Wednesday, November 28, 2012

Gone to Abu-Dhabi

No KEP's T2-21 build-article this week as I'm in Abu-Dhabi this weekend for the second to last F1H2O World Championships race of 2012. :) The race itself is held on Thursday and Friday. Check the official site for live timing.

Link to my pics from 2 years ago when we where there. :)

Friday, November 23, 2012

T2-21 Build-Series #5

Time 2 do the switch mount, switch hole, antenna hole, bottom sheeting, nose block & transom carbon... :)

KEP's T2 .21 Presentation
KEP's T2 .21 Freebie
KEP's T2 .21 Build Series #1
KEP's T2 .21 Build Series #2
KEP's T2 .21 Build Series #3
KEP's T2 .21 "Inspirational" Article
KEP's T2 .21 Build Series #4

The receiver switch mount looks like this. Its made of scrap pieces of 6 mm gaboon plywood & 1.5 mm thick fiberglass sheet. The screws I have used are 4-40x1/4" aluminum or SS. Do the switch holes so they match your switch. The two brackets are glued with ZAP-a-gap CA glue.

Now it's time to drill the holes for the antenna tube holding-tube and receiver switch access hole in the tub-deck / tub-deck doubler.

Make sure that you have sanded the bottom of the complete tub-frame flat and smooth! Then its time to bring out the flat board again and the bar stock angles and clamps... You want to make sure that the sides are straight and square before you glue the frame to the bottom sheeting. Once it's glued to that you're stuck with what you get basically. So don't forget this step to get the tub straight and flat! :)

Cut out a preferably cross-grained 1.5 mm thick plywood sheet that is a little too big. Sand it slightly. Turn the tub-frame up-side-down and add ZAP-a-gap medium CA to the tub sides bottom from the rear and to approximately where the engine will be (= the flat part of the tub bottom) and the rear bulkheads, transom bottom edge and the bottom part of the servo mounts. Then turn it around again and align it in the center of the tub-bottom sheeting. Press down for about 1 minute.

Then you add ZAP-a-gap glue to the front part of the tub-sides and the front bulkheads (use more glue in the front part) and roll-press it down more and more to the front until the glue starts to set... Have the CA kicker nearby if you need it to get the glue to kick but don't use too much of it at this stage. If you have a friend close by that can assist it's even better! :) Let it sit for a few minutes and remove the aluminum angles.

Ps, it's a good advice to also use a fan to blow away the CA fumes while gluing!

Now apply a bead of CA glue on the inside and outside of all bottom sheet glue-joints. Let that soak in for at least 5-10 minutes. Then you can remove some of the excessive glue that hasn't set yet with house hold paper but be sure to be quick. Swipe one time only as the second time the paper will be glued to the joint... After that, spray a mist of CA kicker on all glue joints and leave it for a couple of minutes.

Use a small model-plane tool to remove most of the protruding bottom sheeting - finish it with the std 1 foot long bar-sander with 80 grit paper.

Here is some sanding tips: you know it's easy to sand too much and sand through the outer ply layer of any plywood sheeting right? Three major reasons for that to happen according to me. 1 - You don't pay attention and aren't looking to what you are actually doing... 2 - You use a bad sanding block that is not flat and too fine graded sanding paper (The worst sanding block you could ever use is the old cork-block that you just fold the sand paper over the edges! And if you use too fine of a sanding paper you need to sand more on each part and push harder = more of a chance that you sand to much or tilt the sanding block too much etc)... 3 - You sand too much, too far, too early... On a boat like this you have plenty of protruding plywood parts that need to be sanded down that "work" on the same "surface" so to speak. The trick is to sand just enough each time and when all the gluing is done do a final sanding where you can sand everything together. As an example - wait for the final sanding of the tub-sides until the deck, bottom, nose-block and carbon transom doubler is glued in place and sanded almost smooth. Then you can sand it smooth/flat. The "perfect sanding" is not done until the complete boat is done though and you start preparing for the epoxy sealing process. Get it? :)

In the earlier years we used the traditional hard-wood solid nose blocks on all riggers. But we have done them like this for the latest few years. Especially if you clear coat the tub the look is much nicer (I think). The nose block is glued together (with CA) std 8 mm birch plywood pieces but you can use some other plywood also like gaboon.

