Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
The next step is to cut out the belly hatch. There ought to be no access problems in this aircraft - not only is there lots of access from above via the two quick-remove upper hatches, but this lower hatch is huge, as the photo below shows.
(BTW - I inadvertantly got the TV in the picture in the middle of the hatch. The large hatch makes my TV look pitifully small, so thanks to BVM I think I now need a larger TV in my garage. Wonder if my wife will see it that way too?)
The masking tape that you see on this photo shows the basic outline of the speed brake by the way, and we'll be cutting that out soon as well. The outline of all such hatches, gear doors etc is in fact moulded into the kit's surfaces. Once dust starts to fly from the saw or cut-off blade though, the outline would be hard to see - so the masking tape is simply added to the outside of the cut-line to aid visibility during the cutting process.
< Message edited by Gordon Mc -- Oct 12 2002 5:12PM >
Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
The two wing halves attach to the fuselage by sliding in from the side and then being retained by bolts internally. The forward carbon fiber spars each have 3 pre-drilled holes in them to attach them to bulkhead F-4, while the rear carbon fiber spars will be held in place by U-shaped brackets with a friction-based retention screw preventing the spar from moving in the mount.
Here you can see bulkhead F-4 sitting temporarily inside the fuselage. The bulkhead is made up of two formers : F4 and F4a. One is a sandwich of balsa and thin carbon fiber cloth; the other is a 1/8" thick carbon fibre part. These are glued together and then threaded aluminum inserts are installed for the wing bolts to screw into. Where the manual tells you to put the inserts into the front side of the assembly, that means the side that is the 1/8" carbon fiber part - F4a - (as shown on the detail plan).
Next, the wings are temporarily attached so that the fit of F4 can be assesed. In my case. I found that I had very minimal adjustment to make here - I only needed to shave 1/16" or so off of the very top part of F4 above where it fits around the curve of the wing fairing. I initially just pushed the wings in firmly to the point where I could get all 6 bolts into F4, and then found that the F4 fit to the fuselage was so tight that I could not get the 80-grt sandpaper in there to make the adjustments.
So - instead of putting all 6 bolts in, finding out that the F4 fit is too tight, removing the bolts again (etc., etc) I would recommend that you simply use one bolt (the inner one) on one wing at a time, to see how much your fuselage will pull in towards the former - then adjust the former repeatedly until you are happy, and only then should you start adding the other bolts.
< Message edited by Gordon Mc -- Oct 17 2002 6:49PM >
Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
Former F5 is used to retain the rear spars. It is a 1/8" carbon fiber part to which we will glue and then bolt a couple of long u-shaped brackets to retain the spars.
Like F4, this former will remain free (unglued to the fuselage) during the early work of mounting the wings, and only glued in place once we have everything perfectly aligned.
Initially I lined the wings up with the fairings on the fuselage as best I could, and tacked the brackets to former F5. I then removed the former and looked at where the brackets had been positioned, and was not 100% happy that both sides were absolutely symmetrical. Although there was not much in it, I wanted to ensure that the method of visually aligning the wing to the wing fairing wasn't going to introduce a slight anomaly that would annoy me for the (hopefully) years to come, so I used debonder to disolve the small tack-glue joints holding the brackets to F5 and opted to take a slightly more time consuming approach for the alignment.
In the following photograph you will see the start of this process. As shown on one of the fuselage plans, a couple of 1/2" balsa blocks are placed under the fuselage to wing-joint to raise the assembly slightly off of the belly. The wings are retained to (the still loose) F4, and the rear spars are not attached to anything yet.
A couple of incidence gauges were checked against each other to ensure that they both zeroed at the same point, and then I placed one on each wing (at the aileron position, which gives more accurate alignment. (If you do this, be sure to use the exact same position on each wing, since the wings do have a small amount of "wash" in them. Then I placed a balsa block under the TE of each wing, and slid them in towards the fus or out towards the tip in order to adjust each wing so that not only did they seem aligned with the fus fairing, but they also both had the exact same incidence.
