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Webbit example build: IC Power Installation


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Naturally there will be many of you that have installed engines before and perhaps could teach me a thing or two - everyone has their favourite methods but if this is your first go at a kit build then this thread could be just what you are looking for.
 
Please feel free to make comments and other suggestions, they are all welcome - to misquote a well known phwase, there's more than one way to skin a waskely webbit
 
Let's have some fun!
 
Cheers, Ian

Edited By Ian Jones on 31/03/2011 23:32:17

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A little word about side & down thrust.

A friend of mine has already built a webbit & found it needed 3 degrees of side thrust and “1 or 2” of down thrust. There is nothing in the plan or instructions about this. So the question arose as whether or not to build some in. Perhaps it was just something peculiar to my friend’s model?

Well I spoke to the man, Steve Webb himself and as a result I concluded that I would not include any thrust direction changes for the following reasons:

  • The use of a 15 size engine is within the design limits for no side or down thrust on this model – indeed many of them have been built and flown this way.
  • For many this is a first time build, so deviating from the plan to build in side/down thrust into the firewall would introduce complications that a first timer embarking on a quick & straight forward build should not have to deal with.
  • The ‘square’ build of the firewall & tank table help to form the shape of the fuselage during the build and contributes a lot of the aircraft’s rigidity, best not messed with.
  • How much side & down thrust to add would be pretty much guess work and may still need changing afterwards.
  • I have built and flown models with up to 25 size engines with no side/down thrust and they were okay. I did alter one at a later date but it has never been unflyable.
  • So I am sure the model will fly okay without it, however if after testing it is felt that the characteristics can be improved by changing the side/down thrust then it could always be done afterwards by packing the mount. I will let you know if I find this necessary in due course !
So if later on in the installation you would have wondered when I was going to deal with side/down thrust, you will not have to wonder anymore.
 
In the next post we will have a look at the parts list, ah, some photos at last!
 
Ian. 

Edited By Ian Jones on 01/04/2011 01:03:15

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Yes Doug you are so right and your solution will certainly be a good one
 
As you will I see I stayed with a nylon engine mount but doubled up the thickness of the firewall so that the T nuts wouldn't go right the way through. Actaully the T nuts did just protrude through the firewall a smidgen but that was easy to fix.

Edited By Ian Jones on 01/04/2011 10:44:36

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If you are in a hurry to get started…
 
…then head over to Big Bandits Example Build: Fuselage,Tailplain blog. He has made a brilliant, well explained start on the build already. Come back here when you reach this part of his blog though:

01/04/2011 09:15:55
“Now I've sobered up an taken my medication for the day, and every thing has all night to dry properly, it's time to start with the formers.

Identify and mark out the formers on the plan, If your taking the ic route the ones provided in the kit are fine……”

Ian
 
It's all shaping up nicely
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Parts List

So to get down to business we need some parts:

The engine I have chosen is an AP15 (more about that later) but there will only be minor differences in the way it’s installed and I will cover those as we go along. Blind nuts & screws are to secure the engine mount to the fire wall and the M3 socket head bolts are to secure the engine to the mount aided by nylon lock nuts.
 
With the SLEC 4 ozs fuel tank I’m hoping to get 15 minutes flight time and I will be using a nylon snake to connect the engine throttle arm to it’s servo.
 

And here is the servo I will be using, a bit of an experiment this “New Power XL-16HM and on reflection the smaller “New Power XL-9HM” would have done the job. I will be using one these smaller servos later in the WebBIT build but the operation of that is Top Secret at the moment. Why am I using metal geared servos? Well just because I want to try them out, no other reason. Finally we won’t be going anywhere without a propeller, a master airscrew 8x4 in this case.

More about the AP15. I’ve been looking to try one of these out for some time and the WebBit provides the opportunity. Some feature of this little engine:

  • Rear exhaust which can be rotated to other positions to that shown, however I will be sticking to the default downward pointing exhaust. A short extension will take the exhaust gasses out below the fuselage.
  • Dual ball bearing crankshaft
  • No idle needle
  • Rearward inclined fuel mixture needle
  • RPM 3500 to 18000
  • Price around £39.99 – a standard Enya 15 is around £55.99, Enya SS15 around £69.99 and an Enya SS15 BB (ball bearings) £79.99. I’m not expecting the performance of an £80 engine in one half the price but I think I can expect a reasonably good performance for a relatively small price.

continued in next post...

