Building "VK Navajo" as Float Plane - RC Groups
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Oct 31, 2012, 07:02 PM
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GLGofLB's Avatar
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Building "VK Navajo" as Float Plane

I love RC Group build logs almost as much as buying stuff on RC Groups. I of course have a few Scale dream builds stored in the closet but those can take a LONG time. Before I tie up the work bench forever I want to round out my stable of Sunday and everyday fliers. I have the usual amount of half built projects laying around but I do mangage to complete an airplane every now and again. On Memorial day I bought a Carl Goldberg Super Chimpmunk online. Thought I would knock it out in a month. Well ten weeks later the shop gave birth to an Art Scholl style Super Chimpmunk.
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Description: Super Chipmunk with homemade fiberglass cowl, wheel pants and strut covers.

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Description: Quick Cockpit detail
RC Club has a monthly Float Fly at our facility and after 10 years I still dont have a decent float flier. A few months ago I won a VK Navajo kit at a club meeting, and I decided this would make a cool float plane. I like the high wing and the fully symetrical sheeted stab and all balsa sheet design fuse. I figure I can fiberglass the entire plane and floats cover the wing in matching Monokote and be off to the races. So if your so inclined please join me on this build, hopefully this will be done in a couple of months and I will a post video of its maiden flight at our February float fly.
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Description: They call these instructions?

Belive it or not this was four nights work sorting this stuff out. Now i have to get going and start gluing sticks together.
Last edited by GLGofLB; Nov 20, 2012 at 12:19 PM.
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Oct 31, 2012, 10:16 PM
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I'll watch. Our oldest club member built up a Navaho to the point of priming it with dope/talc and then stopped and he has had it unfinished for probably decades. But seeing how pretty it was in primer made me curious about the plane. They never caught on like the Cherokee, so you don't see much about them.

Oct 31, 2012, 10:41 PM
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tailskid2's Avatar
Ah, that looks exciting....real BALSA and a Kit to boot Brings back memories......
Nov 01, 2012, 06:51 AM
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Engine must be either 62V or 95V...which one?
Nov 01, 2012, 12:42 PM
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GLGofLB's Avatar
I just recently started flying 4 strokes and I really like their performance once they break in. I am also an OS person on on alcohol engines, I thought the the OS-62 would be a perfect compromise between size and power. I like to have turnkey airplanes so I purchased the new V twin design specifically for this plane, actually less expensive than the Surpass and the only new one of that displacement. This kit is a 60's or 70's vintage and the box calls for a 60 engine however at 64 inch wingspan it could easily fly well on a 46. Back in the day the engines did not put out the power we do now. With the added drag of the floats I think the FS-62V should be sweet.
Nov 01, 2012, 12:46 PM
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On another note. Does anbody know if the "Ventral Fin" in the Great planes Float kit which sticks out the bottom of the fuse is really necessary/
I think it is intended to take out adverse roll tendencies when attempting to yaw a float airplane.
Nov 01, 2012, 02:58 PM
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Originally Posted by GLGofLB
On another note. Does anbody know if the "Ventral Fin" in the Great planes Float kit which sticks out the bottom of the fuse is really necessary/
I think it is intended to take out adverse roll tendencies when attempting to yaw a float airplane.
The ventral fin added to the fuselage on a float plane is to compensate for the forward side area added when floats are installed.
There is more side area forward of the CG than behind the CG on a typical set of floats. This can make the plane act like it has too small a tail.

Some planes don't need the added area, while some actually become slightly unstable without the added tail area.
Nov 01, 2012, 04:05 PM
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Thanks for the input, I have seen quite a few models without it and they flew fine. Is there a way to tell in advance of test flying? Because on this model it will be a minor hassle to add it after it is complete. I am inclined to leave it off
Nov 01, 2012, 04:08 PM
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I think the 62V will prove to be a great choice. I think the 95V would have been a lot of weight in the nose and the power unnecessary for a plane of this type.

Agree with pd1 about ventral fins with floats. Very common on full scale aircraft for just that reason.
Nov 01, 2012, 06:27 PM
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The VK Navajo looks very similar to a full sized Cessna with the Omni vision rear window.

The "newer and improved" Cessna rear window reduced the fuselage side area aft of the wing.
The older ones didn't need the ventral fin.

Seems easy enough to add one while you're building the plane, at least it's easier now than later.
Nov 05, 2012, 02:45 PM
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Okay, this work every weekday thing is getting in the way of model building. There is so much sorted wood laying around it is time to get started. Since no instructions I chose to start with builing the tail plane (stabilizer) first. Thought tail plane would make me sound smart

Pretty straight forward plans taped down with wax paper. I build on 1 inch thick glass, so I weight every thing down with home made lead weights. Lower spar die cut ribs first
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Description: Plans taped downName: Lower spar and ribs.jpg
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Description: Getting the ribs on straight

Okay now my first mistake I spot glued the TE an LE. Well the LE is non- symetrical and I glued it on 90 degrees off and the TE was not centered I used CA solvent to melt the spot glues and re-glued everything correctly. Then CA ed the top sheeting. CA is okay because I can flip the stab over and add more CA to secure the sheeting internally. Note hinge holes in TE, this model is fairly small so I chose to use Carl Goldberg pin hinges. Nice clean look, easy installation and a buddy of mine gave me about 50 extras he had laying around.
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Description: Top spar and LE-TE spot gluesName: top sheeting.jpg
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Description: Top sheeting

Finally I cemmented the bottom sheeting on with thin coat of carpenters glue spread on all the mating surfaces. Then lots of weight and walk away to run weekend errands. Best to keep the peace The overhanging TE and LE are not just excess, they capture the wingtip blocks that are yet to be added.

