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>> Home > Boat Building Blogs > H.M.S BRAVE BORDERER
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mdlbt.com/40884
H.M.S BRAVE BORDERER Print Booklet
Author: RHBaker   Posts: 18   Photos: 35   Subscribers: 2   Views: 3401   Responses: 67   |   Most recent posts shown first   (Show oldest first)

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mdlbt.com/42297
H.M.S BRAVE BORDERER - Posted: 30th May 2018
itted 2 x two bladed 35 mm “hi-speed” propellers to the outer shafts only as these are the easiest to change. Can also use the centre shaft measurements as a check of the previous figures as it is unchanged.
With these propellers the current draw and bollard pull both increased. Subjectively, think she was also slightly faster, but the speed exceeds scale speed anyway.
The increased load on one of the 2 bladed props wiped the blades off and several 30 A fuses on various motor circuits blew.
Originally, the battery was fitted as far forward as possible to hold the bow down – some thing it seems to have achieved! Decided to remove the forward battery location frame and replace it with one which will allow the battery to be positioned anywhere between the bow and the centre of the model. The battery can now be located where the best plane is achieved. Once the correct battery is fitted the final location will be determined. This frame movement will also allow adjustments for any weight gained during final finishing.
Whilst the idea of using a load cell and ammeter/wattmeter to measure bollard pull and motors loads sounds logical, it is fraught with challenges. The vessel both bucks and the readings fluctuate wildly under load making getting steady, consistent results difficult.
Off now to cogitate over the results and decide a path forward.

Attached Photos - Click To View Large


mdlbt.com/42058
H.M.S BRAVE BORDERER - Posted: 24th May 2018
Looks like everything is set for the first open water test. Sun is shining, ice has gone and water smooth.
Intention is to start the open water test program with a repeat of the pool test, except this time with everything wired correctly; the load cell positioned so the “pull” is more horizontal and ballast available to hold the propellers underwater if necessary. Hope these improvements help reading stability.
To modify the “pull” arrangements, wrapped a light cord around the propeller shaft struts and fed the loose end above the transom shelf and out over the stern. The load cell was hooked into this and then tied to a fixed grating on the pond side.
Started by measuring the electrical requirements for each of the three motors and the propeller bollard pull, using the 2 S battery. Found the bollard pull was up slightly at almost 3 lbs per propeller. Probably because they were now held at a greater depth in the water. Also blew several 20A fuses, so fitted 30, which seem to work.
A series of runs showed adequate performance with plenty of spray, although the bow did not lift much onto the plane. The forefoot did raise almost above the water surface.
Then tried a 3S battery. Although this was much heavier, the performance improved dramatically. The bollard pull was up to almost 18 lbs per shaft. The bow still did not lift much to a plane, although the forefoot was almost clear of the water at full speed. The battery was located just back from the bow, so it is suspected that it held the bow down. The impact of the transom flap down angle could also hold the bow down, but have decided to leave as is for the time being and avoid the temptation of making too many adjustment at once.
Whilst it is still too early to draw definite conclusions, it seems as if a 3S battery will be required.
The model sustained some slight damage due to the test arrangements, so will repair that and also fit the 2 bladed Hi Speed propellers. Will then repeat the program and report. Should be able to draw some definite conclusions then on the best power train.
Neither of the batteries used, neither the 2 S nor the 3S are ones I would choose for this model. As a result the capacities and weights are not ideal. That must also be remembered in future deliberations.

mdlbt.com/41491
H.M.S. BRAVE BORDERER - Posted: 2nd May 2018
From the brief pool test, had decided that the motors could be susceptible to overheating, so connected up the water jacket cooling system and powered it with a small pump. Did not leave enough space to fit a scoop behind a propeller anyway, but prefer the positive action of a pump though.
From feeling the ESCs, was also concerned they could overheat within a confined space such as the hull. Mounted a couple of small fans in a bridge structure above the ESCs, along with the ESC switches. Not sure either of these cooling modifications are really required, but erred on the side of caution. Final weight of the hull, with all electrics (apart from battery) comes to 5.05 lbs. Looks like will not achieve the target weight of 6 lbs, but am hopeful will be able to get close to it..
Built the deck up with gun mount bases and a removable decking over the engine area. This limits access to the internals; so will not fit it permanently until the test program is complete and all modifications incorporated.
Have now reached a point where any further work will be to start finishing the model, unless drivetrain modifications are required. Have thus decided to leave it until after the first open water test date. This will be in late May as am away until then.