Finally, a measurement is taken at the centre-line of each tip (that's what the plastic vernier is for, in the photo), and minor corrections will be made at each root rib, and/or at the former's base to ensure that the amount of dihedral in one wing exacty matches that in the other.
At this point I am probably being overly cautious with the alignment, but I'd rather just err on the side of caution here.
< Message edited by Gordon Mc -- Oct 15 2002 3:54PM >
Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
Once the alignment is correct, continue with F5. In this photo you can see the u-shaped brackets that are tack-glued to the front of F-5.
Where the 4 small holes are in the front of these brackets, we next drill through and then tap the carbon fiber former so that the brackets may be further held in place with 4-40 bolts. Don't forget to add the washers and nuts that get glued to the rear of the former to provide a larger threaded area for these bolts to hold onto.
The wing mounting is completed by applying some beads of thick CA to tack glue the formers to the fuselage, prior to removing the wing and using Aeropoxy to securely glue the formers in place.
Since the wing-fairing area of the fuselage previously was noted to move in & out slightly when the wings were added or removed, particular attention should be paid to tack-glue this area of the fuselage to F-4 and F-5 so that it can not move when the wings are removed this time.
Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
When you make the speedbrake cutout in the bottom of the fuselage, be carfeful about the location of the cut that you make for the rear of the cutout.
If you use the approach of putting masking tape around the scribed lines, and then cutting just inside the masking tape, then you will actually be cutting on the scribe line, not inside it. For the rear edge of the speedbrake, you might want to ensure that you cut just inside the line instead. This is because the scribed rear edge is exactly below where the front edge of F4a is - so if you cut on the scribed line like I did, you end up cutting away the Aeropoxy fillet - that's how close F4a is to the speedbrake.
This can be seen in the attached photo.
< Message edited by Gordon Mc -- Oct 15 2002 6:05PM >
Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
The speedbrake is actuated mechanically by a servo which is mounted on a removable ply platform just ahead of the speedbrake cutout.
As well as containing the servo, this assembly has the speedbrake hinges mounted to its sides, so that the whole servo and moving surface can easily be removed an inserted as a complete unit.
The photo below shows the speedbrake assembly before the door is attached. (The two long C/F pieces on the left will later be glued to the speedbrake door.)
The hinges for the speedbrake each consist of two carbon fiber plates with a washer between them, held together with a 2-56 button headscrew. Note that for each hinge, both plates are tapped 2-56.
What this means is that when the speedbrake is lowered or raised we are effectively tightening one hinge and loosening the other. To account for this, without the possibility of binding, I ended up backing one hinge-screw (the stbd one, I believe?) out 1/4 turn. (I toyed momentarily with the idea of making the outer arms have clearance holes instead of being tapped, but was concerned that if I made this modification then the threads in the screw would wear the C/F part. A quick phone call to Dana at BVM confirmed that a clearance hole would indeed be a bad idea as it would lead to slop over time.)
< Message edited by Gordon Mc -- Oct 15 2002 11:52PM >
Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
If you are building this kit, you might want to deviate from the order of steps in the instruction manual just a bit, when it comes to the speedbrake.
I assembled the entire unit (as shown in the previous post), then made the holes in the fuselage that the 4-40 machine screws go through to hold the asembly in place. I found that the alignment of the rear holes in the fuselage and the blind nuts in the assembly were a little off, width-wise. The rear screw-holes in the fuselage are inside a couple of "dimples" so that the screws do not sit proud of the surface. Opening the holes up a bit to allow for the slight misalignment causes the screw heads to not seat perfectly in those dimples, so I will be removing the blind nuts from the assembly in order to reposition them a little bit.
This is a trivial fix, but for the next Super Bandit I build (it's already waiting!), what I will do is leave the blind nuts out of the assembly until after I drill the holes in the fuselage - then put bolts through the fuselage to check alignment; adjust the holes in the plywood base as necessary, and then insert the blind nuts.
Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
The canopy is retained by 7 slide-in "hooks". These are fitted one at a time, both to ease assembly and to ensure that the initial good fit of the canopy is not compromised by the positioning of the hooks.
