The Sprat - A new year's build

speedbirdted

Legendary member
Some of you know how lately I've had to downsize my workshop considerably so that kinda prevents me from doing any large scale building for the time being until I can get back into my normal shop. But it doesn't stop me from building completely :) So for now I am in small airplane mode. You might have seen the Pacific Ace in my other thread that I built a new wing for and cleaned up the fuselage, and it flies beautifully - however I tried it indoors in a gym and while it could do it it was really begging for more room. So it's now a park flyer - but I still have the indoor plane void to fill :p

Went on Aerofred and found this! Like the Pacific Ace, but it's a 20" wingspan. I think this was kitted by someone (Modelcraft?) because this is a redrawn plan from the early 2000s. I was given this plan ages ago at a SAM meetup and it just kind of sat until today.

I have a bunch of these all-in-one bricks and geared coreless motors lying around out of UMX planes that died horribly (I think this one was from a Vapor that fought a heli and was literally turned to powder) I thrust tested this motor and it gives about 30g which should be fine up to 50g ish. All the electronics by themselves are something like 13g so that leaves some room for airframe weight.

PXL_20210107_024118955.jpg


Other than adding an elevator and somewhere to put the electronics I think I won't really have to deviate from the plans in any major way. This is where they will sit. There's enough room for the battery and board to lay side by side. The wing can come off, which is nice - a lot of the time with rubber planes the wing is glued on and you have to make some sort of weird hatch or secure the battery to the bottom when you use electric power.

PXL_20210107_024058813.jpg


To keep it light... I'm going to cover it in this stuff. Tissue is really not my specialty (outside making a couple test squares I've never even touched the stuff in my life) so I tried to pick a fairly simple airplane to do which would keep compound curves and the like to a minimum.

This was just the stuff I could find lying around my house. I don't know where it came from and frankly I don't know if it'll work - is there a special kind of tissue that's better for airplane use? It seems to shrink up plenty tight...

I'm not sure which colors to use. White for the fuselage and rudder seems like it would look nice with yellow or green wings...

PXL_20210107_023704565.jpg


That also leads into my next dilemma - I'm running out of dope to use! I was given a mostly empty bottle of Eze-Dope by a club member after we had a discussion about tissue models. I don't think it'll be enough to complete an airplane with which makes me think do I either just buy more, or do what some people seem to do which is just use a 50/50 mix of alcohol and water to shrink the tissue and stick it down with school glue? I tried both and the shrinkage and adhesion both seem fine. Are there any cheers/jeers with either method which I'm missing?

I also need to get another balsa stripper before I can even start this build. My old one got lost in the commotion of having to move all my modelling stuff into another room. (it also wasn't really meant to be a permanent solution)

More to come...
 

The Hangar

Fly harder!
Mentor
Some of you know how lately I've had to downsize my workshop considerably so that kinda prevents me from doing any large scale building for the time being until I can get back into my normal shop. But it doesn't stop me from building completely :) So for now I am in small airplane mode. You might have seen the Pacific Ace in my other thread that I built a new wing for and cleaned up the fuselage, and it flies beautifully - however I tried it indoors in a gym and while it could do it it was really begging for more room. So it's now a park flyer - but I still have the indoor plane void to fill :p

Went on Aerofred and found this! Like the Pacific Ace, but it's a 20" wingspan. I think this was kitted by someone (Modelcraft?) because this is a redrawn plan from the early 2000s. I was given this plan ages ago at a SAM meetup and it just kind of sat until today.

I have a bunch of these all-in-one bricks and geared coreless motors lying around out of UMX planes that died horribly (I think this one was from a Vapor that fought a heli and was literally turned to powder) I thrust tested this motor and it gives about 30g which should be fine up to 50g ish. All the electronics by themselves are something like 13g so that leaves some room for airframe weight.

