[Van]

Hi Jean-Guy,

Are you saying that the AP22 responds to SSB transmissions, or are you saying the SSB picks up noise from the AP22? I think you are saying the former.

Remember, fixing this kind of interference is a black art. You just have to try different tricks. Keep notes of what you tried…. It’s not clear whether what you are seeing is HF RF pickup, or surges induced in the power systems. Do any other of your electrical systems interfere with the AP22? For instance, when the fridge switches on, does your AP22 respond? Or to an inverter? Or windlass?

To figure out if the problem is HF RF pickup:

1) Turn down the RF transmit power on your radio and see if the problem reduces or goes away. This is not definitive evidence because this also changes the power load your radio uses.

2) Get a “dummy load” for your antenna tuner output. This is a device that screws in to your tuner in place of the antenna. Transmit into this dummy load at the max power it can handle, and see if the problem goes away. If it does not, the problem is probably power related. If it does go away, it’s probably RF pickup related. You can buy dummy loads for about $25 from Ham radio sources or on eBay. Some of them are aircooled and require a fan, typically using 120V AC. If you only use it for short periods (a few minutes), then just don’t plug the fan in.

Some tricks to try:

If the problem is HF RF pickup:

Ensure that no cables run near to and parallel to any of the HF wires (especially the run from the tuner output to the antenna connection because this is unshielded, not coax). Always keep lines spaced as far apart as you can, and if they must cross keep them perpendicular.

Add RF chokes to all of the power and control lines as close to the AP22 as you can. Check Ham shops for these, they are inexpensive a few dollars each, so get extras.

Rewire the AP22 power cables and use twisted pair wire in which the + and – wires are wrapped around each other (sheilded if you can get it in the appropriate gauge). The wires to the compass should already have suitable RF shielding. (you may want to check the shield is properly grounded at one end).

Consider detaching your RF system from ground by using a counterpoise instead of a ground connection at your tuner. (Radio power must use the battery ground, but the antenna output can be detached – but it still needs to be balanced, and this can be done with wires cut to the right length – a so called counterpoise. You can buy a commercial one called the KISS SSB counterpoise, which we just got so I have not had time to really test it out.)

If the problem is power related:

Ensure the SSB radio is wired directly to the batteries (using appropriate wire and fuses on both + and – wires). You want to avoid having the autopilot and radio share the same wires to/from the batteries. The radio will cause voltage fluctuations, potentially quite large if the wires are not thick enough. Don’t run them through a common house DC panel.

Add large capacitors in parallel (eg across + and – power lines). Place these near to the AP22.

Hope this helps.

Van

[Van]

Hi Jacques-Paulus – thanks for the photos. It’s an interesting idea. I wonder if it would get too much in the way. Deck space is precious! On the other hand, so is space on the pushpit – we have a Monitor windvane, and on the sides we have solar panels and a spare fluke anchor. Hmmmm. BTW, your English is better than a lot of the people I know here (near Seattle). 🙂
Van

[Van]

Hi Peter,

Interesting reading about your experience taking on water in the cockpit! Do you have the as-installed cockpit drains, or did you upgrade them? They have always seemed way under sized. And did you check how much water got into the engine compartment? Did much get into the cabins?

Cheers!

Van

[Van]

Arild, thanks for this great data. I reran the numbers and here’s what I got.

I assumed the actual hull speed is about 8 knots per your data (remember the old 1.34 * sqrt(LWL) is just an approximation that depends on hull shape, etc). I also extrapolated your data a bit to estimate that at 3200 RPM you’d hit that 8 knots. The slope of the plot of your RPM vs speed data does imply it can reach that.

Anyway, I also assumed the Shaft HP at 42HP.

The theoretical diameter works out to be 16.0 inches, nicely matching what C&N used!

The “slip” works out to be 49% for your 12″ pitch prop. This is at the upper end of the range typically quoted (40% – 45%).

The interesting thing, is that the calculated optimum blade area is 186 square inches. For this area, for a 16 inch diameter prop, the recommendation is a 4-bladed prop with wide blades. Apparently, using the three blade, with smaller surface area, will lead to more cavitation at the higher RPMs. This may also explain the slightly higher slip numbers.

