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[Tim_M]

Onto the building board.

Or, in this case, the building stick! I got a piece of 2x2 from the local wood shop. Fortunately, the chap was patient enough to find me a straight bit. It's only when you look you realise that most of what's on sale is a bend as the proverbial donkey's. The position of the frames is marked on and the end of the stick tapered away so that it doesn't protrude outside the last frame.

I've been using  Gorilla glue for some full size jobs lately and I really like it. On well-fitted joints it give a super-strong result. It's also quite forgiving as it expands while curing to fill gaps (which is just as well because 99/100 of my joints are not well-fitted). OK, you have to use it sparingly because otherwise it foams out of the joint but it's easy to remove any ooze later. I spotted the same brand in a cyano and decided to use it to fix the frames to the building stick.

Nope. The frames need to be a reasonable fit on the stick but not a tight fit because they will buckle. Needles to say, the cyano did not take up any gaps and I only managed to tack the frames in place. It worked out better, actually. There was a fair bit of adjustment required to get everything nice and true; that first spline helps a lot to reveal the alignment. I ended up adding proper Gorilla to the joints and it's curing as I type. By the way, do not glue the frames to the top of the stick, just the sides. (Obviously) the stick comes out later and it would be very difficult to remove if you glue the top.

The clamping isn't as drastic as it looks, I just don't have any smaller clamps. They are not that tight.

You will have realised that I'm posting as I build rather that waiting till the end to report how things went. I suppose from the reader's perspective it might be better to consolidate everything at the end but I rather like the idea of have some experts looking over my shoulder as I go. You may even be able to stop me before I do something stupid! It kind of adds focus - and gives me something to do while the glue is curing. I reckon things will be dry by now so I'm off to fit some more stringers.

[Tim_M]

All strung out.................

I had serious misgivings yesterday about the wisdom of building this boat again when I saw the size of the task for real. Never mind, we are well underway now. The stringers went in quite well. If anyone else decides to try the build, I would not notch the front two frames until you see just where the stringers 'want' to lie. I had to do a fair bit of adjustment to the notches to get them to fit so it's better to mark off from the wood. (The stringers in the CAD model are 'cut' from the solid plug. A piece of initially straight wood does not follow quite the same curve; it's a spline).

You can see the old knife blades used to space the two sheet stringers apart where the canopy will eventually split. Those paper clips are really handy, by the way. Very strong clamps.

The next step was to sand the stringers back. I don't know of any easy way to do this; you have to follow the circle of each frame but also follow the longitudinal curve. I used a long sanding block, which helped, but I still managed to get a few 'flats' on the frames. I'm not unduly worried about that (yet) because I think the stringers will form the skin rather than the frames. (Thinking about it, it might even be better to make the frames deliberately under-flush so they can't cause wrinkles). Three of the stringers were nice, hard balsa. The other two were rather soft. If I lived anywhere near a model shop I would have replaced them but as I don't, they have been given a liberal dose of (..................drum roll......................) Ronseal wood hardener! You just knew I was going to get that in somewhere during the build.

You will also see that I have added some 1/4 balsa block between the first two frames. That area gets cut back to virtually nothing to form the engine intakes. It's a lot easier to fill that are now and sand it out later. Oh, and that square-ish block in the tail? I used that to support the rear frame, just tacked in with a tiny spot of cyano. Now I have the stringers on - I can't get it out! I was going to try to cut it up in situ but I've decided to leave it there till the canopy comes off the stick. Much safer but it does give a disconcerting rattle every time you pick the frame up!

At this point, I decided to take a time out to sort out the lighting round my bench. I have two 150W halogen floodlights over the bench, which is great, but when I'm working on stuff that is facing me, it's in its own shadow. Not so great and my excuse for many a cock up. I now have another floodlight behind me. Is it just me, or is it hot in here? (Will be nice in the winter though).

And so, the next job is to add the final 'deck stringer' and then it's on with the skin. This is new territory and I have no idea how that's going to work out. I have the wood, I have the bandages. I am sure I can't do the whole thing in one piece but I have edge joined two sheets of balsa to give me a 6" wide sheet for starters. I need to soak it in hot water but we do not have a bath in the house. I'm thinking swing bin or...........Dishwasher!  %%Yeah, I reckon that would work - take it out before the 'dry' part of the cycle. It will be interesting to see if the glue holds up. Now, when is Mrs M working next???