View attachment 188190

Other than adding an elevator and somewhere to put the electronics I think I won't really have to deviate from the plans in any major way. This is where they will sit. There's enough room for the battery and board to lay side by side. The wing can come off, which is nice - a lot of the time with rubber planes the wing is glued on and you have to make some sort of weird hatch or secure the battery to the bottom when you use electric power.

View attachment 188191

To keep it light... I'm going to cover it in this stuff. Tissue is really not my specialty (outside making a couple test squares I've never even touched the stuff in my life) so I tried to pick a fairly simple airplane to do which would keep compound curves and the like to a minimum.

This was just the stuff I could find lying around my house. I don't know where it came from and frankly I don't know if it'll work - is there a special kind of tissue that's better for airplane use? It seems to shrink up plenty tight...

I'm not sure which colors to use. White for the fuselage and rudder seems like it would look nice with yellow or green wings...

View attachment 188192

That also leads into my next dilemma - I'm running out of dope to use! I was given a mostly empty bottle of Eze-Dope by a club member after we had a discussion about tissue models. I don't think it'll be enough to complete an airplane with which makes me think do I either just buy more, or do what some people seem to do which is just use a 50/50 mix of alcohol and water to shrink the tissue and stick it down with school glue? I tried both and the shrinkage and adhesion both seem fine. Are there any cheers/jeers with either method which I'm missing?

I also need to get another balsa stripper before I can even start this build. My old one got lost in the commotion of having to move all my modelling stuff into another room. (it also wasn't really meant to be a permanent solution)

More to come...
I’ll be following! I think it would be a lot of fun to try a tissue built at some point. Would it work on any of the Willy Nillies kits?
 

flyingkelpie

Elite member
Some of you know how lately I've had to downsize my workshop considerably so that kinda prevents me from doing any large scale building for the time being until I can get back into my normal shop. But it doesn't stop me from building completely :) So for now I am in small airplane mode. You might have seen the Pacific Ace in my other thread that I built a new wing for and cleaned up the fuselage, and it flies beautifully - however I tried it indoors in a gym and while it could do it it was really begging for more room. So it's now a park flyer - but I still have the indoor plane void to fill :p

Went on Aerofred and found this! Like the Pacific Ace, but it's a 20" wingspan. I think this was kitted by someone (Modelcraft?) because this is a redrawn plan from the early 2000s. I was given this plan ages ago at a SAM meetup and it just kind of sat until today.

I have a bunch of these all-in-one bricks and geared coreless motors lying around out of UMX planes that died horribly (I think this one was from a Vapor that fought a heli and was literally turned to powder) I thrust tested this motor and it gives about 30g which should be fine up to 50g ish. All the electronics by themselves are something like 13g so that leaves some room for airframe weight.

View attachment 188190

Other than adding an elevator and somewhere to put the electronics I think I won't really have to deviate from the plans in any major way. This is where they will sit. There's enough room for the battery and board to lay side by side. The wing can come off, which is nice - a lot of the time with rubber planes the wing is glued on and you have to make some sort of weird hatch or secure the battery to the bottom when you use electric power.

View attachment 188191

To keep it light... I'm going to cover it in this stuff. Tissue is really not my specialty (outside making a couple test squares I've never even touched the stuff in my life) so I tried to pick a fairly simple airplane to do which would keep compound curves and the like to a minimum.

This was just the stuff I could find lying around my house. I don't know where it came from and frankly I don't know if it'll work - is there a special kind of tissue that's better for airplane use? It seems to shrink up plenty tight...

I'm not sure which colors to use. White for the fuselage and rudder seems like it would look nice with yellow or green wings...

View attachment 188192

That also leads into my next dilemma - I'm running out of dope to use! I was given a mostly empty bottle of Eze-Dope by a club member after we had a discussion about tissue models. I don't think it'll be enough to complete an airplane with which makes me think do I either just buy more, or do what some people seem to do which is just use a 50/50 mix of alcohol and water to shrink the tissue and stick it down with school glue? I tried both and the shrinkage and adhesion both seem fine. Are there any cheers/jeers with either method which I'm missing?

