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SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conversion ... - 10/16/2006 3:25 PM   
HHjul


 

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Status: offline 		Hello all Super Cub fans!

I have made one 1/4 Super Cub by converting it from Sig´s Piper J-3 Cub kit. Just because there wasn´t and there still isn´t any 1/4 Super Cub kits available. Enclosed you find some pictures of my plane. My Super Cub has got a lot of attention lately, I´m very happy because of it. I have wanted to build another one for float flying for some time, and now it is time to start that another project. I will show all details how to make this conversion with lots of pictures and other stuff.

I will use the Sig kit contents as much as possible to make things go smoothly and quickly, anyway some minor extra wood is required. Also, I have started to make a plug for engine cowling, so I will offer a cheap 2-piece ABS plastic cowl kit for sale. I will sell and ship these cowls at very low price if somebody else is willing to build same kind of converted "Sig 1/4 Super Cub".

Check out the pictures enclosed, that´s the idea... to make the plane really look like a Super Cub.

I´m gonna process the following modifications:

- wider firewall and changes in fuselage
- rudder and elevator modifications
- flaps
- engine cowling (will be for sale after some time)

Except the above mentioned modifications, the rest will be build precisely like the Sig plan shows. So, the flying performance will not be changed.

I will use Zenoah G20EI gas engine as a powerplant (also known as Titan ZG20 in Europe). The plane will be covered with Solartex and automotive paint.

I have already ordered the kit and the cowl plug carving is already being started, so the building will start in couple of days. Stay tuned!


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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub convers... - 10/16/2006 7:05 PM   
Siesta


 

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Status: offline 		What a great idea Hannu!

This thread will not only attract many Super Cub fans, but also spread the fascination of float flying.
Have fun building and don't forget: All your big and little brothers around the world are watching you - with envy! ;-)

Kind regards from Switzerland

Matt





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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/16/2006 10:25 PM   
Navy18



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Status: offline 		Glad to have this to build by.... I am about 2 weeks out from beginning mine. Look forward to it.

Glad you have a nice camera.... pics are what make a build thread come alive.

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/17/2006 4:57 AM   
HHjul


 

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Status: offline 		There´s one or actually two issues I´m thinking, please comment:

In my earlier project, I changed the fuselage and wing root structure in cabin area quite a bit. There is a large roof window between the wing roots in real Super Cub, and I made the same to my plane. Also, I built a scale-like two-piece door system precisely like the Super Cub has. If we build the cabin area like the plan shows, there will be no large roof window (only a small one) and no doors.

Those modifications are no difficult to build at all, the Sig plan´s outline is followed all the time. Anyway, a bit more extra wood (mostly hardwood and plywood) is needed.

So, at this point we have to make a decision between "Super-scale" or "Sport-scale"...

Those modifications mentioned make the Super Cub a real scale model.

How do you like it?




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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/17/2006 10:34 AM   
Siesta


 

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Status: offline 		Personally, if I invest the extra time to come as close to the original as possible, then I always try to at least get those things correct which are obvious at first glance.
Even if we do not participate in semi-scale or scale competition, the roof window is rather prominent.
Most of the time, when an RC model is not up in the air, it will be standing on the ground with our fellow modellers looking down on it.
So, yes, I would install the correct size of the roof window as used on the Super Cub.

Hannu, one question comes to my mind: Where did you find a precise 3-view of the PA 18 that shows these details?
Is Piper selling documentation?

Good luck!



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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/17/2006 10:39 AM   
Siesta


 

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Status: offline 		Having a scale opening door would not only have the effect of better results in competition, but would also give better access to the interior.

I believe, this picture shows an additional STC for the baggage door which is not standard on the PA 18.



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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/17/2006 11:47 AM   
HHjul


 

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Status: offline 		I try to avoid "The Snowball Effect" in this project...

I will enlarge the roof window to correct size. But the scale door requires some heavy-duty modifications to the cabin area. If the door is to be added, we have to get rid of those a-bit-clumsy vertical balsa members inside the cabin. I have done that once, of course it is possible to do that again. But, if so radical modification will take place, I will also join the wing center section (roof window area) permanently to the fuselage. I did it in my earlier project. Also, the wing connection to the fuselage has to be modified.

You know, that´s what I mean about "the Snowball Effect"... one thing leads to another etc...

I have some scale 3-views and a big pile of my own close-up photographs of local Super Cub.






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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/17/2006 3:52 PM   
Navy18



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Status: offline 		I am of the Semi-scale mindset... if the roof window is a realtively easy fix which will not effect wing strength, I would go with that. The operable side doors will not find a place on my Cub.

What I am targeting is the correct cowl, the correct tail dimensions, a correct pull-pull setup on the rudder, a proper wing which I suppose will include the window and a good working, dependable G26 in the nose.

Any other details are for the super scale guru's out there....

I look forward to breaking the kit open very soon.

