[Cougar429]

Here is the latest update with good and bad news. The bad news is with my ongoing problem with Slimline. During our last conversation Tuesday I was told this would be taken care of and an Email would be sent to cover details. I did get one that evening stating again to expect one the next morning, but nothing yet and they simply will NOT answer the phone.

Anyway, I had much better luck with the supplier of the RCLANDER retracts and they addressed a problem of slop with the gear extended. The mod they came up with was very easy, (if you have the materials) and took less time to accomplish that expected. The only negative was the requirement to remove part of my carefully cut well blockoffs and I am going to leave them out till I worry about the gear doors. I sent them the pics with the recommendation the factory incorporate this during assembly as it compensates for manufacturing variances very well.

All it required was the installation of heat shrink tubing over the stop block rod. It does not have as much of an effect retracted. While apart I took the opportunity to Loctite all the screws and using one of my heli tricks I lubed the geartrain with beeswax.

Ignore the masking tape. It was there to protect the motor and sleeve while cutting the plastic well material.

[mcmartin]

wow great post

thanks for sharing,

[Cougar429]

The muffler adapter(s) arrived after 4 months of calls and Emails, (for all my troubles they threw in a new side mount muffler for my other 125). Set the F-15 aside and have the Bear back on the build table.

The only problem is the muffler does not sit rigid and there is no bracket to fix it in position. Due to this I will have to figure out some way to hold it solid. Any movement would obviously wonk how it will fit the cowl, but it can also move against the mount, possibly melting the plastic.

While I had it apart I decided to address another concern I mentioned earlier. The stock design has the fuel tank residing against the firewall at the bottom of the fuse. Originally I had the A123 pack stuffed above it. This meant a lift of at least 2" from the top of the tank to the centerline of the carb. One option was installation of a Perry VP-20 pump, but a much simpler and more elegant solution was to swap the two and move the tank more in line with the carb.

Simple, right! Stuffing the battery down in the tank location required nothing more than adding more padding, never a bad idea. Unfortunately all my carefully fabbed retaining systems, including the one holding the throttle servo and regulator, were removed. That meant I now had to relocate the servo, meaning I now had to rip out and install a new cable run, meaning the throttle servo lead is now close to being too short............and so on.

At this point I am building a new retainer, one that will slide beneath the nose battery tray and also have a rear bulkhead to keep the tank from sliding aft. The nicely rigged switch tray needs to be cleared and at this point it is simply fitting everything in place. I figure how to hold it there will come last.

On that note I looked at moving back up to the stock 16oz tank capacity, but think this would be pushing too close to the switch panel. I opted to retain the 12oz for now. On the Saito 91 powered Skybolt landing after 9 minutes of honking still leaves me with half a tank. At this point I have no idea of the fuel burn on the larger motor and rarely do my flights run longer than 10 minutes each, so the first few flight tests will be conservative to check both fuel useage and pack charge state.

I will post some pics soon of the new mounting, along with the promised set of the inside of the cowl and fuel system with the filter installation.

Only bugger with the new camera is having to crop the pics so much to upload them here.

[Cougar429]

Some problems have a way of working themselves out. Last evening when I shut down I did not have a clue how to hold the tank retainer in place. Figured it out this afternoon. In the first pic you can see the retainer. Looking up front you can see just the tips of two C/F rods embedded in the cover poking into the lower battery tray lip. Those help hold it in place, but were more useful in locating it until I fabbed up a retaining system for the more important back end. You can also see the sill plate running between the two side bulkheads that the foam forces the plate against. Simply push down and slide aft to remove.

Due to concerns of heat buildup in what I suspect will be a location of stagnant air I have not decided if the regulator will be remounted to the top of the retainer. I could add a duct from the firewall, but worry about engine heat and other contaminants making the problem worse. In pic 2 you see another possibility. Mounting to the side of the frame, (it is just sitting in place now) I could run the duct from the aft face of the wheel well. Again, this may cause problems since if the plane works out the way I hope fabbing up some F/G inner gear doors may be a future install. In either case the air would exit through the tailwheel cover.

