I have been putting together my seamonster float plane ( my first float plane by the way ) and I have come across a problem. The plane is almost finished and I have built it as per the planes with a TT46 pro engine. With the battery and rec as far forward as possible the CG is still almost a whole inch to far back. As far as I can see my only soloution is to cut a hole in the front section and add lead, I dont really want to do this. Has anyone else had this problem? Any advice?

I do not have this plane but I do float fly. What I would do is tape enough lead on the front to get the CG correct and then test fly it. Make sure you get the weight taped on so that water spray doesn't cause you a problem.

The CG is not always where the plans call for it to be. Most often the best CG is back from the plans. The forward CG is conservitive and ment to be safe. After the first test flight you will know if it needs to be moved back, or in your case, reduce the amount of lead taped on.

You may find that the CG is OK where it is now. But you need to fly to make sure.

Where is the CG as a percentage of the MAC? Any farter aft than 33% is asking for a dunking.

I flew mine for the first time thinking that the recommended c.g. location was conservitively too far foreward...
BIG MISTAKE![X(] The first flight was an adventure, to say the least!
Anyway, I ended up cutting a hatch opening in the "bow" and added 5 oz. of lead epoxied to the back of the nose block.
It flys great now, with a TT .46 Pro and if you try a few vertical manuvers (like hovering, etc.) you'll find a certain "self leveling" effect due to the pod mounted engine (pulls the nose down, or "tucks" ). It also flys inverted quite well, with the heavy engine/tank pod hanging pendulum like underneath

If you feel adventurous, you could stretch the motor mount forward, or even re-mount the whole pod forward. Keep the same thrustline and you should not get in much trouble. The TT.46 is a pretty light engine. The plane is probably designed also to accept a 4-cycle (heavier).

Other possibility: Lightening holes in the tail fins, or substituting a lighter grade of balsa for the rudder-elevator. Sometimes elevator stock is hard to tell from pine, it's so hard and heavy. An ounce off the tail is worth several ounces in the nose, due to the longer lever arm to the tail. .

Third possibility: relocate your servo tray farther forward and install longer pushrods, and a (light where you need it) pullpull linkage to the rudder and elevator.

I am persnickety in that I will do almost anything before I add lead to a plane.

I agree with you about lead Jim, as it's just dead weight. The Sea Monster already has a pull-pull rudder, and the fin and stab. are built-up and really light, and my rudder/elev. are pretty light too. I thought about making a new engine mount, but I like the laminated fiberglass/ply factory one. I suppose you could move the servo tray foreward some, but the lead is an expediency that I figured would be worth doing, rather than re-rigging the whole control set-up.
One thing about mine though, is I think the wing has a little bit too much + incidence, and I'm thinking of putting a thin (say 1/32" ) shim under the T.E. because it still has a bunch of down elevator trimmed in to maintain level flight.
I also think a few degrees of up thrust wouldn't hurt, to help lessen the diving tendancy when applying full power.

If you shim the wing, remember that on a flying boat the wing saddle is where the water gets in. Silicone sealer and saran wrap to restore the seal.

Upthrust is good. Last flying boat I had wound up with about 3 degrees up, and 3 right. That's part of the reason for a t-tail: gets the tailfeaters into the prop blast so that the decalage od the motor mount has an immediate effect on the control surfaces.

GRANT ED, if you want to put your battery up front you can probably forget the lead. Just use an extension, and run the wires thru the bulkhead and seal w/ silicone. I was gonna do that, but we had a float-fly the next day and I said aw the heck with it...
The recommended C.G. is @25% which I thought was too far foreward, so I originally balanced it @30% which was hair raising, and with a little too much + incidence caused a steep first climbout, and a few slightly(?) over-controlled porpoises [X(]
Another thing man, make sure all your seams are sealed down real good, 'cuz that covering (whatever it is) has a tendancy to lift, and you'll be gettin' water inside. The rear bottom of the fuse. is a bit weak too (un-supported) and I popped a split in mine on the first landing in 15 m.p.h. winds w/ swells...

Haven't seem much up-dated info on the "Sea Monster" ! I just finished mine using an OS 50fx engine but won't fly it until Spring. I live about 15 minutes from the old Griffiss Air Force Base ! I'm concerned about sealing the seams & the CG . Dan Helmer , Remsen, N.Y.

I used a solid aluminum prop hub and mounted the battery forward. No problems.

Dan...you have a PM...

Tom

Hi Tom, I water proofed the inside of my 'Sea Monster' today ! I haven't heard much in the past year about the performance of the Sea Monster & was wondering about the positives & the Negatives ! Went down near Green,N.Y. to a float fly where there were several Sea Masters that were flying & one Mariner, but NO Sea Monsters ! It has a big fat wing making me think that it would be a slow flying seaplane. I'm putting an OS 50 engine on it & can't wait until Spring to fly it ! I think You have a Sea Monster & being just a few miles away was wondering what You think of it, take care & thanks for getting back to me ! Repectfully, Dan

It flys like a big "Fun Fly" type
It's a lot of fun to shoot touch-and-go's with, and you can do just about anything with it that a "land" plane can do...

My TT .46 Pro w/ APC 12X4 pulls it along very well.
It will slow waaayy down for landing...

Good luck with yours Dan!

One thing I would do now, that I didn't know about before is either seal the covering seams all in the area where the exhaust oil gets to...OR strip all the covering off and re-do it with a better material like Ultra or MonoKote...

Have you installed the horiz. stab yet? I would remove the fin covering, and sheet both sides of the fin to make it more rigid.
Also, the exhaust oil has soaked in, and the whole top of the aft fuse. and tail is getting oil soaked...[:'(]

Edit: Did you read the part about perhaps using a different elevator pushrod?
You know Barry, right?! I built a Seamonster/Seamaster (ebay ) clone for him last year, and I used a red tube "Goldenrod" and ran it up the leading edge of the fin, over the top of the stab...(the stock S-M wire elev. pushrod binds in the tube, and when it gets rusty, that makes it worse )

In spite of the few "bugs", it's a good airplane...