Hi Rogal

Wonderful model with great detail in particular the mast detail and radio aerials. A long time ago I was a National Service man in the RAF and after my initial trade training as an air wireless fitter was posted to RAF Mountbatten at Plymouth, this was in 1961. By then the marine craft service in the RAF was being greatly reduced due to its primary role in air sea rescue being taken over by helicopters the main roles then were target towing and general range duties. Mountbatten had become the maintenance unit of marine service and when I was there we had some RTTLs, and a number of smaller boats. It was an unusual RAF station in that we were both the Maintenance Unit for the service and an operational camp. I was only there for a year and was initially only involved with the normal daily activities of testing and repairing the radio gear fitted to the boats. But as in civilian life I had completed a engineering apprenticeship I was capable of producing engineering drawings, so I took up residence in the small room nominated as the drawing office with just me as its resident. The job I was given was to produce the drawings of the installation of the UHF radio in the RTTL this was to be used as the locator system in the recovery of Sonobouys. The aerial arrangement for it is the twin multi dipole system you so skillfully produced in your model. The thing that looks like a cage is the di pole for the VHF radio system which was the main comms provision for the boats.

I had a few trips on RTTL's but generally not too far. There was an original build of the RTTL that still had 3 Napier Lions as the prime movers and I set off one very fine day for a joy ride on this, but not long after getting outside of the Plymouth break water one of the engines packed up and we sadly had to come back.

I have never seen before a canopy fitted to an RAF boat and as a RTTL was capable of going quite fast I wonder if it was something a bit unofficial, done locally near the end of its service.

Glad to see a bit of history recorded and achieved, you have done a great job.

I have now taken the batteries out of the chair the voltage barely detectable have connected them up to the charger to see if some life can be brought back to them but I do not expect I will get very far.

Checked charger output at about 0.75 amps and voltage from open circuit only fell from 25.3 to 24 volts. Trying to workout circuit diagram of chair charging system.

Great job but I am not sure that 2762 ever had that arrangement. When I was at Mountbatten in 196/62 the boat still had its aluminium hull showing, I think it had its timber outer skin added at that time. I was involved in the initial fitting the UHF radio to the RTTL at the time, when I finished my National Service in May 1962 it had only been fitted to one RTTL. Later pictures of these launches show that the UHF system was fitted to them and the mast was somewhat modified to fit the twin multi pole aerials and stays. Some pics of 2762 show it was fitted at some later time. Your new mast system also does not include the VHF aerial, it is possible later in the life of the RTTL the VHF system was removed and fitted with the UHF system because that was the intention for aircraft.

What number are you going to give it 2762E or 2772E ?

My new 24 volt charger arrived to day from e bay, cost with delivery £ 10.69. This is with a very nicely made connector that I will remove. Output voltage unloaded 25.4 which would seem about right for two 12 volt batteries in series at indoor temperature.

Other for sale on e bay nominally for stair lifts ranged from £ 199 down ! which further confirms my belief that a lot of the infirm are being ripped off.

When I have time and the energy, next to get the old batteries out and see what state they are in.

I forgot to attach the pictures.

Nice heat sink but I would have concerns on how well the heat will be conducted out of the switching transistors. I have had failures before getting them into a boat, with these Chinese ESC's.

I took one failed one apart by removing the shrink sleeve that holds the PCB mounted switching devices against the heat sink. Between them is an aluminium foil label. This arrangement does not allow a lot of air to get to the fins of the heat sink or provide a very good heat path out of the switching devices, there are a total of six, I assume they may be operating in parallel for the three switching channels. I do not know much about the theory of brushless dc motors, so do not know what their back emf characteristics are, but they are very unlike a brushed motor in that the speed is changed by altering the switching frequency and possibly if there is no back emf, the current switched does not vary much with speed, rather like the squirrel caged motor where the current is nearly constant with load and the power factor changes, this gives a problem due resistive losses.

I have attached some pictures of one of my failed ESC, showing the construction. If you do not mind butchering your one and cutting off the shrink sleeve and attaching the PC assembly directly to your water cooled device, preferably with some heat conducting paste, it might stand a better chance of surviving.

I shall watch with interest, as usual, your progress with water jet power.

We all started off quite a long time ago, me with model aeroplanes with balsa, tissue and strong smelling glue. I did not come to boats until much later in life, in my case, as with so many others the Keil Kraft Fireboat, I still have mine some 40 years ago since I made it. It has had a couple of re fits the last quite comprehensive.

Boats last and probably give greater satisfaction in the various versions you can build than aeroplanes. Most of us move to a scratch build, in my case the Coromandel which has family history connections.

