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alienx
04-29-2009, 08:49 PM
I finally glued up my GWS floats. I wanted to do this last Summer for a trip, but it took me a year to get motivated. I read a lot of the GWS float threads in here and they answered some of my questions (like where to line-up the floats relative to the fuse, front to back). But I have a couple more questions I guess.

I would like to use the stock float gear legs, but I imagine they will give me a narrower float gap than I would like. Is it worth trying to bend my own gear legs so I can separate the floats a little more (give a wider stance)?

Also, I didn't see anyone mention an issue which seems to be critical to me. That is, what should the incident angle be between the floats and the wing? And would I measure it using the top of the float (is that the chord line??)? Since you have to add a second (rearward) attachment point to most planes, if the fuse belly slopes upward towards the tail, you would end up creating a relative nose-up attitude when you attach the rear of the floats to the fuse. Am I correct, or does this even matter? I don't have the Tigermoth in front of me, so I can't say how big of an issue this is going to be.

Thanks. Andy

Jim Casey
04-30-2009, 02:58 AM
Normal rule of thumb is that with the tops of the floats level the wing should have a 2-3 degrees upward incidence.

Separation between floats is normally guidelined at 25% of wingspan, but with a bipe you might want to stretch that a little because the span is usually less with the bipe.
Narrower spacing won't hurt massively, just progressively makes the plane tippier if there's any crosswind while taxiing.

Larry3215
04-30-2009, 06:45 AM
Thats a great float page you've got Jim! Lots of stuff all in one place that Ive had to dig around for.

I've added it to my Fav's :)

Jim Casey
04-30-2009, 12:53 PM
Thanks for the kind words, Larry. All I need now is a bunch of large corporations paying me for ad space.

alienx
04-30-2009, 01:19 PM
Thanks! I think that is all the details I needed to start. I'm going to get the plane in front of me, take some measurements, see what parts I have laying around, and then go from there.

alienx
05-17-2009, 12:57 AM
Just a quick question. I am getting ready to mount the floats to the plane. How do you know where the tip of the floats should be relative to the front of the plane?

The GWS directions show that the CG should be at or about 3/8" behind the CG of the plane (more or less). But this seems to be just mounting the floats so the CG of the floats doesn't disturb the CG of the plane. But it gives no consideration to the plane actually being able to skim across the water on the floats at that position. It seems like you are supposed to mount the floats in the correct place for takeoff andd landing and then rebalance the plane if you need to.

I attached a pic of the float next to the plane. The CG of the plane is at the leading edge of the lower wing or -10mm. The CG of the float is the outside edge of the step. I probably set my plane's CG at 0mm, so if I set the float at that spot, I have about 5" of float in front of the cowl. if I set the float back to about the -10mm CG of the plane, I still have about 3.4-4" of float in front of the plane.

Any ideas about how I am supposed to do this?

Thanks!

Jim Casey
05-17-2009, 02:57 AM
Step of the float is important. Location is Variously reported as on a 10 degree-back line from the actual CG, or under the 40% line of the Mean Aerodynamic chord, or in your case, 3/8 behind the CG. This lets the plane pop up on the step and skim along stably while it accelerates to liftoff speed.

If the floats are sized well, this will put the nose of the float about 1/3 to 1/4 of the prop diameter ahead of the prop. If you have too much float in front of the prop it can be squirrelly.

5" of float ahead of the prop is a lot unless this is a 1/4 scale plane. Mostly float in front of the prop just protects the prop if you beach the model or taxi it up to a dock.

Larry3215
05-17-2009, 03:55 AM
Jim is correct, the floats need to be placed according to the step and the planes normal CG position.

How long are the floats and how long is the plane from prop to tail? The floats are generally about 75% of the length of the plane.

The reason adding floats make some planes squirely in the air is because the side area on the floats is mostly in front of the cg. That extra side area ahead of the cg reduces the yaw stability.

Thats why many planes need to have enlarged rudders or extra area added to the vertical fin or an added ventral fin when flown with floats to fight that tendancy. The larger fin/rudder adds more side area behind the cg and makes for better yaw stability.

