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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: 15   Photos: 30   Subscribers: 1   Views: 2358   Responses: 38   |   Most recent posts shown first   (Show oldest first)

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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 colmax on the 10th Apr 2018
Can you advise how your new hull fairs against Sarik version for Brave Borderer as they are both at 1/32? Thanks again
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.

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