Hi

I'm just changing from an ABS DF65 to a CF RG65. A personal choice as I don't like ABS. But I'm concerned about the Faraday Cage effect of CF hulls. Do owners with CF hulls place the antenna above deck? If so where and do they protect the aerials. Radio flyers use neat slated protection posts for example.

Thanks in anticipation

Stuart

If you mount the two aerials at right angles around the central or forward hatch with a patch covering you should be fine. I have used that on two different RG65's with no problems in range to at least 100m.

Where will you be sailing the RG65?

Thanks for the advice. As to sailing, not competitively but the RG 65 is an eassy boat to launch and retrieve for my 'oldies' social sailing club. Maldon and Blackwater Sailing Club. We have 5 IOM's sailed semi socially and a similar number of DF 65's. Plus J class and scratch built.

But its a 7 acre lake and a carbon boat may go out of range if I'm not careful.

Many thanks

Stuart

It can be useful to set your failsafe to a slight turn, and sails mid way out, in case of loss of signal due to range, it may then sail back into range 😊

You could always try a check with the boat on a cradle and see how far you can walk away from it before you lose the signal or get a warning. It's not quite the same as on the water but will give you an idea and you could always do a comparison with your DF65 setup to see how different they might be.

You wouldn't really want to sail it more than 100m away as it's usually difficult to see what is happening with your boat and other boats around it after 70m especially boats the size of the DF65 and RG65.

Peter

Thanks again. There is a problem with 'dry' range checks. I did a lot of research into this and found a solution. ELRS.

2.4gHz is an awful wavelength for rc boats. Remember the old 47 mHz, a much longer wavelength and much better albeit not digital. So digital replaced analogue for flyers and land vehicles, us boat users had no option.

It is all to do with the Signal to Noise ratio. When the signal baloons out (sort of a dohnut shape) the lower parts of the signal hits the water and is reflected, interfeering with the small bit of the signal that is travelling in a straight line from the radio antenna to the receiver antenna. Now if the Signal to Noise is poor, the signal is corrupted and being digital, cuts out. So the point is, you need to range check with the boat on the water.

What I would do is tether the boat to the pontoon and put it into the water, then walk around the lake and find the range across the water.

Another solution comes from the geeks who fly drones. They invented ELRS. This is still 2.4gHz and digital but uses a new technology delveloped for WiFi used in office blocks etc. WiFi (commonly 2.5gHz) is disrupted by printing machines, coffee vending machines, concrete lift shafts, people.... so the SN is poor but designers want to connect the printers and coffee machines to a central 'control' WiFi had too much noise. However they did not need to send as much information as they do in homes, they do not stream video for example. So instead they send a much reduced set of information, hundreds of times. A smart chip in the receiver recognises the majority as uncorrupted. ELRS does this for RC users and extends drone range from 1 or 2 KM to 10!

I use if for my boats. It is good. And cheap. Radiomaster have just launched a transmitter ideal for boat users, the L8R, costing £35. Fully programable by plugging your pc into it at home, so you can set end points, failsafe positions and a lot more.

But I don't know if it overcomes the Faraday Cage effect of a carbon hull.

6 hours ago, Stuart Munro said:

But I don't know if it overcomes the Faraday Cage effect of a carbon hull.

Other than extreme wavelengths, a carbon fibre hull is still going to have significant Faraday Cage effect...

Yes, I thought so hence my question about placing antenna outside of the hull. My intention is to place one antenna alongside the backstay and the other across the deck a few mm above one of the patches. Probably using an acetal bar to support it. The (almost) vertical one alonside the backstay will normally be enough with ELRS, the other will give backup.

However, my cautios approach tells me that if the boat keels away from the transmitter, both antenna could still be shielded by the hull. So it would be interesting to know how existing RG65 captains with CF hulls fare.

I have had some very helpful replies but I'm not sure if they are sailing CF hulls.

Stuart

3 minutes ago, Stuart Munro said:

Yes, I thought so hence my question about placing antenna outside of the hull. My intention is to place one antenna alongside the backstay and the other across the deck a few mm above one of the patches. Probably using an acetal bar to support it. The (almost) vertical one alonside the backstay will normally be enough with ELRS, the other will give backup.

However, my cautios approach tells me that if the boat keels away from the transmitter, both antenna could still be shielded by the hull. So it would be interesting to know how existing RG65 captains with CF hulls fare.

I have had some very helpful replies but I'm not sure if they are sailing CF hulls.

Stuart

Two antennae definitely sounds wise - as you say they [dipoles] have a doughnut radiation pattern.