I also need to get another balsa stripper before I can even start this build. My old one got lost in the commotion of having to move all my modelling stuff into another room. (it also wasn't really meant to be a permanent solution)

More to come...
Why is it called the sprat? Nice plane though! I'd like to get into balsa. (y)
 

TooJung2Die

Master member
This was just the stuff I could find lying around my house. I don't know where it came from and frankly I don't know if it'll work - is there a special kind of tissue that's better for airplane use? It seems to shrink up plenty tight...
I've had good results with tissue from the greeting card dept. Wet the tissue and see how it holds up. You don't want tissue that dissolves when wet. The best gift wrap tissue has a shiny side and a dull side with a herring bone water mark. It'll have fine fibers. The tissue made specifically for modeling is Japanese Esaki tissue. I covered the Twin Cyclone with tissue and it has held up great after a lot of flying.

That also leads into my next dilemma - I'm running out of dope to use! I was given a mostly empty bottle of Eze-Dope by a club member after we had a discussion about tissue models. I don't think it'll be enough to complete an airplane with which makes me think do I either just buy more, or do what some people seem to do which is just use a 50/50 mix of alcohol and water to shrink the tissue and stick it down with school glue? I tried both and the shrinkage and adhesion both seem fine. Are there any cheers/jeers with either method which I'm missing?

Use Elmer's glue stick to stick down the tissue. It gives you time to reposition and smooth it out before it dries. Then use 50/50 Eze Dope or thinned Elmer's school glue to seal the edges and smooth down the tissue. Thin it to the consistency of milk. Shrink with straight water sprayed from a cologne or perfume bottle. Use a hair drier to shrink if you feel in a hurry. I stopped using dope on tissue and find that clear aerosol lacquer like Krylon Crystal Clear works even better. I like gloss but most prefer matte finish.
 
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speedbirdted

Legendary member
I’ll be following! I think it would be a lot of fun to try a tissue built at some point. Would it work on any of the Willy Nillies kits?

Yes! I've seen people use silkspan and butyrate dope - Silkspan is essentially just heavier tissue so going lighter wouldn't pose any problems other than you'd just have to be a little gentler to it.

Why is it called the sprat? Nice plane though! I'd like to get into balsa. (y)

That I have no idea. I didn't design it...

I've had good results with tissue from the greeting card dept. Wet the tissue and see how it holds up. You don't want tissue that dissolves when wet. The best gift wrap tissue has a shiny side and a dull side with a herring bone water mark. It'll have fine fibers. The tissue made specifically for modeling is Japanese Esaki tissue. I covered the Twin Cyclone with tissue and it has held up great after a lot of flying.



Use Elmer's glue stick to stick down the tissue. It gives you time to reposition and smooth it out before it dries. Then use 50/50 Eze Dope or thinned Elmer's school glue to seal the edges and smooth down the tissue. Thin it to the consistency of milk. Shrink with straight water sprayed from a cologne or perfume bottle. Use a hair drier to shrink if you feel in a hurry. I stopped using dope on tissue and find that clear aerosol lacquer like Krylon Crystal Clear works even better. I like gloss but most prefer matte finish.

Tested the stuff I've got, the strength when it's wet seems workable. It doesn't just disintegrate, it can be handled. I saw in the Cyclone build how you wetted the tissue so it could stretch slightly which helped pulling it over wingtips and the like, and it looks like I'll be able to do it with this (not like there are any huge compound curves here anyway) The near-transparency that the clear coat gave it was really cool though. I might have to try that out...

I did notice with the tissue one side is more matte than the other. Is there any way it should be stuck down, matte side out or in?

In other news with the help of a laser I made another balsa stripper. This one is similar to my old one but it has some improvements (most notably it can cut stuff thicker than 3/32 now)

PXL_20210107_202753696.jpg


Calibrated it by cutting some strips of 1/4x3/32 before adding the ruler. Accurate enough for my liking...

PXL_20210107_202403803.jpg


Now let's make some sticks.
 

