Fairey Huntsman 31

[Chris FellowsParticipant @chrisfellows72943]

You're a braver man than me Ray!

The Fisherman, eeerrr!

I wanted to get my 5 Fairey builds to the painting stage, which I pretty much have now. But then got side-tracked by the Faun, which I was going to build first to get some practise with planking a hull. And I've now got involved in another project, which may be hard to believe, isn't a Fairey! It will be a quicker build though and maybe done in parallel. Trouble is, summer is coming!

Chris

[Philip OxleyParticipant @inonowt]

Hi Chris.

Iv’e read through your account of building the Hunstman 31 today with quite some awe.  I’m quite new to this though I have 3 boats.  Sea Hornet (circa 1970), Arrow and Mowe 2, (both circa 2018).  The reason being is that my grandson wants me to build the Huntsman 31 for him and I was after any build assistance I could find.  Well done by the way, it was all fascinating for me.

I do have a question (only one, he laughed). I am trying to understand the relationship between motors and batteries.  The Arrow has an Etronix Photon 3450Kv motor with 45A ESC powered by a 13S 11.1V battery.  This gives me 38295rpm and the boat performs well.  The Sea Hornet is fitted with a Radient Reaktor 2 4000kv motor  with a 45A ESC and, if I power it with a 7.2V (28800rpm) it only just gets up on a plane, but with an 11.1V it performs well (44400rpm).  Both boat are fitted with 4mm prop shafts.

In reading your posts, in January 2022 you said “The 4mm shaft is rated to 15k. rpm which is more than I will be running it at.”  I didn’t know they were rated.  My question is, to limit the rotational speed to 15000rpm with a 3s 11.1 Lipo, the motor should be only circa 1350kv.  In my (limited) experience, this doesn’t seem ‘big’ enough.  Am I running ridiculously fast motors for the prop shaft?

I’m ready to be educated (if that’s possible).

Also, 1st time on here so apologies if I’ve broken any protocols.

Thanks

Philip

[Chris FellowsParticipant @chrisfellows72943]

Hi Philip

Glad that you are interested in building a Huntsman 31. Sorry that my build is protracted and along with my other Fairey builds it isn’t finished! Also I haven’t touched this build for quite sometime but having just returned to my Huntsman 28 I’m eyeing up the H31 as well as the Swordsman again.

Are you looking to build from one of the kits that SLEC does? As I probably mentioned in my posts I’ve scratch built mine as I wanted one at a scale of 1:12 to match my other builds.

As to the motors, yes you are running ridiculously fast motors! 😁 When I read those RPMs I thought wow! Those sorts of kV are really only needed for race boats and waterjet units with many of the former using flexible drives rather than prop shafts as such. The 1350kV you arrived at is about right for a planing boat where you want about 10k. RPM when running the boat on the plane (around 12k. unloaded). Whilst those RPMs are theoretical given the kV and batteries being used in practise you’ll probably find that the actual figures are much less. Partly because (as per my figures) you tend to get about 80% of the unloaded figure on the water and also because higher kV motors have less torque. At 28800 your Hornet should be going like a bullet! But as it’s not I’m surmising it isn’t getting anywhere near that revs.

You should get all the performance you need with 3S batteries and if you want to replace the motors with something less manic I’m happy to recommend.

As regards the prop shafts, in my planing Faireys I use Raboesch maintenance free prop shafts which are rated to 10k. and 15k. with the latter being fine for the RPMs I want. Some folks use traditional prop shafts with plain bearings and say they are fine at higher revs so it just comes down to choice really.

Anyway, thank you for reawakening interest in my H31 and if you want any further information on the Huntsman 31 and motors etc. then happy to assist as indeed will other forum members.

Chris

 

[Colin BishopModerator @colinbishop34627]

Philip,

If you are building the 1:16 SLEC kit I built the review model for the magazine under designer Dave Milbourn’s advice. I can share info if you want.

Colin

[Philip OxleyParticipant @inonowt]

Just wanted to say thank you Chris and Colin for your replies.  I’ll reply in depth (probably) Monday now.

Thanks

Philip

 

[Philip OxleyParticipant @inonowt]

Good afternoon.

Once again, thanks for your replies.

