Hi, I would be inclined to fit one just above the waterline, 1/8 or 3/16 square. This is to reduce the risk of swamping the boat at high speed, esp. in a tight turn 😲 There are some excellent tips on the site about how to retrofit them. Attached some pics and notes I downloaded from Dave_M's contribution. May need to do this to my Sea Scout, depending on the sea-trial😉 Cheers Doug 😎
Thanks for all of your help. This is really useful information. I think I will leave the camouflage and just keep to the base colour. Would you paint to the waterline in matt red. I have looked at the shapeways site and they sell Mk 12 carriages in 1:35 scale which I think yours is at 28" over 80`. The gun tub was only placed on the deck for the photo. I have several pictures now showing the correct position. I will alter it and fit just before painting.😊 Thanks again. Peter.👍
[Score: 7/10] 52"/5000g CB90 Capable of 8mph and a runtime of 25mins Twin Propellors (3 Blade 45mm) Direct Drive to a Graupner 700 Turbos (3 Blade) Powered by NiCad (8.4v) 4Amp/h Batteries Controlled Through Mtroniks (25Amps) ESC - Comments: Scratch built at 12th scale from pictures and profiles of the original boat, hope to upgrade batteries to 11.1v lipo. The boat was originally built in Sweden a class of fast military assault craft originally developed for the Swedish Navy by Dockstavarvet The CB90 is an exceptionally fast and agile boat. Speed: 40 knots (74 km/h) Draught: 0.8 m (2 ft 7 in) Length: 15.9 m (52 ft) Overall; 14.9 (48') Waterline Builders: Dockstavarvet, Gotlandsvarvet In commission: 1991 Complement: 3 (two officers and one engineer); Up to 21 amphibious troops with full equipment Armament: 3 × Browning M2HB machine guns; 1 × Mk 19 grenade launcher; 4 naval mines or 6 depth charges
We hear a lot these days about encouraging the younger generation into pastimes such as model boats and model engineering and probably these issues have always been a topic for gloomy discussion. The very fact that we are still at it probably gives the lie to the gloomiest predictions. Anyway, this train of thought was brought about by a discovery in a dark corner of my workshop: Many years ago (in a different life) I was involved in primary education and following a BBC schools tv series on Nelson and naval history the class project developed into one about ships and all things naval. One group was fascinated by sailing ships after we had visited both HMS Victory and the Mary Rose ( still lying on her side then) and inspired by some drawings of different rigs in a Model Boats Scale Special they made some simple models to illustrate them. This is what I found, along with an Airfix HMS Manxman and two of those superb 1/700 (?) waterline models, of HMS Hood and the Bismarck, these three made by me to add to the display. These pictures show all these items which have survived years tucked away among the junk in the garage! The sail models were simply made with balsa, dowel, cotton and cartridge paper for sails, and some had even started to acquire rigging and staysails before the term ended. This all happened many years ago and I have been retired from teaching for 20 years, but I can still remember the names of all the different rigs, despite never having been a sailor - I hope it inspired some of the class into modelling, if not getting involved in the real thing. Smiffy
The plan seems to indicate weight in the keel, which is where you will need it. I suggest you put the model in your bath add the steel and see how the model floats. All the keel and an inch or so of the hull should be submerged with the weight battery and servos resting in the hull. Add or remove weight to get about right. I would cut a slot in the keel to add the weight as low as possible. The plan seems to suggest this. Seal temporarily and recheck for correct waterline. You could use cling film to seal whilst checking. When happy make good the keel and fit the servos etc and check again before fixing the deck.
The Sea Commander and others from the 1960s all seem to lack any real waterline. Primarily they were designed to race round the sailing waters whilst runing a IC engine and were not normally static the water unlike today. We have several in our club and I have attached a few pics. The Tarpon was a similar model and the waterline is shown on the example. Two shots of my Sea Queen at rest and at low speed. The propshaft adjustment from the original design is minimal, really just lowering the angle to allow the motor to sit lower whilst allowing the prop to clear the hull. On all my models I fit the shaft in a slot in the keel and make good with Car Body filler (Plastic Padding). This avoids the possibility of twisting or bending the shaft when fitting in a tight slot. Merry Christmas and I hope Santa brings you all you desire.
ChrisF I have now floated the boat in the bath tub and measured the top edge of both the front and rear down to the water, back in the workshop I put some masking tape from the waterline mark from front to rear keeping the tape as straight as possible, it is not a million mile away from the Keel less than 2 degrees difference. so the prop will stay where it is. I have also now rubbed one side of the hull down and masked it to the water line and resprayed the top half white, the lower part of the hull will be resprayed black, the waterline line will be put on this. I will then repeat on the other side. I hope this will be correct.
Doug makes a good point about the prop shaft angle with regards to the waterline. Having said that I reckon once on the plane the keel/bottom of the hull will be fairly parallel to the surface of the water so using the keel as reference in this type of boat is fine. Also if you start changing the angle you might have a larger hole in the hull which you have avoided so far! In addition you might have problems with mounting the motor lower down. Chris
Doug, Richard hereit is me that has the digital angle, I got it from a company called Rutland's here in the uk, www.rutlands.co.uk/, Thanks for the info about the water line, looks like I am going to have to use the bathroom bath again as I do not have the waterline marked as I have been experimenting with batteries and their position, the way I see it although I have arrived at a decision using a 56mm prop at the present angle, how do I decide the correct waterline at rest?
Hi Chris, Hi Mark, "the flatter the better" is absolutely right to get more forward thrust and less forward pitch which pushes the bow down. My concern is using the keel as the datum line! Is the keel line parallel with the actual waterline when the boat is at rest? I doubt it, maybe - maybe not. I try to measure against the waterline in order to obtain the maximum forward thrust from a standing start. Chris: I am also very interested to know where you got the digital angle device. I have something similar but it's for building fitted cupboards and such and much too big for model stuff🤔 Merry Christmas all, Doug 😎
Andy The original model was produced in the early 1960s when IC engines were the norm and scale and RC for sailing models were in their early development stages. Supplies were limited and we made do with whatever was available. The plans were typically sheet on frame, probably plywood from an old tea chest and cascamite resin glue ( it was water proof and slow setting). The designer would suggest suitable wood to use but many chose to use what they could acquire and as a result the finished models often finished up heavy or very heavy. Coupled with the large IC engine and flywheel and large heavy RC escarpments and big drycell batteries, it is not surprising that the hulls sat well in the water. To the modellers of the period the waterline really didn't matter as we were after speed, control and endurance. This may explain why the early plans did not show a waterline, as in my experience the draught varied greatly between models. Today we have scale plans and supplies that allow us to build true replicas and all the important detail is a must for a true scale model. Personally as an ex flyer I try and build lite, bricks tend to fall or sink, and my Sea Queen rides high in the water with a slight bow up. A 42xx brushless and LiPo add little weight and I have two 8oz lumps of lead in the stern section to achieve this. If it looks right, sails well and you are happy, then enjoy your model.
I'm afraid my project for the 'lesser known dreadnought' has foundered. Plans from Greenwich have become just too expensive at a net sixty or so quid and photos seem to be virtually non existent other than from long distance. I have acquired some drawings of the 1906 HMS Dreadnought, and have started on her as a waterline model. Any photos welcome!! Attached current state of play.