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Hi Neil, am I getting too predictable!? 😲 Transducers; yes, above the waterline as much as possible, unless you want to stick your ears underwater to hear it! Thickening the hull might just improve the bass and dampen the treble by shifting the resonant frequency of the hull down a bit.
'New Posts'; just hit the 'Refresh' button of your browser. Ciao, Doug 😎
Young at heart - slightly older in other places 😉 Cheers Doug
Thanks for that Doug. Was wondering about using 4 small ones spread about so could keep them high up. Would that be series or parallel to match a digisound unit?
Re 'Posts', I mean in the 'threads' new first. I have pressed the 'oldest first button' to no effect...................
Hi Neil (or Neville?), There are two issues with using four. 1) Since these 4 Ohm transducers work by bringing the surface they are mounted on to move like a speaker cone, there may be no advantage. In fact two on the same surface may create waves through the hull side that partially cancel each other and thus reduce the volume. True, they may sometimes combine as well. This effect will happen in specific frequency ranges depending on the stiffness of the hull. Put one each side on the largest open area available as we discussed for the tug. Cheaper anyway 😉
2) Speaker impedance and the minimum that the amplifier can handle. Check the Digisound specs Output Impedance to see if the amp can handle 4 Ohms or only 8 Ohms, which is the case for all sound modules I have seen or used. As with your tug, two x 4 Ohm transducers in series gives 8 Ohms for max volume from an 8 Ohm amp output. Four in series would give 16 Ohms which would significantly reduce the volume produced. Two x 4 Ohms in parallel though only presents 2 Ohms to the amp, which highly likely will blow the output transistors 😡 All four in parallel would be only 1 Ohm which would most definitely produce the 'magic smoke' 😭
Don't forget to put a little enclosure around the back of the transducer after it's stuck to the hull. Cheers, Doug 😎 PS What 'Oldest First' button? I don't see one. If you are using the dumbphone App I can't help you. I DON'T!
Young at heart - slightly older in other places 😉 Cheers Doug
Hi Neville, where did I get Neil from?😲 Sorry can't help with balance point cos I don't know the boat. All I do is trim out in the 'Domestic Test Tank' for best balance along the waterline. Cheers, Doug 😎 PS I forgot the oilers😲 I only bother to fit them in fast boats with high revving brushless, like I did with my Sea Scout renovation, see 'Jessica' blog. For scale 'plodders' I don't usually bother. Just pull the shaft now n again and use a plastic syringe to inject some oil or Teflon grease.
Young at heart - slightly older in other places 😉 Cheers Doug
Thanks John👍 Hmm! Those guys should clean the bench once in a while😲 before they injure themselves on the swarf! Or it gets somewhere it shouldn't in the machinery or electrics😡 That cross bed looks exactly like the one on my Proxxon mini miller! Doug
Young at heart - slightly older in other places 😉 Cheers Doug
Hi Neville, The largest open area between bulkheads or stiffeners is the main criterion, not nessa-celery the thickness! BTW: What is the vessel anyway?? Doug
Young at heart - slightly older in other places 😉 Cheers Doug
No ouch with gloves on Doug. Works a treat on shafts etc. Shifts the scale alright. Follow up with wire wool for a nice shine. BTW your French let you down. No x in bureau unless more than one. Sorry. Same with gateau. Ciao signor😁
Ah! You mean the Forum Threads not the Build Blogs. Strangely blogs are as you want but Threads the other way up. Never bothered me. I just press Ctrl and Pos1 to go to the top or Ctrl and End to go to the bottom of either. Theses as Threads in the appropriate Forum topic please 😁 Doug 😎
Young at heart - slightly older in other places 😉 Cheers Doug
Hi Neville, you can't get newest on top in threads, but at least you can jump to the newest or the start! Congrats on the promotion👍 Welcome aboard HMS Pinafore Admiral😉
Attached Files - Click To View Large
Young at heart - slightly older in other places 😉 Cheers Doug
Thank you Doug. I still have to salute you of course................ I have been reading some of your 'builds/ refurbs.
Picked a lot up from those.
I assume 'Build Chit Chat' is the right place for the RAF Tender work.
Also, as a result of having issues with 'scale' sizes, I now have some extra bits for the Richardson!