Yes, the boat will be a SLEC 1/16 kit.  I was putting together a list of the parts required to complete, and bearing in mind my experiences with the other 2 boats, I thought the Overlander 1000Kv motor would not be powerful enough and had thought to buy another Etronix 3450KV motor and ESC.  Until I read Chris’s comment about prop shafts.

The Arrow is fast but I wouldn’t have said it was ‘race’ fast, and the Hornet is not stupid fast either.  There are certainly other boats on the pond that are faster.  I think they look about right, when powered by 3S Lipos. The Arrow has a 40mm screw (which I might reduce to 35mm) and the Hornet 35mm.  Thinking that I’m not getting the RPM as you suggested, I demounted the motors today.  The Radient revolves freely but the Etronix is a bit notchy.  The mounting screws aren’t fouling it.  And there doesn’t feel as though there is any binding in the shafts & tubes.

So, I thought I would buy an Overlander 1000Kv (I’ll need it for the FH31 anyway) and swap them out in turn and see what happens.  If I get the same performance, I can swap them put permanently.

Colin,  I shall be most grateful for any information and advice you can give me.  I haven’t got the kit yet, it’s on my list for next week and start building nexy month.  I’d like to try to enhance the boat with deck planking and such like.  I modified the Arrow at the aft as an homage to the Unowot.

Thank you both for your support

Philip

 

 

 

 

 

 

 

But Of course, I have no point of reference, so maybe they are.

‘m needing huge RPM the results

[Colin BishopModerator @colinbishop34627]

Philip,

My 10 page review of the Huntsman was published in the 2018 Winter Special issue of the magazine. If you have a subscription which includes the Digital; Archives you can see it there otherwise Pocketmags will sell you a download for £5.99.

https://pocketmags.com/model-boats-magazine/winter-special-2018

Colin

[Chris FellowsParticipant @chrisfellows72943]

Hi Philip

I surmised that you might not be getting the revs quoted because of the lower torque of higher kV motors rather than being any issues with the motors or drivetrain etc. but they can happen of course, especially due to binding if not set up correctly i.e. as straight as possible and when you mentioned the size of the props you are using only added to my thoughts that you aren’t attaining the revs stated.

I don’t know the motors you are using and so had to Google them which adds to my thoughts even more! Reason being those are inrunner brushless motors which usually offer less torque than comparable size outrunner motors. Sorry to be the bringer of bad tidings but I think those motors are unsuitable for those boats! Especially the Radient which is only 24mm diameter and in the Hornet with a 35mm prop it’s really going to struggle. The Hornet is a fairly heavy model and really needs a torquey motor with enough kV to get it planing. So an outrunner of around 1200 to 1500kV would be my choice running on 3S and as you say a prop of 35mm.

The Arrow is a sleeker faster boat but you don’t want race boat speeds (unless you really do!) and a similar motor would do the job.

As far as the Huntsman is concerned Colin can tell you what motor is recommended for that, probably a 35mm, but I would suggest going a bit higher than 1000kV, as I said at least 1200kV.

Having said that it might be fine? Reason being that even though I said you usually aim for 10k. RPM on the water my Huntress 23 on 3S gets on the plane quite easily and I doubt at anywhere near 10k. as I have plenty of throttle left. Must try one of those rev counters. (Edit: I see from the SLEC site that an Overlander 2826/18 1000KV motor Tornado Thumper motor is recommended).

I use Overlander motors in most of my builds with my ESCs of choice being HobbyWing Quicruns.

Seeing your Arrow, which is very nice, one of my next projects uses a similar hull, which started off being based on the Arrow/Stiletto hull and with a different superstructure and which really does need a high revving inrunner motor as it’s going to be fitted with a water-jet!

Chris

 

[Colin BishopModerator @colinbishop34627]

Just checked out my boat and it is fitted with a Turnigy 2830 1100kv outrunner. At the moment it is fitted with a 35mm 3 blade brass prop but the plastic two blader supplied with the kit worked well enough.

The Mk 2 Turnigy 2830 is a 1000kv. SLEC’s recommendation is an Overlander 2826/18 1000KV motor Tornado Thumper which appears to be the same motor.

Chris’s suggestion of a slightly larger motor is correct for a model of this size with conventional construction but the SLEC kit is built of Liteply and is VERY lightweight! Some people are a bit suspicious of Liteply but build the kit according to the instructions and you will be fine

With 3S the model is way overpowered and I was concerned about it rolling over. It is more than fast enough on 2S.

