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Thread: U-3 1/8 scale Hydroplane.

  1. #31


    Got a bit done in the last few days.
    I made some paper templates for the sponson deck skins, transferred them to the ply & cut them out.
    To make the paper shapes I lay a sheet of good old butchers paper over the area & run my fingers along the edges of the framework, creasing the paper.
    Cut the paper about 1/8" bigger.

    After trimming & sanding the inboard edge of the panel to match the main stringer, that runs from the tip of the sponson to the transom, they were given a coat of epoxy fiberglass resin on the underside.
    The whole inside of the boat was also coated with the resin at this point.
    Foam blocks were cut & fitted into all the spaces & sanded to shape.

    Then on went the sponson deck skins.
    I placed a bead of 1 hour epoxy on all the internal frame work, placed the skin in it's exact place & tacked it down at the transom & at the main bulkhead of the heels of the sponsons.

    The left hand skin needed a cut on the underside of it to relieve the pressure where the framework sort of curves down & then levels out towards the chine, creating dip in the skin.
    Then I stitch glued around the edges, keeping the skin pressed down & flat. Working forward from the transom. Some CA accelerator in the pump spray bottle is a great thing to have here, as everything is held in place by hand during this operation. The boat needs to be rotated upside down & sideways to get the CA to flow where you want it to go.
    Then a bead of CA is run along the joins, a section at a time, allow the glue to wick into the joint then squeeze together & spray with accelerator.

    Of course the other method of Epoxy on everything & an array of weights, tape & clamps also works.

    Creasing the paper templates.


    The dip in the left side deck.


    The cut in the underside of the deck.


    All glued on ready for final trimming & shaping.


    The left side skin with the dip.

    Last edited by 785boats; 02-10-2018 at 04:49 PM.

  2. #32


    Are you going to build the tiplets/hydroshoes, at aft end, like the full scale. If so please document with pics, Thanks.

  3. #33


    Hi lambo.
    I did give them a mention & a photo in post #23.
    Here's a bit more detail.
    I simply cut, bent & sanded to shape, the bottom ride pad. I chamfered the edge that glues to the anti trip skin to the same angle, & glued it on flush with the air traps. To keep it level I ran a straight edge across from the other side of the boat, & overhanging the ride pad while the ca glue set.
    Then the side of the pod was cut & bent to shape & glued on. A little infill piece was added to the transom & then a piece of thin 0.04mm ply was glued on covering the whole transom of the pod to cover the join in the ply.
    If I had been thinking properly earlier in the build I would have cut the rear skin on the hull to the correct shape so the last couple of steps wouldn't have been required. Maybe you will learn from my mistake & get it right.
    All the edges were sanded to shape.
    I had no dimensions to work with, so I just winged it from the photos & videos on the internet.

    Because the rear transom is a different shape on each side of the boat, the transoms of the pods are different too. See the pics below.
    I hope that helps a bit.

    Port side sponson.


    Starboard side.


  4. #34


    I couldn't help myself this morning & had to assemble a few of the bits for the engine. The intake & exhaust manifolds were joined together, as were the 4 turbo casings.
    A lot of sanding was then involved in reducing all the banding lines on everything.
    Then I coated everything with high build spray putty to fill in the all the lines that were left.
    I'm back into the sanding again now,
    Man it's hot today. I had to wash the dust down my throat with some Coopers Original Pale Ale.


  5. #35


    Hey Paul......I'm smelling more of that birch ply sawdust clear over here....LOL

    I just saw this thread.....great project and the boat is looking amazing! Wouldn't expect anything less! It will be interesting to see how the final turn fin is mounted on this. I'm trying to visualize it. I know on my Elam the sponson heels had that same angled piece coming down just above the ride pad. I ended up mounting the turn fin to the heel of the sponson to get the fin 90 degrees and then built a box shape around the turn fin bracket. Not quite to scale but it worked....LOL

    I love that motor.....the things the 3D printing world can put out there is amazing. I actually ordered a Anet A6 ( Prusa i3 clone) printer last week...LOL. Have to build the darn thing first...HAHA. But I am looking at all the things that can be built.....rear wing sets, canards, canopies, drivers...etc. It's endless!

    I'll be watching the build as it develops....Looking Great!