Attached Photos - Click To View Large


mdlbt.com/41422
H.M.S. BRAVE BORDERER - Posted: 30th Apr 2018
An unexpected opportunity arose to try the unfinished hull in a small pool. Whilst the performance envelope could not be explored, was able to try and measure operating parameters and get a “feel” for the model.
Used an electronic scale and a combination voltmeter/ammeter/wattmeter to measure propeller thrust /bollard pull and motor power requirements. If it is necessary to fit different drivetrain components, or a 3S cell this will serve as the baseline.
The model floated levelly and well above the waterline. At about 8 volts the motors drew around 20 amps each at full speed; so only about 35% of the potential output capacity was being used. Tested each motor individually and measured the bollard pull at just over 2 lbs. A considerable amount of spray and wash was created making stable readings difficult. For further testing, will add ballast at the stern to hold the propellers further underwater. Should help reading stability.
Currently using 20 A fuses; which as one failed seem marginal. For sustained use think 25 or 30 Amp better. With these high-speed, low torque motors establishing the “dry” propeller rotation is deceptive. Found one motor to be reversed! Nevertheless, the model accelerates quickly and is sensitive to engine speed movements.
Left the pool with a list of modifications to make before assessing the installation properly on an adequate body of water. Some conclusions can be made though. If it is necessary to add a second cell this needs to be located around midships, not in the bow or stern. Still hoping a 3S cell will not be necessary and that 2S may be adequate.
The suggestion to do testing using the bare hull with a minimum of detail was a good one. For a models with a sophisticated power train think this is a good approach. Nothing worse that finishing a boat just to find the performance disappointing, then have to to rip it apart to make major modifications or adjustments!

Attached Photos - Click To View Large


mdlbt.com/41302
H.M.S BRAVE BORDERER - Posted: 24th Apr 2018
Whilst waiting for the ice to melt, decided to make up the deck and transom flaps.
The deck was made from styrene sheet, again for lightness. Made the deck beams out of square styrene sections to avoid traditional, heavy, full width bulkheads. Hoped the stiff MTBH hull would resist twisting without bulkheads. First impressions are that this is the case and when the deck is finally bonded to the hull, should be even better..
The transom flap was made from thin aluminium plate and added simulated stiffener ribs in styrene.
Understand that about a 2 degree flap down inclination works best on this model.
My original plan was to operate the flap using a servo with another radio channel, however once the best plane is achieved it is unlikely the flaps will need further adjustment. Unlike the real vessel, the operating weight will remain fairly constant. So, abandoned the servo idea to use adjustable bottle-screws instead. The flap angle can still be adjusted, but not in motion. These screws are much simpler, lighter and cheaper than a servo.
One challenge was to make the very small hinges required for an adjustable flap. After much thinking and investigation, decided the simplest and neatest way would be to use thin, self adhesive aluminium tape, as used on forced air heating ducts. Would stick the self adhesive surface to the underside of the flap and then onto the inside face of another thin aluminium sheet, which could then be fitted to the transom using double sided tape and small screws.
This seems to work so far, it also avoids drilling through holes into the transom .

