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Jul 08, 2018, 06:01 PM
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Build Log

Custom(ized) Privateer...


Having built a couple of Navigators, I have always liked Don McGovern’s designs. I bought a Privateer short kit and also picked up what I thought was a complete Privateer Super 15 kit, but it turned out to be a mostly missing partial kit with plans. And in the corner I have a set of enlarged Navigator plans for a 65” version.

But I have always been interested in the Custom Privateer, so when a kit showed up for sale, I bought it, despite the fact I now have more potential/actual projects than I can reasonably ever expect to finish.

So I spent some time cutting out parts, and once I had a reasonable number done decided I would start this thread. Did not want to start it until I had something to show. I was able to get a bit more done faster than usual because of the holiday and me taking off Thursday and Friday from work. I was able to squeeze in a bit of extra hobby time that way, as I still have family I need to support.

Wings

I found and read Jeanskydive’s thread (and later Bigjohn’s), and gleaned some info nuggets from it. I pulled out the plans and looked at them, read the notes, and decided to add a few changes to the design (honestly, I can’t remember the last time I built a kit or ARF stock, I always find something to modify). After some discussion on Jean’s thread, I determined to change the airfoil. I was going to go with a Clark Y, but after Bigjohn’s input, went with the SD7037. Since I had to cut out new ribs anyway, I decided to push it  Then, after looking at the rest of the kit, I realized if I cut out a set of fuselage formers, the rest of the kit is essentially strip wood. So I decided to use the kit for templates and plans, and once I have the model covered, will just resell the kit—and someone else can have the chance to build a remarkable model.

So planned wing changes. First, the most practical thing would be to build a simple dihedral wing ala Jeanskydive, but I like the look of the upturned outer panels. But I did decide to make the center section flat, and will raise the outer panels. Also, the constant taper wing means every rib is different, so rather than cut out that many different ribs, I am making the center section constant chord and just tapering the outer panels. That means 14 different rib sizes instead of 33.

Other planned changes: 2 wing panels for ease of transport, carbon tube spars, change balsa spars and locations, built up sheet trailing edges, Depron center section ribs, ailerons, flaps, and making it a 10 foot wing (9 ½ feet? I can understand 9 or 10, but 9 ½? Just had to change it—and of course bigger flies better, right?).

I printed out the 7037 airfoil, root rib 14.75 inches, and then printed out reduced sizes in 2% increments down to 74% (11”). First step was to cut out plywood root ribs, 2 of them, to allow me to cut a set of ¼ inch Depron center ribs. The pattern gave me the full size airfoil, which I then reduced 1/16” top and bottom to allow for capstrips. Why Depron? Well, not lightness since ¼” Depron is actually heavily than average 1/16” balsa (Depron is ~2.43 lbs/cu ft), but at ¼” thick is easier to work with than 1/16” balsa, IMO does just as well in compression, and has a lot more gluing surface. I also feel it does better with the spar tubes. I was also able to cut them out quicker with the templates--the pics tell the story on that.

Rest of the ribs I cut out from 1/16” balsa using the printed patterns, since I needed only 2 of each. I did maintain the 2” spacing between ribs per the original design, although 3” probably would have been ok, but did go to ¼” wide capstrips (to match the Depron ribs) instead of 3/16. And to save the kit blocks, will do a combination of balsa and foam for wing tips.

Anyway, some pics and comments...Pete M
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Jul 08, 2018, 06:29 PM
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hi Pete,

I've used depron - salvaged from grocery store meat/produce trays - as wing ribs, with balsa cap strips, at times and they have worked well. I've cut the depron ribs with a scalpel #11 blade, using a plywood template.

I've not seen the use of depron as a filler/support as you have used toward the trailing edge - interesting.


Michael in Ontario, Canada
Jul 09, 2018, 08:59 AM
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Yes, I normally cut Depron ribs with a knife and template as well, but when cutting 1/4" thick material, it's too easy for me to cut at an angle. Since I needed 32 of them and wanted to keep them as uniform as possible, decided to go with the hot wire approach. It let me cut about 8 at a time easily.