  6. #36


    Quote Originally Posted by Speed810 View Post
    Hey Paul......I'm smelling more of that birch ply sawdust clear over here....LOL

    I just saw this thread.....great project and the boat is looking amazing! Wouldn't expect anything less! It will be interesting to see how the final turn fin is mounted on this. I'm trying to visualize it. I know on my Elam the sponson heels had that same angled piece coming down just above the ride pad. I ended up mounting the turn fin to the heel of the sponson to get the fin 90 degrees and then built a box shape around the turn fin bracket. Not quite to scale but it worked....LOL

    I love that motor.....the things the 3D printing world can put out there is amazing. I actually ordered a Anet A6 ( Prusa i3 clone) printer last week...LOL. Have to build the darn thing first...HAHA. But I am looking at all the things that can be built.....rear wing sets, canards, canopies, drivers...etc. It's endless!

    I'll be watching the build as it develops....Looking Great!


    Thanks for the kind words.
    The turn fin bracket won't be a problem. I'll just copy the full size ones. Sort of.
    Sounds like you've got some fun in store with that printer.
    As for the motor?
    Well the paint shop & the engineering shop at Wet Track Racing have been busy.
    The motor is ready & awaiting transport to the dyno shop.

    It all went together effortlessly. A great little kit from 3dparts.

    A few bits painted.


    Start of the assembly.


    All done.


    Another view.

    Last edited by 785boats; 02-14-2018 at 03:00 PM.

  7. #37


    I haven't had much of a chance to do much to this ol' girl lately.
    But this afternoon I cut out some aluminium sheet for the vertical fin tabs & drilled some holes into them for the epoxy to get a better grip. A slight kink at the deck line gives them the outward angle as per the original boat.
    They will be glued & screwed to the inside of the main stringers.

    Then I cut out the fins .
    Each one is made up of two pieces of 1/8" ply with a center section cut from 1/16" ply. This is the same thickness as the aluminium tabs.
    A piece was cut out of the ply to match the tabs. The pieces will be epoxied together & then shaped to an airfoil section. When the time comes for final assembly they will be slipped over the tabs with copious amounts of epoxy in the slot.

    All the bits.


    The tabs temporarily screwed in place.


  8. #38


    Nice job, looks pretty solid, are you thinking maybe nylon break away screws for the center wing? Maybe magnets for the motor? They always seem to be the parts that take a beating in a flip. Keep up the awesome work man.

    Sent from my iPad using Tapatalk
    Namba District 16
    1/8 Squire Shop nitro,1/8 59 Maverick nitro, 1/8 Executone FE (UC)1/8 Smokin Joe FE,MLGSX380,AC Pro40II Q Sport,AC Pro40II nitro,Twincraft mono 10s,Vision AOPC,VS1 FE,Insane 30.

  9. #39


    Thanks for the kind words.

    I haven't really given the break away screws much thought. But I guess it would be prudent as the wing has such a big surface area.
    My 1/8th U-95 has had many flips in the 70mph region. The wing & fins are all solid ply & bolted together with steel bolts & aluminium brackets. They haven't broken yet. But to be fair there is a center fin too. The wing is bolted down onto that as well. Makes for a very strong assembly.

    Now that you've brought up the subject, I think I will still have the adjustable angle brackets under the wing, but with nylon bolts through the fins to fasten them. Thanks for bringing it to my attention.

    Magnets sound like a good idea for the dummy engine too. Thanks.

  10. #40


    I'm glad to say that the egg pod, canard wing, & ramwings arrived yesterday. So now the front end of the boat can be worked on.
    Unfortunately the pod is more narrow than the main stringers. So I can't bend them inwards & blend them into the pod as I had hoped.

    So, after looking at some images of the underside of the boat I noticed that there is a raised belly pan down the middle of the hull.
    I decided to fashion one similar from some 1/8" ply long enough to reach the front of the pod.

    The bottom half of the pod was then cut to fit the rear sponson bulkhead & the belly pan was epoxied into the pod.
    The pan needed a kink put into it first to follow the lines of the floor pan. This was done by scoring a V halfway through the ply & bending the kink to suit the angle. Some CA glue was wicked along the score line. When the CA sets, the kink maintains a high degree of strength.

    Pod & wings.


    The bellypan on the original boat.


    The 1/8" ply pan with the kink & the pod base cut to suit.


    Epoxying the pod base to the ply.


    Sitting in place on the boat.

    Last edited by 785boats; 03-02-2018 at 11:47 PM.

  11. #41


    Build is coming along nicely, Sir.
    There's a hole at the center of earth where the rest of the world sinks but i stand still...

  12. #42


    Thanks for that.
    Setting up the framework & skins around the pod is next on the list.

