1 on October 02, 2013, 08:41:28 pm
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I've decided to have a go at one of Frank Russell's free IOM plans, the Goth. It's going to be a glassed balsa hull and deck.
I'm using balsa shadows, reduced to allow for the thickness of balsa and glass. Building board is chipboard with stations set up along a centre line as from the plans.
Chris
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I decided to use a 2.5mm spruce keel, stem and bearer pieces either side of it in line with the keel box to help spread the lateral load. The rest of the hull is 2.5mm balsa, cut into 10mm strips with a balsa stripper. I'm using white pva glue to join the wood and tape over the shadows to ease their removal later.
Chris
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Once I'd got the middle three planks in place, tapered to fit the stem, I next placed the plank that sits below the chine to establish a fair line for this chine. This chine starts about 1/3rd from the stem and is quite marked at the stern.
I superglued the planks at their ends if there was any chance of them springing and let this set before I bent the rest of it in place.
Whilst the stem is the final piece, the transom is a sacrificial shadow at this stage. It will be replaced with a nice piece of wood later.
I want to do as little fairing as possible later to keep an even thickness of wood under the glass, so the pegs help keep the planks aligned while the glue sets.
Chris
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Then it was just a matter of working out which plank worked best as the next one to go in. I laid them as a matching pair to prevent the hull twisting and also to try and get them to look equal.....(just in case the hull looks good when finished; I might save some weight later by not painting it).
The side light showed up my hope for getting the planks exactly aligned as a lost cause!
Chris
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The topsides of the Goth are slab sided at the front with a tiny bit of tumblehome at the stern. I replicated this by using two wide planks of 2.5mm balsa either side.
Chris
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I inserted my proper transom piece from a clean plank of 2.5mm balsa.
Then it was time to sand the hull down. 2.5mm is not a lot to play with so this was done with care, a softwood sanding stick and finally a piece of sandpaper in my hand along the line of the grain. There's little hope of getting cross scratches out at this thinness.
Chris
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I'm using West 105 epoxy with 206 slow hardener and 100gm glass twill to cover the hull. With the smooth side of the twill uppermost, there is less to sand.
To keep weight down, I decided after weighing up the pros and cons of both methods, to lay the glass down on the bare wood and stipple the epoxy through it to wet out the balsa. I know a lot of people brush on a layer of epoxy and let that set first before laying down the glass.
A friend gave me the tip of laying masking tape on the glass in the area you will be cutting it (before you cut it), to stop fraying. It worked well.
I was able to use just one piece of twill. This adapted to the shape of the hull well, needing just a few relieving cuts around the hull edges, especially stem and transom chine areas, to allow the shape to conform properly without lifting.
Chris
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Then a second layer of epoxy was applied.
After a couple of days to let this cure, I started the slow process of rubbing down. That's as far as I've got at the moment, but she feels very fair and smooth. I've got to 800 wet and dry so far. I'm leaving her on the shadows while I sand her as it's much easier and less chance of twisting her.
I like the colour of the balsa now, so I'm going to leave her unpainted with just a thin waterline painted on.
I'll post again when I can get her off the stocks and do the inside. That will be a few weeks I'm afraid but I'll keep posting as soon as I've done more.
Chris
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Quality workmanship there keep this blog going I LOVE IT
Dave
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Brilliant Chris :-)) .......may I ask....what type of tape [shown below] are you using over each frame?......[to stop the planking sticking to the frames].............Derek
(http://www.modelboatmayhem.co.uk/forum/index.php?action=dlattach;topic=44927.0;attach=129448;image)
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Derek,
I used thin electrical insulating tape cut in half lengthways. I tried PTFE but it was all over the place! Just wouldn't keep still.
Dave,
Thank you for your kind comments. I'll certainly keep the post up to date.
Chris
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What a pleasure to follow this build. :-)) Excellent work.
ken
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What a pleasure to follow this build. :-)) Excellent work.
ken
Ditto that O0 :-)) Makes me itch to get the balsa stripper out again. I built a Triple Crown in the same way, but no way as good as yours.
Looking forward for further episodes
Mike
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:-)) Enjoying your build.
Will be waiting for more.
Terry
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Very nice. :-)) :-)) :-)) .
Len.
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I like the colour of the balsa now, so I'm going to leave her unpainted with just a thin waterline painted on.
Love it! The finish is turning out really well. Love the p-o-f look. Keep up the good work!
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Thank you for your kind comments guys. What's a p-o-f look? I'm having a senior moment here!
Chris
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Plank on Frame :-)) :-)) :-))
Ned
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You'll make a model maker out of me yet! Thank you....I learn't one more thing today.