TooJung2Die

Master member
I did notice with the tissue one side is more matte than the other. Is there any way it should be stuck down, matte side out or in?
Shiny side out. I was really surprised how much stretch I got with that tissue. The tissue that came with the kit had the wet strength of toilet paper. It was really bad.
Silkspan tissue is the same paper that tea bags are made from so it stays strong when wet. It's strong but it is proportionally heavier than regular tissue.
 

speedbirdted

Legendary member
Started on the fuselage sides. Normally I don't build in this order - I like to start on the wing. However, the wing has 1/8 hard balsa spec'd as the leading edge and I have none suitable at the moment. The store is closed by now so I'll have to run by tomorrow. But for now I'll build with the materials I already have.

PXL_20210107_233830752.jpg


Only change here was a 1/16 sheet was spec'd here but I changed it to a gusset because the only purpose it serves is to hold it in a stand while winding the rubber band.

PXL_20210107_233845974.jpg


Then laid down some paper directly onto the fuselage side already there and built the other side directly atop of it.

PXL_20210108_001829760.jpg


End result is two fuselage sides that are pretty much 100% identical with minimal sanding required. After I took this picture I added a couple rails that go on the inside, to mount a cross member that the electronics will go onto.

PXL_20210108_005616224.jpg
 

TooJung2Die

Master member
Very nice. I'll have to try the technique you used building the sides in two layers on the plan. It was smart to leave out the parts needed for the rubber motor mount. A lot of people leave that stuff in and it's only extra weight. I see your plan has a fuselage top view so may I make a suggestion?
This foam board jig is very simple and results in a perfectly straight and square fuselage.

fuselage jig.jpg
 
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speedbirdted

Legendary member
Very nice. I'll have to try the technique you used building the sides in two layers on the plan. It was smart to leave out the parts needed for the rubber motor mount. A lot of people leave that stuff in and it's only extra weight. I see your plan has a fuselage top view so may I make a suggestion?
This foam board jig is very simple and results in a perfectly straight and square fuselage.

View attachment 188306

Funny you say that as after I made the post I decided to cut one out before throwing in the towel for the night :p

PXL_20210108_182611428.jpg


I also cut out the few formers that are used. I didn't need the scroll saw, except for the firewall. Speaking of the firewall, 1/16 ply is spec'd however I used 1/16 basswood because it's a tad lighter. The hole is cut to fit the motor and gearbox.

If only I knew the horrors the formers would cause later on...

PXL_20210108_044235735.jpg


It appears whoever drew this plan had absolutely no idea what they were doing. Check out how asymmetric the firewall template is! The centerline is offset almost 0.5mm to the left as well as the notches for the top stringers. I ended up actually importing the former into Gimp and mirroring it around the center then printing it out again and using that, just to make sure it would line up a lot better.

PXL_20210108_034806537.jpg


The "dashboard" piece had the same problem. The notches are set too low. The top one has the notches as the plans specify which did not fit even with the most pushing I was comfortable with. The bottom one is with the notches moved about 1 mm up. The fit is near perfect that way.

PXL_20210108_193215648.jpg


Sticking everything in the jig. It fits together fine but man it took a lot of fuss. I nearly put the fuselage sides on the wrong sides which would have been majorly stupid but I caught my error right before I was about to lay down glue. o_O

PXL_20210108_194055479.jpg


Taken back out, looking good. The jig might seem like a lot of work, but it's totally worth it. Fuselage is arrow straight.

I also added about 1 degree of right thrust. The rotating mass in these rubber converted airplanes is relatively high compared to the weight of the fuselage so side thrust is pretty much a necessity. If you've ever looked at a Champ you will know what I mean. You can also see where I goofed and dropped the fuselage on the floor while I was sanding the nose sheeting and doinked the little bit at the top right side of the windshield. Luckily it weighs nothing so that was the only damage. I need steadier hands.

PXL_20210108_205839808.jpg


I'm not sure if i will make the nose block or not. The gearbox really leaves no room for it. It will have to be really thin if I do make it.