As promised I included pics of the firewall forward detail. Pics 3 and 4 show the unexpected fun I had routing the filter. The three lines from the tank are plastic, similar to what is used for aquarium air systems. I've used this in a lot of builds due to the fact it is lighter than copper and with careful application of heat can be easily routed where required. Even with this there remains enough flexibility to allow for removal and reinstallation of the tank without having to fight with bent alloy tubes. Internally the three lines work the same. One is the fuel pickup, with the standard clunk. The vent is curved to the immediate top front of the tank and the fill/defuel line follows the front of the tank contour to the lower left, then aft to the very left rear. It should not interfere with the clunk line in any way and still allow me to empty the tank without resting the plane on its nose, (what I have to do with the Skybolt as that line stops at the front left corner).

Pic 5 shows the cutout milled into the mount to clear the Slimline. I kept the mica insulator tube from a defunct heat gun and could bond that to the mount for insulation. The first few runs of the motor will hopefully indicate one way or the other if that will be necessary.

Pic 6 is a view of the top of the nose battery compartment. This is where the small receiver only battery resides. Not a lot of room in there and the padding had a tendency to deform the cover, breaking the seal. I added the reinforcement webbing to counter this.

The last pic shows the inside of the cowl. You can see the wood backing plate for the radial and the cutout and air dams used to direct air to the cylinder. The fitting for the fill line is opposite.

At this point the regulator and throttle servo mounting are hopefully the last of the construction jobs needed inside the fuse. After that the retract and aileron leads need to be fabbed and then the cabling neatened and protected. Then for the final stretch it's just waiting for the right weather to take it outside and fire it up for the first time. This will be done with the cowl off to allow for the inevitable carb adjustment and system checks.

Oh, one other thing. One of the substandard issues with this plane is the weak gear mounting. If I REALLY want to ensure it will hold together I may cut into the wing and fabricate a new setup. I can embed the gear further down so the gear doors would not be bowed out. Oh to finally get the list of tweaks completed.

[Cougar429]

I think other than detailing and system organization the fuselage is complete. As noted the gear mounts were notoriously substandard and with the arrival of a set of EFlite 60-120 mains I had reason to tackle this mess. One of the difficult decisions was to remove my carefully fit wheel wells, something that would cause some damage to the wing skin and covering to accomplish. Oh well.

Started with the right wing and soon had most of the hack and slash worked out. I left the remains of several nose ribs to give me some indication of position and dimensions. First was to carve out test ribs from high grade 1/8" balsa sheet. It took a few first attempts to get the contour correct with the smaller outboard ribs following along quickly. This slow first step was the same when fitting the L/G mount pad as the retract and leg had to be fit to the mount and then dropped approximately in place to get some measurements.

Then it was back to the test ribs, repeatedly measuring and cutting to get the pad to sit where intended. Again, it was the first rib that took the longest. The end result has the axle sitting right on the seam between wing and fuselage and to get it recessed enough for comfort some trimming of the original mechanical gear wire guide was required.

Transferring the balsa patterns to the ply was quick and easy with the table saw doing short work of all 8 ribs, (yes, this should be STRONG!). The first test and glue worked well and the assembly comes out of the wing complete for final bonding. There is some work to get all the ribs sanded in perfect line, but all told it came to this stage pretty well.

Time to attack the second wing. Knowing where to cut saved a bit of time and this loose assembly was sitting in place within 20 minutes. At this point I need to do some more fitting to try and get both gears as close to identical as possible. Once the mounts are bonded in place it will be time to work on a skin and gear door setup. Doubtful any of the stock gear pocket will be reinstalled due to interference with the gear offset.

A few points of note: The original wood was held in better than expected from my prior bracing, but the wood itself practically fell apart. Whatever they use for ply was seriously deficient. The second note was that the EFlite retracts are very nice bits of kit. One of the nice differences is that the mount holes are further out from center, meaning I have no interference problems with the blind nuts. In that regard I borrowed the 87 degree countersink bore and worked on both sets till the screws fit flush. Not really necessary if I had button head 6-32 cap screws.

In the set of pics you can see the sequence up to now. In the last shot you can see the assembly fit to the R/H wing. It may look off, but the leg is within a few thou of straight to the spar. Some have found it necessary to angle the gear forward to reduce the tendency to nose over. I'm hoping the fact I am using Robart gear instead of the original spring gear that would bend aft under load work the same.

[chuebner]

Very nice work on the retract mount, Coug....me likes.......I will send you mine to do in the future

[Cougar429]

Latest progress pics shows little of the attention paid to the framework to get the skin and doublers set at the correct height all the way along. As usual all the hard work gets hidden.

