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[Waiting2Retire]

After a bit of a sanity check on my next build, I have done as much research as possible but still undecided on a few things and I am hoping  the collected wisdom here can set me straight.

So I am getting there with a (SLEC) River Police boat for a family member, didn't quite make last Christmas looking on track for this Christmas    starting to think about what next. It's been a good exercise to work on a kit because you have some clear guidance and can experiment and refine your technique with glues/clamps and making mistakes.

I always liked the RTTL models, a couple years back when I started with the police boat I ordered the police boat Veyron plan and the Veyron RTTL but I have decided I want to go for for the slightly larger Vic Smeed version at 1:24th scale (mm530). The 1/12th scaled up version I have seen here and YouTube looks amazing, but I already have one big boat to store and it's not very transport friendly scale for RTTL!

I have a digital copy of the plan ("found" on the internet), but will probably order the printed version from Sarik as it's the same cost as getting the digital printed locally. I printed it on 12 sheets of A4 for now to get a good idea what I was in for.

Currently I am thinking:

• Order the laser cut frames from Sarik with the plan
• Skip the wood pack as its sheet material
• Add 1/8" (3.2mm) square stringers to support planking
• Double Diagonal plank the frame (as John/Bluebird did with his)
• lightweight glass cloth and resin the hull after

What I am wondering about still is:

• Is 1/8th the right size to order for stringers?
• The Smeed plan is curved deck, so need to extend frames to I assume from build board. Are the Sarik frames likely to be cut to size to get the most on each sheet - if so how to extend or mount to the build board?
• Is the wood pack going to have all the strip wood for the chines and inwales? Sarik have vague disclaimer its not enough wood to build the model...

I have some stock of ply and balsa, but its the strip-wood I don't want to be short, but also don't want to order extra to find its in the kit (wood is expensive!).

Not worried about the planking wood for now, likely a problem for next year and I am fortunate to be close to Mantua who have a good stock of wood and I try to use them when I can to keep them in business.

Any comments or pointers appreciated. I realise its a jump from the SLEC kit to diagonal plank on frame but I am in no rush and as its a longer term project I can learn as I go - really good build guides on the forum layout the process and plodding along I am sure I will get there.

[Waiting2Retire]

Ok so 1/8" square stock for the stringers might be too small looking at other Vic Smeed plans I can find digital copies of online 1/8"x1/4" might be better, I decided to skip ordering stringer wood from Sarik and make a decision when I have the kit in hand and pick some up locally.

Placed the Sarik order over the weekend, only used them a few times but never found them that fast so expect I might see it next week sometime.

Turned my attention to the power train the last few days in the old mental gears. I will be running on 3S or 4S LiPo as that's what I have already for planes.

Not quite sure what's a good RPM for a prop on an RTTL, 10,000RPM? So 13,000 or so unloaded?

• 3542, 1450Kv = 16,000 on 3S, 21,500 on 4S - Too fast for an RTTL
• 3542, 1250Kv = 14,000 on 3S, 18,500 on 4S - Still too fast?
• 3542, 1000Kv = 11,000 on 3S, 14,500 on 4S - Sounds about right?
• 3548, 900Kv = 10,000 on 3S, 13,500 on 4S. This sounds good for an RTTL? I already have one spare so it halves the motor cost!

(can't seem to copy a table easily into the forum so the RPM above are rounded as I typed it out of my spreadsheet by hand)
I am not sure an RTTL needs water cooling as you have a lot of airspace for the ESC to air cool with a fan.