I am sure Admirals should not have issues understanding 'scale', but I struggle to make sense of some of the proportions of deck furniture for example and windows.............
HI John So I wasn't far off with the 'boat transporter' was I!? 😁 Thanks for the tool links, You're right - I have those already, for my mini miller and the drill press. Cheers, Doug 😎
Young at heart - slightly older in other places 😉 Cheers Doug
These look useful Doug.I just ordered some----https://www.manomano.co.uk/miscellaneous-multi-tool-accessor... Also nice cross slide on Bang good but you have one--or two don't you. Boat transporter was the nice silver saloon on my drive which I stupidly let go to scrap😡😡😡😡😡😡😭👍. We need a thumbs down emoticon here.Hasta la vista senor. P.S. Why aren't keyboards standardised. For instance no END button on mine or accent tabs. Like cedillas etc.
Thanks John, have a good set set of milling, routing, grinding, drilling, finishing, polishing tools for my Dremel and Proxxon. Thinks! We should continue this in the Hobby Chit Chat section; thread 'Useful Tools'? before we overload Neville's thread too much! Will reply re emoticon and keyboard in 'Anything else'! Cheers, Doug
I got some of the rubber polishing buffs. They work well so I ordered some more.They wear down quickly though. Wore one out doing most of one engine.👍 Oops wrong thread.
Arternoon Neville, If you're happy with the way they work in the Richardson then leave the covers off. If you want to experiment fit covers around the transducer but not touching it, analogous to speaker cabinets😉 For simplicity it can be square/cubic in form, with the back about 1cm from the back of the transducer. Glue some thin, fairly dense foam rubber in the back. With luck this will concentrate more noise outside where you want it. The flyboys cut a hole in the fuselage and cover it with gauze, just like a Hi-Fi box. NOT very practicable for a boat😲 Cheers, Doug 😎
Young at heart - slightly older in other places 😉 Cheers Doug
A thin dense foam might be good, in case sticking it hard to the hull dampens the propagation along the hull side. If that does seem to happen leave it off, but bench tests are not much good for this sort of thing, only the acid test on the wet stuff is really useful😉 Doug 😎
Young at heart - slightly older in other places 😉 Cheers Doug
Im not on here that much, so a little late picking this up. Are you talking about TT25 transducers like the ones Mrrcsound sell/ I suppose they all work the same, I've used these a lot, in planes mostly, and experimented with boats, so can offer some hands on advice. Firstly, you don't cut any holes to let sound out, as this isn't how they work. Its all about the vibrations. The centre ring is epoxied (that's the best way, they have to be permanent, but with some teasing they can be removed it required, rather than cyno) to the surface, which obviously needs to be flat. The thinner the material, the more sound, but its marginal, as the thinner you go, the less bass, or deeper tones. With planes, the best material by far is the epo foam, so when mounting into a ply or balsa plane they work best going to foam, then the ply, and the same will apply for a boat. 2-3mm is generally the optimum thickness. Remember, the area is going to vibrate, so use an area that can do this, the sides of a hull are ideal. The back of the transducers get hot, so don't cover the back, the heat has to dissipate and once secure, make sure the unit can move in and out, its easy to drip glue in the wrong place and the whole thing gets stuck, it wont vibrate now, so won't do the job. Also, its worth epoxying the transducer to 2mm foam, epo that the ready to fly planes works best, its close density, the stuff that packs white goods is poor as its a more open density and falls apart. Once you have this, you can move it around by just holding it against the hull to see where the best sound is.
All this is relevant to the Mrrcsound transducers, I use a number of his sound units, so cant really comment on what you are using as I cant find that info on this thread (did a man read!) Here are a couple of my models to give you an idea👍
Great stuff. Really useful. Interesting that they do not want boxing in. It is the mrrc ones that I intend to use on the Launch. Have Dayton ones on the tug. Away at the moment but will check out you YouTube stuff when back. Are you saying more open foam/polystyrene works better than the more dense stuff? Cheers. NPJ
More dense really. The epo foam used on the ready to fly rc planes is ideal. I used Depron on the fire boat it’s the stuff used to insulate flooring. It was ok but a bit brittle.
30th Jul 2018 12:13