  13. #43


    You sir, are a building animal. Wish I had the time and storage for more rigs. Always enjoyed reading your posts.

  14. #44


    You are too kind.
    But let me tell you this. I have nowhere to store this boat. It has to stay on the bench for now, & gently sit on top of other boats when I need the bench space.
    Time to sell off some boats methinks.

  15. #45


    On your fins, are you going to sheet the adjacent section or will that be part of the hatch? In other words, will your hatch span three bays or just one and you are going to sheet the rest?

  16. #46


    Hi Lambo.
    The two side sections will be sheeted. Only the center section will be the hatch. I'm working on the side sections as we speak actually.

  17. #47


    I have a day off work today. But of course the body clock still has me awake at the normal work time of 3:00am.
    Needless to say, it was down to the workshop with a a good strong cup of coffee in hand.

    The first step was to cut the top of the pod to suit the rear sponson bulkhead, & epoxy it on to the base.
    I needed to tack in a few braces first to make sure the pod kept its shape. The sides just wanted to bow inwards.

    The whole assembly was then tacked into place with some CA, & the framework & bottom sheeting was assembled each side of the pod.
    After that, the top decks were cut to fit.

    The pod & base plate was removed & all the spaces in the hull were filled with foam blocks & trimmed to shape. All except the forward section on the starboard side. I might cut the side out of the main stringer & place the ESC in there.

    A pine block was also glued in that section at the deck level for the Safety Loop connectors that will be added later on.

    A quick coat of resin on the underside of the decks & in the front sections of the hull, & the decks were glued on.

    After a bit of sanding & shaping, I refitted the pod assembly temporarily to check for fit. But this time I added a bit of 8mm dowel through the pod & into the sponsons. I'm still waiting for the carbon fiber rod to arrive, then I'll be able to epoxy everything in place permanently, & add the ram wings to finish it off.

    Braces in the pod so it kept its shape.


    Top glued on & the assembly in place for the framework & sheeting.


    Framework & bottom sheeting completed.


    Foam blocks & decks cut, shaped & pre-bent


    Decks fitted.


  18. #48


    More pics.
    Pod assembly refitted with temporary dowel in place.


    The top view.


    At the transom.


  19. #49


    That's a nice boat.

  20. #50


    That it is Beaux.
    I feel the main beauty of this version of the hull is that the side view is so low without that huge turbine snorkel up on top of the deck. Just the beautiful twin turbo Allison V12.
    It just looks tough.


  21. #51


    Another 'rostered day off' today, so I permenantly epoxied the whole pod & baseplate to the hull this morning.

    For the main spar supporting the front of the pod (and the ram wings), I was going to use some 6mm tube epoxied into an 8mm tube. But it seemed a bit too small once I had it in by hands.
    So I had some 5mm rod that I glued into the 6mm tube. And then I epoxied the whole thing into a piece of 10mm aluminium tube that had a 1mm wall thickness. Now it is a solid rod.

    Then I started on the hatch cover. A piece of 1/16" ply with the center cut out for the dummy motor. I will build a dropped floor in it for the motor to sit in.

    The rear part of the pod, that I had previously cut off, was then shaped & glued onto the hatch.
    To strengthen both pieces I glued a strip of 0.5mm ply around the inside of them.
    Then on the inside of the rear piece i glued on some locating pins made from some 3/16" sq wood.

    I had to sit the engine in place for a bit of a look. As you do.

    The pod epoxied into the hull.


    The ply strips & locating pegs on the inside of the cowl pieces.


    Hatch locked in place.


    Engine & hatch sitting in place.


  22. #52


    A successful morning , this morning.
    I epoxied on the spar pieces. I always thought they were called the 'Ram Wings'. But apparently not.
    The term 'Ram Wing'( so I just found out) refers to the whole body of the boat from the leading edges of the tub to the transom, between the sponsons & the air traps.
    Anyhow, the spar covers were not long enough so I had to add a bit of wood to make them fit.

    Then it was on to assembling the Canard wing.
    A couple of timber blocks were shaped to fit inside the ends of the wing for the mounting bolts to have something solid to attach to.
    Then a light piece of balsa was glued to the inside of one half of the wing, as were the wooden blocks. The balsa is for flotation should the wing get ripped off & broken.
    The other half was then epoxied on to finish it off.

    A couple of adjustable brackets were made up from some aluminium angle, & temporarily screwed to the wing. I will use nylon breakaway bolts in the final assembly.