Looking at a Hobbywing 10BL120 car ESC with Fan (as the 60A version is marginal for some of the above motors), in smaller boats I have used ZTW Shark, which are probably cheaper in 80A or 100A and support up to 6S (could run 3S in series if I wanted) but I am worried with no heatsink and the reliance on the water cooling they will overheat without water loop and I am not keen on water loops if I can avoid it. The ZTW Seal look good as they have a alu heatsink and water capability, but they are all in big ratings for powerboats and significantly more £££

[ChrisF]

I haven't built one of those but hopefully my general comments are of use. With regards to the stringers you are right with your conclusion on sizes. With most of my builds (hard chine ones) I use 2 layers of laminated 1/8" x 1/4" deep at the deck and chine as this gives you enough material to sand to shape to suit the side and bottom of the hull. I then use 1 layer for the inner deck stringer if it has one. 1/8" x 1/8" could be used as intermediate stringers (as you are planking) as long as the distance between frames isn't too great - the smaller section is easier to bend at the bow for instance. If the hull is fairly straight (apart from the bow) and little bending is required then you could use the bigger stringers.

As for the motors that is the basis I work on, 10k. unloaded to give good planning performance, so if you aim around that by taking 80% of the unloaded rpm you should be good to go. I'm guessing with my Faireys I'm actually planing at well under 10k. but that seems to be the common rule of thumb and will depend on the hull design. Looks as though you are planning on using 2 motors? If so, for brushless you will need an ESC for each. I agree that 60amp is borderline and I use the HobbyWing Quicrun and SeaKing ESCs in my builds - don't forget the program card. If the motor, ESC and prop are correctly sized then unless you are racing there should be no need for water-cooling.


Photo shows the stringers on my Huntsman, which is a bit smaller at 28" but I also used the same size on my 33" Swordsman. This has ply sheet for the hull bottom and sides so no need for intermediate stringers.

[Waiting2Retire]

Thanks Chris, I am aiming to follow in the footsteps of John on the forum who built an RTTL with double planking:
https://www.modelboatmayhem.co.uk/forum/index.php/topic,20758.0.html


(frame above is John's from the linked post, not my work!)

The plan has the chine stringers in that dimension, see attachment, but it's not 100% clear in the image from John's thread what dimension he used for the extra intermediate stringers to support the planking.

Looking at the curves, I think the framework needs to be assembled, the extra's laid on top and marked on each frame before cutting/filing the slots in the required positions as there is a a lot of curvature towards the bow.

Prop Speed: Your thinking aligns with what I have read on the prop speed, the RTTL is deep V planing hull with dual shafts (early ones had 3 engines/props!), I have spent some time looking at what the people with larger models (sea queen etc) are using, but I still think the motors above might be too much.

The other variable I just started looking at is most of the prop shafts in M4 are rated to 10K RPM, Raboesch do some rated to 15K, but I think its easy to wander from scale to speed boat speeds and powers, the model needs to plane but only do scale speed (maybe a tad over).

I am now wondering if a 750Kv might be more appropriate, I have a number of 3300mAh 4S flight packs, two of these either side in the hull down low might be a good option for power but most people run 3S (or 7.2/8.4v packs) so a lot of the motor advice/comments on the forum are at lower voltages with higher Kv motors.

I shall ponder further... an MFA 850 is 12V and pulls nearly 11A giving almost 10K RPM, so 130w, on that metric motors like the ones listed with 1000w or more potential are massive overkill.

[ChrisF]

I did think about suggesting lower power motors e.g. 28mm dia. but as it's quite a big model with I assume plenty of space I thought you may as well go with the 36mm dia.

For planing models advice is usually to go for around 1200-1500kV to give good performance on 3S but as you already have 4S then you can use lower but I think 750kV is too low. Could work but if it doesn't then you'd have to change the motors. Within reason too much power/revs isn't a problem as you don't have to use it and if the Tx allows you can limit the throttle. Brushless motors are very powerful for their size and I'm guilty of oversizing so that the motors have an easy time  - I don't think that really matters as it's achieving the desired revs that's the important part with as you know choosing a suitable kv/battery combination. Obviously less powerful motors can be used as you are spreading the load over two but you still need to achieve the required prop speed.