The procedure called out in the manual is to glue one hook in place on the canopy, then transfer the location to the fuselage, making a slot in the fibreglass for the hook to pass through... then adjust the slot sideways as necessary to ensure that the canopy sides and fuselage sides match perfectly. Any "slop" introduced by widening the slot is then removed by putting thick CA on one side of the hook (to make the hook wider).
I have used the above procedure previously, and it works just fine. I now use a slightly different approach though, just because I find it to be a bit neater.
Here's how I start off. Instead of firmly gluing the hook into the canopy, I only tack-glue it. Using my trusty plastic vernier, I measure the distance between the outer side of the hook and the outer side of the canopy. I then transfer this measurement to the fuselage in order to verify or adjust the pre-marked positions, as shown in the photo below.
Next, I trial fit the canopy, check whether any adjustments need to be made, and if so, I undo the tack-glue joint of the hook to the canopy, adjust the slot in the wooden canopy frame, re-tack the hook in place, and repeat until a perfect fit is achieved. In this way, I do not open up the slots in the fibreglass at all and don't need to widen the hooks with CA.
Like I mentioned though - my use of a different approach is just a personal preference - the procedure that BVM outlines works just fine, so you should not be put off from following it.
< Message edited by Gordon Mc -- Oct 26 2002 2:52AM >
Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
The manual indicates that "You can also sand the square edges off bottom and back edges of the hooks to ease canopy removal", and it mentions this after you have added plywood shims that serve not only to strengthen the fuselage areas where you have cut slots, but also to pull the canopy firmly downwards when you slide it into place.
I would recommend that you round the edges of the hooks before you add the ply shims, otherwise you may find yourself in the position I got into, where the canopy did not want to come off after I glued the shims in place. At first I thought I had screwed up and managed to get a drop of glue in the wrong place, but then I realised that couldn't be the case since the canopy would slide backwards about 1/32". I finally realised that what had happened was that for one of the hooks, the rear edge of slot in the fuselage was catching against the rear edge of the hook, not allowing sufficient movement for removal. This had not previously shown up because the thin fibreglass flange on the fuselage had simply flexed a little bit, allowing the hook to move. With the plywood stiffener/shim in place though, (a) the hook was drawn further down into the slot, and (b) this flexing could not happen. Once I identified the problem, the solution was simple - insert an X-acto knife in gap between the canopy and fuselage flange and apply enough pressure to allow the hook to pop out.
After I rounded the edged of the hooks this was not a problem, as the rounded hook edge could no longer catch on the slot edge. In other words, BVM's suggestion of rounding the parts is spot-on, but you might want to do it before adding the shims.
My camera is not very good with real close-ups, so I appologize for the quality of this picture. It attempts to show the initial square edge of the rear of the hook (left-side pic, look at closest hook), and then the rounding of the part to remove that edge (see right-side pic, look at furthest away hook).
< Message edited by Gordon Mc -- Oct 26 2002 2:53AM >
Posts: 6746
Joined: 1/30/2002 From: San Jose, CA, Status: offline
The bottom hatch is retained by having a poly-ply tongue on the front of the hatch, which slides up inside the fuselage, then four screws that go into plywood tabs which you attach to the fuselage.
You then apply poly-ply to the inside of the fuselage, at the rear edge of the hatch. This helps the hatch maintain its curved shape. I got a bit carried away and put poly ply on the sides too - which is not called for.
When it comes to gluing material like poly-ply I use a special version of CA that is designed for use with composites. In this case I'm using [URL=http://picglue.com]PIC[/URL] Plasti-Stic. There are other CA's for plastic (etc) too, but I particularly like the PIC version. It's a MIL spec glue, which does not seem to be advertised to the modelling community (mostly military / industrial use apparently), but I'm currently trying to get the manufacturer to send some of his product to RCU for review so that more of us modellers can hear about it.
< Message edited by Gordon Mc -- Nov 10 2002 1:06AM >
Printable Version
All Forums >> Radios, Batteries, Clubhouse and more >> User Product Reviews >> Hatches 
Hatches - 
Wonder if my wife will see it that way too?) 
