Topic: 1/12 Severn Marking out Transom (Read 8204 times)

lesfac · « **on:** January 16, 2016, 04:28:16 pm »

I could do with some advice on marking out the transom.
I cannot see a clear link on the RNLI drawings between the base line and a point on the hull.(A point that is not a hole to be drilled.)

It should be possible to scale the drawing (Docking Plan Transom) but I think some of the dimensions on the transom drawing don't measure correctly when you scale them so I don't want to scale the required dimensions unless there is no alternative.

I have a set of photos of a build of a Severn and there is a picture of a marked up transom with dimensions but even here the dimensions I work out are a bit different to those shown in the pictures.

Before I go for "Best Guess" I would be grateful for any advice.

Les

Canterbury Coxswain · « **Reply #1 on:** January 16, 2016, 05:43:19 pm »

Les,
You might have seen this picture before that I have posted of 17-09 's 1/12th Severn transom markings - I'll send him an email and ask him to contribute and help on this matter, as he has measured off and finished his superbly!
All the best and do keep asking away - best way to both learn and hopefully get it right.
Kim

17-09 · « **Reply #2 on:** January 17, 2016, 11:08:24 am »

Hi Les
Start with an accurate vertical centreline, mark this with a line of tape, all the measurements to the centres of the exhausts, trim tab guide plates and other fittings can be marked off horizontally from this mark, the measurements in mm’s are simply divided by 12 to give the model sizes, i.e. the 850mm distance from centreline to centre of exhaust is 70.8mm and therefore the exhausts are 141.6mm apart. The vertical height is trickier, you will need to accurately set the boat up on a flat surface and make a baseline which is 11.6mm higher than the lowest part of the keel, the drawings show this clearly, 140 divided by 12 will give you 11.6mm. The vertical measurements can be marked off again by using tape. It is now some time since I done this work but do remember it gave me some headaches, if I recall the hull size did not work out to be totally accurate and some minor adjustments need making. I also had the advantage of being able to view the real boat and take certain measurements myself, not always possible as the boat is obviously afloat. The waterline changed on the Dover Severn, I believe due to new engines adding to the weight, I was able to mark the new waterlines accurately and most of the transom fittings worked out correctly when viewed from astern, the old adage, “If it looks right it probably is” was applied. If it helps, the distance from the top curve of the transom to the top of the waterline is 139mm, vertically, 140mm actual. The exhaust centres are 40mm up from the top of the waterline, the waterline is 6mm thick aft. Remember the rake of the transom and to some extent the curve on the plan view will alter the measurements slightly, the plan being flat. All this is of course from the Dover Severn boat, others may be different
Regards 17-09

Canterbury Coxswain · « **Reply #3 on:** January 17, 2016, 11:41:30 am »

Les,
I knew 17-09 would not let you down. He and myself do a DVD of over 2,000 photos of the Severns at Dover and Newhaven, with the modeller in mind. They are mostly close-up detailed shots, but obviously there are many that show layout and relationship between items on the boats. This sometimes helps and a pair of dividers and small ruler allows for better judgements to be made, especially it a 6"x4" or A4 photograph is made off the the disc, using your printer. All I charge [as this is now a double DVD] is £7.50 and ALL the money will go to either RNLI Dover or Newhaven [or both]. I pay the cost of production, case and postage. If you want one [no obligation at all!] drop me a PM with your address and I'll do it.
Keep up the good work and enjoy the research and trying to get it right, that's what pays dividends - but keep it all in proportion, it is a hobby!
Kim

lesfac · « **Reply #4 on:** January 17, 2016, 11:56:19 am »

Thanks 17-09 and Kim for taking the time to help.
Your last post has just come in so I need to digest what you have said.
I have been working this morning with scaled photos of the plan in Corel Draw and marking up over the photo of the drawings.
On the Docking plan looking at the side view I scaled the distance from the flat surface under the hull where the rudders are to the centre of the engine exhaust port. I arrived at 92.7mm at 1/12. I was thinking once you have this you can transfer it onto the docking plan transom view and get the other dimensions you need.
I attach what I ended up with.
I can see that your method follows the drawings and must be accurate.
Thanks for the info on the waterline. Can you tell me as the model water line is 6mm high where do the dimensions apply? Top, Bottom or Centre? I would guess to the centre of the 6mm waterline?
Once again thanks very much for taking the time to educate me.
Les

17-09 · « **Reply #5 on:** January 17, 2016, 07:02:01 pm »