As Chris says, Inrunners are not usually recommended for model boats due to their limited torque.

Colin

 

[Len Morris 2Participant @lenmorris2]

Hi Colin,

You mention a Turnigy 2830 1000kV motor.  As kV means a thousand volts, 1000kV would mean a million volts!

I need to come up to speed on this new battery and motor terminology.  Is there a good reference?

Len. 🙂

[Colin BishopModerator @colinbishop34627]

Len,

Yes it is confusing at first but Paul Freshney provided me with the following explanation in my Motors and Props article back in 2021 which explains it.

Colin

A typical Brushless Out-runner may be described as 2822 – 1100KV. To confuse things, some manufacturers may add an oblique after those first 4 digits (as do Turnigy) with another number such as 8, 12, 14 or 17 as in the Mersey Lifeboat motor example, Photo 1. Here, we are only concerned with the first four digits.

The first two digits (28) refer to the case diameter and rather handily this means it will bolt into a standard traditional 360/380 brushed motor mount. Likewise, if the first two digits are ‘35’ this means it will bolt into a 540/550 brushed motor mount but of course be of a larger diameter.

The next two digits ‘22’ refer to the case length, Photo 1. However, what we are really interested in is the KV rating and somewhere within the specification will be listed the motor’s maximum Wattage which is 102 for this particular motor. In this particular motor series, Turnigy offer an identically sized motor Ref: 2822/8 – 2600KV but 260 Watts, a truly remarkable performance from something just over an inch in diameter and barely an inch long. Physically size for size, a brushless motor will be much more powerful than a brushed type.

1100Kv means that the example pictured will produce 1100 revs per volt with no load. So, on a 7.4v two cell LiPo battery this means it will (if it is running at maximum speed) produce 7.4 x 1100 rpm = 8140rpm or on an 11.1v three cell 11.1v LiPo, 12210rpm. Let’s be clear though, you can use ANY battery to power a brushless motor, including a Sealed Lead Acid, NiMH, Dry Cells or whatever. The critical thing is that the volts supplied meet the motor’s minimum needs nor exceed its specification or that of its associated speed controller.

[Len Morris 2Participant @lenmorris2]

Thanks Colin.  The dimensional data is very clear.  Seems the electrical nomenclature kV has been high highjacked to mean revs per volt.  I now understand so once again many thanks.

Len. 🙂

[Philip OxleyParticipant @inonowt]

Good afternoon.

Thanks for your advice and information.

The Hornet, being  a 1970s kit and is heavy.  The Arrow is much lighter.  The Hornet had been fitted with an IC engine.  In about 2018 I decided to convert to electric and took it to a local shop who supplied me with everything I needed.  I completely refurbished the boat and installed the kit.  The motor was small to fit the existing space, since the prop shaft was fixed. The shop had sold me a Quicrun brushed esc and a brushless motor so the motor burned out.  Can’t remember how I landed on the Photon, but they work with the motors and I saw the results I was expecting.

Thank for researching the motors and giving me the solution and not just identify the problem.

It’s not bad news, I know a little more than I did a few days ago thanks to you guys.

I’ll put a Overlander Tornado Thumper V3 3536/06 1300KV – Brushless Outrunner RC Motor with a QUICRUN 10BL60 60A Brushless Sensored ESC in the Hornet.

In each of the Arrow and the new FH31, I’ll put a Overlander Tornado Thumper V3 2822/27 1200KV – Brushless Outrunner RC Motor and I can can retain the eTronix 45A B/L ESCs.

Plus new couplings, 35mm props and motor mount.

There’s some swings and roundabouts since I was having to buy the new gear for the FH anyway.  I can also reduce to 2S as Colin mentioned.

If I hadn’t read the blog, this wouldn’t have happened and I’d have fitted the wrong motor in the FH too.

I’ll be buying everything this week with a view to starting building next month.

I’ll take out a Mag subscription and will download your build review Colin.

I’ll let you know how I get along with the motor swaps and resulting performance.

Can’t thank you enough.

Philip

 

[Chris FellowsParticipant @chrisfellows72943]

Good afternoon Philip

Glad that we’ve been of help and will be very interested to see how your models perform after the motor swaps. Your choices should be ideal.