The Tiger Moth is a fairly snub nosed plane so Id expect the floats to stick out front more than on a normal model, but thats just going to make the yaw problem worse.

You may end up having to add a larger rudder/fin to the plane for it to be flyable.

alienx
05-17-2009, 04:19 AM
Thanks. It looks like I came to the right place!!

OK, so I am probably way ahead of the location I want. If I move the CG of the plane back to the -10mm area AND put the step another half inch or so back of the CG, I still have a solid 4" of float in front of the cowl (maybe a little less in front of the prop). If I move it to the point were I have 3" in front of the cowl, the stock float mount locations seem to almost lined up with the gear mounts in the fuse. I guess this doesn't really mean anything because I had to cut the second mount into the fuse, and I simply put it as close to the back of the wing as I could to keep the two gear legs close enough to mount on the stick that gets glued to the top of the float body.

The Moth is about 29" long, and the floats are about 21", so I guess almost as long as they should be. The span is about 37". I bent up some fresh gear legs to get the floats out to the sides a little further. I went as far as I thought I could get away with while using the wire I had. It "looks about right."

I am not so much worried about moving the floats back to a more appropriate spot and then maybe adding a little lead to the nose if I have to. I just didn't want the plane to nose-over because I mounted them too far aft.

I hope this plane still flies nicely. It is a treat off the ground with the wheels on it. I imaging the same characteristics with the floats, but maybe I am asking for too much.

So what do you think. Should I just move the float tip to within about 2 or 3" of the cowl and see how it works?

Larry3215
05-17-2009, 06:52 AM
I think there is some confusion about cg.

You keep saying your going to move the cg on the plane - but if you do that it wont fly correctly. You are also talking about the cg of the floats - but that doesnt enter into it at all.

If the plane is flying well now - without floats - then you need to keep the CG - the point where it balances - the same. You do not want to move it or the plane will either be too nose heavy or too tail heavy and wont fly well.

With the plane in its normal flying setup - with wheels and battery installed - see where it balances now.

Mark that spot as the CG on the plane. You do not want it to move after the floats are installed.

After the floats are installed, the plane should still balance in the exact same spot - or very close. You may need to add nose or tail weight to get it to do so. You do NOT move the floats to get the cg set.

If it balances a little more forward than before thats probably ok as long as its within the range shown in the instructions. If it balances a little behind - that depends on how good a pilot you are and if you can handle a tail heavy plane. I dont recomend flying tail heavy with floats. Its not easy :)

Now - the step on the floats needs to be positioned just behind that CG spot you just marked on the plane.

You dont need to worry about the cg of the floats. That has nothing to do with anything.

The only critical thing is to get the step set just behind the point where the plane balances - the planes cg.

The nose of the floats will end up where ever they end up. Nothing you can do about that unless you want to re-carve the floats into a shorter version.

You certainly dont want to move the floats to fix the nose over hang issue if it messes up the step to cg relationship.

So here is the sequence of events.

1)Find the CG of the plane without floats and mark it.
2)Mount the floats so that the step on the floats is just behind the CG on the plane.
3)Add weight to the nose or tail to get the plane to balance back at the same place after the floats are mounted. I add the weight to the floats rather than the plane so you dont have to remember to do it each time you swich back from wheels.
4)Set the floats so that the wing has a slight positive angle of attack relative to the top of the floats.

Go fly :)

If there is any sign of Yaw instability - squirley flying - then enlarge the rudder/fin area.