I use Spektrum gear. My IOM has an rx with two perpendicular antennae - a decent system will/does use diversity to choose n meld between them. My DF has a very cute rx the size of an eraser -'only' pcb antennae, but I've never had range issues on our lake. Of course, neither hull is carbon...!

If there's a way to have external antenna (without water ingress) then I'd def aim for that. But other RG people probably have real world experience/advice

There are a lot of carbon Marbleheads around that are not having problems, my Marblehead aerial pair are just under some deck patch material at deck level, and I don't have a problem. The 2.4Ghz doesn't really like going through anything, including water and people. Stand with 5 other sailors between your TX and the boat and you may get a problem. Don't forget that for maximum signal ideally your tx aerial and rx aerial should be parallel, i.e. don't "point" your tx aerial at the boat. With respect to distance I have recently been sailing a DF65 on a large lake at 350m away, and with model aircraft much further away.

John, thats very helpful thanks. Of course the DF65 is plastic so no problems. Agreed 2.4 Ghz is the worst frequency for sailing but in reality is OK for the range we require as long as you are sensible with antenna placement, as you say.

Most sailors place the antenna level with the deck, just under it at 90 degrees from each other but in theory, a vertical antenna paralell to the transmitter antenna which is also pointing upwards is the best configuration, as long as the exposed 3cm or so of the one in the boat is all above water.

Here's the rub as they say; I don't race so watching the boats closely is not critical, but ranging across the lake some 200 meters is common. To be comfortable I will place one antenna above deck by making a plug from delryn with a small hole in it. The plug 'glued' into a hole in the deck with silicone bath sealant and the antenna pushed through and sealed the same way. This antenna will slide into a piece of plastic tube during rigging, to hold it to the backstay. The other antenna as you do with the Marblehead, just under a deck patch.

I've run a simple 3D printed plate in my Marblehead, and currently a SAILSetc fitting in my Six Metre, both carbon hulls, without problems. They fit inside the pot.

Thanks for a great IOM site. My go to bible!

I'm sure that fixing the antenna just under a deck patch will work - most of the time. The question at the back of my mind is what about an extreme condition. 200 metres away, keeling over away from the transmitter. Those awful reeds seem very close!

So putting one antenna through the deck at the stern, just alongside the backstay and then using the backstay by inserting it into a plastic tube that is already around the back stay will support it. Easy. My only issue is the length of the lead for the antenna. I use Radiomaster (ER6 ELRS) and I believe this has IPEX 3 connectors so a FrSky IPEX3 250mm or 300mm will do the job.

Then a much reduced risk level.

Keep up the great work on onemetre.net

Stuart

Just with my experience with carbon boats I tend to put a lipo 7.4v in my transmitter just give it more power through to the signal and I never loose signal that’s with my futuba t6j I use

Cheers Olly

Hi Stuart

In case it is helpful, a quick distance estimator using your extended thumb... (smile)

"Thumb Tip" distance estimator
Arm length (A)	550	mm	eye to upright thumb
Boat size (B)	650	mm
Width of thumb tip (W)	20	mm	eg, at nail base
Size in the distance (Z)	0.1	thumb tips	that is, approx 2 mm
Distance to boat (DtoB)	179	m	= (A*B) / (1000*W*Z)
			= ROUND((B4*B3)/(B5*B6*1000),1) if the data is in Excel
Relationship			DtoB : A ≈ B : W*Z

AR410 or AR620 if using spektrum. Great bits of kit.

Thanks evereyone, you have been very helpful. Olly, I use a Radiomaster TX which is capable of 1w output but limited to 100mw by UK law. So the battery makes no difference but some older TX systems were built to only output 80 mw or so, I suspect higher voltages will help in those cases. RoRo, I originally had a Spectrum system but found a major flaw in it, the radio could not swim in our salt water lake! Then I discovered the Radiomaster ELRS systems and never looked back. The programability is not for everyone but if you are comfortable with it you can program complex systems. So for example I am working on a 60 inch J with genoa, the main will have a traveller but as this moves to port, or starboard it adds 3cm to the sheeting length. The sheeting servo is set to automatically loosen by 3cm when the traveller is activated. But the ELRS is what sells it providing much inproved radio reception.

But my star award goes to Lester. Great fun idea. Radiomaster has a toy for this. For £23 you can buy a GPS position transmitter to plug into the RX, The Transmitter screen can produce a map of the lake and you can see where the boat is. Rest assured I've not done it but seen the results for a drone flying around a field. Impressive toy.

