jeff naul

My Feedback: (16)

what is the difference in the tail feathers on the cub v/s super cub?

HHjul

Well, there is only some small differences like a bit more curved rudder and elevators. It´s easy to study the differences by comparing J-3 and PA-18 photos found for example from www.airliners.net. I will show how to do the modifications when it´s time to make them.

Navy18

My Feedback: (4)

HH,
I have also finished the main frmaes and will incorporate youe extension tongiht.... I will need to read it over a few times but thanks for the picture to help out.

HHjul

No problem, I will do the very same tonight. My instructions can be somewhat confusing, anyway I´ll post more pictures tonight to help you out.

Navy18

My Feedback: (4)

As I see it, we are just moving the sides forward 15mm with exact size balsa sticks. I know it sounds simple but want to double check all the mods before I add glue.

WacoCabinaero

Hannu,

Your opening pics look great. I am taking the lazy way and have ordered a cowl for converting Sig J-3 to Super Cub from Fibergalss Specialties. They have one for the Robert Sweitzer plan as metioned before. I am using the plans for Balsa USA 1/4scale Edo floats as well. The super uses a bigger float I think but shouldn't work any different.

I am adding a couple pics of a chaps 1/3 Balsa USA Super Cub build. They may help out as well. They have for me.

Bill

HHjul

Here´s some help how to construct the enlarged fuselage front side pieces.

I make mine the same way the plan says - but with altered measurements. I use my own 8 mm balsa here.

Enclosed you find a picture (not very sharp, sorry) where you see exact measurements in millimeters. Upper left corner angle is 90 degrees. After you´ve done that piece, just glue the 8 mm square balsa stringers around. Final thing is to reshape lower front corner.

Measurements from left to right are: 100 mm, 141 mm, 27 mm and 132 mm.

HHjul

OK, here´s a picture of finished pieces. Exactly like the original ones except the missing cabin wire groove and an extra 15 mm extension at the front.

Now it´s time to glue these finished side pieces to the fuselage main frames. Pin the pieces to flat building board to ensure straight fit. It has to be done now because front side pieces and fuse main frames must be in straight line.

Next thing to do is to cover these completed fuse sides with 3 mm lite ply. You can use the ply parts from the kit, there is only this 15 mm extension to cover with extra pieces. I will cut my own custom lite ply parts so that I use only one solid piece to cover the entire front area.

After that, it´s time to get into fuselage formers.

WacoCabinaero

I like your resolve to use a G26 as that is what I will be using. A friend has 1/4 scale cub that flies well with or without floats with a Quadra 35. I think the ZG20 is a little jewel but may not give much authority with floats. I haven't tried it, just a guess.

In response to the top window query you mentioned before, I opt for strength than window. I have plans for the Balsa USA L-4 Cub and as a observation platform and litter carrier I felt that that much open structure compromised strength of the fuselage given the wooden medium we are using. In fairness I have seen it done well when chaps have put in full bulkheads but painted them drab or chromate to match interior.
Pic of cowl being used. I am lazy sometimes.

HHjul

Your cowl looks pretty much the same I received some time (almost 2 years) ago when I ordered a cowl to convert Sig J-3 to Super Cub. I think you can´t use that cowl if you follow my conversion instructions. In my conversion, the cowl is a bit over 8 inches wide in the firewall area. Please measure yours, in my conversion the cabin area outer width and the firewall width are the same.

About the enlarged top window, it will not weaken the structure if constructed properly because the wing stress in our 1/4 Piper is mostly taken care by those fully working wing struts. I will use some kind of plywood frame around the window to ensure its rigidness.

mintie

Hi...interested in your Cub build....I have a PA18 super cub myself,that I scratch built.It is now 16 years old and done high hours. Built my own fiberglass cowl,and it has working wing struts. full glass cockpit and opening doors with pilot and passanger.All radio gear is under the rear shelf and under the front seat. Power OS40 and built to 1/6 scale. If you want any pics of a full size Super Cub I can supply as we have one at work. I am an aircraft engineer and work on the said plane. Will take some pics of my model and post them in the weekend. There is always a place in my hanger for a cub.

HHjul

Yes, Super Cub model pictures are something I´d really like to see in this thread. So please post them. I think other modellers who read this are equally interested as well.

I will glue fuse side ply panels today, also I will start making those three fuse formers. Other formers can be done straight from the box except F5. Cabin wires are gone, that´s why the former F5 will be redesigned.

Ouch, I almost forgot: before gluing the ply panels, I have to make small grooves to both fuse sides for 8x8mm hardwood windshield brace installation.

Navy18

My Feedback: (4)

HH,
I already glued the light ply onto the aft section of the Main frame.... post procedures for that "ouch" in the previous comment so I can try to cut what I need.

Thanks

HHjul

OK there´s no problem to cut the groove for windshield brace even if the plywood is already installed. I´ll post some pictures in couple of hours or so.

