Just started a 40" model of a 41'6" seaplane tender. I have been wanting to do one for years and now that my 36" 100 series 64ft HSL is done I was getting itchy fingers. Started with drawings from the 1976 Model Boats mag (part of the series on ASRs they did back then) which show frame shapes and positions, and enlarged them to 40" (A-O paper after rearranging the images on the A4 primary enlargement used as printing 'pattern' to enable max size on A-O. )
I did the same with the HSL and with a bit of fiddling got all the frames to line up nicely to shape. You have to be a bit inventive building this way regarding framing material etc, but it's possible if you have previous building experience. I found with these particular drawings that the frames were not drawn with identical profiles (left and right sides) so I had to create 1 side and flip it for the opposite side. I also had to create an extra frame between 2+3 as there was no real support for the stringers without it.
The front top deck frame is cut from 3mm ply, as are the frames,-(ply is from packaging of a big Toyota Landcruiser axle recall which was done during my time at Toyota, which is 3 ply, very light, and perfect for this type of job, and not to mention, free!) I borrowed this frame method from the old 60s Vic Smeed MTB plan and it makes a good strong bow section to work with (used it on the HSL also.)
Ply longerons are run through from transom to F2 with hardwood stiffening between transom and F4. Chine, gunwale and mid stringers are 4mmx2mm Beech, bottom stringers are 3x3 beech with mid stringer doubled. I may have to put extra stringers in the sides but that will depend on how the planks lie in the flares. planking will be 1.5mm balsa as the flares are quite pronounced especially in the bow area, and you just can't get sheets to go round the compound curves.
Hull will be glassed and faired when finished and sealed with thin resin inside once everything is ready. Cabin is reasonably easy but takes a bit of working out and fiddling with due to lack of any plan, but it seems to be working out reasonably with the use of photos etc.
The model is going to be a representation of a tender which was imported privately in the 50s by a doctor in the Milford sounds area here in the South Island of NZ, to enable him to visit patients, due to there being water access only in many of the remote areas. I have modified the drawings to represent this boat, which included changing the mast and removing the rear oval port and replacing it with a small round port, (not sure why this was changed, maybe an interior modification made the large port unnecessary ?) The boat ended up in Auckland at some stage and was owned by a family not far from my place for a number of years (pic is on the hard at our local yacht club in the 70s, - colour pic is from a friends super 8 movie taken from his boat, on an outing together with Jaguars owner 60s/70s). It is now apparently back in the South Island being restored.
The model will use brushed 540 motors with twin ESCs etc but still a way off yet. I have to work out a way to make the cabin removable either with or without the rear cockpit, but more likely it will be a 2 piece job. It's a bit of a make it up as you go project.

Model Boats frames boat sheets Landcruiser motors ESCs
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Finished planking hull, now started on fairing it. Planks (1.5mm balsa) were just pulled in to the center stringers by clamps and thick cyno'd to those first, then once set, top and bottom ends of the planks cyno'd. When dry, a bead of balsa glue run along every stringer to keep everything in place. Once faired, it will be glassed and once done the inside will be worked on. Deck will be 1.5mm marine ply, but I will have to resist the urge to stain it, as the subject boat had painted decks.

bead decks
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Hull planking and fairing finished, but had to drop the up-sweep of the chine at the bow by about 1/4" (using filler) as the 12 frames chine positions shown in the drawing were too high. The bottom faces of the 12 frames need re shaping to bring the chine down to the correct progressive curve. Bit late now but is looking ok, apart from a slight hump at frame 2. Once glassed I'll work it a bit more. Always hard to see what the hull shape will be till you cover it.

frames
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Motors I'll be trying in the ST are either the 'Gool' (black motor) 540 (replaceable ball bearings and brushes and adjustable timing) or the Feilun boat spare 540 motor complete with mount and cooling. Also bought 4x stainless 250mm driveshafts with ball bearings ( $8 NZ on a big discount on Banggood) remains to be seen how good the bearings are. Will be running twin motors through twin car ESCs.

A bit more fairing work and sorting out the chine near the bow. F1 and F2 need modifying to get a more gradual curve towards the bow (bit late but nothing a few shovels of filler won't fix (just plastered on another batch to blend in the flare). F2 also should go back slightly as bow looks a bit 'full' at that point.
Forgot to mention earlier that the center top 'spine' (10x6) spruce is glued into the frames with keel to help keep everything straight while fitting stringers etc. This can be cut out where access is needed when hull is complete (see pics). Makes a good strong handle while working on the hull also. Chine looks like it has a slight 'hook' but it's a tropical delusion caused by the bottom getting flatter towards the stern.