Edited By

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...continued from previous post.
 
Right so gather up your bits and head over to Big Bandits Example Build: Fuselage,Tailplain blog. He has made a brilliant and well explained build of the fuselage already so you can make a start but stop when you get to his entry…

01/04/2011 09:15:55
“Now I've sobered up an taken my medication for the day, and every thing has all night to dry properly, it's time to start with the formers. Identify and mark out the formers on the plan, If your taking the ic route the ones provided in the kit are fine……”

... because at this point we set to work on the firewall & tank table part of the engine installation which will feature in my next post.

Have fun, Ian

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Posted by Doug Ireland on 01/04/2011 23:05:12:
Progress so far. I had a bit of a job uploading this photo then I saw how big the file was so had to resize it.
 

That's going to be a robust job Doug, if it falls apart I'll eat my thinsulate woolly hat.
 
Does strongbow cause more vibration than the usual glow fuel?
 
Cheers, Ian
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Ready To Start & preparing the firewall

 

Hopefully you have followed big bandit’s example fuselage build to the point where you have the fuselage sides joined up and the doublers attached to the inside of each fuselage half, looking something like this at the front end (nice to see you back ):

Protect the engine from dust etc by covering or plugging all holes. Check on the plan that it's all going to fit – in this case it isn't. The mount is too long so that will be shortened just a little. More of a problem is that he front former will not fit around the carburreter and would also make access to the engine and mount fittings difficult if any maintenance is required.
The strip of balsa in the above diagram show how leaving off the front former will give better access to the mount. To maintain some strength at the front we will add in some braces later.

 

Okay then, we are ready to prepare the firewall - identify the firewall by checking on plan. Mark the centre line from the plan onto the firewall.

The mark a vertical line down the middle of the firewall - resulting in "crosshairs" to guide positioning of the mount:
To save any frustration later it's not a bad idea to mark the mount to show which way up it goes. I did it later but actuall now is a good time to fit a back plate of 1/8" ply to the back of the firewall. This will be much stronger and also it will thicken the firewall so that the T nuts will not go right the way through. Actually they will protrude a little but we have a fix for that
 
On this Tornado mount it's easy to visually check it's correctly positioned as the crosshairs will go through the middle of the indents in the back of the mount on all four sides.
 
The threaded part of the T nuts are 5mm wide so mark the position of the screw holes with a point (a 4mm wood drill bit is good) through the firewall screwholes - be very accurate about this, it will save you trouble later taking your time at this stage. When you know these are right drill the 5mm holes in the fire wall:
The firewall also needs a hole for the fuel tubes to pass through - about 20mm wide. I had a 19mm wood bit that was the nearest this so I use that.
Continued...
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...continued
I've positioned tube hole in the firewall above the centre of the mount so that the pressure pipe connected to the top of the SLEC tank will not have so much bending to do. If you are using a tank with the tubes coming from the centre you will be probably still find that this will give you the best straight line for the tubes.
 
Next is drilling the hole for the throttle snake.  Mark a line on the firewall that lines up with the throttle arm hole when it is at the extreme range of it's travel. Check the size of the snake outer and using a matching drill bit, drill the hole on the line, halfway between the side of the mount and the edge of the firewall.
 
Fit the T nuts, this is much easier done now than when the firewall is already fixed in place.
There's a risk of damaging the firewall with the screw heads when doing this so:
use a large washer under the screw head to spread the pressure, alternatively use the mount.
 
I found that the thickened firewal still wasn't quite thick enough, so a quick & easy fix for that:
use a countersink (or a very large high speed dril bit) to make shallow countersinks in the back of the mount. This works a treat.
 
We're getting there
 
Now assemble the mount on the firewall, check that the mount is hard up against the firewall. It's looking good but the screws are to long so while it's still assembled cut theme to length:
See those sparks flying? Wear goggles and gloves if you kinow what's good for you . Smooth off the cut ends of the screws with the face of the cutting disk then remove the screws. Doing it this will mean that as you are removing the screws any burrs that are left will be straightened out and so it will not difficult to re-insert the screws.
 