In the last update the gear mounts were simply held in place with clamps. Both are bonded in permanently now and the extra sub ribs to support the skin between the main ribs were installed. Next it was to pattern the skin outline, cutouts for the doors and the door bulkheads and I ran into a bit of a Homer there. I used the originals to pattern these and missed the fact they would catch the scissors on the gear legs. Of course, as you can see in pic #4 that was found after the skins were bonded down......DOH!

For a bit of fun the leading edge and inboard skin make a bidirectional kick to encircle the inlet and this took a bit of time to make the skin outline follow with good accuracy. Even after wetting the wood a gell cell batt had to weigh each skin down till fully bonded.

A new pattern with a bit more room was called for and I tried to remain true to the original outline as much as possible, but nitpickers may find fault with them once installed.

This afternoon I finished final sanding one wing and decided might as well work on the covering. Luckily the prior note they used UltraCote seems accurate, as the new covering blends in well, (at least indoors).

Don't know if the second wing will be on the table right away. March break is here and the family is heading to visit. Everything sharp, sticky or even mildly dangerous is hidden away. And at this point I have not decided if anything will be done to contour the inner wells.

[Cougar429]

Down to the wire now. Early this week I decided to dress up the wheel wells and was looking for something to sheet in the openings. Light balsa was too brittle, even when wet so I opted for thin cardboard sheet, (or very thick paper depending on your definition) like those separating gangs of forms at work. Once the pattern was cut I transferred that to the paper and glued them in. Thinned some epoxy and brushed that in, letting it soak in before curing. Worked out well until I wet sanded it and found the penetration was less than hoped for. Ripped it back out and went searching again. Still had some white plastic sheeting used originally to protect the bottom of the Polaris and tried that instead. Seemed to work fine so completed the other 3 sections the same way. Saved having to sand and paint, so even though it took two attempts in the end it worked out better.

I fabbed new extensions and fished them through the wings yesterday, bolting down the retracts for hopefully the final time. Now it is routing the Y-adapters for the gear and ailerons and it should be ready for weight and balance and first run up. Will be interested to see how much that larger Saito shakes.

[Cougar429]

With the nice weather had no excuse not to take it outside, fuel and fire it up for the first time.

I checked the CofG beforehand and with the huge stock spinner and 3-blade Graupner prop it comes remarkably close to the aft wheel well bulkhead. However, with a 2-blade and the smaller spinner it may require some lead to fall back in range,

It took some fiddling to get the mixtures close and it still needs tweaking to run the way I like, but 9000 RPM with a 14/8 prop is pretty respectable, especially considering the 10% fuel is left over from last season. I hope to grab a case of 15% at the Toledo show soon.

There were the inevitable bugs that cropped up. One of the switch nuts vibrated loose and the left aileron did not work. Already pulled the extension and found the ground wire had broken at the pin. Already repaired.

As for vibration, even though the motor did shake enough to make fitting the allan wrench and screwdriver to the HS and LS needles entertaining, the fuse and systems did not vibrate anywhere near the level I had feared. The tail and radio tray were relatively solid.

Sorry for the ugly grass. It is supposed to be under a foot of snow this time of year.


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[Cougar429]

No pics this time, just some info. I went to do some final fitting and decided to do some weighing with more items fit together. Unfortunately I ran into a bit of another problem that will need to be addressed and that was the fact the wing tube bound in one side and pressed too hard against the end on the collar. There were sounds of wood splitting, so I need to get a mirror to have a boo inside the wing from the aileron servo pocket. I think marking the tube to show when fully seated may be a good idea.

As it stands the weight of the plane sans cowling is pushing 12 lbs. I have read many riding around 13.5 due to the lead ballast required due to the extremely short nose moment. I knew the mods would add weight and think the most significant were in the gear and mount alterations. Still, the Saito 125 weighs considerably more than the stock ST90 recommended and I will accept the power in place of lead.

In that regard the recommended prop range for the Saito is 14x10, 15x8 and 16x6. Getting 9000 RPM with the 14/8 may seem low. Likely that will straighten out once the motor is broken in.

I will need to maintain care when landing. The Harvard is 11 lbs, powered with an OS FS91 and with the much larger wing practically leaps off the ground. This one will be riding further down the backside of the power curve and lacking flaps will likely tend to sink pretty fast with power reduction. I also want to avoid what I found with the Skybolt, my first with 4-strokes. Slow speed, lots of available power and a relatively large diameter prop makes for some exciting torque effects.