That drawing shows an unusual layout for the makeup of the chines, well for me anyway. As they are usually laid vertically to assist with bending. As for John's sizes you can always ask on his thread or send him a message.

I mainly use the Raboesch Maintenance Free prop shafts that are designed for 15k. but many use plain bushed prop shafts and run faster and longer than me without problem.

[John W E]

hi there


Couple of things to have sorted first.


Bear in mind, that this plan of Vic Smeed's is quite ancient - from the days when materials were quite scarce (just after the War) - materials such as plywoods compared to what we have today were quite rare as regards thicknesses etc.  So, that is why some of the chine stringers and deck stringers were laminated - to give extra strength for the plywood to be bent around.   Also, 9 x out of 10 there would have been a diesel engine fitted and the majority of the models would have been of the free running type.   Radio gear in them days - were made by oneself - or, if you were well off enough - people could afford one (on about 3 months wages).


To move to the serious side, have a look at the side profile of the blueprint and also the photographs.   You will see the actual chine of the boat is very much similar to that of the Percassa, in fact, it is the forerunner design of the Percassa.   As the chine comes up to the bow, it has a slight 'S' shaping to it.   On Vic's plan, he simplified this.  He allowed the chine to go straight up to the bow - but it is up to yourself if you wish to copy the original design and put a bend in the chine at the bow, which I myself did.


Next thing to look at is the profile shape of the frames.   Vic gives you 2 options, straight side for ease of planking or a concave side, as per the prototype hulls.   There again, I did the concave profile.   Now, how you work out the spacings of your intermediate stringers, you take the height of the middle frame of the hull from the gunnel to the chine and you divide it by the number of stringers which you wish to use.   You do the same at the stern and the same at the bow.  When you have calculated this, you lay a strip of straight wood over the marks you have put on the frames and mark through with pencil on the rest of the frames.


For the bottom of the hull you do the same as above, only from the keel to the outer chine.


Power from the model - for my particular model - comes from 2 MTroniks Vision 600s, on 7.2 or 7.4 (trying to remember that   )  On the real vessel both props do turn in the same direction, and, mine do the same - they are brass 30 mm diameter 3 bladers.  This diameter could all change mind, then I can be bothered to measure them, but, from where I am sitting they do look like 30 mm.


As a last thing, 70% of the photographs of the RTTL I did, disappeared when Mayhem crashed online about 7-8 years ago - and you may never know they may reappear on Mayhem when we all go round this universe one more time  .


Any more queries, just post them.


John

[John W E]

Short clip of my model in slow mo
video 1558266007


john

[Waiting2Retire]

That drawing shows an unusual layout for the makeup of the chines, well for me anyway. As they are usually laid vertically to assist with bending. As for John's sizes you can always ask on his thread or send him a message.

Hi Chris, I think the confusion is that in typical "Vic style" the outline of half the frame is tessellated into the plan where there is white space, so you need to rotate 90 degrees mentally then they are bonded vertically not horizontally. Paul.

[Waiting2Retire]

Bear in mind, that this plan of Vic Smeed's is quite ancient - from the days when materials were quite scarce (just after the War) - materials such as plywoods compared to what we have today were quite rare as regards thicknesses etc.  So, that is why some of the chine stringers and deck stringers were laminated - to give extra strength for the plywood to be bent around.   Also, 9 x out of 10 there would have been a diesel engine fitted and the majority of the models would have been of the free running type.   Radio gear in them days - were made by oneself - or, if you were well off enough - people could afford one (on about 3 months wages).

Hi John, thanks for the reply.

Yes well aware these designs/plans are over-built for today, in that the heavy diesel and need to start it were both weight and loads that a modern boat with modern motors do not experience. I have seen advice in various places to drop the thickness of the bulkheads when working from Vic Smeed Plan.

I have ordered the laser cut kit from Sarik, so waiting to see what thickness wood arrives.