I did try steaming a small scrap of balsa (with a small steam cleaner). I wrapped a 1/8 sheet round a 40mm pipe without it splitting. That's going to come in useful  later. There's another 3D skin to form that is much more difficult than the cowl. Worked out what yet??

I'll leave you in peace for a while now as the next parts will be rather slower than the frame build.

[Tim_M]

The learning curve has a few slippery patches............

I would like to say that the cowl skins went on without a hitch but that's not the case. On the plus side, I found out that popping the balsa in the dishwasher for half an hour really did the job. The wood comes out soft and pliable and it will conform to just about any form to strap it to. That will be very useful when I come to make those concave curves in the lower aft part of the hull. On the minus side, I found out that popping the balsa in the dishwasher for half an hour really did the job. The wood comes out soft and pliable and it will conform to just about any form to strap it to. Yes, you did read that right. I fitted (not glued) one double-width sheet and two single width sheets to the cowl frame. It was quite an effort to pull everything in with the bandages and I had to make a split towards the stern as there was just too much wood. I had my doubts when I looked at the bandaged shape and so I took a look today. The skins had pretty much taken the curves but had stayed flat between the formers (obvious in hindsight). I might have got away with a lot of sanding and some filler but I was not happy with the result. I have seen the level of craftsmanship that 'plank on frame' builders apply on here and I would be ashamed to leave it as a total bodge.

I had a think. Plan 'A' had been to use a number of segments to form the skins. That has to be the way to go, I realised. Having thunk, I also realised that I need to make sure the segments retain some 'spring' as they come off the formers. So, I rough cut two segments and glued them edge to edge and flat to the top former, following only the long curve. When that was dry, I tacked some 1/4 balsa strip to protect the edges and then pulled the skins down to the next former, having first applied steam for a few seconds. This time I bandaged in two stages - first layer pulled everything more or less into place, second layer pulled everything down tight - and I mean tight! That 2x2 stick is working hard! I put a couple of the first try skins over the frame too to protect it and give the bandages something to bear on.

The idea is that by gluing the skins together down the former I will get better 'tangency' and by leaving the wood hard it will follow the other curve better, not flatten out. I will find out next week if it worked. If it did, I will add each segment in turn. If it didn't I may cry.

That means skinning the cowl is going to be a long, slow process. Fortunately, the cowl and the hull are two completely separate things so I can crack on even though the cowl is going to take about a month, bit by bit.

Nothing more nautical for today; I have husbandly duties to fulfil 

[Perkasaman2]

Have you thought of thickening the frames and planking/skinning the other way to achieve the shape. You could also possibly use 1/32 ply for added strength and rigidity to the monocoque if the shape allows. Just a thought.

[Ramon]

Tim,
Though I haven't done this method of moulding balsa to this degree before I am very familiar with the approach. I think the problem you face is simply too much space between the supported areas. The pressure of the bandage will pull the sheeting into the air space between stringer and former. When used for developing fuselages for control line aerobatic models the form or 'buck' is usually made from block balsa or higher density blue foam carved to shape. This supports the balsa completely. Fuselages made like this have nice contours and are extremely light and very strong whilst having little internal structure to support them.
It's been quite a while since I last looked at such but some very accomplished proponents of this method were Windy Urtknowski, Joe Adamusko and Al Rabe. Googling their names along with 'control line aerobatics' might prove beneficial - you could try 'Stuka Stunt Works' - 'moulded fuselages' too as I'm sure something will come up.

If you really don't want to go down that route then I think it's likely that to get the best curvature of your formers and stringers is to apply the sheeting as thinner planking - preferably diagonally and two layers. That will produce the curvature you seek but will prove immensely strong for low-ish  weight though not quite so low as a single moulded sheet.

Hope this is of use - Ramon

[Tim_M]

Thank you very much for the advice chaps. I took a quick peek under the bandages tonight and things are looking promising for the first two segments. Yes, the former should ideally be solid or at least have a lot more stringers. I will be using solid forms for some of the other parts and I'm very confident that will work. I'm trying to get as few joints as possible. It looks like 30 degree segments has a good chance of working. That will give me six skins to fit. I'm so glad it's not four.

