surfdabbler

I'm building a Volvo 70 series remote control sail boat. I started the boat a couple of months ago now. I said I would post a build-log, and with a little free time tonight, I figure I may as well start the build log.

My background - no remote control experience, but I have built one wooden sailing ship from a kit. I decided that the next project will actually sail by RC instead of just sitting in a display box. However, the aim is not to get it built fast so I can sail it. The aim is to work slowly and peacefully, spending all necessary time and effort building a boat that looks great, and will be able to sit in a show-off box. Occasionally, it will get out into the water for a sail.

So, after a little research, the boat of choice is the Ericsson Volvo 70 replica boat.

First step was to get the plans off the net from [link=http://www.velarc.it/index.php?option=com_content&task=blogsection&id=2&Itemid=28]www.velarc.it[/link]. A canting keel will be nice. The headsail will hopefully operate on ropes without a boom. Accuracy of look is more important than being able to gull-wing on a downwind run.

Here's a photo to get you all enthused while I prepare the next post...

surfdabbler

I rescaled it from 1:17.5 down to 1:25. I had previously worked out that 1:25 was a nice scale for a VOL70 boat. Then adjusted the station profiles to remove a 2mm seam from each panel, allowing 2mm for the balsa and fibreglass. Panels printed, transferred to 3mm mdf, cut out and mounted on a baseboard. The profiles are spaced up from the baseboard to give some space to work right up to the edge of the hull.

surfdabbler

Next step was to strip-plank the boat with 1.5mm balsa. I had some 1mm balsa, but it's really too thin for a hull. 1.5 seemed to be just thick enough. 2mm, as everyone recommended, would probably have been better, but the store only had 1.5 and 2.5, so I went with the 1.5. Stripping the balsa into planks was done using a home-built tool, made from a couple bits of wood and a spare stanley knife blade... (the masking tape is to stop me cutting myself on the top end of the blade. As for the cutting end, well, I just had to be careful. It's pretty easy to use once you get the hang of not slicing your fingers. My strips were about 15mm wide, but in some places, this was a little too wide, and I had to cut them in half to follow the curve of the hull nicely.

surfdabbler

Strip planking...lots of cutting and shaping of strips, and gluing long thin edges with balsa glue. Notice that the profiles are covered with masking tape. This was done so that I could spot-glue the strips to the profiles to hold their shape properly without pins or staples. Ok, yes there are pins in some of the photos, but these are only there to hold while the glue dries. Once the hull gets glassed, the shape will hold itself, and the profiles will come out easily, just being glued to the tape.

The 3rd photo is completely planked and sanded smooth.

surfdabbler

Next came the first fibreglass. I’d decided by now that the construction was going to be balsa and fibreglass. I’m not going to try to build a complete fibreglass boat on my first go. I also think that surely balsa with glass on both sides will be lighter for a given strength than straight fibreglass. After all, real boats aren’t solid glass – they use some sort of light core with fibreglass inside and out. Anyhow, that’s what I’m doing.

I used Epoxy resin and ‘tissue’ cloth glass, which I’ve been told is around 20gsm (1/3 oz). The guy at the shop told me that tissue cloth was useless, and probably no different to using epoxy without any glass. However, I was actually surprised at how much strength the tissue cloth actually added, and 1.5mm balsa, with the tissue cloth, I think it’s strong enough for most of the hull. A few places will get interior reinforcement later.

surfdabbler

Once the glass was done, the whole lot was taken off the baseboard. Most of it was easy to just break the glue off, but a couple of the profiles needed sawing the ‘legs’ to get them off the baseboard. Once the boat was free of the baseboard, all the ‘legs’ were taken off all the profiles, and the deck was laid.

The completed deck was then fibreglassed. Again with the tissue cloth, with the pieces cut to fit the shapes of the deck. I took a little too much time with the epoxy, and it was quite thick by the end, so the front of the deck has maybe 1mm of epoxy thickness, which is far more than necessary. So, I’ve learned that when the epoxy starts to gel, don’t try to finish the job quickly. Just throw it out, and mix another batch.

Oh, I nearly forgot, before laying out the deck and glassing it, a strip of tape was put around the top edge of the hull, so the deck wouldn’t get stuck to it. It’s all gotta come apart again to get the profiles out.

surfdabbler

OK, so the glass is all dry now, so the deck is taken off the profiles. The masking tape worked fairly well, and the deck peeled back without much trouble. Once the deck was off, the profiles were taken out of the hull. As I mentioned earlier, the hull and deck at this stage are quite stiff enough to be used as the final boat. The outside surface with the tissue cloth and epoxy is plenty strong enough to withstand scratches and bumps that it may get during its life as a boat.

