Questions: Ace Seamaster 120
 

I am planning to build this plane. A close friend has the prints and a full set of drawings with all the fuse formers.

I had the opportunity to see a fully framed Seamaster 120 last week. It's an impressive plane, but I can't get over all the hardwood in this thing. The model I was lucky enough to look at before it got covered - well, it had 3/32" lite ply ribs. It had spruce stringers on the wings. It had massive lite ply formers in the fuse. It had lite ply vertical fin and horizontal stab. It had a piece of PVC tubing for the leading edge.

After several searches on this design, I can't find anyone else commenting on the, IMO, abusive use of heavy wood in this design. I can see using lite ply for the fuse. The old Midwest kits were all the same tab-lock construction. But hard wood for the leading edge stringers in the wings? And PVC pipe for the leading edge? Seams just about every heavy building material was used except lead.

I have not had a chance to look over the plans in depth. Only glanced at them. Is it normal for this plane to use so much hard wood and ply in the framing or was the one I looked at overbuilt?

I can see all kinds of places to lighten this plane. Any reason for all the heavy wood?

Thanks

RE: Questions: Ace Seamaster 120
 

There is always a balance between building it lite, and building strong enough to take abuse.
Sounds like Ace was big time leaning toward strong when they designed the Seamaster

Lite-ply is usually a good choice for strength when you don't want to have to add fiberglass reinforcing, For hull material that will just get iron on covering, that seems reasonable to me. Balsa is not strong enough on it own for that size (weight) plane IMO

I'd have to see the plans to comment on if it need the hardwood stringers you ask about,, the PVC too, but I'd guess it just convenient since it's round already??

good luck

RE: Questions: Ace Seamaster 120
 

The Seamaster was pretty "over-built". There is a newer version of it called the Neptune, which is much lighter. Same design, but better engineering.

https://www.quicktechhobby.com/Airpl...arf_Flames.htm

RE: Questions: Ace Seamaster 120
 

I have the 120 built from a kit and it is powered by a magnum 180 4 stroke. Flys great. I did add some vertical stablizers to help with an adverse yaw. I did glass the bottom with .05 glass and H2O poly on the bottom.

RE: Questions: Ace Seamaster 120
 

I agree about balancing the build. A wise old pilot once told me, "Build them to FLY, not to crash. None of them will survive a crash anyway. They aren't meant to crash. So build them light. Build them to FLY."

I've taken that philosophy to heart and always tried to build as light as possible, while still adding a gusset here and there. Sometimes it's as simple as adding a small and carefully cut/sanded piece of tri-stock to add strength without much weight. I built one model so light in the tail that the stabs ripped off in flight - note to self - that one was TOO light. A couple pieces of tri-stock around the glue joint might have saved that one... [sm=lol.gif]

I'm fine with the lite ply fuse in the Seamaster. Again, it's the typical tab-lock construction so many of the Midwest kits were famous for. It's heavy, but this is a boat plane and water landings can be harsh. I'll probably add a few more lightening holes in the formers. I swear, the lite ply former at the beam (step) was 10x10 and solid wood. [X(]

I am not fine with all the lite ply ribs. I just about fell over when I saw all those big ribs and every one of them was lite ply. I had to do a double-take to be sure my eyes weren't playing tricks on me. I'll definitely cut those out of 3/32" balsa. The leading edge PVC is NOT going to happen on my plane. I can't imagine how heavy that plastic is compared to a balsa leading edge. The span wise stringers in the wing just about made me fall over as well. 1/4" and 3/8" SPRUCE stringers on a wing? You have got to be kidding me. I can see using spruce for the main spar - even the rear spar. But spruce stringers on the leading edge? [X(] Thats got to be 1/4 lb heavier than balsa.

Also, the shear webs were lite ply. Lite ply shear webs? Really?!?! [sm=stupid.gif]

Yeah, saw that. But it's too small for my 35cc Craftsman chainsaw engine. :) Would be interesting to look inside though.

I found your picture a couple days ago. Looks good!! I like the vertical fins on the horizontal stab. Whats the flying weight?

RE: Questions: Ace Seamaster 120
 

That's my point. You can take the original plans and lighten it up as you see fit

RE: Questions: Ace Seamaster 120
 

One of the things with the Seamaster is the fuselage near the stab is so small that you get some vibration. Probably why they did it with lite ply. My Big bingo also uses ply ribs in the wing. As I said it is exactly the same wing. If the wing hold down bolts were in the same place the wings would be interchangeable.

RE: Questions: Ace Seamaster 120
 

Sorry Minnflyer - I wasn't getting your suggestion at first. Good idea though. [sm=thumbs_up.gif] I think one of the guys in our club has one of those.

I did notice the fuse is quite narrow in the back. Seams a vertical rudder post could be fabricated to help stabilize this area. I don't like the lite ply tail at all. I'll probably stick and sheet these areas instead of using the ply. Also noticed there isn't much gluing surface where the horizontal meets the vertical stab. The plane I saw had a removable horizontal stab.