I'll keep you posted - mistakes and all!

[Tim_M]

This week's thrilling instalment............

The skins are on. It was a slow process; each piece was glued on one edge and left overnight, then steamed, pulled into place with bandages and left overnight and finally the second edge glued down. I managed to work on the two sides in a different sequence so it all happened in a week. The result is that I'm pretty confident I'm into reasonable sandpaper and filler land. The photo (rather unflattering) was taken straight after gluing the last pieces on so I haven't started to sand yet. I have resigned myself to the fact that I will need to add a very light glass finish otherwise I'm sure I will get cracks coming through at some time in the future.

I can't put my hand on heart and say that I thoroughly enjoyed this part of the build. It was pretty difficult but I did manage to re-use the wood from my first trail using a wide sheet. My advice to anyone embarking on this build would be to look at your own skill set and preferences (Oh dear, that sounds like management speak!) before deciding how to go about the build. It is, after all a scratch build so you can do whatever you like! The plank on frame boys will walk all over this. I reckon double-diagonal planking would work a treat if you know what you're doing. You could skin it with a series of rings and then sand out the bumps. The fibreglass department could knock up a plug (you do have a lathe that can swing a 8" X 2ft lump, don't you?).

In retrospect, if I were starting again, I would make a wooden former - not the whole thing, just a 30-40 degree segment - and pre-form the skins pieces over that before gluing into place. That is what I will be doing later for some of the other parts.

I've now given the whole thing a light spray with water (hardly needs it in this weather!) and I will leave it alone for a week or so to relax before I start to sand. Fortunately, I enjoy sanding. But the build isn't stalled there. You may notice the hull floor is lurking in the background, marked out ready for the frames. Next week I will be cutting the frames and starting to build something more boat-ish.

Ramon? Any time you like my friend! It won't be long before I want to line up the drive train. (But I can do it without the motor mount  so no pressure)

[Tim_M]

Today's thrilling instalment..............

Things are starting to happen. In the week, I found time to cut out the hull frames. I've started assembling the hull now. You can see I like things well anchored down. That transom isn't going anywhere in a hurry! I doubled up the transom to 4mm and I will be adding a carbon fibre plate on the inside later (only because I have some). The frames look a bit skwiffy but the edges are glued in the right place. The ply is moving around all over the place as the temperature and humidity change. You can leave the frame and come back half an hour later and all the free bits have moved. It will be OK when everything is tied together properly.

I've also started to sand the cowl. It's looking pretty good so far; most of the lumps and bumps are out. It's got to the stage where it's difficult to see what's going on because of the wood grain, shades and joints so I have now given it a thin coat of emulsion so I can see the high and low spots. I'm still working on shaping rather than finishing. Up to this point, the best indicator has been feel. Mrs M gave me a very sideways look when she caught me fondling the cowl out in the garage. Don't get me wrong; my wife is the nicest person you could wish to meet but she does not understand modelling.
"I don't get it"
"What, dear?"
"You spent hours and hours making these models".
Yes , dear."
"Then you take them down to the boating lake and crash them."
"Yes, dear."
"And start again!"
"Yes,dear   ...................And your point is????"

I don't understand why anybody needs 25 handbags, so we'll call it a draw. (At least, I will )

I digress. The glass cloth and Aerokote resin for the cowl arrived. Had to shop around a bit for that as most websites stated they could not post the resin. RC World did the business and it arrived in 24 hours.

And how about this for a rudder! I wanted a twin-feed rudder and spotted this on Ebay, from Hong Kong. About £15 all in and it arrived in 8 days! It's rather big (160mm) but I can cut it down a bit if I need to. Nicely made, too. Even got brass bushes in there. The reason I went for this one is that the bracket is in two parts. I'm planning to attach the rudder to the back of the prop strut again and this will work really well - just lose (hoard) the right angle section of the bracket.

I also got some white Letraset. Might be a bit too big but certainly better than writing 'DO NOT STEP HERE' in Tippex It will be a long time till I get to that point but I like to be prepared.

