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Many years ago I built a 49 inch wooden hulled Perkasa which I powered with a Merco 61. In those days suitable water was hard to find so I got rid of it and am now kicking myself for doing it. I am in the market for another one but whilst I can find many wooden hulls I am really looking for GRP or plastic. Any ideas chaps?
Thanks to a member of this site I have now acquired a part built GRP hulled 49inch Perkasa, which will make an excellent winter project. As you can see, my previous boat was i/c powered, but this time I am going electric. Twin shafts have already been fitted but I would welcome any advice or thoughts on motors and props please? Thank you.
Hi I believe President don't do the glass hull now due to a fire at the factory who produced them so now only have the wood hulls. I also have the 49" Perkasa (grp) hull you can see a picture in my profile, I run mine on a single prop with the following set up and it runs very stable and very fast although you need a big water to open up to full throttle..........
Leopard 4074 brushless motor Tinergy 120A ESC 35 prop 2x 500 4S lipos wired in parallel....... gives about 50 mins fast sail time even longer at a more scale speed. Mtroniks digisound sound module Spectrum DX2e wheel type transmitter.
Thanks for that. Mine is already fitted with twin shafts and a friend has suggested that I use two 900kv outrunners with 60amp esc's. I notice that you are using an Mtronics sound system, I assume for the motor sounds. What sound do you use as I understand that these boats were fitted with gas turbine engines?
Can't find a gas turbine sound anywhere but I used the air start diesel (details below off there advert)better than nothing and quite impressive ( I think ).
MTronik Digisound Large Multi Cylinder Air Start Diesel Ref: 4462 The digiSOUND5m is the new marine sound module from Mtroniks Ltd. It is the worlds first 100% waterproof, plug n play sound module designed to take the hassle out of giving your model a realistic sound! The sound module requires NO programming or set up, it comes with a realistic sound pre-installed leaving just the installation to complete before you can get under way! The unit comes complete with built in amplifier, wiring loom and even a 75.0mm diameter waterproof speaker! You simply install the unit in your model and go! There is no complicated PC interface to deal with or complicated set up, you REALLY do just have to plug it in and go!!! Add this to the legendary Mtroniks waterproof construction and you really don't need to look any further! Peter
Peter Had a look at the Mtroniks unit. Looks good but the price puts me off. I have found this one, http://www.modelsounds.co.uk/index.html which does various gas turbine sounds. Unfortunately the sample is voiced over warning not to download it so I can't really get a good preview. Have you come across this one before? Steve
Hi Steve Yes I did look at the Masterblaster but it appears to be an on/off devise the Mtronics sound is portional to the motor speed I.E. From a tick over it increases as you throttle up or down to relate to the motor speed, it picks the motor speed up from a sensor that is joined into any two of the three motor wires and must say the installation is very simple with the pre made and plugged wiring harness. Hope this helps Peter
Hi Steve The model sounds units produce realistic sounds but are not that loud if you intend to use them on the water. I agree the Action and Mtronic units are not cheap but do mimic the throttle setting. Which ever sound system you use you will need a good 20watt amp and large 5" speaker mounted on a baffle to get realistic sound on the water. My Trent uses the original Action sound unit with a Technobots 20w amp and 5" speaker mounted on a baffle midships. The sound is easily heard on the water and I had to fit a potentiometer to reduce the sound when I display the model. One of our club members downloaded a gas turbine sound from the internet and used a simple solid state player in the model. Sounded very realistic. I will ask him for the link and let you know the details. Dave
Gentlemen Thanks for your advice and thoughts. Dave I look forward to more info from your club member. I'm still waiting impatiently for the new year to make a start so am spending the time gathering a few things together. Advice on the power unit inclines towards two 900kv outrunners with 60amp esc's. Not got as far as props yet. What do you think? Steve.