Jim Casey
05-17-2009, 01:06 PM
Nicely said, Larry.
I thought I had seen TigerMoths with a Cub-Style subfin to add Vert Stab area.
However, a query on Google Images for "Tiger Moth with Floats" revealed no images with additional vert stab area.
Not that it's a bad idea, just apparently not necessary for the TigerMoth.

alienx
05-17-2009, 01:22 PM
Thanks guys! I only mentioned moving the CG of the plane because I probably set it up at the very front of the range. That doesn't mean I would be flying the plane out of balance, I was just thinking of getting the floats lined up a little further back by taking advantage of the aft portion of the CG range (better yaw characteristics that way!?). And I only mentioned the float CG because I didn't know if GWS was smart enough to do the things you guys are mentioning. I figured they simply chose a point on the float that was neutral in balance and then had you line that up with the plane CG. I guess they did a little more thinking on the subject though because the seem to want you to set up the floats the way you guys are suggesting.

OK, so I will leave my plane alone, line up the step of the floats just aft of the plane CG, rebalance if I have to, and then see how well it flies that way!! When I set out to build the plane, I thought it would be a quick throw-together just so I could take it with me on vacation and fly it with my dad ...a disposable plane of sorts. Same for the floats. But I ended up putting a lot of care into it along the way, so now I hope to end up with a nice seabird!

Stay tuned.:)

Larry3215
05-17-2009, 07:38 PM
Thanks guys! I only mentioned moving the CG of the plane because I probably set it up at the very front of the range. That doesn't mean I would be flying the plane out of balance, I was just thinking of getting the floats lined up a little further back by taking advantage of the aft portion of the CG range (better yaw characteristics that way!?). And I only mentioned the float CG because I didn't know if GWS was smart enough to do the things you guys are mentioning. I figured they simply chose a point on the float that was neutral in balance and then had you line that up with the plane CG. I guess they did a little more thinking on the subject though because the seem to want you to set up the floats the way you guys are suggesting.

OK, so I will leave my plane alone, line up the step of the floats just aft of the plane CG, rebalance if I have to, and then see how well it flies that way!! When I set out to build the plane, I thought it would be a quick throw-together just so I could take it with me on vacation and fly it with my dad ...a disposable plane of sorts. Same for the floats. But I ended up putting a lot of care into it along the way, so now I hope to end up with a nice seabird!

Stay tuned.:)

Ah! Now I understand. Thats not a bad idea.

Good luck and keep us posted!

alienx
05-21-2009, 01:58 AM
OK, I got a little closer to done finally. I had to stop for a week or 10 days twice to order simple tools I've got locked away in my storage bin someplace, like a razor saw and Xacto knife, and then I needed a pin vise. GWS gave me one nice piece of wood to mount the gear legs to, but the second piece must be oak. I broke all the 14 screws they gave me as I was upsizing the pilot holes one bit size at a time. Kept twisting the heads right off. Oh well!:{

So I am pretty happy so far. It looks like a float plane. I need to add the cross bracing and then rebalance, but the floats lined up pretty well, even though I hand bent the gear legs. I'm glad I took the time to make my own gear legs. The stock mount would have put the floats about 3" closer to eachother.

The step ended up about 1/2" behind the rear end of the CG range. That left about 3" of float tip in front of the cowl. It looks pretty good. But then again, I have no experience. I have to finish the gear, seal and paint the floats, and maybe add a shim to the front gear mount, then I can test it!!

Larry3215
05-21-2009, 08:52 AM
Lookin pretty good!

be sure to let us know how it does on the water - video prefered :)

alienx
05-26-2009, 05:22 PM
Lookin pretty good!

be sure to let us know how it does on the water - video prefered :)


Thanks. I'll get some video sooner or later. Maybe not of the test flights, but the Maine flights anyway.

I have some more need for advice!! I finally got the floats sealed and painted and mounted. I have a couple issues though and am not sure how bad they are or what to do about them.

First, the floats are slightly off, relative to each other. What I mean is that one tip is about 1/2" to 3/4" higher than the other. I have had some problems with my internet at home lately, so I can't post pics just yet (maybe tonight). I can't tell where the misalignment is coming from. If I twist them into the right place, with no collars on the outside of the gear legs, one of the mounting points on the float sneaks out to the end of the axle. It fixes the alignment problem, but it means I would have to re-bend another gear leg because I no longer have enough axle extension to get a collar on it. But even as such, I can't visualize where the actual problem is. I bent both legs on the same plan (drawing), so they are not different shapes. One of the float-to-float cross members is about 1/16" longer than the other, but they are almost 11" long, so I didn't think that small of a difference would translate to a problem???