I think I'd rather have my rudder pushrod come out on top of the fuse, like the elevator pushrod. Wouldn't be that hard to modify that rudder pushrod so it wasn't under the water line when taxiing. There's space next to the vertical stab where you could run a pushrod and just attach your control horn a little higher up on the rudder. Would still work and would keep the pushrod opening out of the water.


Also, I don't care for the "4 bolts through the top of the wing" method of attaching wings. I don't see why the front of the wing saddle couldn't be modified to accept a couple hardwood dowels. The main vertical motor support comes up out of the fuse in this same area. This is a spot where I would most likely modify the construction to incorporate the hardwood dowels, since it's already beefy here to support the engine pod. I like the traditional method of 2 wood dowels in the front and bolts in the back.

RE: Questions: Ace Seamaster 120
 

I personally don't like the Idea of using dowels on a high wing,, kinda risky depending on how areobatic you like to fly, size and weight of plane etc.

We use 4 nylon bolts on quickie 500s and they never fail

RE: Questions: Ace Seamaster 120
 

I don't plan to fly it like I fly my GS aerobatic planes. It's a big ole boat plane. Not meant to do high speed snaps and flat spins. The most this plane will ever see is a few rolls and loops. Maybe a rolling circle or two for "wow factor" and just to see if it'll do it. I love touch-n-gos on the water more than anything. It's probably gonna get a lot of that. :)

I'm totally fine with 5/16" hardwood dowels on a plane this size. Lot easier to build and align IMO. The bulk head thats directly in front of the wings is also the rear engine pod support. Wouldn't be hard to reinforce in this area for wooden dowels and the added reinforcement won't hurt since it's already in need of beefing up to support the 35cc engine I plan to use.

RE: Questions: Ace Seamaster 120
 

It not the Dowel, that won't break, it's what it goes into and what supports it in the wing,,, You build it right you should be OK, If you're going with the balsa LE, I'd back that area up with a lite ply doubler at least.

Sounds like you have enough experiance to know what's strong enough.


I remember way back I had a 20 size HOB p-51, it used a dowel @ the LE, I was flying around inverted on flight # maybe 200 when the wing left the airframe,, It was a spectacular lawn dart. :D

have fun

RE: Questions: Ace Seamaster 120
 

I've built a few kits. ;) I agree that it's necessary to add some ply to the area where the dowels lock into the fuse. I usually end up inserting a 1/2" brass tube as well, to prevent the dowels from wearing on the raw wood. Looking forward to the build. It's been 2yrs since I built a kit and I'm getting excited.

RE: Questions: Ace Seamaster 120
 

When ACE first came out with the Seamaster 120, I was an ACE dealer. Another ACE dealer and I had completed the first production kit planes.

They were pigs.

There was a steady stream of telephone calls between ACE and me, as well as ACE and the other dealer to sort out the problems. It flew lousy, wallowing through the air with the tail down, especially in turns. It was all but uncontrolable in most cases.

We adjusted incidences, thrust angles and added a large dorsal fin ahead of the existing fin to tame the thing. Shifting balance location did not help. It sort of flew OK after that, except for one major issue.

You are absolutely correct that it is an extreme heavyweight. You'd think that the kit prodcution created a worldwide lite ply shortage. Virtually all the wood parts were lite ply. This did not help the vertical stab, which was very heavy and weakly attached. It also had metal rod struts with metal clevises on the stab - 2 per side - for some added stability and strength. However, there was so much shaking that those rods kept vibrating badly. I was concerned that it would generate RF which would put the plane out of control.

The engine pylon was constructed of fir plywood, and consequently weak and prone to twisting.

Overall, it was much too heavy and weak in some important areas as designed.

My first engine in the plane was a Super Tigre 2500. That proved to be inadequate and it was changed immediately for a Quadra 42, which provided sufficient thrust. I cannot imagine this plane flying on a 1.20 4 stoke of that era, as claimed.

Since it was a test vehicle, it was built as it came. As far as the rudder pushrod opening is concerned, I never did have a serious water problem there. Sitting in the water was not an issue. As the plane taxied or took off, the opening was clear of water. The bowden cable system to the elevator worked very well.

Wing attachemnt worked very well too, without any snags or issues, following numerous loops, spins, rolls and so on.

My advice: keep it light, keep it strong and trash most of the lite ply in favor of balsa. And put in lots of power.

RE: Questions: Ace Seamaster 120
 

Thanks very much for the response. Sounds like I am on the right track. I'm sort of wondering if my 35cc chainsaw engine is going to be enough power now. [X(] I LOATHE underpowered planes. It doesn't have to hover, but it needs to do a loop from horizontal flight.

I plan to build all the ribs with balsa. I plan to use balsa stringers on the LE of the wings, balsa sheer webs and balsa on the LE of the wings. I plan to build the vertical and horizontal stabs from balsa sticks and sheet with thin balsa. I'll probably go ahead with the lite ply fuse and formers, but I'll make sure it has PLENTY of lightening holes in most formers. Obviously, you don't want to put lightening holes in the 2 formers that hold the engine pylon [sm=tongue_smile.gif] but there's still plenty of places to put holes in all those ply formers.

