The Comet Stinson SR-7 - Another Free Flight conversion project - Video Addeded - Page 4 - RC Groups
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Aug 30, 2010, 11:50 PM
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PaulBrad's Avatar
All of the covering has been stripped and a new set has been printed. This is a new batch of tissue and I am optimistic that it will behave when it comes time to do the shrinking.

In an effort to make some forward progress today I did finish up the wheels and got them installed along with the wheel pants. The wheels received a coat of flat black Testorís Acryl paint. To create the look of aluminum hubs disks were cut from silver tissue. This is not the exotic silver tissue sold for model airplane covering but silver tissue purchased at a store that sells supplies for parties. They had a nice selection of metallic tissue. The sliver is pretty opaque and works great for things like the disks for wheel hubs.

Hopefully tomorrow I can get the flying surface covering redone so I can move on to the fuselage.

Paul Bradley
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Aug 31, 2010, 06:29 AM
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glewis's Avatar
Nice wheels.
I saw that metallic tissue somewhere and wondered if it would be usefull for our purposes. Think it would be any good as a covering material?
The silver tissue gives me ideas of how to simulate the mag wheels on WWII aircraft.
Thanks Paul

Aug 31, 2010, 10:09 PM
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I have not tried the metallic tissue as covering material. My initial though is it would not be suitable, but who knows?

The flying surfaces for the Stinson have been recovered. They are now on the building board going through the dope curing process. I like to allow them to stay pinned down for at least 5 days. After that things seem pretty stable and don't seem to warp. I have several "life events" that will get my time over the next several days. As a result I will likely not be posting any new progress for a few days. A good time for the flying surfaces to do their curing.

Paul Bradley
Sep 07, 2010, 09:22 PM
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The Stinson project has been on hold for several days due to external life events that needed my time. I was able to get back to the project today.

I was able to complete the process of covering the fuselage. Basically that involved first installing the side window plastic. I do that before the covering so the edges of the plastic will be under the covering. That creates a more scale look in my opinion. I like to cut the windows out of the tissue once it is in place and has several coats of 50/50 clear dope. My process for doing that is to apply a coat of rubber cement to the plastic just before the tissue is placed on the fuselage sides. The tissue is positioned while the rubber cement is still wet. Any positioning adjustments can be easily made. If I blow it I just remove the tissue, rub off the rubber cement, and then do it again. The rubber cement really sticks the tissue down and also provides a nice protection barrier from any dope damage.

After application of all the tissue to the model it got a single coat of 50/50 clear dope to seal the ink jet printer applied ink. The tissue was then water shrunk using steam. A second coat of 50/50 clear dope was then applied and allowed to dry.

Once the clear dope was dry the windows were cut in the tissue. This was done using a fresh single edge razor blade and a straight edge. Several light strokes with the blade is all that is needed to cut the tissue without cutting through the underlying plastic. Once all edges have been cut a corner is teased up with the single edge razor blade. The tissue panel is then removed with tweezers. The result is a nice neat window opening that does not have a non scale edge. This process works really well for the Comet war birds that have canopies formed from sheet plastic. I simply apply printed tissue to a piece of plastic with rubber cement, give it two coats of 50/50 clear dope, and then cut away the tissue window panels. The frame that is left behind is crisp and looks great on the finished model.

Next on the agenda is installation and covering of the cowl. That will involve making all of those pesky cowl bumps.

Paul Bradley
Sep 08, 2010, 11:46 PM
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I was able to make some additional progress today. First up was applying the printed tissue to the cowl. Once that was done the cowl was glued to the forward fuselage former. The printed tissue has light outlines for the cowl bumps that will be added later. Having the cowl bump outlines sure does make it easy to get them all in place and properly aligned around the cowl.

I should have next made up the 18 cowl bumps that are needed. I was not in the mood to do that tedious task so I took care of a few other details. The windshield panels were cut out and installed.

Following the windshield installation the tail surfaces were installed and the control surfaces were connected to the pushrods. The controls work perfectly with the magnet connectors. Way more separation strength than is needed. The equipment tray pulls out with no difficulty and the stops on the pushrods work as intended in keeping the control surfaces from being over deflected. I am quite happy with the overall arrangement.

After getting the control surfaces hooked up I just had to try taxing the wingless fuselage around the house. I wanted to see if the rudder would be responsive enough a low speeds to steer the model ... yea, thatís why I wanted to taxi the model. Barely moving the throttle had the fuselage scooting across the floor. The rudder did indeed have enough power to easily steer the model. I am very happy at this point.