Inside of the hull was coated with resin just for some water protection, and a couple of reinforcement patches of 90gm cloth were added at the transom, rudder and keel locations. The reinforced patches are amazingly stiff, even where I only used tissue cloth on the inside as well. At this stage, I have no worries about strength.

It seems to be the thing to do at this stage to weigh the hull, so I did. Hull alone is around 130 grams, or 5oz. With the deck, it’s about 230gms, or about 8oz.

surfdabbler

Along the way, I have also started the keel bulb. The keel bulb will be cast from lead. I made a balsa blank in 2 halves, based on the profiles given in the plans. The bottom half was laid into a cardboard box, covered with cling-wrap, and then plaster of paris poured into the mould, carefully prodding and smoothing the plaster to ensure the cling wrap wasn’t trapping bubbles, or pulling away at the sides of the bulb. Once the plaster was dry, the plaster was turned over inside the cardboard walls. A couple of location holes were drilled into the first half-mould, and the 2nd half of the keel-bulb blank was placed on top and pinned into place. Again, cling-wrap was used to cover the balsa. Plaster was poured, and prodded and smoothed to make sure the plaster got into the location holes, and fully surrounded the keel blank.

Once all was dry, the two halves of the mould separated very easily, and the balsa was easy to remove from the plaster. There are a few traces of clingwrap still stuck in wrinkle cracks in the plaster, but on the whole, it is a pretty accurate mould.

I’ve drilled a pour hole in the top, and when I have time, it’s ready for pouring.

surfdabbler

A few more details in the hull, some bulkheads, and some reinforcement patches in the hull. The bulkheads are 1mm balsa with 90gsm cloth on both sides. They are reasonably rigid, but I had some problems with the glassing and vacuum bagging. First go, I got distracted and only mixed the resin for a couple of seconds, so it didn’t set properly. 2nd time around, I mixed it really well, and then vacuum bagged everything with peel ply, but that seemed to suck all the resin out of the cloth. However, the bulkheads are good enough to use (and super light!).

The deck is also not holding the right curve, as it only has glass on the outside, so the bulkheads have been reattached to the underside of the deck, and some reinforcement glass will be put on the underside of the deck. I think that will hold the right curve really well.

Anyway, I'm pretty much up-to-date with this build-log now, covering the last couple of months. I will probably be quiet for a little while, while I do some more more work. I've done some work on deck details, rudders and keels, but made mistakes, mucked up some fibreglassing, and stepped on parts and completely squished them. So, I will be redoing them.

surfdabbler

Just a small update today... I have added a layer of glass to the inside of the deck, and a couple of reinforcement patches to the hull, around the keel and the rudder areas. Hull now weights 200gm, and the deck weighs 140gm. I'm surprised that a very small amount of extra cloth has added 70gm to the hull, and a full layer of tissue cloth and resin added only added 30gm to the deck! Something wierd going on there. Anyway, the hull and deck together are now 340gm (still a long way to go though - hopefully I can stay under 500gm fully detailed and painted).

I've also remade the rudder, with much better results. The glass looks good, and it's much stiffer now. I used a perforated PE sheet around the peel ply, and that seems to have done the trick, keeping the cloth from being sucked dry in the vaccuum.

Interestingly, I did some strength tests on small pieces of balsa and fibreglass - 5mm wide balsa strips, with glass on both sides, to test how best to make the shroud standoffs. Tested with 90gsm cloth, as well as tissue cloth. Not a lot of difference between the two cloth weights, but a huge difference between 1mm balsa, and 1.5mm balsa. That extra bit of balsa thickness increases the flex resistance by a LOT - maybe double. So, if I find the keel section is not strong enough, I won't be adding heavier cloth. I'll be adding an extra 1.5mm layer of balsa, then 1.5oz cloth over the top of that. Thickness seems to be the key to rigidity, not cloth weight.

I did consider using PC circuit board to cut out the standoffs, as they are made from solid epoxy glass. Not sure yet if I'll use circuit board for the boom, or anywhere else. Still tossing this idea around in my head. It could be a cheap/easy way of getting some strong building material, rather than moulding my own little fibreglass pieces.

GRANT ED

Looking good. Keep those pics coming.

surfdabbler

A quick update… I’ve found some great reference photos, so I am checking and measuring the little details and seeing how things fit together on the real boat. At this stage, I’m doing a lot of thinking, and not much actual building anything. [8D]

Now that I have a clearer mental picture of the boat layout, I think I may have to move some of the bulkheads – move the back one further back to directly support the bottom of the mainsheet (I don’t want it ripping out the deck!), and probably move the middle one forward, and put some extra supports in a few other spots. Anyway, it’s a while off before I join the deck to the hull, so I’ve got time to finalise them.