One last thing, we are considering getting a Featherstream feathering prop. The manufacturer (darglow.co.uk) claims to have installed these on at least one Nic 38 – does anyone reading this know anything about them? They claim it fits in the aperture.

Thanks again for the data, Arild.

Van

[Van]

Hi Jeremy, you are right! Butane is heavier than air, my mistake. I think I was confused with methane, the main component of compressed natural gas, which some people on this side of the pond actually use, and which is lighter than air.
Cheers,
Van

[Van]

Hi Arild,

Thanks for the info.

Very interesting comments about your speed vs RPM. Since you can throttle up to 2900 RPM (which is only 10% or so from the nominal max at 3200, and which is easily within the errors of the tachometer) it sounds like the prop is not overpitched much if at all. It does seem about right.

BTW, the 4-108 is rated at about 50 BHP (brake HP) which means running on a test bench under ideal conditions with no gearbox, alternator, etc. The HP at the shaft, so called SHP, is supposedly only 35-40 once you add all the other stuff.

Thanks again!

Van

[Van]

Am I right in thinking the blue Gaz bottles are butane and not propane? In this case, butane will not collect in the bilge as it is slightly lighter than air, unlike propane. OTOH, at some future point you or a future owner may want to use propane.
I like the idea of keeping your petrol on deck. We should do something like that….
Van

[Van]

When we had Rainshadow surveyed, one of the top areas the surveyor focused on was gas storage. The ABYC has lots of rules around this, and the insurance company wanted us to fix all issues related to this – so it makes sense to know the rules in your area.

We have two long propane cylinders, one 5, one 3 US gals. The cylinders lay on their sides, and the valves are located on the top sides of the cylinders.

These are stored in a purpose built locker located in the aft starboard corner of the boat. The locker floor appears to be fiberglass on top of plywood. Access is through the aft deck locker – you get into the propane locker via a door in the side of the aft deck locker. The propane locker is vented at its bottom through the transom (per ABYC) by a small approx 5mm hole. The locker is about 1 m long, and 1/2m wide. The two aftmost chainplates are inside.

Getting the bottles in an out through the door is challenging – it’s a tight fit.

The propane locker contains a manifold with a solenoid and one hose for each bottle. One propane line (copper, approx 5mm OD) and the solenoid wire runs from the manifold, through the locker wall into the region of the steering mechanism/rudder post, then down along the inner wall and down to the limber hole just forward of the rudder post. From there it runs forward along the port side of the bilge into the engine room, where it around the wall on the port side. Then it heads into the galley, entering under the sink. It then T’s off – one way to the stove, the other to the Valiant hot water heater.

To meet the standards we had to:
1. Make the access door gas tight by rebuilding it with a good epdm seal.
2. ABYC standards require a top access into the locker, so we added a 6″ deck plate. Through the plate we can reach both valves and read the gauges.
3. The standards also require separate gas lines to each appliance, with no extra junctions outside of the locker. In other words, each line must start inside the locker, and terminate at the appliance. T’s are not allowed. This is on our list of things to do.

I like this arrangement because the bottles are out of the way. The deck access port makes them easy to open and close.

Van

[Van]

Hi Trevor,

I 100% agree about the poxy outhaul. I also have had visions of getting flung overboard when it breaks. I’ve resorted to easing the sheet and letting the sail flog a bit to minimize pressure on the main.

I believe it has a 3:1 mechanical advantage inside, but I did not measure accurately (just used my hands to measure how far the outhaul moved when I pulled the “string” a set distance). Hoping to inspect it, I tried to get the end fittings off the boom and failed at both ends. I even resorted to an impact driver. The SS screws are impossible to move.

Looking forward to hearing how you implement an external outhaul! Our boom is already a bit of a mess of lines – 2 reefing lines and lazy jacks.

Re: the bent boom, unless it’s badly bent, you might be better off just ignoring it. It’s not good to bend metals past their elastic yield point too often.

Van

[Van]

Just stumbled on a boat I’ve never heard of that sounds of similar pedigree to the Nic 38 – the Fisher 37 (Fisher makes a variety of sized boats). It’s a British built motor sailer (ketch) from the mid 70s with the interesting difference that Fisher still makes these boats.

Fisher seems to have an active user group at
http://www.fisherowners.org/. Their classified ads suggest comparable boats to the Nic 38 have asking prices in the mid-50s (GBP) and up.

