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FT Sea Otter troubles

#1
Hey everyone! After reading at this forum for years here is my first post!

I just build a Sea Otter but I'm having an hard time making it fly. It just wants to dive nose down, despite of the full back on the elevator, so right after launching it, it dives in the grass. The CG is 70mm after the leading edge, as "prescribed" in the plans. Now I'm playing around with the motor angle, tilting it up like a bixler, but it still has the same attitude.
I'm missing something here, with that motor mounted high up, it just makes the airplane tilt. Honestly I'm completely lost here:)

any tips will be greatly appreceated, I really want to fly this plane!
 

Ketchup

4s mini mustang
#2
First off, welcome to the forums! I have never flown a sea otter, but I know some ways in which you could find out what the problem is. You should try a glide test with the plane, just throw it without throttle. If the plane glides straight then your problem is because of thrust, and if it doesn’t then your problem is because of something else like cg. Also, check to see if your elevator is moving in the right direction (when the elevator goes up the plane should go up).
 

Hondo76251

Well-known member
#3
Are you hand throwing it?

This can be tricky due to the low airspeed of a hand launch, especially in a bird with a high mounted engine (ie: if your wings aren't making lift, and your motor is producing thrust it can be a fast ride to the ground and there isn't much the elevator can do about it)
 

Sero

Well-known member
#4
Peter says in the video on this plane that thrust angle isn't needed as the tail is directly in the prop wash which help keeps it straight.
As Hondo points out the wings don't have any prop wash and therefor no artificial lift when launching. I would make sure I have enough elevator throw and all the controls are going in the right direction. Then when launching give it a bit more throttle and a harder toss. Also most water planes you can use grass as a runway and just take off as if you had wheels.
 
#5
Hej everyone! Sorry if I haven't replyed but I've been away from the hobby for a while... I manage to solve the problem! First, I increased the elevator throw as suggested by Sero, and then I researched a bit about the CG... The thing is that in the build page of the Otter they reccomend the CG to be 70mm from the leading edge, wich it makes it incredibly tail heavy! In another video though (don't remeber wich one) they recommend for the CG to be between 1,75 and 2 inches if I'm not wrong. Now she flies sooo good! And glides greatly even if the whole build is quite heavy.
Thanks every one for the help!
 
#7
Hej everyone! Sorry if I haven't replyed but I've been away from the hobby for a while... I manage to solve the problem! First, I increased the elevator throw as suggested by Sero, and then I researched a bit about the CG... The thing is that in the build page of the Otter they reccomend the CG to be 70mm from the leading edge, wich it makes it incredibly tail heavy! In another video though (don't remeber wich one) they recommend for the CG to be between 1,75 and 2 inches if I'm not wrong. Now she flies sooo good! And glides greatly even if the whole build is quite heavy.
Thanks every one for the help!
I'm glad I saw this thread before trying to maiden my freshly built Otter. The plans have the CG at 2.5" from the leading edge on both the templates and the the cover sheet. Peter mentions in the build video that it should be 1.75" - 2.00", and then even mentions as close as 1.50" for new pilots. That's a BIG difference! Glad to hear you got it sorted out, hopefully it will go smoothly for me also. I've never flown off water before, this should be interesting. Attached is a pic of mine.
IMG_1827.jpg
 

slowjo

Well-known member
#8
nice looking plane, I just finished my "snow" otter : ) Side note, half way thru building this I found out this is the P51 wing, thinking about a "water world" smashup plane, integrate the wing, stab and fin from P51, for the fuse, make a p51C with the belly scoop mounted on the front but backwards for the step, then a tractor pod over the canopy, then I will have a P51C Otter , jo
I'm glad I saw this thread before trying to maiden my freshly built Otter. The plans have the CG at 2.5" from the leading edge on both the templates and the the cover sheet. Peter mentions in the build video that it should be 1.75" - 2.00", and then even mentions as close as 1.50" for new pilots. That's a BIG difference! Glad to hear you got it sorted out, hopefully it will go smoothly for me also. I've never flown off water before, this should be interesting. Attached is a pic of mine. View attachment 137486
sea otter 1.JPG
sea otter 2.JPG
sea otter 3.JPG
 