Chris

[Philip OxleyParticipant @inonowt]

Hi all.

Well that was the plan.
The reality is that the 1300kv 3536 motor won’t fit in the Hornet because the prop shaft is too low for a straight couple to the motor.  Removing the wooden mount and modifying the set up is not an option.  It’s well fixed.

It did fit well in the Arrow with a little realignment and tweaking. You’ll note I used a flexible coupling, but found it wasn’t straight. Having connected the drive without fixing the motor mount down, turning the prop by hand caused movement in the motor/mount. I fixed it inline but there’s always going to a be an inclination for the coupling to cause  a rotational imbalance and thus, wear. I also fitted a 35mm prop.

The 1200kv 2822, with the smaller mount fitted easily in the Hornet though as it was closer to the prop shaft, I had to use a UJ coupling.  I thought this was better than the flexible one.  It has a 35mm prop.

I took them to the park to test.  See photos.

The Arrow was great, probably a little faster than before.  The Hornet looked ‘nice’ but didn’t get up on a plane.

The Arrow weighs 1.46kg, the Hornet 1.54kg, both exc batteries.  The performance seemed vast considering only 100g more and 100kv/1100rpm less.  With this in mind  I thought I should check the ESC parameters, particularly the throttle limit.

I reset the throttle range calibration with the help of CML (Etronix) over the phone.  I had to reverse the throttle servo on my transmitter to do this, and then reverse the motor (on all my boats).   I checked the ESC parameters to find that the Hornet throttle limit was set at 90%, while the Arrow was set at 60%.  So I’m even more baffled.

I have to test them both again of course, but I’m now thinking of getting the 1900kv 2826 Thumper.  The 2822 is giving me 1200×11.1×90%=11988rpm unloaded, whereas the 2826 would give me 1900×11.1x 90%=18981rpm unloaded.  Hmm, 58% more kv= 66% more rpm????  Limiting it to (say) 60% would then give me 12654rpm unloaded.  70%=14736rpm unloaded.

The 3536 is supposedly giving me 1300×11.1×60%=8658rpm unloaded.

While this arithmetic stacks up,  am I getting the theory right?  When I re-test them, might the performances be different as a result of the throttle range re-calibration?

Sorry for the large content, but the more I learn,  the more confused I get.

On a different note, my grandson and I started building the Fairey Huntsman.  Maybe I’ll start a separate thread,  from an ‘improvers’ point of view.  I found Colin’s build report in MBM very informative, thanks.
As always thanks for your support.
Kind regards.
Philip 

[Chris FellowsParticipant @chrisfellows72943]

Great that the Arrow is performing well.

You need to be able to get the throttle to 100% initially via the ESC rather than compensating by using more powerful motors and so I would suggest getting the Photon program card which makes setting up the ESC so much easier and with more confidence of the settings. I assume you had to use the bleep method? I’ve used that method with my 30amp Quicrun ESCs as they won’t use my program card but I’m not entirely happy with it. Not an issue in the boats using that ESC as they are only slow moving models and I’ve got the forward and reverse and speed that I want.

Does your transmitter allow changing of parameters like the throttle setting as that is the best way of altering it if you need less than 100%?

I think the motor now in the Hornet is too small. The revs if achieved would be Ok but I think you need more torque to get that model to perform.

I’ll come back to you once I’ve had a look at what motor I’d suggest.

Chris

[Chris FellowsParticipant @chrisfellows72943]

Ok, I’ve had a look. I don’t think the 1900kV motor is the way to go. In theory it will give you more revs but given the design of the model which does tend to plough through the water I think you need more power for it to rise up and onto the plane. And for driving a 35mm prop.

The power output for the 2822 1200kV is only 85watts (only an indicator/comparison as that would be for the max. battery of 4S) and that for the 2826 1900kV isn’t much more at 105watts. Longer motors generally give more torque and so I would suggest the 2830/09  1300kV which gives 210watts.

This will give you 1300 x 11.1 = 14430 rpm unloaded (11544 unloaded) which is pretty much ideal. Assuming of course you achieve that 100% throttle!

Out of interest, as I mentioned before, I must get one of those devices for measuring rpm on the water as I’m pretty sure my smaller Faireys are on the plane at well below 10k. rpm but the hull design does mean that they get onto the plane easily and don’t need a lot of power to maintain speed. But it would be good to see how theory compares with reality.