Make sure the nose piece of the tub is completely flat! Then use plenty of ZAP-a-gap CA and cover the nose of the tub completely with glue. Press down towards the nose-block until the glue sets. As you have used so much glue it will take a while for it to actually kick but don't use kicker yet. Wait until it has actually start setting and then use kicker as you want he glue to soak in good.

Use the band-saw to remove excessive nose-block material. The rest is sanded away... So make sure the bar-sander you use has a really fresh/new 80-grit sand paper glued to it as this takes some time to do.

When the rough first stage of sanding is done you need to make it smoother and more round... Take your time and do it in small steps (slowly) so to speak... Practice makes perfect... ;)

Time to add the carbon sheet to the outside of the transom also. Make the part a little to big and sand the surfaces slightly before gluing. It's also time to check that the transom actually is straight before gluing the carbon sheet... When you have fixed that use plenty of CA glue on the transom and press down on the carbon. As you use plenty of glue it can float around a bit before it kicks. When it has started to kick you can finish it off with a mist of CA kicker. CAREFULLY sand the protruding carbon edges down smooth with the plywood. Take it easy and go slow! Sand from the rear to the front only as the carbon could de-laminate if sanded the other way.

Done for now - Have a nice weekend! :)

Next: KEP's T2 .21 Build Series #6

Thursday, November 22, 2012

T2-21 Build-Series #4

Transom stiffener, rear cowl rests & servomounts etc. Interesting stuff... ;)


KEP's T2 .21 Presentation
KEP's T2 .21 Freebie
KEP's T2 .21 Build Series #1
KEP's T2 .21 Build Series #2
KEP's T2 .21 Build Series #3
KEP's T2 .21 "Inspirational" Article

Even if you have used a laminate made of two 3 mm (1/8") thick airplane birch plywood the transom still can be upgraded and made stiffer with some added flat sheets of carbon. I use 0.7 mm. ZAP-a-gap medium CA glued in place with plenty of glue. That will take a while to stick so use some gloves and press down until the plate doesn't move around any longer. Then use CA kicker.

The cowl rests are made of scrap pieces of 6 mm plywood. They are glued 1 mm below the tub deck with CA glue.

This is what I start out with when making the servo mounts for all three servos. Its 6 mm thick gaboon plywood scrap pieces where the top part is glued at the end so its easier to drill and tap the holes (instead of doing it in end grain). CA glued of course. Sand the top piece flush with the sides.

Steering servo mounts for Futaba S9551 or BLS551. Note the hole for the servo wires. See the PDF's for measurements. Note, they should be slightly too high as that will be trimmed down later. That means they will also be glued to the tub bottom of course.

This steering servo alignment/angle template was the one I used when doing the T2-21 prototypes. In the 2of2 PDF I have included some cut-out templates that you can use instead. See below.

Note, this picture is not to scale. Use the paper-copy of the PDF freebie you have already downloaded and printed out in 1:1 scale (2of2 file). The lower one in the illustration is used to get the angle right for the steering servo - see here below.

Steering servo attached with Futaba original rubbers & eyelets with Du-Bro #4 screws and aluminum #4 washers. The angle of the rails are sanded while attached to the servo. Just put it over the paper template to view if you have got the angle right... Align the complete servo set-up in the tub and tack booth mounts to the inside of the tub with ZAP-a-gap medium CA. Then carefully remove the servo and add more glue to the outside of all glue joints. Let set for 5 minutes and use a little kicker to get it to finally set (and build glue fillets).

The protruding servo mounts are cut-away roughly with the band-saw and then sanded flush with the Great planes bar-sander and you guessed it right - 80-grip sand paper. :)

It's the same process with the CH2 & CH3 servos. Note, here the mounts are just plain 6 mm plywood (gaboon). No added fancy stuff. :) See the PDF's for measurements.

This side-view template is also included in the 2of2 PDF (this picture is not to scale). Cut it out to help with the alignment for gluing the CH2 & CH3 servo mounts.

The CH2 & CH3 combo servo mounts are glued in place at 90 deg vs the tub side and then sanded smooth with the tub side bottoms.

Additional pics taken from building the prototypes (note the soft 4 mm gaboon tub sides etc). Nope, there is not a lot of room so stick with the specified servos. :)

First clear the threads with a M4 or 8-32 tap if you haven't already done that. Then make 1 or 1.5 mm thick pieces of scrap plywood to cover them up. The numberplate covers are glued with epoxy. Make sure no epoxy is dripping down into the threads...

All for now! :)

Next: KEP's T2 .21 Build-Series #5