Attached Photos - Click To View Large


mdlbt.com/41213
H.M.S. BRAVE BORDERER - Posted: 19th Apr 2018
Once the rudder, propeller and shafts were installed, the position of the motors could be established. A light aluminium bracket to hold all three was fabricated and bonded to the hull. Due to the high speed capability of the brushless motors, particular attention was paid to alignment. Also kept to the shortest prop. shafts that could be fitted to avoid whipping.
Although the motor type might change, whatever is best will require a sound electrical installation as the current requirements for each brushless motor could reach 50 Amps. Wired each motor and ESC separately with its own dedicated fuse to give the maximum system protection. There is an extra fuse section allocated for auxiliary circuits, such as a cooling water pump and lights.
Will try the original planned layout of 3 x 2835 motors with 30mm propellers and a 2S Li-Po battery first. Am hoping the reduced voltage will also make these motors more tractable.
For the test program the three ESCs will be each controlled from an individual Rx channel. Once the final layout is determined, a more sophisticated and flexible control system can be installed.
To minimize ballast, particularly around the stern, the battery will be housed as far into the bow as possible. After the test runs the final battery type, size and location can be established. To assess performance, hope to try both 2 and 3S Li-Po batteries.
Planning to reduce heat build up by fitting cooling water jackets to the motors, these are easiest to instal at this stage so the wiring or mounts are not disturbed in the future. Have not decided the layout for the water circuit yet, but this easily can be added later.
All that is needed now is the ice to melt off our local lakes so tests can commence.

Attached Photos - Click To View Large

Response by RNinMunich on the 20th Apr 2018
Hi Rowen,
snag with the ESCs is that bY connecting all 3 red leads to the the RX you are shorting the outputs of all the Battery Eliminator circuits together.
If they are not protected by fast diodes you may do serious damage to the ESCs 😡 The RX only needs one supply anyway. If you are going to use a separate RX battery then DEFINITELY disconnect all 3 ESC red leads!
Cheers Doug 😎
Response by reilly4 on the 20th Apr 2018
Hi Rowen,
I have had water cooling on all my patrol boats running at 12Volts, whether brushed or now brushless.
For the brushed motors I have used aluminium tube coils with water pickups between the propellers and rudders. I did try water jackets a couple of times but found too much friction loss and therefore lack of flow.
For the newer brushless outrunners I use a brass tube soldered to a brass plate across the front of the motor fitted between it and motor mounting bracket.
I agree with Doug with regards to the disconnection of the red wires on the ESC's. This is now common practice, especially if you have an external receiver battery.
Response by RHBaker on the 20th Apr 2018
Thanks for your advice. Guess am stuck with the water jacket style now, will see how they work.
Was intrigued by these rubber ones though, they have an internal scroll which defines the water path. Rather like a coil.
Intend to make the small ESC wire mods you and Doug recommend. Thanks

mdlbt.com/41058
H.M.S. BRAVE BORDERER - Posted: 13th Apr 2018
Just to clarify. Shipping was only 7 days to Canada, manufacture slightly longer.
Examined the hull closely and was pleased. It is dimensionally accurate and robust, but light. It had also been reinforced in strategic areas and trimmed to the correct deck line.
My many questions to Christian Sheppard – Capurro of MTBHulls were quickly and knowledgeably answered. A company I would recommend others.
Reviewing the build blogs and U Tube videos of the both the Brave and Perkasa models, shows most use either single or twin screws. The original vessel had a triple screw contra - rotating layout. Experience from others suggests the third screw just adds weight and complexity, but little to the performance. Nevertheless, it was how the Braves were built, so that was how it would be.
Christian gave several suggestions for other modelers who have built this vessel. Contacted them and was readily provided with information and advice.
The finished weight of this model is important and a target of around 6 lbs recommended for a 1:32 scale version. This is to achieve the potential performance.
Plans for drivetrain are 3 x 2835 4500kVa brushless motors, direct driving 3 x scale 3 blade 30mm screws. Decided use a single Li-Po battery for the best performance with minimum weight.
It was suggested three batteries, each powering a single motor would be the best layout. After some research, concluded this would introduce a weight penalty and was discounted.
There are various ideas for the best drivetrain. Unfortunately none for triple screws. Decided the best approach would be to fit the bare hull out as planned, then try it. Leaving all the finishing features for later. A contact in Australia had already done this using a single screw layout and kindly sent pictures of his hull layout and then under test. Very informative.
The positions of the rudders, propellers and shafts are established by the scale dimensions and were permanently installed. Everything else was to be temporarily fitted, so it could be moved or replaced if necessary.