Oh yea, I did place everything on the scale. Allowing for a few more details to be added to the model it appears the final weight with a 160 mah lipo cell will be 52 grams. That is 7 over my target but should not be an issue in terms of flying performance.

Paul Bradley
Sep 09, 2010, 07:10 AM
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glewis's Avatar
WOW! Outstanding work Paul!
You are the master of the printed tissue process. That looks fantastic and adds almost no weight.
How is the CG position looking ? Looks like you have plenty of room to move the battery around if necessary.

Off topic, but I built the Starship Enterprise out of dollar store foam from your plans. The thing is a hoot! It flies kind of wierd with the low aspect wing but that's to be expected. I had trouble getting the printed tissue to stick to the foam, it's kind of wrinkly, but so am I.
Guys at the field kid me about a foam model but I tell them hey, at least it's a scale model.
Sep 09, 2010, 11:18 PM
QuAd FaNaTiC
Razors edge 29's Avatar
Sep 10, 2010, 12:14 AM
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PaulBrad's Avatar
Thanks Glenn and Razors edge 29.

Glenn - Beleive it or not the CG is actually coming out slightly nose heavy. I currently have the battery located as far back on the equipment tray as I can. It will be close to spot on but I may to have add a tad of ballast to the tail. That will be a first for me and a scale model.

I am glad to hear that you have built a Starship Enterprise from the plan package that comes from my web site. Depending on the adhesive you used to attach the tissue it may be possible to get rid of those wrinkels. I had a similar problem when I built my examples of the model. I used Elmer's purple School Glue stick to attach the tissue. That worked fine but did leave some wrinkels. I ran the covered model through some steam. That applied enjough moisture to get it to shrink a bit but not enough to cause the ink to run. I ran my covering iron set to low heat over the tissue after shrinking to make sure it was stuck down well. The heat from the covering iron reflows that particular brand of glue stick. The process worked for me and I got rid of the wrinkes. Well most of them anyway.

A bit more progress was made on the model today. While gearing up mentally for doing the cowl bumps I decided to develop a decal of the Hamilton Standard Propeller company to use on the prop. Developing the decal artwork was not much of an issue, but actually getting a decal of the size needed for this model was something else. The prop logo decal is only 1/8" high. When the artwork is shrunk to that size my printer could not reproduce the detail. While you can't read any of the detail on the finished decal, it does add a bit of character to the prop.

When making such decals there is a process I use to help achieve results closer to those achieved with a commercial decal. Decal paper for use with ink jet printers is either white or clear. No big deal you say, just print the artwork on white decal paper. The down side to doing that is being able to trim the image cleanly. Unlike commercial decals, you don't have a white background with a clear edge. You have to trim the decal to the edge of the artwork. For a small decal like the one I wanted for the Stinson prop that is a major challenge. At least for me it is. To get around the problem I use a two layered approach. I first print the basic shape of the decal on white paper. That decal is then cut out of the main sheet. I try to actually cut just a tad under size. I don't seal the ink that defined the outline so it will wash off when the decal is placed in water. This creates a nice white background.

The actual color artwork is then printed on clear decal paper. A color outline, normally black, is used on the decal. After printing and sealing the decal is cut close to the outline color. You don't have to be precise here as the clear edge will basically disappear when the decal is placed on the target object. When ready the decal printed on the clear background material is placed on top of the white background. The color edge hides the edge of the background white decal and gives a nice neat finished look.

For reference I have provided a few photos of the Stinson prop decal results. The first is the artwork that was developed and then shrunk for the actual prop decal. The second photo shows the white background decal. As you can see the white background oval is fairly rough in appearance. Please remember this is a very small oval and hard for these aging hands to cut cleanly. The last photo shows the finished logo after the artwork printed on the clear layer has been applied. When standing back from the model you at least get the impression of Hamilton Standard Propellers logos on the prop blades.

Paul Bradley
Sep 10, 2010, 06:45 AM
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glewis's Avatar
Nose heavy? What's that????
A bit of ballast in the tail will be no big deal. Have you used that power system on your models before?
If not, you're in for a pleasant surprize.
It'll have plenty of power and at your estimated weight I would think it'll cruise at just a bit over half throttle.

Good idea layering the decals. I'll store that one away in the old noggin for future use.
Now, if only I don't forget where I put it!