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/17/2006 5:39 PM   
HHjul


 

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Status: offline 		This will definitely be a semi-scale project, more like kit-building than scratch-building. Sig´s kit is a very good semi-scale kit but relatively poor if you really want to build a Scale Masters -level masterpiece. All I want for this project is quick to build, rugged and reliable everyday flyer... strong enough for hard landings and everyday hauling. That´s why I´m going to build mine straight from the box except these few modifications... which will not weaken the structure at all. I´m not bringing this into scale contest, I have another plane for that purpose. Also, I would like to build this project so that if somebody not-so-experienced modeller is willing to do the same, this thread will also serve as an excellent reference.

OK guys, the final list of modifications goes as follows:

- cowl, firewall and fuselage front
- larger roof window
- flaps
- tail feathers

I want to get mine flying in May 2007, so there is 7 months to do the job. I already have the floats for this plane, I just have to fix and finish them a little bit.

I will receive my kit before weekend, the building will start on Sunday by putting together the fuselage sides.



< Message edited by HHjul -- 10/17/2006 5:42 PM >

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/17/2006 8:09 PM   
Navy18



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Status: offline 		HH,

A question on the landing gear with the kit. Is it strong enough to build stock or did you use another method? I know you are going floats for this one so it may not come up. I understand the stock tail gear is good.



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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/18/2006 2:24 AM   
Wayne22



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quote:

Any other details are for the super scale guru's out there....


Go with the Robarts or Wallace articulating gear..It is well worth the money.... The soldered wire ones will break in time....

< Message edited by nony -- 10/22/2006 6:42 AM >

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/18/2006 8:17 AM   
HHjul


 

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Status: offline 		I have used the stock gear from the kit, and I have never had any problems... except once when I lost a wheel during a flight...
Anyway, the stock wire gear is strong and will last a lifetime but the soldering has to be good enough. Poor soldering means poor durability.

Cowl news: ABS material ordered.


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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/18/2006 2:39 PM   
HHjul


 

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Status: offline 		I decided to change my engine in this project to Zenoah G26. I will install my G20EI to my red-and-white Super Cub to replace its Saito FA-120. I´d like to have a bit more power, it´s good to have some extra when flying floats. Also, it is possible that I try glider towing some day.

I will move the firewall a bit forward compared to Sig J-3 plan so that I can bolt the G26 straight to the firewall. Also, there will be more room for fuel tank. G26 will fit almost completely inside my cowling.




< Message edited by HHjul -- 10/18/2006 2:41 PM >

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/18/2006 4:15 PM   
Navy18



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Status: offline 		HH,

Glad to hear you switched to the G26; now I can crosscheck my dimensions with you..... I plan on the G26 also.

Also glad to hear you think it wil fit insode the cowl.

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/22/2006 2:14 AM   
Navy18



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Status: offline 		The RV4 is finished and first flight went fine.... bring on the Super Cub. Can you provide a small list of differences in the manual so I can kick off and start building? Are the fuse sides built stock?

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/22/2006 6:59 AM   
HHjul


 

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Status: offline 		I received my kit yesterday and the building starts today. Before starting, I just have to change winter tires to our cars because we just got some snow here in Finland last night.

You can build the fuse main frames (sides) stock (drawing plate 2) but only the long main frames. We have to modify those separate front pieces (incl. parts MF-1 and MF-2) a bit, so don´t build them yet. I will provide some pictures later today.

Also, I´m not going to use any metal wires in windshield area (connected between short fuselage front pieces and fuselage former F5). Instead, I will build that big fuselage former F5 using hardwood and plywood so that it is strong enough for any possible loads without any metal wire reinforcement.





< Message edited by HHjul -- 10/22/2006 7:14 AM >

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/22/2006 1:53 PM   
Navy18



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Status: offline 		Sounds good... I will do some inventorying and might start the side this afternoon. Looks like alot of wood to sift through.

Thanks.

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/22/2006 7:53 PM   
HHjul


 

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Status: offline 		Ok, project started. I spent two hours, inventing the box contents and started to put together fuselage main frame.

Sig balsa is quite heavy as well as is the structure of their J-3. Normally I would lighten that kind of structure a bit, but this time I´m not doing it because of my engine selection. G26 has more than enough power for 1/4 Piper, I think it is good idea to build a kind of "heavy-duty" structure straight from the box to handle the vibrations and weight of a G26 gas engine.

As told earlier, I have already purchased one Sig J-3 kit before this project. Now I decided to take full advantage of my earlier plan set by cutting it to suitable worktable pieces. So, I have not destroyed my new plans.






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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/22/2006 10:08 PM   
WacoCabinaero



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quote:

ORIGINAL: HHjul

Ok, project started. I spent two hours, inventing the box contents and started to put together fuselage main frame.

Sig balsa is quite heavy as well as is the structure of their J-3. Normally I would lighten that kind of structure a bit, but this time I´m not doing it because of my engine selection. G26 has more than enough power for 1/4 Piper, I think it is good idea to built a kind of "heavy-duty" structure straight from the box to handle the vibrations and weight of a G26 gas engine.