The other thing is if I get the floats true, do I need some type of gear leg to gear leg cross member for support?? I bought some spider wire and figured I would bend and tie some cross members on but I am not sure where they would do the most good, if anywhere??

Thanks. And sorry about the lack of pictures. As soon as my internet gets fixed, I'll post a few.

Thanks. Andy

Jim Casey
05-29-2009, 03:13 AM
Yes it is a good idea to use "spreader bars" which are really anti-spreader bars.
X-Bracing really locks things in place. None of those have to be large diameter since the loads can be handled by tension only. Small wires are fine.

alienx
06-04-2009, 03:39 AM
Thanks Jim, I am going to put some x-bracing in before she is done. I am at that 90% stage I guess!

I painted the floats with aluminum, after a couple coats of polycrylic. I am happy with them. I got the mounts pretty much worked out too. I will probably go back and bend one more front gear leg. I bent a taller one after my last post because the nose looked too low. It seems to have taken the alignment issues out. But I think I am about even with the top of the float now (as best I can see), so when I feel like bending another wire, I'll go back and make one more even a little taller.

I also painted the plane with poly to try to keep it from absorbing too much water. I painted all the wood wing bracing too. So I still need to get the nose a little higher, water-proof a bunch of things, make the x-bracing, lube everything metal, and add some weight to the float tips, and drill a couple other mount locations in the top of the floats in case I need to move them fore or aft at all. 90% to go:roll:. Then I might try to fly it over the land to retrim and work out any handling issues. I had a bad warp in the wing when I built the plane but I trimmed it out in the radio. I got tired of looking at the warp so I bent some of it out when I had the plane apart. Now I have to dial it in again. Hopefully the gear won't tear out with a grass landing.

That's it. Maybe another week or two to finish it up and get it to the field.

Thanks for the help.

warhead_71
06-15-2009, 09:30 PM
Here is my TM400 on floats. I simply added a rear LG mount behind the bottom wing, same as you did, and everything else was simply the stock setup: stock spreaders, stock landing gear braces, and the floats are attached to the LG struts at the stock "indicator notches". She's stable on the water and ROW's easily with sufficient speed.

I've seen another thread somwhere that someone added a small spacer at the front float mount to slightly increase the float/wing decalage... just the thickness of a popsicle stick.

I had the same problem twisting the heads off those thin screws... I had to run to ACE to buy better wood screws.

http://www.rcgroups.com/forums/showpost.php?p=12455158&postcount=2939

http://www.rcgroups.com/forums/showthread.php?t=1048531

http://www.rcgroups.com/forums/showpost.php?p=12455520&postcount=7

P.S. -- I'm looking at adding a plug-in ventral fin to help with yaw stability with the added drag of the floats. The tail certainly seems to wag when banking through a turn, even with rudder coordination.

Something like this: http://www.rcgroups.com/forums/attachment.php?attachmentid=2444345

alienx
06-15-2009, 09:57 PM
That's a nice looking Moth you made there (coming from a scale minded RC enthusiast!).

Looks like it flies nicely. Is that a saltwater puddle you flew from first? I am woried about the battery and battery connection. Yours seems to be exposed like mine is. I figured I would wrap it with some cling wrap to keep the splash damage to a minimum. If I dunk it ...well, that's another story.

I keep tinkering with my float mount. I did end up bending a third front leg. But I think I am a little too tall now. And I need to put a third set of mounting holes further forward on the float to take some of the stress off, which is caused by the angle of the front mount in the fuse. But even as such, I would fly it as is now. I am going to try to get it to the field this weekend between rain showers. The rain might actually allow me to use an entry-road puddle we have at the field. It's tiny, but I think I might have to do it anyway. I'll try to get my video guy to come out in the bad weather.

warhead_71
06-15-2009, 10:32 PM
No saltwater. I'm in Chicago. My first flight was from Lake Michigan, and after that my flights were from a pond/lagoon.