    Then the holes were drilled into the sponsons for mounting, & the wing was temporarily attached, just to make sure everything is straight, square & level.

    I'm waiting on some threaded inserts to arrive to screw & glue into the sponsons to take the 4mm mounting bolts. A tip borrowed from Tom G on his Budweiser T-6 thread. Thanks Tom.

    The spar covers added.

    The wing assembled & the adjustable brackets completed.

    Temporarily fitted to the hull.

    Full up adjustment.

    Full down adjustment.

  23. #53


    This is one of my favorite unlimiteds. Love the piston power. I am actually building this boat in 1:10 scale right now and I'm about where you are in the build. I scratch built it from plans I drew and it's primarily wood over foam construction, without bulkheads and stringers. I've been building boats this way from the beginning and it's worked well for me. On this build I laid fiberglass decking down over the foam, but the whole center section is decked with 1/32" plywood, like the rest of the boat. My U3 will be the 2016-17 Griggs Presents Miss Ace Hardware. I'm very excited to get more work done on it. Super nice building job on your 1:8 scale project. It's looking great and I love your attention to scale detail. I hope I can do the boat justice too. Thanks for posting the thread. Happy Building Brother!!
    Mitch Dillard
    1:10 Scale Hydroplane Enthusiast,

  24. #54


    Thanks Mitch.
    Yes, a beautiful boat.
    A 1/10 scale is cool. I take it that you are building it for 1/10 scale racing to mix it up with the turbine looking hulls.

    Could you post a few pics here please, showing the foam construction. Sounds interesting.

    I too am setting it up in the Ace Hardware livery.
    Mike at Thunderboat Graphics is doing all the graphics for me. He would do them in 1/10. Or do you make your own, like all the other scale items you make?

    PS. I'm never happier than when I'm building a boat.

  25. #55


    I only took a few pics during the build, but I'll try and post some of them soon. There is a build sequence of photos I posted years ago of my Mr. Pringles boat that shows the foam construction much better. I'll see if I can find a link for you if you haven't seen it. Mike is also doing the graphics for my boat. They're on their way. He does really good work and happened to be finishing up the set when I contacted him about this build. I've got the hull and wings all fitted and hoping to get the motor, driveline and rudder servo set up when I get back on Sunday. Then I can tear it all down, do some final prep work and shoot primer on the boat. The turbo Allison will be built and fitted soon too. Building is a lot of fun for me too. It may be the most fun part of this hobby, but I enjoy the competition and kinship in our club too.
    Mitch Dillard
    1:10 Scale Hydroplane Enthusiast,

  26. #56


    Oh, I remembered that the Pringles build photo gallery was posted on Rum Runner's forum. You may have to go there to view it.
    Mitch Dillard
    1:10 Scale Hydroplane Enthusiast,

  27. #57


    Thanks for the info.
    I'll look into the gallery.

    Yes the mateship & racing at the club is a great part of the hobby too.
    I'm just packing up the wagon for another day of racing now actually. 5 classes with 3 races in each class.
    Our club also has an extra 'Shootout' race in a pre selected class at each meeting. Today's is the EB 6s mono class.
    Top 5 point scorers through the day in that class are entered. It's usually a cracker of a race. There's a couple of different rules for it.
    Instant disqualification for hitting or cutting a buoy.
    Contestants choose their lane before the race starts. Highest point scorer from the day has first choice, next highest has second choice etc.
    It all adds a bit more fun for the day.
    Must go, or I'll be late.

  28. #58


    Been back on night shift & overtime lately so not much energy for boat building.

    I've only managed to put the false floor in the cowling & cut the base of the dummy motor to the desired angle.
    I might have to cut a hole in the floor & allow the rear end of real motor to fit up inside the crank case of the dummy motor yet. But I'll fit the real motor first to see how much needs to be cut out. hopefully none, depending on the final angle required.

    Then a couple of timber pieces were shaped & fitted to the sides of the section of dropped deck at the transom. One for the side of the center tub, & one for under the fin.

    Nothing very exciting really but a few fiddly little jobs out of the way.

    The floor of the hatch.

    Motor base cut & sitting in position.

    timber filler at the center tub.

    Timber filler under the starboard fin.

  29. #59


    Hello. I got this similar kit from ML boatworks, and it came with 5 pieces of wood labeled "Jig". I have no idea how that goes together or what it is for. Any help would be great. Thanks.

  30. #60


    Sorry mate. I can't help you there. Mine didn't have a jig with it, & I've never seen one.
    Hopefully someone will sign on with an answer soon.

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