[Ray Wood 3Participant @raywood3]

Hello Guys

You know I don’t work anything out 🙂 (master of trial and error)

The Sea Hornet goes well on a good old fashioned 600 brushed motor and a X35mm prop 🙂

Regards Ray

[Philip OxleyParticipant @inonowt]

Hi All.

Yes, I agree the 1900kv motor was me having a senior moment.  I didn’t see the 2830/19 1300kv at the time.  After I posted, I looked around a bit for a 13/14/1500motor and found some.  I’ll go with your suggestion thanks.

Your mention of wattage was a ‘thunderstruck’ moment.  I’d never looked at that.  It explains why the Arrow is so much faster as the 3536/06 1200 in it produces 442W.  So yes, the 2830/09 1300 may well do the job.  Thank you.

After I sorted out the throttle end points last week, I did run through the settings to check them also.  I do have the programming card  and it is much easier than lights and bleeps.  The Arrow throttle limit was at 60% and the Hornet at 100%.  At the park I set the Arrow first to 20% and then to 90% but there was no noticeable difference between any of the 3 settings.  I phoned Etronix but they were unable to suggest anything but did say that the instructions were not right.  I.e., the higher percentage is the greater limit rather than the lower being the greater restriction as the instructions say.  So I guess I’ll have to play around with the settings on the water to see what’s what.

My transmitter doesn’t allow changing of parameters like the throttle setting.  It’s a basic Futaba T6L.

I’m very grateful for everyone’s input and I’m sorry I hijacked your thread Chris.  I’ll be looking forward to hearing about your water jet boat when the time comes.

Now back to planing and sanding chine stringers and keel on the FH.

Best wishes

Philip

[Philip OxleyParticipant @inonowt]

Hi Ray.

Thanks for your post.

In my case, as the name on the Arrow suggests, “I know nowt”.

Philip

 

 

[Chris FellowsParticipant @chrisfellows72943]

No problem hijacking the thread Philip, it’s blown the dust off it! And it’s prompted me to dust off the H31 as well in readiness to get some paint on the hull.

Let us know how the Hornet goes with its replacement motor. As your Tx doesn’t allow adjustment of the throttle setting then it should be giving 100% and therefore the ESC will be the limiting factor.

Chris

[Paul WhiteParticipant @paulwhite63149]

Chris, really enjoyed your article in this months issue of model boats on the Fairey’s, came he to see if you have finished any of them but clearly still a work in progress!

[Chris FellowsParticipant @chrisfellows72943]

Thanks Paul, glad you enjoyed it.

Not doing anything much at the moment due to the hot weather but having started my latest two projects I have returned to three of the earlier builds to progress them.

I should really finish the Huntress and River Cruiser off as seen in the article but I’m keen to try the other three on the water first, so once I’ve done that I will.

Chris

[Paul WhiteParticipant @paulwhite63149]

I came across your various threads about 2 years ago, you seem to be making slow but steady progress!

Don’t knock the heat, it’s much better for painting than the other damp half of the year!

I might start finally on a huntress 1/12th myself soon, I bought the plan a few years back – as well as the 1/12th Vic Smeed huntsman plan so they could both be to the same scale – which I learned about from your various threads on the models and kits over the years – although this months article takes out all the detective work for future builders by consolidating all the history in one place!

[Chris FellowsParticipant @chrisfellows72943]

Great that you will be building a couple of Faireys and I will be interested to see your progress on them.

Slow and steady progress indeed, though as some have said because I’m building so many at the same time (currently seven!) I will have a number of models completed around the same time and the time per model isn’t too bad considering I only spend part of the year building. Part of my comment about the hot weather is that my wife prefers that I’m doing other things in the summer rather than building model boats!

I could have built the Huntsman 31 using the Vic Smeed plans but decided to do my own as I like being able to print off my own drawings and introduced a spine to help with aligning the frames and of course originally I was going to build the Sport version, which I might do one day.

In fact if I do I will use the drawings for the hull I drew up for someone who wanted to build a 60″ H31. I will stick with a scale of 1:12 but I added in some extra frames and stringers because of the increased size and also to reduce the span of the stringers and ply sheeting. Additional frames were also added to help with forming the pronounced flare at the bow which I had trouble with in my build. If I do build again I will try planking the bow area.

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