Hi Steve Spoke with my friend today and was advised he purchased a cheap MP3 player form ebay and serched on-line for Sound effects. Downloaded a sample clip and made it into a full length sound using Audacity (free) or similar. As it's a gas turbine you do not need to have rising and falling sound so it sounds OK. He also loaded some gunfire sounds just to add to the realism. Sorry he dosen't have the link but there are plenty I found on the web. I do have some video with sound of his Al Muzzia and will load to U-tube and send you the link. Dave
Hi Dave I am having trouble coupling the motors to the shafts, due to the shafts being threaded BA. According to Cornwall Models rubber couplings are only threaded metric, so unless I re-thread or change the tubes I can't use them. However, they have suggested I use Raboesch Needle Couplings as an alternative. What do you think? Steve
Hi Steve I have looked at the Raboesch site and can't see any BA threads on any of their couplings. The pin type couplings are noisy and more suited to an IC powered model. 😀 I probably have some couplings for the Perkassa but what exactly are you wishing to use? Ie what kind of coupling? Can you post a pic of the coupling? Do you know the BA size of the propshaft? I'm sure I can help you with a bit more info Dave
Dave The coupling I have been advised to use is the rubber one, due to the speed of the motor. Ordinary universal couplings won't be strong enough. When I got the boat, the original inserts (for universal joint couplings) were screwed on to the shafts, but neither the existing shafts or the inserts can be used with rubber couplings, as these are only threaded metric. I seem to have three options:- 1. Replace the tubes and shafts which would mean cutting big holes in the hull. 2. Re-threading the shafts to metric to take an appropriate sized rubber coupling. 3. Use Raboesch needle couplings which you can see here - http://www.cornwallmodelboats.co.uk/acatalog/raboesch-coupli... Malcolm, at Cornwall Models, initially suggested option 2 but then suggested option 3. He did say that the needle couplings were suited to i/c, but said the coupling itself was enclosed and unlike universals, not prone to expanding and breaking. Hope this makes more sense? Steve
Hi Steve I see the needle file couplings are nylon so should be much better than the original metal variety. Both types of Fittings on the link say they are good up to 2.5cc ic engines so I assume the advice given relates to use with ic engines where the power is not as controllable as with electric power. I refer to the fact that ic engines are often started out of the water then launched at high revs resulting in considerable shock to the couplings. My own experience is that universal are ok with electrics even high powered brushless. I believe I would go with option 3 assuming you can get the fitting with the correct thread. Re threading the shaft is not that easy and a possible better option is to re-thread the coupling. You will need a lathe to do this accurately to avoid misalignment damaging your bearings. Should the joint prove to be noisy I suggest putting a sleeve of Silicon tubing ( as used for ic engine exhaust coupling) over the joint to take up the tolerance in the ball and pin coupling. Regarding replacing tubes I usually obtain a new tube and shaft of the correct dimensions remove the shaft and bearings from the new and old fitting and replace the new in the old shaft. Only works if the old tube is serviceable and straight but usually works fine. As I have a lathe I can make new bearings should the tubes be of different diameters, but often this is not a problem. Good luck and please post how you resolved the issue. Cheers Dave
Hi Dave Chris, who you met when I collected the boat, suggested looking at replacing the bearings and shaft, but as it was non metric, I didn't think it would be as straightforward as you suggest. I'll store that info away in case the needle couplings don't work. The couplings will be with me tomorrow, so I will let you know how it goes. I have attached a pic of my previous boat, unfortunately I have none of the power train. As you can see, it's pretty basic and all the fittings came with the kit except the gun barrel (machined metal) and torpedoes (broom handles). Thanks once again for your help and advice. Steve
Hi Steve I would go for a left and right hand brass 3 blade prop of a similar diameter to the motors. A quick test with a wattmeter should indicate if all is working within its power rating. You can then move up or down a size to correct to the optimum on water performance. You may need to water cool if heat is a problem but tghis is easily added later. Good luck with the tests - any chance of some video on the water Dave
Thanks for the advice Dave. I'm sure Chris will be on hand to do some video if I ask him nicely. Not too sure about the mechanics of a 'quick test with a wattmeter'. Can you elaborate please? Thanks Steve
Hi Dave Power train installed and working. I am currently using 55mm 3 bladed brass props supplied by Jotika (Propshop and Cornwall Models haven't bothered to reply to my telephone and emails). Chris only managed a short video and I didn't push the speed due to an open hull and rough water, hence the stills. Looking promising so far and I will keep in touch as the build progresses. Steve
Hi Steve Looking good. Its does look very mean and when finished will look the part. You may have seen my P150 36" version when you collected the hull. I sailed it on Sunday in some rather rough water. Good job it was so cold so I didn't mind the short sailing time. I look forward to seeing some video of your model in due course. Dave