I'm on holiday for  couple of weeks so things should move along. There's some interesting stuff coming up; what this space!

[F1 madness]

Looking good and coming together nicely
Couple things on the rudder
Use small file and open up the water intakes so they do the job effectively as they quite restrictive
Other 1 makes sure you thread lock the grub screw that holds the pin in place as they do come loose
I learnt the way on both and nearly the expensive way   

[Tim_M]

I'm taking a short break from building as I have glue, wood and resin drying in the garage. Nothing I can work on!

Progress is far better than I expected. I've deviated from the original plans in a couple of places - nothing major. Mainly I had a bit of a re-think about how all the various bits of wood join together around the bow and just tapered the longitudinal beams in at the front.

I have the bow section built up now and I have built the boom boxes. There's no heavy wood in there, the stiffness and strength comes from the shape. That whole area is really stiff now. I have also built the battery box and fitted the runners that guide it. It may seem a bit early in the build to be thinking about battery location but you may remember the battery is 'moveable ballast' in this design. The CAD model (and experience from Mk1) says that the battery needs to go right up under the cockpit. Now is the time to build (and waterproof) that area - while I can still get to it!

My biggest dilemma is what colour curtains to put over the opening. 

[Tim_M]

I'm feeling like the cat with two tails at the moment. One of the tricky shapes to build on this model is the convex cut-away from the transom running forward. In geometric terms, there is a constant radius swept along a curve that lies at an angle to the centreline. (How many times did you read that?  ). Whatever. This bit gave me some jip on Mk1 and I didn't even try to do the 'double curve' shape.

I made a former from a lump of 3x2. I started by cutting the big curve then formed the radius on one edge. If you have a router with a 21mm rounding bit that would work fine but I don't. I set to with my trusty, new spoke shave (4 quid from Toolstation!). I have to tell you that making that former was a complete joy. I love using a spoke shave! Next, I soaked a piece of lite ply, bound it to the former with bandages and clamped a hefty lump of timber on for good measure. I left it for a couple of days. I decided to use ply rather than balsa because it's quite a tight radius and a pre-feel suggested that balsa would probably split. I was pleased when I removed the dressings to day. The form had taken well. Even more impressed when, after the required trimming, it fitted! That's where the weird shape of the floor comes from.  The waviness in the free edge is not a problem. That will pull into place easily when the side skin and deck are added.

So today I cut the opposite radius on the former and have soaked (dishwashed) and bound another piece of ply for the other side. Hope this one goes as well, otherwise I may end up feeling like the cat with no .......

Oh, forgot to mention. I've switched from Gorilla glue to Resin W for most bits now. I think it will be tougher, dries quicker and is less messy on the hands.

[Tim_M]

The cowl.
I found the best way to sand this was to take a long band of sand paper (I always buy mine on the roll) and wrap it around the cowl, sanding across the grain. I worked away until I had removed most of the 'revealer' coat of emulsion, then touched in with filler and finished it off. I did find one area that went paper thin so I filled it from the inside with some two-part filler. That worked well. I'll remove the excess later.

I have now applied the 0.6 oz glass cloth using easycote fuel proofer. Worked a treat! Thanks, Ramon. One more coat of resin I think then cut back ready to prime.

The next job on this bit will be to  cut the air intakes, remove the cowl from the stick, attach it to the hull and finally split it. Carefully!

And with respect to the rudder, Lookit the dust on that!

[Tim_M]

I forgot...........

I tried an experiment adding panel lines to a scarp of balsa before applying glass cloth. I tried scribing the lines with a ballpoint, a pencil, a scalpel and sandpaper. None of it worked. The glass cloth obliterated my efforts.

Any suggestions on how to add some panel lines after the glass?

[Ramon]

Tim - I realise you did it before glassing but personally I wouldn't consider trying making panel lines into the glass covered surface using any kind of scribing method - I fear this would create stress lines and affect the strength of glass at that point (and consequently effect the wood beneath).

This may be of use ........