Attached Photos - Click To View Large

Response by RHBaker on the 14th Apr 2018
Hi Doug,
Thanks.
Yes, there was a trim tab. To avoid your enjoyment of future epistles, all will be revealed in the fullness of time
The motor control circuit is also something I am thinking about. For my current test program am going to use a simple 1 control - 1 motor.
Do not know of the name Tasmanian Devil, the guy who has been very helpful is called Michael.
You are probably right, think it could be "overmotored", but that will be revealed in the tests.
Rowen
Response by onetenor on the 24th May 2018
You could use just two motors for running and fit the 3rd screw to a dummy shaft for judging etc. Yes?????👍
Response by RHBaker on the 25th May 2018
Yes, that would work. At present though am making steady progress in getting all three screws running. If that optimism is unfounded may well use your suggestion
Rowen

mdlbt.com/40885
H.M.S BRAVE BORDERER - Posted: 8th Apr 2018
Thinking of a future project and decided upon another launch type vessel. My earlier Daman 4207 project gave an interesting model with good performance.
The Brave class of FPBs (Fast Patrol Boats) caught my attention. Can remember the incredible performance they offered when entering service. Only two of the class were used by the RN, although variants were used by other navies.
Have decided to use proprietary Glass fibre hulls in future as they probably cost little more than building from scratch using wood and resin. They give a robust and watertight hull, but one which still requires thought to complete properly.
There are several companies that offer a “Perkasa” hull, a Brave class derivative with an almost identical hull. From previous experience have decided to limit my models to 40” long, larger vessels become difficult to transport and handle. After much research considered the hull offered by MTB Hulls in Gibraltar met my requirements best.
The inquiry to MTBHulls was well handled; the quotation acceptable, so placed an order. Was pleasantly surprised at the shipping costs. From the UK these often approach the cost of the hull, but from Gibraltar they are much more reasonable. Delivery only took 7 days.

Attached Photos - Click To View Large

Response by boaty on the 10th Apr 2018
Good to mention the 40 inch length hull ref ease of transportation.

I adhere to this as well due to there not being much room in the car. Back in the 1960s I had a very large pond yacht which we struggled to get into the back of dad's Austin A40. To add to all this we had to remove the rigging so it would fit in the back.

Things got worse when dad was at work and grandad and I used to take it on the bus.

Cant do that now as health and safety has taken over and we don't want passengers contacting a "no win no fee" solicitor.

Boaty😋
Response by RHBaker on the 10th Apr 2018
My only experience of a vacuum formed hull was a slightly smaller Tyne class lifeboat. Was satisfied with it, but glass fibre seems more robust, stiffer and stronger.
Imagine a Vac formed hull will need full size stiffening bulkheads, which can be avoided with the GF version. Weight is very much a concern on this model and whilst Vac formed is probably lighter, this advantage may be offset by the additional structure.
Response by nick on the 23rd Sep 2018
A little anecdote to add to this build is that I was used to seeing both Swordsman and Boarderer in both Portsmouth and Portland whilst I was in the RN. (1960 "s}
In fact we gave one of them a "lee" ie. got to windward of her in foul weather and helped her into Portland. She had some sort of mechanical problems.
The stories one of them was moored on the smaller, walled wharf that they used away from the big one we on HMS Aurora used.
As I said it was another rough night, most were in Portland . A yachtsman had crept during the night and tied up behind HMS Boarderer.( restricted area)
Capt. told number one to go get the yachtsman to move his boat. Time was about 0400. Very tired yachty told no.1 to F off.
No. 1 came back onboard and relaid to the skipper who went down reraised the yachty and got the same message!
Skipper came back onboard and contacted the engine room and as it happened got a 'wet" start on the turbines.
The loosely stowed sails on the yacht melted rather well!!
Moral to the tale, Never tell a sailor to F off!!
Bye the way both these boats had a top speed in good conditions , of in excess of 80 knots and in theory could circumnavigate uk in 12 hours. I remember that the always ran very flat on the water at planing speed.
Regards, Nick.

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