I soaked my electronics with CorrosionX, a dielectric penetrating oil that forms a water barrier over your electronics. Instead of Cling Wrap, which loses its "cling" when wet, some people also squeeze caulk into the ESC where the wires come out... or cover with a rubber balloon, or cut the fingers off a latex surgical glove, or a condom. :)

alienx
06-15-2009, 10:37 PM
Yea, I guess I am going to have to take this little experiment a little more seriously before I put it on the water. I think I am going to like it a lot (if it works!) and I am going to want to fly it more than a few times!!! I still have 5 weeks to waterproof it before it comes on vacation with me.

warhead_71
06-15-2009, 11:06 PM
I searched around and found this link to REAL Tiger Moth's on floats:

http://forum.keypublishing.co.uk/showthread.php?p=1384198

From looking at the photos, a real Moth appears to have the step aligned about even with the back seat/bulkhead of the front cockpit, and the nose of the floats just stick out in front of the prop about 4-5ft - or about 2 inches "to scale". This coincides nicely with my "stock" placement of the GWS floats. The only modification I think I'll try is to add a small spacer at the front mounts so the wings have a slightly higher angle of attack when the floats are level.

Your longer spreader bars certainly won't hurt your lateral stability, but I found the stock width to feel quite adequate.

Larry3215
06-16-2009, 02:02 AM
Here is my TM400 on floats. I simply added a rear LG mount behind the bottom wing, same as you did, and everything else was simply the stock setup: stock spreaders, stock landing gear braces, and the floats are attached to the LG struts at the stock "indicator notches". She's stable on the water and ROW's easily with sufficient speed.
xxxxxxxxxxxxxx

P.S. -- I'm looking at adding a plug-in ventral fin to help with yaw stability with the added drag of the floats. The tail certainly seems to wag when banking through a turn, even with rudder coordination.

Something like this: http://www.rcgroups.com/forums/attachment.php?attachmentid=2444345

Ading the ventral fin is the correct solution but its not the drag of the floats thats causing the yaw problem.

The problem is that the floats have increased the relative side area ahead of the CG location. That reduces the yaw stability. Its the same effect on yaw stability as moving the cg rear ward.

alienx
07-12-2009, 02:36 PM
OK, she flew!! It was a dry maiden but I didn't have anyone at the field to shoot the video. But I have another set of issues now and need some advice.

The plane flew very nicely, even considering how many things I changed on it and waterproofed and wrapped in rubber!!!:<: It didn't seem to need another fin on the tail, it was very well behaved as far as I could tell in a gusty wind. But it has some kind of pitch issue now. That is, I had to use a lot of elevator to get it to climb and then I timmed in a lot of up and still felt like I had to lean on the elevator to keep it off the ground. I probably had a good 1/8" of elevator trimmed into it after the first flight. I figured I was nose heavy, but I wanted to ask you guys if the floats add some type of pitch problems like this. Maybe I am not out of balance but have some aerodynamic problem now?

From memory, the plane flew nicely and seemed to be trimmed at 19 ounce AUW and making about 110 watts or so. I added about two ounces of lead to the nose, some polycrylic everywhere, and the painted floats, so I am guessing my AUW is now close to 28 ounces. Even as such, it flew very nicely (scale-like). That is, slow and stable. But it really wanted to pitch down. I took off and landed 3 times and it wasn't difficult to get a decent glide slope on final, even with the power off. I touched on the floats each time and immediately flipped in the grass.

So what do you guys think?

Thanks!! Andy

PS. Two weeks until the water maiden!!!

Jim Casey
07-12-2009, 04:09 PM
Andy, It should balance in the same place WITH floats as without. That's why we say to add weight to the floats for balance, so when you remove the floats and go back to wheels, the plane will still be balanced. That said: I usually find that the floats don't change the balance.
My experience adding floats is that they'll cause the need for a little down-trim. But those were not GWS floats. I don't know why GWS floats would be different, and don't recall this ever being mentioned with them.