Nearly there for this session


Place the firewall in position on each of the fuselage sides in turn and check for fitting, you will probably have to take 1/8" of the front longerons due to the extra thickness of the fire wall caused by the back plate. (sorry I didn't tell you earlier but I'm building and blogging and this is the order things came out in).
 
 

Next post we will fix the firewall & tank table in place 

Edited By Biggles' Elder Brother - Moderator on 03/04/2011 23:27:29

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Fitting the firewall & tank table

This is going to involve the use of some epoxy and if you are using those largish hard to squeeze plastic bottles then you might like to turn them upside down now.
The air will go to the up to base of the bottles and life will be much easier when it comes to mixing time. Having done this I also find that I can hold one bottle in each hand and squeeze even amounts out side by side, rather like those twin syringe type of dispensers. This is much easier to judge than squeezing out one part first which then settles and spreads while you are squeezing out the second part.
 
So anyway, we’ve prepared the firewall and made sure it’s a good fit. Now we need to make sure that it stays in place while the epoxy is setting. I do it like this:
The set square has the corner of a plastic bag fastened to it, this means the square can be butted up to the fire wall without getting stuck to it. Some people use vaseline to do the same job but I don’t like the thought that I could get vaseline somewhere I don’t want it, for example I don’t think the fuel proofer will penetrate any vaseline on the engine bay walls. In test fitting I found that if the elastic band was pulled too low down on the firewall that it would tend to slide the firewall up the blade of the set square, so make sure the band is parallel to the fuselage side and it will be fine. In fact it was excellent, I got a really good result.

Every thing staying in place okay? Right then that makes the next step easy so here we go. Apply a line of epoxy where the firewall will meet the fuselage side. Put the firewall in place and then set up the set square as previously tested.

Go and have a cuppa or even a beer until the epoxy sets

Now we move on to the tank table. Place the tank and battery in their positions and place the tank table between them to find the best fit.

It’s more than likely that where the tank table meets the firewall it will be up against the back of the lower blind nuts. That’s good ol’ Murphy for you . Since we have already shortened the screws that go through the blind nuts then the amount that needs to be trimmed out of the tank table will be quite small. I used a new blade in a modellers knife to do this job. Incidentally if you are short in the modelling knife department then keep your eyes open at the like of Lidl, this handy set was about a fiver:
 
Not quite the quality of the kit I got with my RCM&E subscription a few years ago but all the same quite useful.
 
Continued... 

Edited By Ian Jones on 04/04/2011 00:30:19

Edited By Ian Jones on 04/04/2011 00:40:16

Edited By Ian Jones on 04/04/2011 00:41:35

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...continued
Back to the plot – when you have trimmed out enough room for the tank table to be butted up against the firewall you will need to make sure it stays there. I found that by placing the set square on the fuselage doubler it would be clear of the epoxy and the tank table stayed in place just fine. So next, still holding the tank table in place mark a line on each side of it to mark it’s position. Next run a line of epoxy between the two position lines you have just made, put the tank table back in place and make sure it’s straight with the set square.
When you are happy have another brew. ()
 
The thing to do next is to finish the fuselage by following the rest of Big Bandit’s example fuselage build but before covering there’s a few other things you need to attend to:
  • Add two 1/8” ply braces across the bottom of the engine bay and fit a balsa lip to the front of the engine bay floor (if like me you are leaving off the front former)
  • Check that the engine will fit without the exhaust interfering with the sides of the fuselage trim, as necessary. (My trimming in this respect is to make a hole in the engine bay floor for the exhaust extension to exit through – could look good on rich engine )
  • Add some triangular section fillets to the inside corners of the engine bay – be generous with the epoxy so that you don’t leave any little gaps for oil etc to get into. Speaking of gaps - don't cover up the hole for the throttle snake.
  • Fuel proof the engine bay with the mounting screws fitted to prevent the threads getting clogged up with fuel proofer. I like to do the entire inside of the fuselage too, just in case of a serious fuel spillage.
 

When you have finished the entire airframe come back here and we’ll go through the final assembly.

Don’t rush into fitting the servos just yet either. What we will do is fit the engine then get as close as we can to estimating the effect of moving the servos backwards & forwards to get the correct CG and that will determine where the servos go. We should then get away with using little or no ballast.