slowjo

Well-known member
#11
i love this idea so much i started playing with the fuse tonight going to call her the Mustter
View attachment 149960
for a proper nose I was thinking of gluing maybe 6-8 layers of foam (minus the paper) on a square nose and shaping a spinner shaped nose, I've made a few spinners by gluing several layers on a large dremal cut off disc , slowing the speed down and sanding a perfect spinner, then seal it with mod podge and paint, jo
 

dutchmonkey

Well-known member
#12
for a proper nose I was thinking of gluing maybe 6-8 layers of foam (minus the paper) on a square nose and shaping a spinner shaped nose, I've made a few spinners by gluing several layers on a large dremal cut off disc , slowing the speed down and sanding a perfect spinner, then seal it with mod podge and paint, jo
for me this is going to be a 2 part build first FT style with paper on simple construction. second build will built more like a depron version with the paper removed then news-papered with titebond/water to make it water proof and more detail added.
 

slowjo

Well-known member
#13
I finally got to maiden my otter, but the snow is all melted, it did NOT want to take off from the grass! but I did get it off the ground and it did seem to pitch up and down hard at take off, I've never flown a plane with a pod up top so this may be normal, once in the air it flew nice albeit nose heavy, battery is all the way up front, then I can slowly work it back. I did put in flaps and it flew very well with them fully deployed.
 
#14
My Otter's maiden didn't go so well.
I lost connection for some reason and it went nose first hard into the ground. Discouraged, she's just been sitting on the work bench since.
I'm going to need to completely rebuild the nose, luckily somehow that seems to be the only severe damage.
My idea is while I'm rebuilding the nose to make it a few inches longer. I had to use a much bigger battery than I expected to make the plane balance. Hopefully with a longer nose I can slide a smaller battery further forward to get to a happy place. I also need to figure out why she decided to stop responding to transmitter inputs...
 

slowjo

Well-known member
#15
My Otter's maiden didn't go so well.
I lost connection for some reason and it went nose first hard into the ground. Discouraged, she's just been sitting on the work bench since.
I'm going to need to completely rebuild the nose, luckily somehow that seems to be the only severe damage.
My idea is while I'm rebuilding the nose to make it a few inches longer. I had to use a much bigger battery than I expected to make the plane balance. Hopefully with a longer nose I can slide a smaller battery further forward to get to a happy place. I also need to figure out why she decided to stop responding to transmitter inputs...
if I build an other one, I would put the rudder servo behind the wing under the piece of FB with the opening to loose some tail weight, I too am using a 2200 3s battery all the way forward, jo
 

slowjo

Well-known member
#17
this weekend we got a little snow in west Michigan so I got to try out my otter again, and almost no wind : ) I never built any out riggers because I don't have a place to fly from water, my intent was a snow plane , but I realized I need something, on first throttle it pitches to the side and nose bad, but always rights itself , it flew great!, I did make flaps for it and with then fully deployed, slow flybys looked really cool, this plane does NOT like sudden throttle inputs!!! touch and goes were fun if you had control on the throttle else it pitches down fast
 

slowjo

Well-known member
#18
My Otter's maiden didn't go so well.
I lost connection for some reason and it went nose first hard into the ground. Discouraged, she's just been sitting on the work bench since.
I'm going to need to completely rebuild the nose, luckily somehow that seems to be the only severe damage.
My idea is while I'm rebuilding the nose to make it a few inches longer. I had to use a much bigger battery than I expected to make the plane balance. Hopefully with a longer nose I can slide a smaller battery further forward to get to a happy place. I also need to figure out why she decided to stop responding to transmitter inputs...
did you figure out your electronics, once I got my otter nose heavy and flying, I could get it sorted, now I know how it reacts its a great flyer, jo
 
#19
did you figure out your electronics, once I got my otter nose heavy and flying, I could get it sorted, now I know how it reacts its a great flyer, jo
Glad to hear yours is flying great!
Honestly, mine's been on the back burner this whole time. Sometime over the winter I'll try and get everything sorted and repaired. I'm working on a couple other models in the meantime...