The problem we have these days is children are not brought up with the skills that come with woodwork in school and meccano at home and the attraction of computer games is great. Perhaps they are the skills that may be useful in the future, computer printing from scratch, probably is not very different from cutting the bits out of wood or metal and it does have the advantage you do not have to have so many tools, other than one very expensive one, the printer and computer.

Hi piers

You are a bit like me have been a member for a long time with big gaps in our building. I have two on the go very slowly at the present time, but have a lot of other things to do.

Best of luck with your re start and this site and its members are a great source of information.

nasraf

Sorry about the failure of your ESC's lucky you got your money back.

I do not know much about them, but I have lost a couple for no apparent reason.

I have bought 3 off Aliexpess and run them just with a bare motor and they seem to heat up quite quickly so when at last I finish my HSL I will try and arrange some cooling for them, the heat sinks do not look very substantial.

Hi Griss

Thanks for the response I will have a look on Aliexpress I am already a convert.

Hi Roycv

It is not possible to add a third terminal, as the connections are made with effectively a pair of brushes at the top and bottom of the rail. So I am afraid that they will have to be charged in series.

Thanks for the suggestion.

Thanks Roy

I should have explained the set up a bit more.

The batteries are 2 AH and are enclosed in the seat structure so it is only possible to get to the terminals of two batteries in series, actually you can only get to the wiring of the sliding contacts on the chair rail. The chair parks either at the top or bottom of its rail and then is on continuous charge.

From the info you supplied it would be probably be best to get a constant current charger with a nominal 24 volt output and run it at something like half an amp, I do not know if there are any relatively cheap chargers capable of doing this on the market ?

This is not specifically a model boat problem but I expect those who use this site know more about charging small batteries than anyone else.

I have a battery powered chair lift that I had fitted to aid my wife through her illness before she died and as I am getting on a bit, I have kept it in case I need it and you getting nothing for them if you put them on the market.

Whilst she was still ill the chair failed to operate about six months after I purchased it and I looked into the problem and found that one of the two 12 volt 7Ah sealed L.A.batteries had failed. At the time a just bought a new one and got the chair going again. After she passed away I left the chair and when I checked a few months later it failed to operate again, but as I had other things to do I just left it, but now want to make it operational.

First thing I did was to see if I could get a circuit diagram of the device, but I think these are closely guarded secrets, so that the rip off companies who sell them to a very vulnerable public, can force them into taking out very expensive maintenance contracts.

I know a reasonable amount about electrical devices so decided to poke about and see what I could do without a full electrical circuit. I also had a look at E Bay to see what was available there in terms of spares. I was interested to find for mine there were two battery chargers available one with an output of 33 volts dc and another with an output of 24 volts dc.. I checked mine and it was one of the 33 volt sort, I think the latter version to be fitted initially to ensure, after a relatively short period you would need the assistance of their expensive maintenance man and a subsequent service contract. As when I worked for money, I was involved in the design of i.c. engined generator sets for guided weapon systems so I had had some experience of charging L.A. batteries over large temperature ranges from minus 30 to plus 52 centigrade. Due to this large range we produced a charger that varied its output potential dependent on the battery temperature.

Its a long time ago that I was involved in that and do not have access to the ideal charging potentials. However with access to a whole heap of experts, what do you think is the ideal continuous charging potential, at say 20 degrees centigrade, for a 12 volt 2 AH sealed lead acid battery. Then after I buy new batteries, as I am sure that what is wrong with the chair at present is that the batteries have died due to continuous over charging, make a charger that will give me a good battery life.

Thanks very much for the info.

I have gone back a long way on your Brave Borderer saga but I cannot get back to the start. I notice this with my first build logs. I assume this is due to the system memory size or perhaps things are still in the old Fireboat site I expect someone out there knows the answer.

I really liked the look of prop and shaft installation. I shall throw away my cheap installation plans on the HSL 100, that at present lies untouched for the last 8 months on my lounge floor and make something more impressive like your drive system.

From the picture it looks like the prop shaft threads through a brass tube in the hull and then to the stern support bracket/bearing. With a bit of the rotating shaft exposed to the water is this correct.

I like the look of your prop, where did you get it ?

Although the HSL 100 had 3 Sea Lions to push it along I am taking the simple route of one motor and one prop shaft. You have given me and the thought that it will not be so cold in my garage soon, the inspiration to get on with my build.

I can remember 2762E from my time at Mount Batten ( 1961 to 1962 ) mainly because of the E suffix. I think from memory, its a long time ago now, that it spent all its time out of the water and possibly is when it had the timber cladding added. At the time I did not realize that it was a prototype its only since I became interested in this site, as like many others and was drawn here when restoring my Fire Boat.

Thanks Graham

I am sure you will find the book interesting, I learnt a lot particularly about the difficulties in rescue in the war.