The recognised method panel lines were/are created on control line aerobatic models was to draw them on using a drafting pen. The paint surface is matted down using 1000-1200 grit wet and dry, the panel lines drawn using masks/tape as guides then the whole coated with fuel proofer - works very well indeed. It's difficult to get consistent adhesion on a gloss surface hence the need to matt it down first - Another visit to a control line site should help -http://stunthanger.com/smf/index.php?topic=25024.0

Hope that helps

Ramon

[JimG]

A standard method used on aircraft is to use 1/64 inch wide chart tape. After the first coat of primer has been smoothed down the panel lines are added using the tape. It is then resprayed with primer , after sanding the tapes can be removed leaving the lines. You need to make sure that you don't overdo the top coat or it will fill in the panel lines.

Jim

[Tim_M]

Thanks for the advice on panel lines, Ramon and Jim. I get the point about not cutting into the glass cloth. Should've thought about that!

The idea of selective masking looks feasible. I'll give that a try on some scrap and see how I get on. I hope to be using an airbrush/tiny spray gun for the top coat. My daughter gave me the kit over a year ago and I haven't used it yet. I have run up the compressor - nice! Something else to learn.

More progress today, will post later when I have a bunch of updates.

[Tim_M]

More glue drying so time to post the progress.

I hacked out the air intakes using a dremel sanding drum. The edge is nice and thin but quickly tapers out to about 1/4" thick for strength (I put the blocks in before skinning the cowl if you remember). Looks really cool, or at least it will do when I finish smoothing. I'm going to close off the opening at the first remaining frame. Although the main hatch should be watertight (interesting - just upgraded to Windows 10 and now the smileys don't work...) I'm not going to push my luck by deliberately flooding the inside of the cowl. There is more work to do on the back end, once I decide how to model the engine.

The cowl is pretty much split now ready to attach the lower part to the hull. Wonderful thing this CAD. It fits!

[Tim_M]

The port deck has been attached and while I was waiting (again) I made the new cockpit canopy. I posted about the method elsewhere but it's very simple. I have the vac-form plug that I made fifteen years ago for Mk1. I modified the shape slightly and stuffed it, along with a tapered packer - the end of the now-redundant building stick, inside an empty coke bottle (PET plastic). Carefully heat it up with a heat gun, starting from the packer side, and the whole lot tries to shrink back to the shape of the original parison the bottle was made from. Really simple and ultra cheap! I reckon you could make a lot more bits and pieces this way. Just need to ensure the label residue is on the waste side of the former. Cut it off the former with a razor saw and there you go. (This is actually much thicker than the PC version I had made 'properly' by vac forming so it's more robust.

At the moment, the port side skin is clamped in place with the glue drying. That will take overnight, I think, because I have some serious trimming to do in situ. Don't want to rush and have the whole lot fly off in my face.

Oh yes, I ordered some tape for the panel lines. I could only find 1.5 and 0.5 mm (in the UK). I will experiment and work out how I will do it.

[Ramon]

Nice work on the canopy Tim - It's quite amazing how well it shrinks around the form isn't it - made quite a few aircraft canopies that way too - I can remember getting some funny looks in the local supermarket when I was scrutinising different coloured bottles for their suitability - contents immaterial!

I haven't seen anything smaller than 1/32" in the past and I think that was for masking printed circuit boards but try 'Jammy Dog' micro masking tapes - they do a range from .5 mm onwards. I haven't used Jim's method on larger models though have done something similar on plastic models and would agree it is certainly feasible way to achieve what you are after - what I would add is you might be better using a white primer rather than the standard grey. White tends to have a higher build which would give you higher definition - as Jim says it's easy to lose it when sanding 

Regards for now - Ramon

[Tim_M]

Funny you should say that Ramon. The tape is on its way from Jammydog and the only primer I could find in the local hardware shop was.............White!

Who's building this model??

Got the other scalloped skin fitted this afternoon. Stb deck and outer skin tomorrow, maybe. Then we will have something that resembles a boat rather than a pile of G clamps.

[JimG]

A source for the 1/64 Chartpac tapes is Fighteraces http://www.fighteraces.co.uk/products/finishing-materials/.

Jim

[Tim_M]

There's a pattern developing here - glue, clamp, post.