See you in while, Ian (hic)

(Big thank you to BEB for sorting out my typos in the previous posts)


Edited By Ian Jones on 04/04/2011 01:00:01

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Brilliant stuff Ian,
 
What do you use for fuel proofer, in the past I've used polyester resin (fibre glass resin), but I've always been careful not to add too much weight, and I'm not sure if it's the best option.
My next Webbitt's been ordered and I'm using a new SC15 in that.
 
Cheers,
 
Chris.
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Thanks Chris,
 
I think the SC15 should be spot on, in fact I can't really remember why I didn't go for one of those .
 
Heck, I haven't finished me first one yet.
 
Brace your pockets, I'm using Spectra spray fuel proofer. 1st coat is on and I'll do another in a few days. It needs to cook for a week or two I find, apart that it's fine. As it's a spray it doesn't (well shouldn't) put a thick layer on the wood, more soak into it, so it's fairly light. Expensive stuff (£7.00+) but I'm on my third 'plane with this can so it hasn't worked out too bad.
 
Ooh, I've also used it sprayed along the leading edge of wings and very lightly sanded to make 'em a bit more ding proof.
 
Cheers, Ian

 

Edited By Ian Jones on 04/04/2011 21:34:41

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Ian,
 
The second Webbitt arrived today and I've had the original plans copied and reduced to 75% and 50% for a Cox 049 Black Widow and a Cox 020 Pee Wee respectively, so I'll start the nano Webbitt at the weekend all being well with the wing build being finished first.
 
Cheers,
 
Chris.
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Posted by Big Bandit on 05/04/2011 20:27:11:
Ian,
 
The second Webbitt arrived today and I've had the original plans copied and reduced to 75% and 50% for a Cox 049 Black Widow and a Cox 020 Pee Wee respectively, so I'll start the nano Webbitt at the weekend all being well with the wing build being finished first.
 
Cheers,
 
Chris.
Wow Chris, they're breeding like webBITs
 
Ian

Edited By Ian Jones on 06/04/2011 00:10:42

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  • 2 weeks later...
Hi Ian
 
I'd be interested in knowing how much your Webbit weighs when it's finished.
 
Mine weighs 3.5 lbs with a 25 four-stroke up front and a tricycle undercarriage.
 
I might but an AP15 like yours as my smallest engine is a ball-raced Irvine 20. How much do they cost and where did you get yours from?
 
Regards
 
David
Webbiteer No 15
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It's been a bit quiet on this thread since I sent you all off to finish building then come back for the final installation.
 
The main reason is that I haven't finished my Webbit so I can't photograph and post on this last stage but how did I let this situation arise?
 
Well I feel I can now explain. After some years of threatening to do it I finally fixed a date for my BMFA B Test, which was today. I've spent the last week or so puttijng in lots of hours swotting and practising which left me short of time for other pleasures.
 
I'm pleased (and proud) to have succeeded so now I can resume the build and therefore resume this thread, so expect more pretty soon.
 
Regards, |an
 
Webbiteer number not known
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Posted by David Davis Telemaster Sales UK on 19/04/2011 19:43:27:
Hi Ian
 
I'd be interested in knowing how much your Webbit weighs when it's finished.
 
Mine weighs 3.5 lbs with a 25 four-stroke up front and a tricycle undercarriage.
 
I might but an AP15 like yours as my smallest engine is a ball-raced Irvine 20. How much do they cost and where did you get yours from?
 
Regards
 
David
Webbiteer No 15
Hi David, sorry to keep you waiting for a reply.
 
I'll weigh my Webbit when it's finished and post it here so that you will be able to pick up on it.
 
The AP15 cost me £39.99 from Barnstormers model shop which is my LMS www.barnstormersmodels.co.uk
 
Regards, Ian
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Posted by Chris Bott on 21/04/2011 22:41:07:
Fantastic Ian very well done.
 
I found I worried about my B test far more than I needed to have done. Lots of practice is definitely the way to do it. What a great feeling to pass though. I felt I could fly much better once someone had told me I could
Thanks Chris. You are absolutely right and I agree with your sentiments, it's a great confidence booster.
 
Ian
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