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Description: Bottom sheeting and lots of weight.
Last edited by GLGofLB; Nov 05, 2012 at 02:49 PM. Reason: wrong Icon, grammer
Nov 05, 2012, 04:10 PM
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Well I put the fin on my four star, not sure if it is needed, but I have had it on there for the first few flights. I think I will take it iff next summer and try it without. The GP Float kit seems to be a good kit, I think you will be happy with it.
Nov 05, 2012, 05:06 PM
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Thanks to pd1 and kylerdinger. I believe that I will be adding the Ventral Fin before I glass the plane. If needs it I am ahead and if it dosen't I will never know the differrence. This is a dedicated float plane, so I might as well stack the deck in my favor. I had a freind who put floats on a Bridi Aircruiser and when we gave full right or left rudder it would respond by doing a full axial roll. I believe the ventral fin might have counteracted that
Nov 19, 2012, 03:32 PM
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The continuing saga

Dont you hate it when builders start a thread and disapear? Well my work and holiday schedule is a little pressing however I am still shooting for the second Monday in February to maiden this airplane model.

This is where we left off with stab pinned and weighted, waiting for its builder.

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Next comes the elevator first the hinging then the shaping, almost forgot to add the ply platform for the control horn. First mortise out the slot with my favorite exacto knife chiesel blade, add ply platform, some filler then assemble. Now through the magic of timelapse photography we have the finished stab and elevator hinged with control horn and shaped stab tip blocks.
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Description: Name: 3 Elevator Mortise with ply inlay platform.JPG
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Description: Name: 3a finished elevator horn platform.JPG
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Description: Name: 4 finished elevator.JPG
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Okay time to move on. Next is the fin and rudder. Very straight forward glue the fin halves over the plans, then sand the under surface to match the stab airfoil. Next I added a mortise to the side of the rudder to receive an inlay ply platform. I sorted through the supplied hardware pack. This pile of rubble will require some serious upgrading. I used to be a purist and only use what came with a kit. I have since learned better.

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Description: Name: 6 fitting fin to elevator.JPG
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Description: Name: 7 hardware.JPG
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Continuing on by mortising out the rudder for a ply inlay, then attachment with 2-56 socket screws to secure the nylon horn. (will trim extra screw off later). Rudder mounted checking throw.

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Description: Name: 9 rudder horn.JPG
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Description: Name: 91 checking rudder throw.JPG
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There is a still an unmanagable pile of wood parts on my bench. So I keep punching out things and laying them out over the plans. Major parts and bulkhead laminate pieces.

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Description: Name: 93 die cut bulkhead parts.JPG
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Keep glueing and something will happen. Laminated nose ring bulkhead and tail bulkhead laminates assembled.

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Description: Name: 95 Assembled laminated bulkheads.JPG
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Finally the plywood firewall laminated to the balsa bulkhead wieghted down leaving us off where we started, looking at lead weights

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Well its pretty late Sunday night and my workshop buddy is tired out and ready to go in to the house for a long winters nap!

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Last edited by GLGofLB; Nov 19, 2012 at 05:45 PM.
Nov 27, 2012, 04:22 PM
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Holiday weekend saga

Time to get cracking on the fuselage, lots of die cut parts and no real instructions, just isometrics.

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Description: First is to laminate the three pieces that make a side.  Always good to flip one side opposite the plan view so we don get two right sidesName: 2.jpg
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Description: Just another view showing the full length of fuseName: 3.jpg
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Description: Side laminated and sanded

Need to do some preparation to some of the hardwood blocks and parts.

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Description: The nose area has multiple hardwood parts. This is one of the two main fuse crutches and has a set of hardwood front landing strut blocks laminated to its underside.  The three holes represent where the engine hardwood mounting plates fastens.Name: 5.jpg
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Description: The blind nuts get completely buried by the landing gear strut block; therefore they need to be double countersunk.

Well believe it or not my digital camera broke! Have you ever heard of such a thing? Well I am determrined to follow this thread to the end and that meant buying a new camera on Black Friday. I really was not intending on going out on that day. To make matters worse the new camera was broken straight out of the box, that meant a second trip to the big box store.Well now I have added further to the economy. Learning the camera on the fly. I apologize for the marginal photography.

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Description: Fuselage side laminations coming along, with a number of die cut parts and doublers added.  Also epoxied in the crutches and blocksName: 7.jpg
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Description: Close up of harwood pieces in the nose areaName: 8.jpg
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Description: Main landing gear doublers in place

Time to make the this fuselage get some depth.

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Description: First two bulkheads glued in place and dry fit of main landing gear plate

The aluminum landing gear block attaches with four socket head bolts I do not believe they will be accessible after the bottom sheeting goes to place. So I will be fuel proofing this area with epoxy and then attaching bolts with loctite and a lock washers before things get buttoned up. The aluminum plate will hold the strut for the forward attachment to the floats.

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Description: Lower hardwood blocks drilled and counter sunk with blind nuts on other side to accept 4-40 bolts that attach front landing gear plate.

Trial fit of chin block.Bottom view with landing gear plate cemented in. Time to mount aluminum landing gear to bottom this will act as main float attachment point. Also time to place servos, engine, throttle cable and pushrod tubes. Easy to layout now, hard once the top and bottom sheeting is in place.

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Description: Bottom view with landing gear plate cemented in.

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