Chris
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I took the hull off the shadows this week. After a little cleaning up of the glue runs inside ( I knew there would be lots!), she looked better than I hoped.
I then used a layer of 100gsm glass across the inside of the hull as a strengthener for the shrouds/mast area and a round patch around where the rudder tube will penetrate the hull.
Next was a single layer of 100gsm glass over the whole of the inside on top of this, trying to use as little resin as would wet out the glass.
The final weight of the hull so far is 362gms. I have no idea if this is good, bad or indifferent!
Chris
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You'll make a model maker out of me yet! Thank you....I learn't one more thing today.
Chris
Looking at that beautiful hull you are definitely a model maker already
Ned
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Beautiful work Chris! :-))
Dennis
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Thank you guys. I'm really enjoying doing it. I've built plank on frame before but not where weight is important. You really have to concentrate.
Sadly I'm having to do this build sporadically and I can't wait each time to work on it. I'll keep posting whenever I am able to finish a bit more.
Chris
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Hi Chris,
Nice work on the build sofar, it's a joy to watch!
Regarding your idea of not painting the hull; I'd add one layer of UV resistant varnish, to stop the epoxy from getting yellow over time, as epoxy isn't UV resistant.
Regards, Jan.
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'I'd add one layer of UV resistant varnish, to stop the epoxy from getting yellow over time, as epoxy isn't UV resistant.'
This advice is a little too late for this build but for future reference there are some epoxies that do have UV filters in them - they tend to be used in the manufacture of surf boards etc, one example being 'seabase' (I've nothing to do with them & haven't used it - it was just the 1st result from a web search). I wouldn't be surprised if the likes of WEST & SP didn't have a similar product.
Fantastic build log & I'm looking forward to seeing your progress.
Row
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This advice is a little too late for this build...
Why?
You can always put a coat of UV reststant varnish as a last coat over the epoxy to prevent it from getting yellow (and brittle) over time.
Regards, Jan.
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Hi Jan,
I suppose the point I was making was that with a future build (and the right epoxy formulation) it wouldn't be necessary to apply an additional coat of UV protecting varnish.
Although my current build is traditional (a J Class) most of my model boat building knowledge has come from friends building Marbleheads & AC120 class yachts where any weight saving is hugely beneficial - more weight can be put to work where it matters!!
Cheers,
Row
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Hi Row,
You're right.
Using the right materials from the start (of the finish) will save additional weight.
Regards, Jan.
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Got back to the build again for a short while.
I made the deck from two pieces of 2.5mm balsa joined down the centreline. The hollow for the vang was made from tapered pieces of balsa joined to a circular former on the bulkhead.
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I then built a sacrificial skeleton on the foredeck on which to form the raised, rounded, foredeck proper. Once the glue on this had dried, the plan is to cut away everything underneath except the longitudinal rib and a shadow in line with the jib attachment for strength. The longitudinal rib needs to stop short of the bulkhead for the mast ram later.
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The two access holes were cut out. One for the servos and electronics and the other for access to the rudder linkage. The outside of the deck then received a layer of 100gm glass with two coats of resin. The underside, I plan to use resin only except in line of high stress areas, where a layer of glass will be applied too.
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Although I already have a rudder I can use, I've made another one to Frank Russell's design so that I can compare the two. Three layers of balsa around a PJ Sails rudder stock with two layers of glass and resin have produced a very stiff and fair shape.
The simple brass rudder tube was resined in place and will receive a cross brace later for rigidity.
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Then in with a PJ Sails mainsheet post and bend up some wire hoops for the jib attachments, jib sheet leads and shroud/backstay fittings. These will be epoxied in through the deck.
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The keel box was next to make. I tried in GRP but failed miserably. Next attempt was in glass covered balsa. This seemed to do the trick. The servo tray is to be bonded to the back edge of the keel box to brace it and the top of the keel box is going to be epoxied to the underside of the deck. That should take the loads properly, especially with the compound curves of the deck here.
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When glassed into place, it lined up on the centre line correctly. I set up a jig so that the keel was already inside the box (covered by clear parcel tape to stop the epoxy sticking to it). The screw is the one that goes into the top of the keel. It gave me an accurate reference to make sure the keel was vertical.
The mast tube is part of the deck now. That sits just in front of the keel box and extends all the way down to the hull for support.
I used wooden braces to align the rudder and keel so that both pointed in the same direction while the epoxy set.
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And then the moment of truth. Would it leak/float/look like a Goth? Only one way to find out. Bung it on the water. The deck is just loosely in place for the photos!
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Yes, that works. So, next job is to glue the deck on. I checked that I had put everything in place that I wouldn't be able to get to later and bit the bullet.