I don't see battery voltage making a difference to rf performance- the internals are bound to be regulated to (probably) 3.3v

Battery might make a difference if it is better able to deliver the current than a smaller one, but I'd be surprised if a Tx with a 7.4v battery worked any better than (with same power delivery capability) a 5v one.

20 hours ago, RoRo said:

AR410 or AR620 if using spektrum. Great bits of kit.

Yup - I have a 410 in the df95, a 610 in the iom.

I had the 410 lying around when I got the 95 - wasn't sure if it would be up to it given the pcb antennae, but never had a problem at LRSC (100-150m range)

Edited January 11Jan 11 by Colin Helliwell

2 hours ago, Colin Helliwell said:

Yup - I have a 410 in the df95, a 610 in the iom.

I had the 410 lying around when I got the 95 - wasn't sure if it would be up to it given the pcb antennae, but never had a problem at LRSC (100-150m range)

I do the same with my smaller models

DF AR410 also carbon RG65 never had an issue a large ranges.

I use the AR620 in my larger models upto 10R never had a problem at the top of the wall of my pot lid at some big lakes where seeing the boat was more of an issue at the windward mark👌🏻

Edited January 11Jan 11 by RoRo

I agree, Spectrum is good kit and I used to have one until I dunked the transmitter in the lake. However the new ELRS technology really does give a more reliable signal butas you say, is most likely not needed where we can keep the boat in range of our eyesight! But for anyone who is having reception problems, after checking antenna alignment and placement, I'd suggest looking at the technology. There are a growing number of manufacturers starting to use it but probably the most popular is Radiomaster. The other big advantage is the an ELRS RX made by any manufacturer is required to work with any ELRS transmitter so the range of receivers available is large.

One warning, the radios tend to use open source firmware, EDGE Tx. This is really good but it is not 'plug and play'. For me, I enjoy the technology and make it part of my hobby,

I have a flysky RX/TX the receiver ariels are at 90 degrees in the centre of the hull just below a deck patch.

When the boat is at long range and healed (so that the carbon hull comes between the TX and RX ariels) it looses the signal. When this happens, failsafe lets out the sheets so the boat stands up and receives the signal again, this causes it to pull in the sheets, heel over and loose signal again etc etc.

So carbon 100% definately screens signals between RX and TX.

I have drilled 2 small holes and mounted the ariels flat and right at the edge of the deck. I havent had a chance to try this yet but suspect it may not be enough and that the ariels need to be stood up proud of the deck.

I will be building from glass in the future - carbon is too much trouble :-(

3 minutes ago, Pie said:

I will be building from glass in the future - carbon is too much trouble :-(

And, in reality, does carbon have advantages? Assuming most of our classes probably have a minimum weight anyway? And they're sailing on mostly inland waters not taking a Southern Ocean pounding. A lot of One Metres are being 3d-printed in PLA these days (don't leave em in back of car on a sunny day tho....), and winning by virtue of the skipper.

I can see carbon spars/fin maybe giving advantage/predictability, but a <2m hull??

Just because new tech can be used, doesn't mean it needs to be. The older simpler and cheaper ways can still be better overall.

Edited January 12Jan 12 by Colin Helliwell

Interesting debate about using carbon and I fully agree for normal mortals, but at the top end carbon will have advantages.

I also sail J class boats (Alan Horne 40" and 60"). These are rather tender ie they keel over alarmingly in any wind. To reduce this tendancy the builder must move the weight down as far as possible. I am currently building a 60" and am using carbon for the internal structure and servo trays, it may not seem much but it shifts about 150g from above the waterline to below it. I've read that this is also an advanytage with carbon IOM's, by increasing the keel ballast by even a fraction the boat stays more upright than a boat thagt does not have a carbon hull.

So as I say, for mere mortal sailors like me the fraction of a second saved is far outweighed by a more skilful sailor, but at the pinnacle of the sport it may matter.

As Colin Halliwell says, the increased stiffness of carbon over fibreglass is also a factor. Not only but certainly for the keel and rudder but possibly the hull. My glass IOM hull flexes quite alarmingly, probably not when in the water but perhaps....

1 minute ago, Stuart Munro said:

My glass IOM hull flexes quite alarmingly, probably not when in the water but perhaps....

In the water, the loading is far more distributed than poking it in one spot with your finger ;)

40"/60" hull - yeah I could imagine the stiffness of carbon being useful there. Personally I'd be too distracted by the plain beauty of a J to notice!

I think IOM has max weight for fin+bulb alone, so there's a limit there. Could move the centre-of-gravity of the hull down tho, I guess. (Getting into the territory where there's far more knowledgable than me on yacht design lol)

Edited January 13Jan 13 by Colin Helliwell