Looked at your drawing, there seems to be a discrepancy in the exhaust height, not sure what, but the distance from the flat trim plane to centre is only 80mm on my boat. The docking plan should be correct but.....The waterline is also higher on mine, this is correct as I measured the real boat for this. The measurements given before should correspond. Your question about waterline height, the measurement I gave you is the top of the 6mm thickness.
I hope to post a photo of the real boat transom for you to better understand.
regards 17-09

craggle · « **Reply #6 on:** January 19, 2016, 04:14:18 pm »

Hi Les

I have just been playing with the 1/12th scale plans in PDF that are supplied on the Speedline DVD.
In my day to day job I get to play around with a rather nice CAD system and one of the things it can do is convert PDF's back into a CAD format. This is especially useful to me as I can then measure straight from the drawing. I have done a dimensioned drawing from the file which is attached below.

I'm not sure what the origins of these drawings are though, were they drawn by a keen enthusiast from photos or are they from an RNLI Cad file. As I don't know I'm reluctant to say they are 100% correct but the Transom layout doesn't look far off visually from the photos of the Dover boat out the water that I got from Kim apart from the different water line as 17-09 mentioned above

Highly recommend Kim's DVD's by the way, very useful images on there. Did you get my cheque Kim?

Craig.

Canterbury Coxswain · « **Reply #7 on:** January 19, 2016, 05:51:49 pm »

Craig,
Many thanks, got the cheque for the RNLI and when I get the money for the few others I have sent out in the past few days I will send the money to RNLS Dover.
Like the plan you have posted for Lesfac - I think it could well be from measurements and software used by Adrian Gosling at Speedline, who too is used to all this sort of thing and I remember some years back now seeing this on CAD drawings he was working on in his upstairs study.
I am glad you like the photos, they really do show what is required and how things 'work' and what goes where! Half the fun..........
I trust both of you enjoy your respective builds - like the initial photos Craig on your build.
Kim

lesfac · « **Reply #8 on:** January 19, 2016, 08:10:19 pm »

I used Corel draw to do the drawing I posted in a similar way to Craig.
On my drawing the 93mm dimension was questioned by 17-09 who thought about 80 is nearer the mark. On Craig's drawing the same dimension is
47.37 + 47.44 = 94.81
I noticed that the exhaust port centres always seem to look to be on the centre line of the flat band running up the sides of the hull to which the rubber fender is glued. (at the transom view).
I transferred a line across the transom from this point and it measured 85.
Obviously I want the thing to look right and visually the exhaust ports are in line with the side fenders.
Ever decreasing circles here

Kim I will pm you for the DVD you mention
Les

17-09 · « **Reply #9 on:** January 19, 2016, 09:16:06 pm »

Les you are correct, the exhaust outlets are in line with the fender rubber which is fitted to the flat section on the hull, if the docking plan measurements are used, the exhaust centres end up 15mm above this line which is obviously wrong. I must assume that the docking plan is correct therefore the hull must be slightly out somewhere. On measuring the distance from the deck to the lower edge of the fender rubber, it is wide by 6mm. This still leaves a 9mm discrepancy.
As my boat has a slightly higher waterline for the reasons previously given, the visual effect looks correct. The name fits between the rectangular trim cable plate and the red/yellow bands, the distance looks and is correct, and the names are the correct size, therefore I think it is in the lower section of the hull where the extra size is lost in the hull. I seem to remember measuring the distance from the fender rubber to the first chine when the boat was out of the water, and noting it was longer than on the model. If you get the CD from Kim, it has several pictures on it that show the transom with the waterline much higher than the drawings.
Regards 17-09

Canterbury Coxswain · « **Reply #10 on:** January 20, 2016, 12:15:40 pm »

I am posting two of 17-09 's superb detail photos that appear in my DVD of Severn Class details. Now that you get more than 2,000 photos [at original Mega bite size] and they have to go on two DVDs, which, with costs of plastic covers, envelope and postage means I am now having to put up to £7.50 on this Class only [all to the RNLI] for my time involved burning and the costs for postage which I pay. I have just had another couple of orders, so the RNLI Dover will be getting another surprise donation of £50+ soon, thanks.
I hope these two photos might help those who have their own photos, but possibly not from these angles. !7-09 has been on and around the Dover boat [17-09!!] on many occasions and many of those times with his handy ruler appearing in the photos too. Myself likewisen[but not so many photos] on 17-21 [Newhaven] never intending to build a Severn Class - et alone at 1/72nd scale, but my shots contain trips out into the Channel and down to Brighton [even a couple of short video clips - unedited].
Happy research and building to all - long may you get it correct.

craggle · « **Reply #11 on:** January 20, 2016, 12:39:20 pm »

Just looking at your photos Kim of the Newhaven boat and that looks very similar to the Dover boat. The white waterline looks to be very close, 1/2 inch or so below the fitting on the inside of the port side trim tab actuator. If the waterline was moved on the Dover boat maybe the Newhaven boat followed suit?