If it needs up trim all the time, it's probably balance. Trim for level flight, go high and, without changing throttle or trim, put it into a shallow dive, hands off. If it's nose heavy the extra speed will give the elevator more authority and it'll pull out of the dive on its own.

If it's a motor thrust issue, it'll change direction when you add power and stop doing it when you pull power back. Motor thrust is built-in to a TM so that's unlikely.

The only other choice is that the airframe is rigged incorrectly. Is it possible to have put on the cabane struts backwards to misalign the top wing? (or other misalignment-like the horizontal stab...)

Larry3215
07-12-2009, 07:28 PM
I agree with Jim completely. Its probably a little nose heavy.

One other possibility is that the floats are adding enough extra drag down low that its causing some downward pitching. Thats a pretty lite airframe so it may be extra sensitive to that.

Like Jim said, if the thrust line is off it will climb or dive when you add power from a hands off cruise.

It sounds more like nose heavy to me though.

alienx
07-12-2009, 09:49 PM
Thanks guys. I didn't weight the float beacuse the location wouldn't have been more than an inch or so in front of the cowl, and I didn't want all that ugly lead up there. I can always pull the pieces back out simply enough.

I'm not sure I am going to get another shot at it before the water maiden, but I think I am inclinded to pull a half oz out of the cowl for the maiden. It flew, and if anything, might have become really roll sensitive (although it was windy, so maybe my imagination).

The only other thing I didn't mention is that I may have a fair amount of incidence between the wing and floats. The two shorter front legs I bent just looked about a little negative and then neutral, respectively. The third leg was the first one that actually looked like I had some positive incendence, so I left that one on. I only mention it because the only other thing I can envision causing this is the actual drag from the floats.

I'm going to read your responses a couple more times and then maybe try to pull a 1/2 ounce out off the cowl like I said. I have an outside chance of flying it one more time next Sunday, but then it is going on the ocean!!

Thanks for the help! Andy

Larry3215
07-14-2009, 02:47 AM
Before you remove any weight, re-check the actual current cg location with the floats still attached.

Leave it right side up and suspend the model under the top wing using your finger tips or a balance machine or what ever works.

Be sure the model is sitting level and note the spot where it balances.

Is it ahead of or behind the recomended CG location? Is it different than with the floats attached?

Larry3215
07-14-2009, 02:54 AM
I searched around and found this link to REAL Tiger Moth's on floats:

http://forum.keypublishing.co.uk/showthread.php?p=1384198

From looking at the photos, a real Moth appears to have the step aligned about even with the back seat/bulkhead of the front cockpit, and the nose of the floats just stick out in front of the prop about 4-5ft - or about 2 inches "to scale". This coincides nicely with my "stock" placement of the GWS floats. The only modification I think I'll try is to add a small spacer at the front mounts so the wings have a slightly higher angle of attack when the floats are level.

Your longer spreader bars certainly won't hurt your lateral stability, but I found the stock width to feel quite adequate.

Here is a quote from that site which illustrates the need for a ventral fin - which they did not have on the full sized one.

“The Sea Tiger was never the best-handling float plane” says Keith Sissons, who instructed pilots on the aeroplane’s idiosyncrasies. “The large floats meant that she wasn’t dynamically stable and you had to work continuously to maintain balance in the turns and avoid side-slipping.


Floats can cause issues for sure.

alienx
07-14-2009, 02:24 PM
I'll check the balance again, but I think it is on the mark. The thing is that I can never say for sure. That is, if I put it on my fingers, I can get it to stay a little more or less tail up or down without tipping, so I would say my accuracy has always been within about 5-10mm. I know that can make a big difference, but I can't get any more accurate, so I accept the fact.

I did look at the float step this morning on my way out to work (for some reason) and it seems like it might be a little far back. But again, it's hard to tell. everytime I look at it it looks a little different to me. I think I am going to have to get a ruler out tonight and check all my facts, and try to find a better way to balance it. Maybe I can fabricate a balance stand or sorts somehow. Whatever I do I will have to do in the next day or two and then I might have to try to fly it again Sunday. That will be my last chance before the water.