The cat has still got two tails and all of his....... The port side deck and skin went on well and I have cut back to the scallop. Still a little more sanding to do as the glue line is really hard and the shape is difficult to work on. The stb scallop went on easier (I used a slightly smaller radius on the former to allow for spring back so there was less fighting to get it into place. Inside the scallops has been waterproofed (wood hardener - not too much). I had been toying with adding foam (polystyrene or polyethylene) in the closed boxes but decided to risk it without. I've got eight or ten closed chambers inside the structure. What are the chances of breaching too many at once? (Titanic springs to mind but at least these chambers are sealed all round, no bulkheads to overflow). Let's just hope I never find out.

Right now, the stb deck is glued up. When that's dry I can trim up and add the sbd skin. Turns out I didn't over order on the wood. I still have two sponsons to make and it's touch and go whether I will have enough ply. Not to worry, I have plenty of balsa sheet left. Strange; I haven't wasted much but the boat itself doesn't seem anywhere near as heavy as four sheets of ply. I'll find out tomorrow when I weigh it.

Thanks for the info on tapes, Jim. The 1.5 and 0.5 mm tapes arrived today. I'll try those first.

[Tim_M]

Something else turned up today...........

And I got caught. Mrs M was not working this morning and she accepted the parcel. Fortunately, she had decided to try out the sewing machine I bought for her a couple of weeks ago so she couldn't be too cross. I think she may even be starting to discover the joy of creating things!

I had been umming and aahing for weeks on this one, waiting for it to come into stock in the UK. I started doing the maths and it actually wasn't any more expensive to get it from Hong Kong, just that there could be a six week delivery. My finger slipped and I ordered it. Eight days ago!!

Nine channels for a boat????

The rationale is this. I have been using my trusty JR 35MHz 6 channel set for 35 years or more. A lovely piece of kit that still looks like new (cue nostalgic photo). The receiver has survived several aircraft (crashes), hovercraft (that didn't hover very well) and boats. It even recovered from a recent dousing in Mk1. I know I shouldn't be using 35 MHz for a boat (though there are no model aircraft around here) but the clincher is the antenna. Three feet of wire poking out of the top of a K7 looks ........ naff. It was time to get with it and go for 2.4 GHz. I was toying with the 6 channel version (that Martin has for his BAT land yacht) but I didn't like the plastic handle (call me Mr Fussy!). Plus, this one is described as 'full range' as opposed to 'Park Flyer'. I have to say that the pictures on the Hobbyking website don't do it justice; it's really rather nice! My next mega-project is the SRN2 hovercraft. That will need at least 5 channels and mixers. The old set will be permanently consigned to my sailing boat, where the antenna doesn't show!

It's amazing how the prices have changed over the years. The JR cost me around £150 pounds (a couple of weeks wages). This new one was about £50; less than the weekly food shop. Now all I have to do is learn to drive it (Chinglish online manual).

[Tim_M]

Not much to post today as we are making the most of the weather together.

This is the first time the hull and cowl have met. The cowl has not been trimmed yet but considering the parts were built completely independently and they are BIG I am very pleased with the fit. The back is kicked up a little because the deck is cambered but the stringer on the cowl is horizontal. When things are trimmed back, I think I will have a very good fit. To be honest, I could live with what I have now but I can see how to get it right.

I shouldn't be surprised. The parts were generated from the same CAD model so all I had to do was cut them to the drawing; they 'could not' be wrong. Nevertheless, when you look at the combination of curves and cambers it's impressive. I would have struggled to do that with a pencil!

For the record (for me as much as anything) the weights so far are:
Bare hull = 555 g
Bare Cowl  = 263 g
(Total) = 818 g

I can't remember the weight of the hardware (I did log it somewhere but I've lost it) but I recall about 1 kg for the motor and battery. If I estimate another 500 g for the sponsons I'm well on track for a significant weight reduction on Mk1 (over 3.5 kg all-up); predicted is about 2 1/2 kg. She'll FLY!

[Jerry Hill]

I've had a quick look, and can find no comment, but forgive me if this has been mentioned. Scale speed, your calculation at Design Philosophy stage is incorrect. You mention you'd welcome correction.  To achieve a scale speed of 300 mph an 1/8th scale model would have to travel at around 106mph.  Your 37.5mph model speed would yield a scale speed of a little over 98 mph.

If you've got this T shirt no problem, I'll get my coat