The original trailing edge is solid balsa tapered stock, so for strength purposes decided to put in the filler on the built up trailing edge. Probably not needed because of the carbon tubes, but did it anyway. I was also going to put sheeting on the wing, from front spar to leading edge, mainly for extra strength, but as the original did not have it and again the tubes should be more than strong enough, am leaving it off--I do want to try and keep some semblance of the original :-)
Jul 09, 2018, 11:14 AM
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Custom (ized) Privateer


Hello Pete... Look verry nice and building technics différent ., look good.........Cheers
Jul 14, 2018, 05:10 PM
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So continuing with the wing. Installed the carbon tubes, and this wing is now stout. I have 9mm tubes in the center panels, was going to put that size in the outer panes as well but only had 3 of them--so used 8mm instead. Don't think it will be significant Installed additional sheeting on the outer panels for aileron cutouts, installed the outer panel root rib and sanded in dihedral angle (going with 2" at the end of the panel, will be a bit more when wing tip added. For the outer panels, as they have balsa ribs, on the other side of the ribs I added baking soda/thin cya fillets. For the Depron ribs all that would do is result in melted foam, so instead I used Titebond wood glue to fill in the space and make a fillet. Ailerons, float mounts, center panel end ribs, wing tips, and it will be time for the center section, which, by default will require the fuselage..Pete M
Jul 18, 2018, 08:57 PM
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Progressing...


Have been trying to get a little time in each night...

Wing is progressing, have capstrips on 3 of the 4 panels, and have root ribs drying on one of the center panels. Since I am in no hurry I used Titebond glue to attach them--this is my go to stuff when I really want something glued well. And wanting a break from all the capstripping, I went ahead and started on the fuselage. Jeanskydive used a jig, that is the elegant approach, but I went with easier and simpler and built the crutch as shown on the plans. Had to finagle it a bit as my work area does not have an 8 foot table, but I managed. However, it was so flimsy and flexible when finished, all I could think of was how many times I was going to break it--so I decided to sheet it on both sides with 2mm Depron. This added 98g to the weight, and did stiffen it up, but more importantly it doesn't feel like it will break. A lot of the sheeting will get cut out as construction progresses so final weight increase will be less. It's worth it for the peace of mind.

I also weighed the wing panels to find out how much weight the carbon tubes and reinforcement added--it was about 40g per panel. Considering I got rid of the huge spars, even after adding the four 1/4" spars I think it will be lighter than if built according to plans.

Will soon be cutting out stab ribs. I thought I was going to have to use the kit ribs for patterns, but found a set of plans on line that had all the rib sections, so I printed them out and will use them. Having fun here Pete M

PS--thought I would keep a log of changes I am making. Crutch uprights are 1/8x1/4 instead of 1/8 square on plans as I will be gluing the formers directly to them. This will increase the fuselage width 1/8 inch
Last edited by pmisuinas; Jul 19, 2018 at 06:30 AM. Reason: Added info...
Jul 19, 2018, 09:49 AM
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Quote:
Originally Posted by pmisuinas
Have been trying to get a little time in each night...

Wing is progressing, have capstrips on 3 of the 4 panels, and have root ribs drying on one of the center panels. Since I am in no hurry I used Titebond glue to attach them--this is my go to stuff when I really want something glued well. And wanting a break from all the capstripping, I went ahead and started on the fuselage. Jeanskydive used a jig, that is the elegant approach, but I went with easier and simpler and built the crutch as shown on the plans. Had to finagle it a bit as my work area does not have an 8 foot table, but I managed. However, it was so flimsy and flexible when finished, all I could think of was how many times I was going to break it--so I decided to sheet it on both sides with 2mm Depron. This added 98g to the weight, and did stiffen it up, but more importantly it doesn't feel like it will break. A lot of the sheeting will get cut out as construction progresses so final weight increase will be less. It's worth it for the peace of mind.

I also weighed the wing panels to find out how much weight the carbon tubes and reinforcement added--it was about 40g per panel. Considering I got rid of the huge spars, even after adding the four 1/4" spars I think it will be lighter than if built according to plans.

Will soon be cutting out stab ribs. I thought I was going to have to use the kit ribs for patterns, but found a set of plans on line that had all the rib sections, so I printed them out and will use them. Having fun here Pete M

PS--thought I would keep a log of changes I am making. Crutch uprights are 1/8x1/4 instead of 1/8 square on plans as I will be gluing the formers directly to them. This will increase the fuselage width 1/8 inch
Verry nice work..Pete
Jul 19, 2018, 01:51 PM
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Thanks :-)
Jul 21, 2018, 01:25 PM
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No longer a noodle


So I am happy to say my fuselage crutch has lost its noodle status.