Epoxy thickened up with a little colloidal silica was the joining medium I used, plus a new reel of good quality masking tape to hold it together.
Can anyone spot the deliberate mistake?
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When I made the deck, I put in place the top bearing for the rudder in a fit of enthusiasm. That meant I had to have the rudder in place when the deck went on as a reference to make sure it lined up again. There's no room underneath on the building jig so that's why it's upside down, looking for all the world like a Goth with a wind vane.
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Hi Chris,
Nice to see the updates to your cracking Goth build,
a great insight into modern light weight construction, superb workmanship!
I have a question please - re the inverted U shaped wire jib attachment/sheet leads -
are they literally epoxied into the balsa decking and that's it job done,
or is there more to the wire U shapes we cannot see in the pix or extra reinforcement etc ?
I appreciate your thinking, going for the lightest possible option,
but there appears at first glance, to be a great deal riding on a simple wire into balsa glued joint ??
I am considering building a modern competitive IOM from plans myself,
guessing Goth is the latest plan to become available to the general public.
By nature a very slow builder,
I need to start a build with the most up to date design possible,
to have a fighting chance of a competitive model when eventually finished,
not a nicely planked antique!
many thanks, keep up the interesting posts.
Regards Paul
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Hi Paul,
In view of the forces the deck fittings have to cope with, on other builds the eyelets are extended down through the keel, folded and embedded in the the wood where they're covered with glasscloth and epoxy.
If the eyelets are not extended with the same material as the eyelets, than a piece of polyester, or Dyneema line, attached onto the eyelet is extended down through the keel.
I expect Chris will have a similar construction, or the eyelets will get ripped out one way or another...
Regards, Jan.
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Hi guys,
Yes, you are right. The shroud and backstay eyelets you can see are the through deck extensions of a shape that goes down the hull sides and epoxied and glassed over and for the foredeck, are bent aft either side of a midline stringer and then epoxied and glassed over. The hull also has an extra layer of glass internally from gunwhale to gunwhale in line with the keel/shroud complex. The number one jib attachment point also has a lateral half bulkhead to take the upward load. Sorry, I didn't take photos of those before I bonded the deck on.
Chris
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Hi Guys,
Thank you for the info re the wire deck fittings, it's all perfectly clear now.
regards Paul
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With the deck edge join tidied up, it was time to see if the old rig fitted. I have an old Bantock Ikon, which is the donor boat for this hull. So the fin and bulb, servos and rig are all being transfered over. The idea is to have a wide beam boat (the Ikon) and this one to compare. The Ikon is 3inches, 8cms, wider than the Goth.
The hull and deck with fin box, mast box, servo tray and all deck fittings (but not servos or battery) and a couple of coats of clear primer has come out at 605gms, so on target so far.
I have to say that I'm new to IOM racing, and at the moment with the Ikon, usually at the back of the fleet, so I'm hoping a newer, narrower design will help me improve!
Chris
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Here's the difference between the two.
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this is a beautiful boat build and is very inspirational.
Exceptionally well done - I hope it sails as well as it looks.
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Thanks for your kind words.
I've finally raced the Goth, in Andratx harbour, Mallorca. Quite quick despite a rubbish, twice mended, mast (still can't buy IOM masts in Mallorca!).
Here's the link:-
http://youtu.be/rKBHwZBwhWQ (http://youtu.be/rKBHwZBwhWQ)
Chris
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Again, in Andratx harbour taken by one of the club members.
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Very impressed with this build and I hope that CJ1 does not object to me attempting to build similar. Having just completed a Aero-Naut yacht kit I think I am ready to have a go at something more challenging.
Some coincidence, I have spent many happy hours in the marina at Port Andratx not sure I would trust a beautiful build on that large expanse of water.
Happy New Year Chris G
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Thanks for the comments Chris. One thing I had to bear in mind when I built this boat was that the local guys race on open water here in Mallorca and in quite big seas at time. Early this year, with the Ikon up at Can Picafort yacht club, I got hit by a breaking wave and rolled the boat enough to have the keel bulb out of the water. That focuses the mind when you're building a new boat! But these IOMs are tough little things, so in the relatively sheltered water at Andratx, it copes well. And the organisation and support from the yacht clubs is excellent so we always have a rescue boat provided.
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Last race of the season in Mallorca. Down to the last 6 or 7 of us racing as the weather gets hotter.
My Goth is ESP 25. Still dry inside and slowly getting faster.
https://youtu.be/eD8YtHYMLKs (https://youtu.be/eD8YtHYMLKs)
(you can change the setting to 720HD)
Chris