To move to the serious side, have a look at the side profile of the blueprint and also the photographs.   You will see the actual chine of the boat is very much similar to that of the Percassa, in fact, it is the forerunner design of the Percassa.   As the chine comes up to the bow, it has a slight 'S' shaping to it.   On Vic's plan, he simplified this.  He allowed the chine to go straight up to the bow - but it is up to yourself if you wish to copy the original design and put a bend in the chine at the bow, which I myself did.

Yes I noticed that, and that Vic's plan has both options of the straight side or "plank to this profile for scale". I will definitely shape the bulkheads to the scale line - I am thinking now the Sarik ones are going to be straight cut as their extra wood pack for the skins was sheet (hence I didn't order it).

I might compromise somewhere between the approximated plan position of the chine and your dedicated reproduction depending on how hard it gets to achieve.

Now, how you work out the spacings of your intermediate stringers, you take the height of the middle frame of the hull from the gunnel to the chine and you divide it by the number of stringers which you wish to use.   You do the same at the stern and the same at the bow.  When you have calculated this, you lay a strip of straight wood over the marks you have put on the frames and mark through with pencil on the rest of the frames.

For the bottom of the hull you do the same as above, only from the keel to the outer chine.

Thanks for the intermediate stringer strip guidance, I will try following your process, suspect it will take a while to get to that point. I also need to work out how to attach the hull to the build board, depending on what arrives from Sarik in the laser cut parts. I have a feeling now they will not be extended to build upside down but might assume you clamp the keel to the board.

After no communication from Sarik on order process I had a text from DHL its on its way this afternoon so guess I find out tomorrow!

Power from the model - for my particular model - comes from 2 MTroniks Vision 600s, on 7.2 or 7.4 (trying to remember that   )  On the real vessel both props do turn in the same direction, and, mine do the same - they are brass 30 mm diameter 3 bladers.  This diameter could all change mind, then I can be bothered to measure them, but, from where I am sitting they do look like 30 mm.

As a last thing, 70% of the photographs of the RTTL I did, disappeared when Mayhem crashed online about 7-8 years ago - and you may never know they may reappear on Mayhem when we all go round this universe one more time  .

I found an album of your build on one of the other boat sites, the American one with the gaudy colours and intrusive adverts I forget the name! but it did have pictures of the planking process that gave a good clear idea.Your motors have enough power it looks like, from the video as well. Mtroniks site does not list the M600 anymore, but the 550 is 200w and the M775 250w. This is all a helpful reference as it's looking a lot like 300-400w per motor is more than enough power.The prop info is also appreciated [size=78%]

Thanks for helping out with my questions and providing guidance, Paul.[/size]

[ChrisF]

Yes, I misread the drawing, thought it was upside down rather than its side!   

[Waiting2Retire]

Chris - if you turn your monitor on its side... all will become clear

Well the Sarik kit arrived, and I have to say I am rather underwhelmed by what you get in the RTTL kit.

I ordered the 1/12 Huntress kit at the same time, that arrived well cut in its sheets, with supporting strip wood and you got plenty of wood sheets for the money (£45) to complete the model. The extra wood pack was just lite ply sheets for the skins.

The RTTL kit does have note on the Sarik page that extra wood is needed to complete the superstructure, but does not mention there is no required strip wood included with the laser cut hole kit, and for £55 the wood does not look the best and its scorched in a lot of places from over-zealous lazer'ing that will need some attention. I had (wrongly) assumed it would contain what was needed to build the frame of the hull.

It does at least answer the question about the frames, which are cut with a curve interestingly not straight, I need make up some form of plan holding board arrangement and overlay on the plan but I don't think they are straight cut like the discussion above they are cut with the scale curve in.

Sadly no extensions to a building board level (to be expected), so either need to jig and build keel up or need to consider using them as templates and re-cutting the frames with extensions so I can build off a board to get it straight and true. As planking that is a concern.