Unfortunately, you have to buy membership to look at their forums.

Van

[Van]

Hi Mike,

Just a comment about the “30 deg. out” statement you made. That might mean one or more of your compasses needs adjusting. Have you ever had a compass “swung”? I don’t know how this is done on the Neco compass, which sits under the settee just abaft the mast. It might also mean your trim control (top left) has some kind of offset.

Our NECO about 10-20 degrees off vs the binnacle compass, but it seems to depend on the direction. That’s close enough that the error we have in setting it is probably not much less than that. In other words, we read the compass and set the Neco to the same and then switch it on, but actually both are off enough that we always have to adjust it again or use the trim control to get it right.

I experimented a bit with using it to tack – basically, you have to set the sensitivity control (the bottom right one) to the correct speed so that it doesn’t turn too fast. Then, you just quickly rotate the dial 90 degrees in the direction you want to tack, and the autopilot will slowly turn the boat while you handle the sheets. It seems to work.

It’s a pity it is such a power hog.

Van

[Van]

Thanks – I’ll assume our messenger wire is gone too. Pity! Our mast has mast steps all the way up, so it’s easy to get up and down. So, I’ll probably try to avoid dropping the mast to put up the transducer.

Ollie, does the wiring run between the polystyrene and mast wall, or inside the polystyrene? Maybe it does not matter, although it would seem better if wires were trapped between the polystyrene and the mast wall.

Cheers,
Van

[Van]

Hi Trevor,

I had wondered if having two sheets was a viable solution, great to hear it works for you. It had not occured to me to up the purchase as well.

I’ll look into this some more, but it does sound very feasible and not too expensive.

Van

[Van]

Thanks Neel, that’s a good idea. I was contemplating using a “snake” (here in the US you can get long metal tapes that are normally used to clear drains). However, I don’t fancy being up the mast and fighting one of these. They tend to go beserk since they are pretty stiff and quite springy.

[Van]

It’s interesting to read the background for the Jordan series drogue. His design goal was to enable a boat (monohull) to survive a rare “worst-case breaking wave”, which he claimed was the cause of most dismastings and lost boats in storms – he also claims non-breaking waves, even in hurricane force winds, are not a real threat to well found monohulls.

His argument is summarized here:
http://oceanbrake.com/jordan’snotes.html

From the above web site:
“A monohull is directionally unstable when moving backward because the center of pressure of the underwater surface is behind the center of gravity. As any skipper knows, it is possible to run off before a storm – but it is not possible to run off backwards as the boat will yaw.”

The point he’s making is that whether you are using a drogue or sea parachute from the bow, you will be moving **backwards** through the water. Given how badly the C&N 38 moves in reverse, I can only assume it is really unstable in that direction and would yaw badly, frequently being broadside to the waves and wind. However, the boat is stable moving forward through the water with the wind behind, as it would be if using a stern-tied drogue.

He also claims that in the event of a breaking wave, the bow will bury itself in the wave – while he claims the stern is not as likely to do that. On the C&N 38, we have quite a lot of bouyancy in the stern (engine in the center of boat, chain fwd, etc) so he may well be right about it in our case.

He also advises (less convincingly) against using primary winches to attach the drogue. The forces generated in a breaking wave strike are enormous – >10,000 lbs. Instead, he recommends attaching to custom “chain plates” built into the hull (topsides) at the transom end. Must confess, having just spent a bunch of time over the last couple of days pulling chainplates (think seized nuts on the capshroud chainplates, which resisted every penetrating lubricant I had, a blow torch and two impact drivers) the last thing I want to add to our boat is more chainplates!

[Van]

The foam sounds interesting – but note that there is a bunch of wiring running between the head lining and the underside of the cabin top. You’d have to think of a way to make that look good, or else reroute it somehow.

On Rainshadow, the wires under the lining go to the obvious things like the two lights, but also I think for some reason they routed the windshield wiper wire via the galley light. Does anyone know if the wiper as originally installed, was on the same circuit as the galley light? That would explain the wiring.

The head lining as installed does use a pretty nifty fastening but it does seem to need some special tool or at least lots of hands – not sure 3 is enough!

Van

[Author]

Posts