I got out the fuselage formers and squared them up two by two using my sanding block. Then cut out the foam over the crutch uprights for gluing them in. Would have been easier to just glue them to the foam, but location would not have been as accurate and more strength gluing to wood. Used a triangle to get one side of formers in, but had to improvise for the other side since I couldn't lay the crutch flat now. So used a block clamped to the installed former that then served to square the other one. A lot of formers later I had a good start on a skeleton, but still no stiffness.

Per building instructions, then installed the 1/4" square longerons. There are 2, one on top the other for the first half, then a single one to the tail. Had to be careful to keep the fuselage straight, but with a little work it came out well--and it's nice and stiff now. Time to install all the 1/16" strips now, which will then lead me to installing sides and planking. What has made this interesting so far is I am building this 90+ inch fuselage on a 48" building board....

And still cleaning up remaining wing construction items. Cap strips almost done, about ready to cut out ailerons, and have to finalize how I want to do flaps. I may wimp out on those...Pete M
Jul 23, 2018, 03:09 PM
DHG
DHG
Kinetic Sculptor
1. That is truly a work of art! Thanks for sharing!

2. I'm a big fan of wood in general, balsa in particular ... but wouldn't it have been great if Don McGovern & the designers of other classic models had had access to Depron? Even if just for the formers & ribs.

It's wonderful watching this project take shape!
Jul 24, 2018, 05:28 AM
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I agree, a combination of wood and Depron works really well. I have done a lot of plan builds, a couple of scratch builds, and taking a classic model and replacing wood with Depron in selected areas saves a lot of weight with little loss of strength. Unfortunate the Depron industry quit doing runs for the hobby, there really hasn't been a suitable replacement for it (6mm flat Depron). I have almost a case of the 6mm and a bunch of 3mm that I dig into when warranted. And let's not forget carbon fiber tubes with respect to strength to weight. Having access to those would have really let Don get creative.

I am cutting out stab ribs (balsa) for the moment, should finish that tonight and maybe will have time to do construction as well. I want to have radio equipment in for the rudder and elevators before I close up the fuselage, as once the sheeting and stringers are in place there won't be much in the way of access. Will have to preplan an access hatch just in case it's needed. The desire is to have the servos as far in the rear as possible to avoid all the weight of long pushrods--the narrow fuse makes it a bit more challenging...Pete M
Jul 24, 2018, 11:52 AM
DHG
DHG
Kinetic Sculptor
Quote:
Originally Posted by pmisuinas
Unfortunately the Depron industry quit doing runs for the hobby, there really hasn't been a suitable replacement for it (6mm flat Depron).
Pete,

Wow, I didn't realize we'd been orphaned again. I bought about a dozen sheets of 6mm Depron when I was all excited about little flat foamies (still enjoy them but haven't built a new one in a while), but always assumed it would continue to be available. A reasonable substitute, at least for ribs & formers, might be to cut high-density styrofoam (pink or blue insulation) into thin slabs as Keith Sparks recommends in his book, "Building With Foam." Keith includes a link and other handy tips in another thread on this forum, in case you hadn't already seen it: https://www.rcgroups.com/forums/show...mman-Albatross

Guess I'll have to set up for slab cutting too ... oh, well, when have modelers not been forced to fend for ourselves a bit? It builds character, I suppose.

Cheers,
Duane
Jul 24, 2018, 02:55 PM
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Yep, that would work, I did something similar to that when I built my Cutting Edge (there's a build log on rcg). The Model Plane Foam stuff that appeared shortly after Depron went away is not as good and really doesn't fit the bill. The only workaround I have heard established is Model Aero went to 9mm Depron for their Polaris wing since the 6mm wasn't available any more (at least flat 6mm--what did come on the market after the industry stopped doing "hobby runs" was curved, sometimes quite badly)...Pete M
Jul 29, 2018, 05:47 PM
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So feeling I need the stabs to install servos for them before closing up the fuselage, have been working on them. Cut out the ribs for both of them and began the horizontal. 26 more ribs. The horizontal stab with tips will be 50", so since I put a carbon tube in a 26" wing panel, decided to put one in the stab. I suppose I could have reduced the stab size but decided to keep it.

I joined the stab halves so I could be sure to install a straight elevator. Still have to do a joiner rod for the elevators but should be no problem since they are straight across. Will be easy to run a single pushrod to a control horn from the point in the fuselage where it is wide enough for a servo installation...Pete M


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