I have two sheets of ply (shown in photo in attachment underneath) that are from SLEC and look to be much better quality, so have options. Will need to go out and get some strip wood though to pad the keel, chine stringers etc per the plan. At this point, rather than shortcut to a frame it feels like I just wasted some money as there is very little wood in the kit for the price!

This will probably be put at the back of the bench for now while I start the Huntress (and finish the police launch from SELC that is up to decking, needs paint, superstructure and finishing).

When the frames are stacked, you can really see the curves and lovely shape down the hull.

[ChrisF]

Without seeing the plan for the RTTL I don't know if I'm reading this right? I can see why John planked his hull because the convex sides make it difficult to use sheet and then it's almost impossible to bend in two directions at the bow. But looking at the Sarik parts there doesn't look to be much curve to the sides and I'm guessing that Sarik have modified the frames to suit ply sheeting? Planking is a lot of work and just wondering if you should use the Vic Smeed option that John did to make the plank on frame worthwhile and accentuate the curves? Particularly as you're thinking about recutting the frames with extensions so that you can build upside down which you need to do when you're doing plank on frame.

[John W E]

hi there


after looking at the photograph of the parts that you received from Sarik I was a bit surprised.   I have done a bit of investigation on their website and I see there is an extra wood pack to go along with this one.   That extra pack is another £29 on top.   I note that you can obtain the full bundle (plans and the 2 wood packs for £90 odd) and to be honest with you I would not knock Sarik as I have obtained a lot of good stuff from them - at good prices as well - but I cannot see where the justification for the £90 odd is.   Even £50 for what you paid for your pieces of wood - that being supposedly burned out with a laser; I would have thought a red hot poker from the old coal fire would have done a better job    .   To me, a newcomer purchasing this kit would be in a for a bit of a shock if they thought it would be easy to build.


Ok, enough waffle.  If you want a good explanation, have a look in the masterclass build for the Whaleback build - she is double diagonally planked with a good few pictures to help you out. 
 63 FOOT RAF AIR SEA RESCUE LAUNCH by Bluebird


There will be a way to actually use the frames you have from the kit and add on extension legs.  I will have to do a little drawing on here of the way I myself would do it.


Food for thought.


John

[Waiting2Retire]

Just about to reply and John added to Chris's comment from yesterday.

I didn't mean to knock Sarik as a whole just the RTTL "laser cut wood pack", the Fairy Huntress kit was very good value in my view, just expressing disappointment at the RTTL kit which I feel was very poor value.
Huntress (£45): 2 Sheets Birch Ply (1.5mm/3mm Poplar core), 3 sheets light ply (2mm,2*3mm).
RTTL (£55): 2 sheets 3mm Birch ply poplar core.

I asked about the extra wood pack for RTTL before I ordered without it, I should have asked what was in the laser cut wood pack. Sarik sell the 3mm Poplar core ply at £10.25 a sheet, so at £55 for the RTTL kit seems poor value was all I was saying (Huntress kit has 1 sheet of the 3mm birch core, and 5 sheets that have been laser cut and is cheaper). My other point of reference is the SLEC police boat (£85) that had everything included to make a working model, drivetrain and glues excluded.

FYI Extra wood packs:
Huntress Additional wood pack (£21): 1 sheet light ply, 18* 36" strip wood
RTTL: Additional wood pack (£29): 3 sheets Birch Ply (1.5mm), 2* strip wood.

I knew it was not going to be a simply kit to build, but that's the challenge right? Anyway, views shared to educate anyone else considering the RTTL kit who can make their own decision. I also was frustrated that I made a list of all the strip wood based off the plan, but assumed the strip wood that form part of the keel and the chines would be in the base wood pack.

I have been thinking it over and adding extensions was also the conclusion I reached. I am undecided about having the rear engine cabin part of the frames B4 and B5 rather than a removable assembly. The rear winch house needs to be removable so you can access he rudder and rudder servo.

I have spent some time looking at the whaleback reference build as well thanks John.