Finished fairing hull and correcting chine curve. Glassed hull tonight using 6oz cloth and West System epoxy resin. Took a few hours to dry even though I was using fast hardener due to cold weather, and when still flexible, trimmed off the excess cloth. Will give it a day and de-wax and sand it before giving it another coat of resin, then it will be on to sanding, filling and fairing again. Hull weighed 720g before glassing and 920g after ( probably end up around 1kg filled and painted)

Final coat of resin done and a smidgen of filler where I had to sand through the cloth, (bubbles) and it's on to sanding again and starting to paint. Props arrived today from China- Ali Express (6 days,-not bad at all!) These props are really good and durable and come in a variety of blades, sizes, and in LH and RH. I bought 25mm L & R and 30mm L & R ($8 NZ all up) and worth every penny. Very little cleaning up to do on them. I used these (25mm) on my HSL as well and they are perfect for the job. Not sure of the pitch as they don't show it (40/50 maybe) but they have a nice cupped front edge and good scale shape.
To give an idea,- the 36" 6lb HSL has 2x 2845 2000kv inrunners on 2s 2200 MaH Lipos and with these 25mm props will hit around 12-15 mph silly speed flat out.

Finished sanding the hull after the second coat of resin with 60 grit then 220 wet and dry (used wet) and now hull is matted ready for painting. Have made the chine spray rails and top rubbing strakes and radiused one side of each, - was going to fit them but forgot the 1.5mm deck yet to attach so will wait till I glue the deck on. I can do the chine rails without a problem. Cut out the 1.5mm marine ply deck for a rough fit and added some 5x5 balsa frame top and longeron pieces to help give more deck gluing area. This boat has that much room inside I'll have no probs getting all the gear in, unlike the HSL which ended up getting a bit cramped (mind you 36" with twin everything, 4 batteries and a pump there's little wonder,- wanted to fit a smoker that worked through the exhausts with the water but ran out of space). I'm going to try this out on this boat.

Deck cut-outs done. Deck will go on once I've checked I have everything in that's not going to be a problem to get at later. There's tons of room to get the hands in so shouldn't be a worry. Once deck is on I can remove the top center brace from the 2 front openings to open the space up.
Waiting for the shafts to turn up so I can get the holes cut in the hull (will be making a template) ready for lining up with the mounts / motors etc. Making the rudders later once shafts are done to avoid any clashing with the props, and making sure they are easy to remove for shaft removal etc (unlike my HSL which has no access to the rudders, and the shafts have to come out frontwards through the 'engine room' bulkhead, - better than cutting holes in the rear deck where there weren't supposed to be any)
Something to remember on the future maintenance side!

Glued deck on today (sun was out for a change) using 3 pre aligned/drilled dowels to locate it, as I had trimmed the deck fairly close to finished size and wanted it to go back in the right place for gluing. Just about set tonight so will give it a final trim and sand tomorrow.
Drive shafts turned up and don't seem too bad, not sure about the quality of the bearings but might knock them out and replace them with stainless from MBA if available. Don't want to have to do it once shafts are fitted.
Tested the motors again with universals on the shafts (in a word, rubbish. Thought I'd try them as they looked ok on line (and they are not too badly made) but they are only made for cars and not for high speed running. The small amount of play means that they vibrate due to not being concentric at speed, caused by centripetal force throwing the 'play' to one side. If anyone is contemplating them for boat shafts, don't bother. Perfect for slow angled or straight use (driving winches etc) as they run smoothly at angles.
The black motors Gool + other names) run at 800mA with no load whereas the silver cooled motors (spare motors for Felun boats) run at 2.3 A with no load. The Gool motors are 45T and will run down to a crawl (no load as do the Feluns) but are not as fast as the Felun motors which are bigger and probably have fewer turns.
I tested them with the car ESCs (32A cheapies and they worked fine (apart from the small center stop/reverse problem discussed previously). The ESCs were run on a near flat 2s LiPo and auto cut off at 3.55/6 volts / cell which is quite reasonable (3.3 being a safe min) they will re-start after a few secs then auto-cut again as soon as the voltage drops.
Will cut out center top 'spine' on hull when deck is set tomorrow and start making some floors and a motor mounting base plate. When it warms up a bit I'll spray the hull undercoat.