HHjul

Here´s a picture showing the area where you have to cut a small piece away for windshield brace installation. I think after seeing the picture you get the idea? So, we glue the 8x8 mm square windshield brace bottom end into that groove we cut. We don´t use balsa anymore but hardwood. The upper end will support the fuselage former F5.

My camera turned the picture 90 degrees for some reason... but it´s very easy to make that marking. Lay your fuselage main frame over the plan sheet 1 and just continue the lines. Note! you have to glue the front side pieces in place because the groove locates mostly at the front side area.

About the fuselage former F5, I will put it together totally as the plan shows. I remembered it wrong, somehow I had an idea that the vertical members are balsa but they are plywood.

Navy18

My Feedback: (4)

HH,

Just to check, you want us to glue the front main frame to the rear frame at this time so we can cutout the windshield support? The plans have us making a nose box several steps ahead. I also have exact same sides... is there any side thrust we will need to add later?

Just checking.

HHjul

That´s right, and the cutout isn´t the only reason. I find it easier to make perfectly straight nose by gluing the frames together on flat table. The original nose box idea is good when making a J-3 with its tapering nose. Our Super Cub nose stays straight from cabin area to the firewall. That´s why we can glue the frames together now. I just find this method easier. Trust me, I´ve already made this once with good results.

I will epoxy my plywood side boards to fuse main frames today, my fuselage formers F5, F6 and F7 are ready as well. So, I start to assemble the fuselage. I´ll post some pics as usual.

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I decided to replace my fuse side lite-ply pieces with balsa in same thickness. Lite-ply quality in my kit is poor, pieces are really badly twisted and the ply lamination is falling apart [:'(]. I will also get a small weight saving as a bonus.

About the side thrust, I will study that issue today. Originally, Sig plan does not show any side thrust. Anyway, it´s easy to make the side thrust into the structure when installing the firewall.

mintie

HI ..the pic that I said I would put on..of my Piper Super Club...The glassing of the cockpit area is for real...When I was building my plane I did some research and found a flying example in the UK.So can vouch for the authenticity of this glassing. It comes from the L3 grass hopper J3 cub and was carried over to a few super cubs. My aileron servo is in the roof of the cockpit area and blends in with the mat black used in that area. RX is under the pilots seat,battery under the second seat and the rudder and elevator servo under the rear baggage shelf.throttle down beside the pilots left leg. Both pilot and passenger are full body models to around 1/6 size to match the plane. Wings plug into 3 wires and locked inside the cockpit and the struts hold the wings in place. A custom fuel tank fits in behind the instrument panel and up to the fire wall. A whole 9oz. will fly the plane for 25 mins at 2/3 throttle, which is 80 kph. a complete scratch build taking 175 hours. Have included a pic of my PA38 tomahawk with the PA 18 cub. Both 1/6

WacoCabinaero

I agree with not snowballing and individuals may go to any lengths with their own models. Oh, and I will be one of them but I think this thread may be of interest as the aerodyanmics of a model this large do correspond with it's fill size counterpart:

http://www.supercub.org/phpbb2/viewtopic.php?t=3856

A Question H. :What muffler will you use?

This diagram is self explanatory.

Navy18

My Feedback: (4)

Sides are done.... how about the dimensions for the formers? Are they supposed to be alittle wider?

HHjul

Sides are done here as well, and the fuselage formers also. We keep the fuselage formers - all of them - stock. Also, everything behing fuselage former F5 must build "the Sig way", no modifications. Except the tail feathers, of course. So, after finishing the sides there´s a lot to do.

I´ll start assembling my fuselage today by gluing the formers F5, F6 and F7 into the right fuselage side.

Some pics will follow soon.

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I have a confession to make: I COULDN`T HELP MYSELF!!!

(I have drilled some lightening holes to my fuselage sides... to remove some ounces of the ultra-heavy balsa Sig has supplied in my kit...)

HHjul

Here´s what I have done so far - fuselage sides with modifications mentioned, and the stock fuselage formers. I start assembling the fuselage... now! Pics will follow.

HHjul

Now an important procedure when assembling the fuselage. The cabin top piece has to set as the enclosed picture shows - that´s because the windshield brace top end must meet the former F5 plywood plate. The windshield brace will support the plywood because the cabin wires are no more.

Navy18

My Feedback: (4)

I like the lightening hole idea.... can't do it myself because the plywood sides are already on..... the G26 willjust have to pull it as is. I had held-off on the formers becasue I thought they were going to be wider.... if not, I will fire off on those today and start putting the fuse together tomorrow.

Since I do not have a single piece outer plywood piece, do you think it wise to overlay some balsa or plywood below the forward cutout we made to strengthen the joint?

HHjul

I decided to lighten the structure a bit because of the floats I install permanently... some compensation for their weight and drag. Well, I´m sure G26 will pull your Super just fine without any lightening. My earlier Super flew nicely with Saito FA-120... except on floats it was a bit too lazy.

Your idea of strenghtening the joint from inside is brilliant! I´m sure it will hold if glued properly but some reinforcement to critical areas is not a bad idea. G26 will provide some serious drag to front end joints.