So the drawing I posted above is probably correct apart from the waterline dimension. Gets confusing this model building lark!

I have printed my drawing above at the correct scale for the model so I'll stick that on the hull moulding soon and see what looks correct.

Craig.

Canterbury Coxswain · « **Reply #12 on:** January 20, 2016, 12:58:26 pm »

Craig, I think 17-09 mentioned it elsewhere, but some of the Severns have had their Caterpillar engines replaced by the new MIT [I think that is the correct designation] ones, so might require a different position [sit lower] in the water if the engines sit higher on their mountings. This happened with the Arun class - they moved the datum line up by 1 foot [1" on a 1/12th scale model] and having also reduced the length by two feet and squared off the transom, most Coxswains reckoned it was the best RNLI boat they ever helmed!! This might or might not help!! However, someone building a Trent recently asked me the same - were the plans or the model correct? I said 'you have access to the real boat [as has 17-09 with Dover], build what you see - that is correct!!'.
Kim

lesfac · « **Reply #13 on:** January 20, 2016, 01:20:13 pm »

Thanks to everyone for the information and advice.
My thoughts are now that it is only the vertical reference point that is ambiguous due to issues with the drawings and the model hull. As I said earlier I think the thing that would be noticed most is if the exhaust ports were not on the centre line of the side fender.
So I think I will settle on this as the criteria for vertical alignment.
(Unless someone points out this is flawed thinking)
Les

Canterbury Coxswain · « **Reply #14 on:** January 20, 2016, 02:02:51 pm »

Just a quick one - two points. Firstly, apologies for the 'typos' in my photo attachment posting above, I did it in a hurry and should have read it through - the sort of thing I critisise in other places. Secondly, remembering a conversation from a couple of years ago, when one of my LBES friends in the 'Black Country' fitted five bladed props to his 1/12th scale scratch built Severn, the props went on when the new engine configuration had been fitted. So as the Dover boat exhibits them in the first photo, that might confirm the theory of why the waterline is different to the original drawings [which normally remain the same ones issued to modellers and not upgraded over the years]. Kim

craggle · « **Reply #15 on:** January 20, 2016, 02:04:10 pm »

I think that is a very good plan Les, Mark the position of the rubber fender on the transom, draw a centreline across the boat and work from that. I have re-worked my drawing to use that as a reference point if it helps you out.

According to the drawing the exhaust port centres and trim tab actuator centre top bolt is on the same reference line and that line comes from the centre of the side rubber fenders, not the centre of the short bits of fender on the transom as they follow the curve of the deck. Hopefully that makes sense.

Craig.

craggle · « **Reply #16 on:** January 20, 2016, 02:07:32 pm »

I was wondering why some models have 4 bladed props and I have 5 bladed props in my kit like the Dover boat has.

Only bad thing with this lower waterline is even more ballast will be needed to get it sitting at the right place in the water making it even heavier. May need to invest in a forklift!

Craig.

Canterbury Coxswain · « **Reply #17 on:** January 20, 2016, 03:10:34 pm »

Craig, use the heavy old SLAs low down and they will give both ballast and stability + longer running time - once it's on the water you will want to put off the time when you have to take it out!!