As told earlier, I have already purchased one Sig J-3 kit before this project. Now I decided to take full advantage of my earlier plan set by cutting it to suitable worktable pieces. So, I have not destroyed my new plans.









I am following your thread with great interest. I ordered a SIG 1/4 Cub about a month ago apparently it got sent on a vacation but is supposed to be here Monday. I was hoping to find it viable to convert to a PA-18 or possibly the North Star Company's new improved version of the full scale Super Cub. They have many of Piper's original tools and dies. Located in Perkensfield Ontario they prefab a homebuilt version of the Super Cub that is quite popular as a high performance bushplane in the Canadian and USA north country. The owner is a nice chap and I have toured the factory. First rate facility and products. Their improved version has squared off wing tips at the TE for greater aileron authority. Complete STOL characteristics.

Thanks, Bill


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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/23/2006 8:35 AM   
HHjul


 

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Status: offline 		Thank you for your comments. I would also like to build something special this time, it´s too much of those ordinary models out there. I have considered to build a modern STOL version of my Super á lá Cub Crafters including square drooped wing tips, vortex generators and aft body strakes. I´m eager to see if these modern aerodynamic inventions work in a model.

First fuselage main frame almost completed.




< Message edited by HHjul -- 10/23/2006 9:39 AM >

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/23/2006 1:19 PM   
Navy18



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Status: offline 		HH,
I inventoried the kit lastnight...looks good. I will start on a mainframe side tonight. I have 3 kids so won't be able to keep up with you but keep those pics coming as I will be checking in daily. Do you plan on aft mounted servos for tail surfaces? I assume you will also be using double aileron servos.

I was pleased with the wood quality and think SIG still does a good job choosing wood and placing a fair price on the kit; there is alot in there.

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/23/2006 2:43 PM   
WacoCabinaero



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quote:

ORIGINAL: HHjul

Thank you for your comments. I would also like to build something special this time, it´s too much of those ordinary models out there. I have considered to build a modern STOL version of my Super á lá Cub Crafters including square drooped wing tips, vortex generators and aft body strakes. I´m eager to see if these modern aerodynamic inventions work in a model.

First fuselage main frame almost completed.





Finally, someone has introduced the incorporation of vortex generators for Scale STOL models. It is new to my eyes anyway. Ever since I saw them on an Aviat Husky I thought I wanted to try them. They should work perfect as turbulaotors are included on so many model wings now for the same purpose although with different appearances. I want to make the little one piece toed -in twin vertical fin tab aluminum type that are positioned on each rib at the TE of the aluminum LE strip on the full scale.

It just arrived. Finally! Added some photos of the Vortex generator similar to ones I have seen. The ones I would model were a one piece with the aluminum forming a surface between the uprights flush with wing surface that would easily lend itself to affixing to wing.
Cheers.


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< Message edited by Stearman Flyer -- 10/23/2006 5:42 PM >

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/23/2006 6:04 PM   
WacoCabinaero



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Status: offline 		I am adding a partial brochure photo of an evolved Super Cub Know as the Northstar. I had previously mentioned this AC and it incoporates features the thread author has reffered to already. I have had it in my mind to this subject for it's features and I may just bash my Sig into it. I have plans as well for a Robert Scweitzer 1/4 Cub that I was going to build until I realized that the modest $229 CDN the Sig 1/4 Cub cost is a fraction of what it cost 10 years ago.

fiberglassspecialtiesinc.com sells a myriad of parts for the Scweitzer Cub including a Super Cub Cowl and fenders etc. I know their parts are excellent and wil just order the cowl now. The Balsa USA float kit would of course compliment this Cub perfectly. I will build them from the plans. Those I have already.

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/24/2006 5:17 AM   
HHjul


 

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Status: offline 		Finished the fuse sides yesterday evening, today I´ll start putting together the first modified parts - fuse front side pieces. After that, it´s no turning back!

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RE: SIG 1/4 Piper J-3 Cub -> PA-18 Super Cub conver... - 10/24/2006 6:56 PM   
HHjul


 

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Status: offline 		Now here´s the first thing I do my own way. Fuselage front side pieces. I forget the picture on drawing plate 2 showing the original front side piece. Instead, the part must put together on drawing plate 1 showing the finished fuselage.

Enclosed you find a picture of drawing plate 1 with my own markings added. The yellow area shows how the plan originally presents the size and shape of side piece. We have to add that 15 mm (0,59 inch) wide green area to the side piece. Then, after gluing the firewall in place, we have the correct length for G26 and the propeller driveplate locates correctly when engine is bolted straight to the firewall. Also, the engine thrust line has to drop 15 mm (0,59 inch) compared what the plan shows. That´s one very important thing to make our project look like Super Cub.

There is still enough room for any 4-stroke glow single or twin if somebody wants to use one.

Note! The groove for cabin wire is not needed any more. I will replace the balsa windshield brace with hardwood to support the fuselage former F5.



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