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Tony Nijhuis 63" Spit

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Tim Mackey14/04/2008 21:09:00
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15 articles
Often they are wrapped in foam all around, and then wedged tightly into place, sometimes I held them there with a small strip of padded ply or similar across the back as it were....
Shaun K15/04/2008 13:24:00
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192 forum posts
38 photos

Hi Keith, 

I've used pieces of 1/4" x 1/2" balsa cut to a nice tight fit across the width of the fuselage with success.

Hold the tank in place, put a drop or 2 of medium cyno on each end of the piece of balsa and quickly put it in place, using it to put force onto the back of the tank, pushing it forward into the back of the firewall. Hold it long enough for the glue to take hold and the tank is stuck in place.  If you need to, a cradle can be made by putting one in for a bottom support, one for the top and the final one to hold the tank forward into the firewall.

It's also easy to remove if you need to - a pair of long-nose pliers makes short work of the 1/4 x 1/2 balsa and a new one is quickly and easily made when you need it. I'm sure there are neater ways but it works.

Martin McIntosh15/04/2008 21:11:00
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I just use foam plastic under the tank to keep the front slightly raised with the tank usually protruding rearwards through the former at the wing L.E. Tight tanks make your fuel foam.
Eric Bray15/04/2008 21:25:00
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I used to do similar to Shaun, but I cut a scrap piece of 1mm ply as a dummy former behind the tank, and epoxied two scraps of 1/4 sq vertically down the inside of the fuz so that when the ply was slipped down in between them and the tank, all was held firm, but easily removed for maintenance. (Epoxy because cyano hadn't been invented!)
KEITH MARSON16/04/2008 19:10:00
28 forum posts

Hi, just for info and those considering it ,just engines have said tha an11x7 three bladed prop should be the size for there .61 4stroke engine.

thanks to everyone for your help.

Shaun K05/05/2008 14:05:00
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192 forum posts
38 photos

Hi folks, a major point of Tony's design in this plan was regarding the angle of the main undercariage and the goal being good ground handling.

 Along that same line I'm keen to hear whether those that have finished and flown fitted a steerable or castoring tailwheel.

Which way did you go and how well is it working for you? If you fitted a steerable tailwheel is it all fancy and scale-looking too or did you go with the off-the-shelf tailwheel fittings?

On a general note, I've only ever used a steerable tailwheel and it's pretty sensitive when you're close to take-off speed. Are castoring tailwheels more forgiving or more tricky in general?

 Thanks,
Shaun K.

Eric Bray05/05/2008 16:47:00
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With a castoring tail-wheel, moderate speed taxiing is ok on a flat surface, but dead slow is tricky, as the a/c will keep trying to weathercock into any breeze, you have to 'fly' it along the ground, giving squirts of throttle to get a turn going, just like a full-size one!

On knobbly grass, I wouldn't bother trying to taxi! 

Martin McIntosh05/05/2008 21:12:00
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Shaun, I fly from grass and always try to use a steerable tailwheel. I cheated on the Spit and used a Dubro bracket, which are the easiest to install, with the top of the wire bent to face rearwards and formed to a hook at the end to which is attached a 3mm dia. x60mm spring screwed into the underside of the rudder and cyano`d at each end to prevent metal to metal noise. This gives perfect control on the ground, protects the rudder servo and is hardly noticeable. It is not in the least sensitive at takeoff but very effective at low speed because you can vary the length of the spring to give greater/ lesser wheel throw.
Shaun K05/05/2008 23:40:00
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192 forum posts
38 photos

Thanks guys - steerable it is then... If you described our strip as knobbly grass you'd be looking at it with rose coloured glasses.     Perhaps "well-mown paddock" is too harsh but it's somewhere in between would fit.

Martin -  I've just had a look at your pics and I can now see clearly what you have done. Great idea. Where do you find a 3mm x 60mm spring these days? They don't exactly jump off the shelves at you in the local hardware stores. I'll have a look in the biggest of our 2 local hobby shops but I don't ever recall seeing any springs in there.