RE: Questions: Ace Seamaster 120
 

I received a kit as a gift and I'm planning on building it with a PST 600R I have on the shelf. Anyway thinking most of the ply might be appropriate except the wing ribs. I like goirish's tail design mod as it'll minimize the heat shields required if I can drop the horizontal down to fuse top. Will start a build thread when I get it going. Woody.

RE: Questions: Ace Seamaster 120
 

Hi all have been tinkering with my SM120 and after the first flight it should have been scrap wood, I understand why there are so few around
but having surived the maiden this is what ended up with .
It was an old ace kit and built as per the booklet and I added U/C .

Ballance point shown is OK
+3 deg engine ,stops the power pitch coupling (ASP 160 twin)
+2 wing untouched
+1.5 on the stab (1/4 packing at the LE )

RE: Questions: Ace Seamaster 120
 

Here is some pics
these photos are before 1st flight

RE: Questions: Ace Seamaster 120
 

Nicely done.

I used to fly with a guy in Florida who had one of these. My strongest impression was how high the nose was on the departure turn. It must have had 10-15 degrees of yaw. Always wondered if coupling rudder with the Ails would help...but at the point where I saw all the yaw, the ailerons were pretty much neutral by then.

Back to an earlier post about building light:
I once saw a post with great wisdom. "If you build a plane to crash...it will. "

Sure wish ACE would bring back the Seamaster 40, and that GPwould dust off the Lanier Mariner.

RE: Questions: Ace Seamaster 120
 

I have to support your thoughts on these 2 planes Jim. We are fortunate enough to have one float fly day a week out here from March through early-December so I have 4 float planes in the hangar. Two Cubs and a Northstar, all kitbuilt. But I've always had either a Mariner or Seamaster ARF in the inventory for those less than perfect days. The Mariner is just plain wearing out! May need to check out a Neptune as a replacement but I really like the way the Mariner flys. I guess there is not a really huge market for ARF seaplanes out there.

Just one comment on plywood ribs. I've built 2 or 3 Flair kits and they typically use plywood ribs.....I believe its 1/16", 3 layer ply. Not liteply. I always thought it was overkill but went ahead and used it anyway. The wings came out anything but heavy and I do believe those ribs contributed to the stiffness they display. I'm always a little hesitant to second-guess a designer on wood selection until I've actually built a model and see how it performs. Still, all the evidence described on the big Seamaster seems to point to it being overbuilt. As someone mentioned, it's not really a 3D plane and I'd rather put the strength in the hull for all those touch and goes.

RE: Questions: Ace Seamaster 120
 

>>I've always had either a Mariner or Seamaster ARF in the inventory for those less than perfect days.<<

The SeaMonster looked pretty good but never caught on.  And my fave of all, the SeaCruiser.  I have a treasured set of plans for the SC, and my buddy Art built one for me once and it flew better than great until the embarassing incident with the persimmon tree and the crosswind.

And I have absolutely no interest in the Seawind.

There should usually be 2 plywood ribs in a seaplane wing, in the center.  These take the loads from the wing mounting and the motor mounting strut.  Maybe a couple more where the outrigger floats attach to the wing.  But that's just my opinion. 

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RE: Questions: Ace Seamaster 120
 

This is more fun

RE: Questions: Ace Seamaster 120
 

yea I have been flying the 46 version for 10 years. Grass is always the same height. Water on the other hand is HARD with waves. On rough water you will bounce more. This tends to put more of a beat down on the airframe. If it flys as good as my 46 you will love it.

RE: Questions: Ace Seamaster 120
 

Here's mine at the "CARNAGE" float fly we had in June. I think there were 20 plus crashes. 15 to 20 knots on our backs. Broke my wing. Just about redone. This fully sheeted without ply ribs and pvc leading edge. G38 for power. http://www.youtube.com/watch?v=qvXuQ...4&feature=plcp

RE: Questions: Ace Seamaster 120
 

I just finished the first three flights with my Sea Master 120. I must say it provided a few exciting moments but it survived. Power is a ST 3000 swinging a 18 X 8 MAS prop. Water handling was great and the takeoffs and landings were without incident but WOW, that adverse yaw in flight. The plane has no directional stability whatsoever even though mine has the fin fairing added. After I mixed 50% rudder coordinated to the ailerons things were much better. Now that it's home I'm fabricating sub fins which will add approximately 30 sq. inches to the fin area. Another thing which I think will help is to use differential aileron with tons of up and hardly any down. I think there's hope for the design and it's pretty easy to see why theres so much adverse yaw once you start scrutinizing the design.
I'll post some pictures as soon as I receive some from a friend of mine who fortunately had a camera there.
Peter

RE: Questions: Ace Seamaster 120
 

PeterC
Take a look at the picture in post #4.  I added those to the stab and it corrected the yaw. <br type="_moz"/>