Also, my friend from the 'Black Country' had problems when converting to five bladed props [and he has a lot of knowledge on these matters on real boats too] because there was a lot of torque generated and then too much speed [I can get more information if people wish], so he put an adjustable limiter on his Transmitter [TX] throttle controls so as not to cause further damage to the props [photos I took last May attached].
Now, for some facts regarding the real boats' conversion. I should have said MTU, which stands for Motoren-und-Turbinen-Union, originally a consortium from Daimler Chrysler and Detroit Diesels. To cut to the chase, there have been a number of takeovers and they are now called Rolls Royce Power Systems. The engines were originally CATS, but are now MTU Series 2000 M94s, ninety degree turbocharged V10 units. They will be fitted when each boat comes in for its 25th yearly service [halfway through its life expectancy of 50 years]. The CATS gave 25 knots top speed, MTUs over 35 knots!! They are, therefore, de-tuned as the hull was not designed for that sort of speed. However, they still have the enormous acceleration - CATS were standstill to 26.6 knots in 38 seconds, the MTUs do it in 17 seconds. The engines are unique in that they are designed to go 'start' to 'full ahead' when cold. They are a lot quieter, so the crew no longer have to shout. Finally and back to the point above, the sumps were deepened to so that oil could be 'caught' and recirculated during the 'self-righting' process, so therefore the engines sit higher off the hull. All of this work is done at South Boats on the I.O.W. for the RNLI. Here endeth today's lesson. Kim

Netleyned · « **Reply #18 on:** January 20, 2016, 04:04:45 pm »

I assume the Falmouth model has the outboard trim tab actuators in the correct position.
A lot different to Craig's drawing.

Ned

craggle · « **Reply #19 on:** January 20, 2016, 04:41:02 pm »

The trim actuators are quite different on that model Kim posted pictures off.

Looking at the photos of the Falmouth boat I have the drawing looks correct, All in line across the hull as described above.
I would post a picture of the back of the Falmouth boat but they are Kim's photos so don't want to put them on the forum without him knowing. I will get down there soon as the weather warms up a bit and get my own photos as it's the Falmouth boat I'm building and only a short drive away from me. Should pop up to the fort as well as not been there for many years.

Craig.

lesfac · « **Reply #20 on:** January 20, 2016, 05:27:16 pm »

I printed the PDF file at 1/12 on A4 paper and stuck them together.

I just cut out the printed transom outline and stuck it on the moulding.
Assuming my cobbled together print is something like true The attached might explain some of the compromises we have been discussing with regard to the fender/exhaust port height.

I marked over the photo to show the differences clearer

There seems to be a difference in the angle where the trim tabs go which might have implications for the actuator placement and the angle that the rod meets the tab.

The blue line is the boat outline and the red line is the plan outline

I guess we are in danger of beating this subject to death now.

Les

Canterbury Coxswain · « **Reply #21 on:** January 20, 2016, 05:40:57 pm »

Not sure at what point this model was made - many years ago now, as I've been seeing it at shows before I really got to know the owner. Also some of these items do occasionally get upgraded at re-fit times. The other point is that some people build to get 'working' items, which means there might have to be a compromise against what is going on inside the model, so cannot guarantee the total accuracy here. Please do not take the modeller to task, as I was posting my photos to discus the the five bladed propeller issue. Cheers all. Kim

Netleyned · « **Reply #22 on:** January 20, 2016, 05:49:43 pm »

Just wondered that was all.
Good job the Accountants in the Rivet Assembly Facility are all asleep

Ned

derekwarner · « **Reply #23 on:** January 20, 2016, 11:32:32 pm »

....& Les says.... "marked over the photo to show the differences clearer"

1. yeh....but now we must stand upside down to compare the previous image & read the dimensions......

....
2. in post #16 the vessel has 4 blade props, now in post #18 it has 5 blade props......
3. this same prop confusion has been appearing from post #1 onwards ...& the vessels all have the same name

Do the owners change them just to confuse the readers or do they grow overnight?

Derek

Canterbury Coxswain · « **Reply #24 on:** January 20, 2016, 11:54:51 pm »

Regarding the propeller blade numbers I think I covered that at #17. When they come in for their 25 year re-fit service they are re-engined and re-proped. Then of course the original Speedline kits would have had four blades, but some individuals could buy their own, according to how they ordered - full semi-kit, hull and deck only, hull=deck=wheelhouse, all the above+ running gear, all the above+ internal and external fittings. So like most of us the model is 'created' as at a certain date in time, this fixes other modifications and also the font style on lettering etc.,. Quite a few modellers will not pay the £70+ sterling just to have two new five bladed cast props on their model, especially [and I'm being a 'rivet counter' here] when the blades are not of the correct 'skewed' pattern. Hope this might help explain why some have four or five props. The ones featured here appear to be those from PropShop, but I stand to be corrected - other buy the Raboesch and George Sitek ones, effective, but not cast [brazed] and a little cheaper. However, the producers would say they are not built for brushless motor speeds and power, but so far I have not heard of anyone having a problem them.
Kim

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