Thanks again,
Shaun K.

Eric Bray05/05/2008 23:51:00
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6600 forum posts
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There was someone selling a box of assorted small springs on e-bay, but of course I can't find the item now! Other sources, retracting ball-point pen, old tranny stick centreing spring, elastic band, diy coil of piano-wire.
Shaun K06/05/2008 08:57:00
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192 forum posts
38 photos

The good news is that the local hobby shop just happened to have in their big bag of springs a 3mm x 60mm tension spring with perfect little loops on each end for attaching to a hook or small screw.

Lovely. Couldn't have asked for more...

For the record it's stock # 101 from Century Springs in Los Angeles USA. It's such a close match to what the esteemed Mr McIntosh describes it's quite possibly the same part.

Martin McIntosh06/05/2008 12:40:00
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3579 forum posts
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Mine came in a big assorted bag from a tool merchant at a trade show.
Walts06/05/2008 13:36:00
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193 forum posts
86 photos

Shaun,

   This may be of interest to you for future builds/stock.................LOOK HERE

   

Eric Bray06/05/2008 15:11:00
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6600 forum posts
2 photos
That was it!
Shaun K26/05/2008 04:05:00
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192 forum posts
38 photos

Hi folks, I'm after advice on drilling the required hole for the wing mounting dowl on the centre of the leading edge.  I have no doubt that a drill bit will wander off all sorts of directions because you're attempting to drill a hole in a thin section of relatively hard epoxy with soft balsa & liteply either side.

Any tips for a jig or guide of sorts that might stop the drill bit wandering, without damaging the wing with screws or clamps etc?

Or do you fit two LE dowels to your wings?

Regards,
Shaun K.

Eric Bray26/05/2008 12:08:00
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6600 forum posts
2 photos

Centre-pop it, then run a 2mm drill in first, and gradually enlarge it to suit the dowel.

Of - file a little flat, THEN centre-pop it, etc. 

Shaun K26/05/2008 14:24:00
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192 forum posts
38 photos

Thanks Eric, but whether it's justified or not I'd still be concerned about even a small drill running off the hard epoxy into the soft balsa. The seam of epoxy is definitely not 2mm wide it's a nice neat fitting joint.

I have 1 and 1.5mm drill bits. I'm pretty confident that starting with a tiny drill and woking up in small increments would do the job if I combine it with your file it and mark it approach.

Thanks again.

Eric Bray26/05/2008 15:40:00
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6600 forum posts
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So put the dowel in slightly off-centre, and drill a matching hole in the former! It isn't critical. Next time, put the dowel in BEFORE joining the two halves, if you are that fussy! Then the glass bandage will brace it, as well as the epoxy bond!
Shaun K19/06/2008 04:49:00
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192 forum posts
38 photos

Hi folks, me again with more pesky questions... 

What is the typical weight of glass cloth used for things such as wing centre joint bandages? Having handmade a sailboard many years ago I've got a big collection of scrap glass cloth, but it's a hefty 6oz - just right for standing on what you've built.

Sure I could use it and it would be strong enough to surf on the wing, but it might add an unnecessary weight burden if that's considered above the norm.

Tony's notes don't suggest a cloth weight so I'm curious to hear what's considered normal.

Eric Bray19/06/2008 10:30:00
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6600 forum posts
2 photos

Shaun, I don't know about glass weights, but I used to get my woven bandage from Leigh Dinghies, (alas no more). It was quite light stuff. Chopped strand tends to absorb a lot more resin, and it is the resin that weighs, more than the actual glasscloth. I should think that 6oz cloth is too heavy, really, and would go for something lighter, but it depends on how much area you intend to glass, and how much resin you squeegee out of it!

If memory serves, the quoted weight isn't for just the cloth, but the finished glass/resin combination, over the quoted area. Then, having made a surf-board, you probably already know that! 

Did you learn how to stand up on the board - on water? 

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