All I really need to do is get it to fly level with a little less effort. That might end up to be asking for a lot though. As it is now, it takes off and flies well, but I have to use full power and a bunch of elevator to climb. That isn't going to be good for the battery!!

Jim Casey
07-15-2009, 01:01 PM
Check the plans, find the recommended balance point and mark it on the plane-probably on the upper wing. Grab 2 identical #2 pencils. Put the erasers on the balance marks and see how well the plane is balanced. You can hold the pencils in your hand but you'll be really busy if you do that, trying to keep it level, get the plane on the marks, not drop it, etc. You may be able to drill a short piece of 2x4 to hold the pencils. There is no rule against drillling the holes at an angle if you need to clear the lower wing, just keep the tips of the erasers over the 2x4 so it won't tip over with the weight of the plane. If you accidentally drill the holes to different depths, just adjust the length of the pencils to level the erasers.

alienx
07-15-2009, 02:38 PM
OK, I took a good look last night and noticed a couple things.

First, I noticed that the floats were too far aft. The step outside edge was almost 2" aft of the CG. So I moved them up. They are now about 1/2" behind the CG (as near as I can tell from eyeballing it). The plane also balances better at this location. I used the handle of two jeweler's files to get a more accurate balance. So it looks like taking weight out of the nose is not really necessary. The plane didn't fly as though it was balanced way off the mark, but if it was near the aft end of the balance range, it is probably closer to the front end of the range now.

I guess I am going to fly it this way and take my chances. I am bringing with me the other gear legs, so I can take some of the incidence out by swapping to a shorter leg if I need it. That would take a hint of the downward deflection out of the floats, but I find it hard to believe that that could really account for all the elevator I am needing now. I also have some 8x6 props that I use with this motor on my warbirds. It would give me another 15 or so watts if I remember correctly. But It really doesn't seem to be under-powered. I guess that's a relative concept, but the plane had enough power to climb out (after a hand launch), it just took a lot of elevator to do it. I guess, intuitively, I have some other aerodynamic issue that is causing the need for the elevator. Ah, I wish you gys could all see it fly. It might be painfully obvious to you what is wrong with it.

alienx
07-15-2009, 02:40 PM
PS. Maybe I am going to have to get my logbook out tonight and see exactly what kind of power and weight I was at before the floats. I guess it could be a power issue.

Larry3215
07-15-2009, 04:56 PM
If you move the floats forward, thats going to make the plane even more nose heavy. It will move the CG point even more forward from where it is now.

So, if it was nose heavy to begin with, it will be worse after you move them forward.

So now Im confused by your comment that it balances better after moving them forward. Did you remove the added weights in the cowl?

alienx
07-15-2009, 05:49 PM
You are correct. But having looked over the plane a little more critically last night, I don't think I am nose-heavy. If I put my fingers under that intended balance point before moving the floats, the plane seemed to balance. It may have had a hint of lean towards the tail, but it wasn't falling that way, so "in balance." All the float movement did was solidify the balance. That is, it now sits at an angle that is either completely flat or slightly nose down. But again, the angles I am speaking about are extremely small, so the plane is still technically in balance in my mind. I just feel better being close to the front of the range than the back. But no, I did not remove any nose weight.

Having said all that, I am guessing that the plane will still fly well (controllable anyway) at the new balance. But that would mean that I don't have a nose-heavy plane, or at least I didn't when I flew it with the floats on last weekend. So maybe my issue is not nose or tail heavyness. My scale is in my storage shed and I can't get to it, but like I said, I think I need to get my build book out and see exactly what my numbers were with the wheels on it. I really would like to know how heavy the plane is now. It may have gone from 19 oz to 30 oz for all I know. And that would put me at a pretty anemic 53 watts/lb. I may have just maxed out the motor with all the weight I added with the floats and balancing lead. At least that is the next thing I think I need to check on so I am not guessing. I think we have a small spring loaded postal scale in the closet at work. I may try to borrow it at lunch time and sneak home for a minute. I think that would shed a little light on one of the question marks.

alienx
07-15-2009, 07:09 PM
OK, here are some rough numbers from the spring loaded scale.