I have a vested interest in you liking this message as I am one point away from promotion from 2 nd class to 1 st class, actually looking at the note on the LH side of my screen this message is worth two points, so shall have promoted myself.

Your project has got me into a bit of research into the RTTL's. When I was at Mount Batten there was probably about 5 there then. My billet was on the third floor and we overlooked the Sound, when a RTTL came in it had a very characteristic sound, even with the engine no doubt at a low speed.

We used to do daily radio checks on them, but did not get rides, as they usually, when they went out it was for some time and it was not appreciated if you disappeared for all day. We used to get lots of rides on the Range Safety Launches as these did dingy drill for air crew and you could arrange to be doing a radio check, when they were going out beyond the breakwater to dump the pilot into the sea with his un inflated life dingy.

I did have one day out on a Mk 2 RTTL, but only across the sound and then to anchor there for the day on a nuclear attack exercise. I was glad to get back after rocking back and forward for six hours, it would have given the crew a lot of enjoyment if I had been sick.

I did have another much more enjoyable ride on the one remaining Napier Sea Lion powered Mk 1A RTTL that was still at Mount Batten, I think it had been kept for historical reasons and had not been modified to fit Griffons. As far as I was aware it was never used operationally, although we did daily radio checks. One day I found out that it was to be given a test run so arranged to be on it when it went out on test. It was a lovely sunny day and the sea was calm, we got outside the breakwater and the engines were opened up but the trip at speed did not last very long as one of the engines failed, but we still had two left so could return to the Cattewater safely. It may have been the last day that a RTTL ever ran on Napier power.

Having a further look through " RAF Air Sea Rescue Service 1918-1986" there is quite a detailed account of the demise of 2754 which I have attached.

It would seem unlikely to me that anyone would have taken the risk of attaching an explosive charge to it before it finally sank. In my time when involved with the RAF marine craft activities, some 15 years before the loss of '54, there was very little of any interest to any foreign power on board, other than perhaps the engines.

I do not know if the main long range radio system was ever replaced as in 1961/62 it was the system used by the RAF in the Second World War i.e. 1154 receiver and 1155 transmitter. On my radio course at Yatesbury we were told that you will never see one of these in service so we spent the two days allocated to this equipment listening to the BBC on the receiver. Luckily there was a civilian engineer who knew these units and he kept them going.

Hi All

Sorry made a mistake for RTTL number in photograph should have been 2753.

Hi sidestickflier

I was interested in your project as a long time ago I was a National Serviceman at Mountbatten ( Plymouth ) from May61 to April 62 where was an Air Wireless Fitter, we did not have any aeroplanes but the RAF boats were fitted with aircraft equipment. As I had been, prior to my enforced service to the Queen, employed in the aerospace industry, I had some technical drawing experience, consequently I became the only person in the drawing office, this was better than going round the boats doing the daily radio tests. My main task turned out to be to fit the new UHF radio to a RTTL, the intention of it was to locate and recover sono buoys. Because of the high frequency used the signal was very directional, so the RTTL was fitted with a pair of multi dipole aerials. I never saw the end of the project but I have a book " The RAF Air Sea Rescue Service 1918-1986" that has a picture of RTTL 2754 with these aerials, which I have attached ( sorry its upside down but I have forgot how to change it ).

I have been a member of this site for a long time and supposed to be building a HSL 100, but since the lock down and having got involved in too many other things it has not gone forward for some time, hopefully I shall get back to it. As far as I know RTTL 2757 is in the RAF museum at Hendon but I have not been there for a long time and it was in a sorry state last time I saw it. From my other interest in aerospace museums, the arts university educated curators being put into positions of power are buggering up our heritage and destroying priceless items with their "political correct" activities, so it is even more important that us model makers keep up the good work. There is one thing about model boats is they last, look at all the Fire Boats there are about still and they were the inspiration of this wonderful Web Site, it reminds me I had better make a donation.

Good luck with your restoration.

I wish you had started this build before I started the HSL, particularly on the frame and stringer pre assembly. Also I have now found out that it is a major error not to cut the openings in the frames before the structure is assembled.

You are giving a master class on how to do a scratch build.

I like the block "chopper".

Having been away from this admirable web site for a few years doing something else, I have missed following Mike's story in building his Fire Boat. There is probably not a better one built or such a comprehensive blog of the journey to its completion and I can see why it has taken three years to do. He should be very pleased with his achievement and of displaying the art of the engineer, that I fear is being lost with the younger generations, who have not been brought up with meccano and model making with bits of wood and metal.

Well done from an admirer.