Chris, the curves are part of the character, the original full size was built double planked, so it's all these things and the challenge mixed together is why not sheeting. What I don't understand is as the Sarik extra wood pack is just sheet (and 2* 3mm, 1/8" squares to support the sheet on the keel) why are the frames cut with the curve, not the straight edge on the plan? (see attachment, probably clearer the John's photo above).

[ChrisF]

I wasn't questioning your decision to want to plank the hull (I've done two myself) it was just an observation that the curve of the frames from Sarik seem to have less of a curve to them than as in Johns build and wondered if Sarik had done this as they supply ply sheet rather than planks (if I'm correct with that?).

[Waiting2Retire]

You might be right Chris that they have their own curve, I have not yet dug out a board to use as a plan support and unrolled the plan, I will overlay the cut frames on the plan once I have and compare.

[Waiting2Retire]

So Sarik update, they have been quite good. I enquired if the wood pack should have had more in it (as there is no wood to complete the keel, you can't assemble the frame, no chines, inwales, carlings etc.).

They came back to say the cost was wrong, the kit is as delivered but should be £39 and updated the website the same:
https://www.sarikhobbies.com/product/vosper-rtt-laser-cut-wood-pack/

Due to the confusion they have offered I can return if I like, I need to have a think because their frames have the rear engine house integrated, and I might just be better at this point to cut everything by hand myself. If not they will refund the difference.

So +1 for Sarik for anyone reading this later.

Motor I keep wandering around, I need something about 1000Kv Because now I have seen the full size on the plan, 3S packs will be better than the larger and heavier 4S packs, so 11k RPM on 3S. I don't want to overdo it, but equally don't want to be short of power and have to change them out later!

Leaning 3536 1050Kv, or 3542 1000Kv for more torque (750w each motor seems excessive for a dual prop though!)

[Alan-CJ]

I have found your experience of Sarik very enlightening.  I purchased the RTTL short kit in May of this year as I also really like the boats and had seen some great examples of completed models.  When I received the kit, I was very disappointed with the contents, so much so I just put it all back in the box and shoved it away in a corner, putting it down to experience and vowing to give Sarik a wide birth.  My problem is never having ordered anything from them before I had nothing to compare it to and so assumed that this was typical of the kits they supplied.  I have since revisited the page and they have indeed reduced the price, but they have not changed the wording on the page.  This is their description of the additional wood pack "Our Additional Wood Packs contain MOST of the necessary sheet and strip wood needed to complete a model being built from a Sarik Hobbies plan and using the associated Laser Cut Wood Pack".  This kit is a long way from containing the required strip wood, and I have sent them an email complaining and suggested they reword the description.
PS, anyone want to buy a Sarik RTTL kit     I have since bought a Deans Marine MTB kit which I am finding much better suited to my limited boat building experience

[Waiting2Retire]

Hi Alan,

I was surprised I seemed to be the first to raise it, the RTTL kit seems to sell well? The huntress kit is very good, as is the SLEC police boat I’m halfway through. Can recommend the SLEC kits if you want a model with everything in the box.

My initial impression was “where’s the rest” when I opened the box. Hope you one day tackle it, the missing strip is not expensive, it’s just knowing what you need and not paying postage more than the order! I’m fortunate to be able to get to Mantua models in an acceptable amount of driving so can get wood there as needed.

Sarik don’t do returns usually, I’m still undecided if I use the (still in my view expensive) cut frames or just send them back and do it from scratch off the plan - leaning towards that option as per discussion above I can extend frames to build board for easier planking.

I’ve gone with 3536 1050kV motors in the end for anyone following along, at 11k rpm unloaded on 3s and 500w a piece I’ll be disappointed if it didn’t plane!

[Circlip]

Wonder how big the box is on the kitted Deans RTTL in comparison to the Sarik offering? Wonder if Vic SEED is rotating in his grave?


 Regards  Ian.