Tuesday, November 20, 2012

T2-21 Build-Series "Inspiration"

This is not a T2-21 build-it article - it's an "inspirational" article on some items to highlight before actually doing them... :) Stay tuned for the next couple of T2-21 build-series articles!

In the PDF's I've drawn a simple pipe-mount system (for muffled pipes) based on making your own brass clamp system from a 1/4" K&S strip, a fiberglass plate, a couple of rubber grommets and some screws and nuts etc. This is how it starts out...

...And this is how it ends up. :) Ps, if you look closely at the picture you can see that you can't actually use all three holes when using the VictoSport Needle base (note the plugged hole at the bottom). The lower one is covered by the lower banjo nipple...

Another view of the pipe-mount and the VictoSport needle-base.

Note, the two 4x4 mm neodymium cowl hold-down magnets in the cowl rests.

If you're thinking about using bigger servos for throttle and the remote fuel-needle. Think again. The T2-21 is designed around the Futaba S3150/S3172SV servos and it's not a lot of room. Note, the tub in the picture is one of the prototypes where you can see the stepped-deck we used on those (but not used on the T2 freebie)...

Not that I plan to offer the epoxy T2 cowl in the picture but note the 2x4 mm neodymium magnets that hold the cowl down in the rear. Also note that this cowl has a concave part where the pipe is (the mold is split in two halves).

This in my homemade back-pack-hopper type of tank for the T2-21. The drawings are included in the PDF's. A good way to do it if you like to build the tank yourself. Otherwise order one with an internal hopper from Walter Barney for $50.

Three new turn-fins for test in the spring. At least 5-6 months away... A std T2 fin (as in the PDF's), a one hole shorter then std T2 and one with an more sloped leading edge. I will tell you how they perform next spring! ;)

The new BBH symmetrical 21-45 engine mount rails = same left and right.

I guess most people are looking forward (or maybe dreading...) to do the eliptical-shaped T2 front sponsons... Here is a short description on how to do them. Note, this is NOT the complete description!

First you make sure that the Divinycell H60 block is flat and has square edges. Mark the center-line and draw one side of  the sponson outline viewed from top.

Then use a band-saw that you are familiar with, and has a good blade in it. Also check that the blade is straight and level. Saw a test block of something (same height as the H60 block) and check that the saw is making straight/90 deg cuts.

Carefully (slowly) saw more or less in the middle of the drawn pencil line. You should just barely see any pen-stroke on the foam core.

Sand that sawn vertical surface with a flat bar sander and 80-grip sandpaper. If you have been good in the band-saw then you should not need to sand that much.

Ready for glue. The 1 mm birch aircraft plywood is the same size as the foam block. Sand the plywood lightly. Use CA kicker on the plywood and lay that piece with the kicked side up on the female H60 part that is left-over from the original H60 block. Use plenty of ZAP-a-gap medium CA and apply that on the sponson core (that's the part to the left). Then align the sponson core as exact as you can above the plywood and the lower glue-support and press down. Hard.

Note, there is absolutely no time available to adjust the alignment if you notice that the parts aren't aligned. There is no looking back as soon as the plywood and ZAP'ed has met. Hold an press hard for 30 seconds.

Use a protection gloves and a BIG fan to blow away fumes! If you forget the fan - your breath will go away and your eyes will wet so you cant see... Trust me - use a good fan set on "high".

One side done. Here you can see that there was some CA glue protruding outside of the glue-joint so its good to do this on a covered surface (like, plastic food wrap).

Now you use your top-view template again and mark out the other side of the sponson and repeat the process on the other vertical side...

Kind of looks like a short wing section...

When you have your T2 sponson core's sheeted on booth vertical sides then you use your sponson side profile template and mark out the side view outline and tube-holes etc... To be continued in the T2-21 build-series after the tub is done.

Yes, we have used normal electrical tape to hold the sponson tubes but I will try an additional locking idea that I've thought about for a while in 2013. A 2.0 mm hole is drilled in each aluminum tube (right through) and the hole is aligned vertical when glued in the tub & sponsons. When the T2 is ready and your assembling it after paint etc you start sliding in the tubes to where you want them and drill one 2.0 hole through one side of the carbon tube at at time. Then you press in a 2 mm rod into that hole and turn the boat upside-down and drill the other hole from the other side. Press in a 2x12mm solid carbon rod all the way through the aluminum and carbon tube and lock the joint/pin with electrical tape. Test's done with this system (just in the workshop - not tested by me on any boat yet) creates very rigid connections and super-smooth as you don't need much tape... :)

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