After a number of days doing other things and being put off working on the HSL due to finding that a couple of the frames I had cut by estimating the form, these were nos. 2 and 3 from the bow were not of the correct size. This, using quite thick 3 mm ply, made it impossible to bend the material adequately to contact the frames and chine stringers, I have very little experience in building models from scratch, in addition if I had managed to form the ply covering, the shape of the bow would all be wrong.

Another thing I had wrong was to try and form a too big ply sheet, I had managed to do this for the aft end of the boat where there were no complex curves, but at the bow end this was a failure.

To some extent I think these problems are due to my idea of building the model from the deck up, if it was just frames with fitted stringers the errors would have been obvious much earlier.

However as this is a bit of an experimental project and all my frames are already glued to the deck and I did not want throw it away and start again, I decided to bodge it up, hopefully no one noticing when the hull is finished. This has required lots of little packers to be added around the wrong sized frames. It also took me some time before I gave up on trying to fit large plywood panels in the bow area. I have found that strips of 3 mm ply cut in strips of approx. 15 mm wide can be persuaded to follow the curves required to the first frame from the bow. The bow section I intend to do in solid plywood pieces and sand down to the required shape.

To day I received the two Chinese ESC's that I obtained from Ali Express after the useful advice from jbkiwi. They were very cheap at about £ 10 for the pair including PayPal exchange costs and delivery, but I think I have probably made another mistake in only getting them with a rating of 30A. They took 21 days from ordering to arrival, but I think a lot of this time was due being in customs in the UK.

I have tested both of them on my motor test set up and I found they got hot quite quickly. I think the motor I have, probably needs at least a 60 amp ESC, I now know where to get one and for the initial work the 30 amp units will be OK.

As I had my original defective ESC and this had a finned heat sink, I cut the shrink sleeve off half one of the 30 amp units and glued it to the small aluminium plate heat sink that I found under the sleeve material.

I then ran the motor for 5 minutes at a moderate speed and I would estimate that the sink got to about 50 degrees centigrade using a 3C 2.8 amp hour battery which will be adequate for the early stage of the project.

It is now back to the drawing board as I have an idea to effectively mount the motor off the prop shaft and thus simplify the motor/prop shaft coupling.

I have attached some pics of hull build and esc test set up and modified ESC.

From the book " the RAF Air Sea Rescue Service 1918 to 86" the correct name for your model is HSL 100 Type Two. Evidently all together 69 were constructed between 1940 and 1942 with the following numbers 122-149, 156-190 and 2546-2551.

The general term " Whaleback" I find a bit confusing as this title was also used for the Thorneycroft 67 ft. HSL that followed the Type Two, of which a total of 105 were manufactured between 1942 and 1945.

I am at present trying to scratch build, a HSL 100 Type One 64 ft HSL, but it is going a bit slowly at present at 1/20 th scale.

Hi JB

Very impressed but what happens if it stops working in middle of lake, it does not look like there are many recovery options around site ?

Ref HSL motor/esc problems thanks to your message, I did not know about Ali Express until you let me have the info, it does not seem to be well advertised in UK. I have now joined and ordered a couple of ESC's from there at a very good price and buying through Paypal makes deal easy and safe. I am not sure how long it will take for them to come.

I rather like your idea of fitting a positional mounting tube for the prop shaft assembly. I think I will do the same for my HSL but only with one shaft, bit too complicated with two and the real boat had three.

Hi JB

Thanks for your comments.

A not very successful day today having another go at trying to get the esc to run the motor.

Initially tried with 3 channel FM Tx and Rx could not get any response from motor but could drive ordinary servos through all 3 channels. Had power to ESC from variable power supply most of time between 6 and 7 volts with current monitor current that never went above 100 mA. After messing about for some time the ordinary servos ceased operating, I think the ESC had damaged the 3 channel Rx.

Reverted to 2 channel Zebra with ordinary servos and this worked OK but did not chance to try motor ESC again so gave up.

There is no indication on what the input voltage should be on the ESC label only 60 A which I assume is reference to 60 amps. For the short period that I got the motor to run on the previous attempt I measured a current of about 4 amps at 7 volts.

As I now regard the ESC as a Rx destroyer I do not intend to operate it again.

The blue covering is shrink sleeve so I cut this off to have a look at what is inside. You cannot see much of what is in the small assy. incorporated in the control loom from the Rx, only three wires in and out, there appears to be 4 IC's on the board with a common metal heat sink attached to them. The main power control has quite a lot of components and is obviously the three power switching channels with an attendant heat sink. ( see pics )

There is no desperate hurry to get the motor running, as there is a lot of boat building to do. I will see what there is out there that will do the job.

If there is anyone out there who is into collecting old bits of R/C gear, I have a very old MacGregor Digimac 3 Rx. and sevo.

You can have it for the cost of packing and postage.

See picture.

nasraf