The starship, I experimented with your method on some scrap foam first.
The glue stick just didn't seem to work well here. While it did adhere the tissue ok at first, after sitting in the hot humid garage for a few hours the glue starts to turn purple again and the tissue wrinkled/lifted. I could iron it back down and it would be nice and smooth again, for a while.
I tried a few different adhesives and found 3M spray to work the best. Same tecniquique, spray, allow to dry and attach the tissue with heat. Looked good for a week or two, then it started to wrinkle too.
Steam just might be the answer, it will shrink the tissue a bit.

Sep 10, 2010, 07:18 AM
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I've experimented with sticking tissue to depron using 50/50 Future and water. It works pretty well, but sticks better if the depron is sanded first. Of course, you need waterproof ink, or some such solution to keep from making a mess. However, it's really easy to get a wrinkle-free covering job.

The Stinson's looking great! I wish I could connect to your website, but it just doesn't work from here; I've tried many times.
Sep 10, 2010, 08:09 AM
derk's Avatar
Originally Posted by PaulBrad
I have not tried the metallic tissue as covering material. My initial though is it would not be suitable, but who knows?

Paul Bradley
i have used it a little for covering, it looks really good if you want it to look like a metal plane or a metal based dope finish (like on the hindenburg) its not the lightest tissue though, but it works.
your stinson is looking awesome too Paul
Sep 10, 2010, 04:11 PM
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PaulBrad's Avatar
Derk - I appreciate your kind words regarding the Stinson. I also appreciate your comments about using the metallic tissue for covering.

reylf_gnijieB - I am sorry to hear that you have not been able to connect to my web site. I really don't have an answer for that one. I do wish I could help.

Glenn - I do understand the humidity issue. I live part of the year in central Mississippi and we also get hot humid weather. So far, though, it has not cused the glue stick to release the tissue on the Enterprise I have there.

I was able to get over my mental hurdle today and got the cowl bumps made, covered, and installed. They sure do transform the look of the cowl.

The cowl bumps were not hard to make, just tedious. I first make up a length of balsa that is as thick as the bumps are wide as viewed from the top with a width equal to the length of the bumps. That strip of wood is then sanded to a streamlined cross section. One end is sanded to the profile of the bump as viewed from the side. Much like creating a wing tip. The end is cut off and the process is repeated until all 18 cowl bumps have been created. Each cowl bump was then covered with white tissue to match the base color of the model. Once that was done working around the cowl a bump was marked lightly with a pencil to not the location of the red trim color. A piece of printed red tissue was then applied to the nose of the bump. By doing this it was possible to get the red trim color to register properly with the color trim on the cowl. The process is slow but the results are satisfying. Some photos are provided for reference.

The model is getting close to being ready to fly. The wing halves get mounted next followed by addition of some details like the tailwheel and entry steps.

Paul Bradley
Sep 10, 2010, 05:30 PM
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glewis's Avatar
Come on, you really only made 18 bumps?
I must be a klutz. I must have made 24 before I got a decent looking set.
I sanded a radius in the bottom so they sat flush on the cowl and messed up a few doing that too.
Sand a tad too much off and then it sits lower than the others. , another scrap one...

Sep 11, 2010, 08:13 AM
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This build thread finally spurred me to pick out a stick and tissue plane to convert. I started last night building the tail feathers and fuse sides. It is extremely engrossing and enjoyable to once again be back on a building board. I'll be doing a AP05 conversion to the Dumas Ryan M-1 Mail Transport. It looks like a great first attempt conversion project.

Sep 11, 2010, 10:47 PM
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PaulBrad's Avatar
Glenn - For this project I really did have to do only 18 cowl bumps. One factor in making that happen was not worrying about adding a radius to the bottom of each bump. That greatly reduced the chance of screwing them up. I did do that on the Free Flight version of the model and had waste pieces. The radius is flat enough not to worry about (at least for me that is the case).

Tom - I did see your build thread for the Dumas M-1 Mail Transport. That will be a great model when finished. I am certainly tickled that my Comet Stinson project help you decide to start the M-1 project. I look forward to watching your progress in the build thread.

Not a lot of progress today. Basically the wing panels were mounted. The model is now ready to fly but does need a few more details added to be called complete. I am not sure what will occur first, flight or the additional details. It all depends on my local weather. I want to do the first flights in very calm wind conditions and that has not occurred for a while. Needless to say, while waiting out the wind I will work on the remaining details.

Here a several photos showing the model with the wing finally in place.

Paul Bradley

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