Anyway, I have added triangle section balsa strips to the ‘gunwhales’ (sides of the hull) to help join the deck when that goes on later. Started doing some deck details, and remade the bit that I stepped on. Cut off the deckhouse to become an access hatch for the RC gear, and also for access when attaching/removing the keel. Also started remaking the keel (the right size this time). For the keel, last time I made it from balsa core, and 1.5oz glass on the outside. However, the result is not very strong. I know the glass is very light, and it needs more, but I think even another layer of glass will not be strong enough, and will fatigue over time. One reference document shows to put ply down the centre line of the keel profile, and then shape balsa on either side. I can see that this makes the keel a little stronger, as the strength of the balsa is added, however, it doesn’t fundamentally improve the mechanical structure. The balsa can still compress and allow the keel to flex. So, I am trying a different approach. Borrowing from the mechanical structure of a surfboard, I sandwiched some 1.5mm ply layers into the balsa, but put the ply runs across the keel, not front to back. This is similar to the ‘stringer’ along the centreline of a surfboard. This will then support the fibreglass and prevent the balsa from compressing. This should really strengthen the keel a lot, and with 2x1.5oz cloth, I think will be quite strong, and able to support the canting keel bulb. There is a closeup photo below of the rough-shaped keel, showing the position and orientation of the ‘stringers’. Stay tuned for the next few months if you want to know if it works. [8D]

surfdabbler

Well, some more updates – the keel bulb has been successfully poured. Once I borrowed a working camping stove to melt it on, it all went very smoothly. After reading up on lead poisoning, I was well decked out with plenty of safety gear, and did the whole thing outdoors. The pour went well with no leaks in the mould. I left it for a few hours to cool, and the bulb came out of the mould very cleanly. Once cleaned up, it weighed very close to the predicted 1kg.

I also got a few other pieces made from 1.5mm ply – the standoffs and the keel slot, and sealed them with resin. The Aluminium tube on the bottom of the keel slot will form the rotating column for the canting keel mechanism.

The rudder tube is made from a balloon stick, supported by fibreglass reinforced balsa sheet. The tube comes above the waterline, and the diameter is very close to the rudder post, so water leakage hopefully won’t be an issue. I’ve also made another boom, using a I-beam construction of ply, padded out with balsa. It is much stronger in the vertical direction, although about the same horizontally, compared to the simple balsa core. I’ve also done some more on the hull/deck, but I’ll save those pics for later.

Edit to add - Oh, I also got my Spektrum DX6i yesterday. Yaayy! It's officially for christmas, but I need to start working with it soon to test servo positions and stuff, so the box might be open before christmas, and rewrapped.

zornzack

I wish i can do that man ..... very impressive build

RaceCraftRC

Good lord what a nice job so far man keep us up to date wow!

petesmiff

That is totally gorgeous! real craftsmanship there!! I requested the plans on velarc about a week ago but have had no response yet, Is there any chance you could send them to me?

surfdabbler

Well, Christmas is over, time to catch up on my build log.

I’ve mostly been busy on the keel and the canting mechanism.

First the keel itself – my original straight balsa keel was nowhere near strong enough to support a 1 kg weight on the end, so I remade it with ‘stringers’. This helped a lot, but still not strong enough. With a single layer of 1.5oz cloth, there was still a fair amount of flex in the keel. I measured the flex by measuring the force required to bend 5cm along the full 40cm length. This was longer than the final keel, but was a good reference point. Anyhow, here’s the measurements I got as I added more and more cloth to get the strength I needed. The measurements are rough, as I can’t find my written measurements, and I’m typing this from memory…

Weights to flex 5cm over 40cm length…
1 x 1.5oz cloth = 250 gms
2 x 1.5oz = 350 gms
2 x 1.5 + 1 x 4oz cloth = 500gms
2 x 1.5 + 2 x 4oz cloth = 900gms. Now we’re getting somewhere!

I figured this is sufficient strength. My keel bulb is about 1kg, and the final keel length is going to be 25cm at most, so it’s shorter than my full test piece. If the canting keel works well, I may even shorten the keel to between 15-20cm, for closer to the correct scale length. The keel was also reaching just over 5.5mm thick with all that glass, so I don’t want to go thicker. Anyway, we’re probably looking at only a couple of cm flex on a horizontal keel, so that’s strong enough for me.

The next stage was the canting keel mechanism. After tossing around a few ideas, I decided to get some sealed stainless steel bearings to mount the keel. I fitted these into the tube at the bottom of the keelslot. A friend of mine is a man-arts teacher, so he made up some nice ends and axles to fit. This whole setup will allow the keel slot to be removeable/replaceable if required later, so that’ll be nice. There’s a photo of the exploded keel slot below. Once this was all done, and the end pieces were fitted to the hull, the whole lot was epoxied into the hull.