The plane used to weigh 17 oz and flew with 120 watts. The scale said it weighs 22.5 oz now, but it undervauled the stack of batteries i put on it so let's say the plane was 26 oz. That's still 73 watts/lb. So it's underpowered relative to anything else I've owned, but is it truly underpowered?

I may swap the prob anyway and see if I can't get a few more watts out of it.

Larry3215
07-16-2009, 05:25 AM
Thats on the low side but probably still workable for ROW. Id prefer more power though :)

alienx
07-16-2009, 02:23 PM
Thats on the low side but probably still workable for ROW. Id prefer more power though :)
Yea, I thought about what other motors I might have to put in it but I think I am stuck. I just don't have access to all my hobby stuff over in my storage shed. I swapped the props last night though. Boy an 8" prop seems so small on that plane. Should be good for a little extra oomf though. Worst case, I can hand launch it and then water land it. We'll see how it goes in about a week.

alienx
07-27-2009, 12:19 PM
She flew like a champ!!! I've got some pics and video I'll post when I get home in a week. But I flew her last night. Worked about 400 times better than I imagined it would ...seriously! I did 4 takeoffs and landings on one battery and called it a day. My brother got some video of all of it except the first takeoff. Should be something worth looking at in there I guess.

Thanks for all the help! Makes me want to build a really big Cub!!

Andy

Larry3215
07-27-2009, 05:08 PM
Congrats!

Yeah, float flying can be addictive :D

alienx
08-03-2009, 02:07 PM
Still working on the video. Here's a couple pics though. These are from the day before I flew it. I didn't have a battery charged so I just float and taxi tested it a bit. It worked out for the best though. It was glassy the next night!!

alienx
08-04-2009, 06:46 PM
Here are a couple videos. The only two flights on the plane as a seaplane!!

The first video is mine. My brother caught all of it except the first takeoff. Some of it is a little shaky. He had to deal with some pretty big mosquitos!! Oh, and no audio on this one (had to shrink the file a little to host it). I got 4 takeoffs and landings all together (including a stunt takeoff at the end:red:). The plane flew very very well, in my mind. None of the diving issues I had at the field before I left for vacation. Maybe that had to do with the additional power I was getting from the prop-swap!?

The second video is my dad's flight. He had a really nice ROW but it went downhill after that.:(

Anyway, enjoy the videos and thanks again to everyone that helped me work out the kinks!!

Oh, and I guess you can't embed Vimeo videos, so I hope these links work.

http://www.vimeo.com/5933669

http://www.vimeo.com/5908432

Larry3215
08-05-2009, 12:35 AM
OUCH!

Other than that last 'arival', it looked like it was flying very nicely though :)

warhead_71
10-29-2009, 10:51 PM
I haven't checked this thread in awhile... the videos look great. I did notice that the tail seems to sag in the turns a little. A ventral fin would cure that. I did the same to mine and it tracks perfectly now. 75watts/lb is plenty for a cruiser... in fact you could probably get away with as little as 50watts/lb, but you wouldn't have much reserve power. The elevator seemed a little touchy (especially when your dad was flying)... maybe add some exponential to smooth that out.

One last thing... The wider stance of your floats might be responsible for it not tracking into the wind very well. I noticed on a few ROWs that you were a bit squirrely... yawing left and right into a crosswind (I thought you were going to hit the bank on one particular ROW). With the ventral fin and narrower stance, you'll weathervane into the headwind much more easily.

Congrats... it's a sweet looking Moth.

P.S. -- If you are flying with a GWS 8x6SF, then try a 9x5HD... more thrust, less amps.... overall just more efficient for a draggy airframe.

PaperAirplane
11-04-2009, 12:25 AM
I like the paint scheme.