The keel bulb was also drilled out to fit the keel, and the keel epoxied into the bulb. I discovered that lead is really not easy to drill. The metal is really soft, and the drill bit jams easily. On my first hole, the drill jammed and twisted the whole lot out of my hand and slammed it against the post of the drill-press, bending the trailing edge of the bulb, as shown in the photo. I had to hammer it back into shape.

The keel is epoxied into the hull, and drying now, so hopefully it won’t be long before I can fit it all together. I’ve also squared off the top section of the keel, so that it will fit snugly in the keelslot. With a canting keel, I’ll also need dagger boards, so you can see a couple of those in the keel photo.

By the way, this keel assembly is by no means meant to be waterproof yet. Waterproofing will come later.

nigelpheron

Are you going to have a daggerboard replace the keel, when the keel cants out ward?

I've seen some of the automatic daggers on some of the German V-70's. It just swung in the opposite direction.

I'm thinking of doing a canting hull soon, and ideas are pooloing in me head.

bertauy

Very cool build log. Love the pictures. the canting keel is very cool too, wondering how you are going to keep the water from coming in though?

yann

surfdabbler

Yes, the daggerboards will be necessary to provide sideways lift when the keel is canted. I have made some daggerboards, but they are very flexible at the moment. I'm going to have to put another layer of glass on them to stiffen them. I haven't worked out the control system for the daggerboards yet. I think they should automatically go down when the keel goes beyond a certain angle. I considered an automatic canting keel too, but that might get too complicated.

As for stopping the water coming in, I'm still wondering that myself. I have some ideas, so I have to try them out.

surfdabbler

I did a float test in the pool last night. Put everything in place, keel and rudder, and floated it in the pool, to find out how much weight I have to spare for the rest of the build. Oh no! According to the waterline given on the plans, the hull and keel alone is already overweight. Taking off the deck allowed the boat to float at it’s designed waterline, with a total boat weight of 1.3kg. Scaling from the original plans, the quoted floating weight is 1.46 kg, which is about what my boat is now, without any electronics or sails, or paint, or extras.

The keel and bulb alone are 1080 gms.
Hull is now 240 gms
Deck is now 150 gms
Electronics estimate – 150-200gms
Sails and mast estimate – 150 gms

Totals - keel at 1080 gms, and 700gms in the rest of the boat, for a total weight around 1.8kg.

So, it’s slightly overweight already, and even the quoted design weight was too much for the waterline.

I think at this stage, I’m going to pretty much ignore it. There’s not a lot I can do at the moment, short of rebuilding, and I’m not doing that. I may think about putting holes in the deck and using solarfilm, but realistically, that’s not going to help much, and will probably just look bad.

I just checked out wikipedia, and the keel weight on the real VO70 boats is around half the boat weight. Aha! This design was made with an overweight keel, to suit a non-canting design. So my canting keel should actually be around 700 gms – cool. Removing 400 gms from the keel will be more true to the weight distribution of the real VO70 boats, as well as reducing the servo size required to move the keel. This 400gms will be enough to bring the overall boat weight back down, to acheive the correct waterline weight. OK, I’m happy now, and I’m going to just keep going.

I just have to make another keel sometime, although I’m in no rush to do that right now. I’ll keep the original one too, so I have the option of running the heavier boat without canting keel. The keel just bolts into the slot, so it will be no problem to swap between them at any time later.

Meanwhile, it’s good to see the new Ericsson boats doing well in the race!

Finally, I know everyone likes a good photo, so here’s one of the float test. Sorry it’s so dark. I only do this at night time. You can’t see it very well, but the keel and rudder are in place, and it’s just duct-taped to stop it leaking. I gave it a push in the water, and I was amazed at how much resistance there is to any sideways movement, but how effortlessly it floats forward!

Guiri

You might try to reduce your electronics weight. You pobably need a sail control servo of about 10kg/cm minimum. Servos of that size usually weigh quite a bit. One of the lighter analogue ones is the Cirrus P-CS701/BB which weighs in at about 45g. There are also plenty of mini sevos around for your rudder that put out the approx 3kg/cm you´ll need. Lithium non rechargeable AA cells weigh only half the weight of NiMH cells or you could use a small 7.2 volt 2S lipo pack

canno1797

Hi surfdabbler'
Nice job she is really coming together well. I'm building one of the designers Americas cup yachts ( Alinghi ) just about to glass the hull so I can pull it off the board. I have emailed the designer for the Volvo 70 plans about three weeks ago with no reply, could you please email me the plans so I can get started on one of these as well. Thanks

cheers Andrew

canno1797

Well as it happens the plans turned up today on the email. the same thing seams to happen to every one but anyway time to start building. Any more photos of your boat ?

cheers Andrew

tigertass

Can someone kindly mail me those drwaings? Very intressed in building one myself!
Mail to me: [email protected]

Thanx alot!