Steve-o-RCU

Ok, go with me on this one........

I have access to some 2.5" blue high density foam... and a few 25cc (i guess) engines from commercial landscaping blowers. I am thinking about carving a Seaplane ala the 1.20 Mariner. Carving wings with a yardstick spar, sheeting in balsa with wing floats.

I plan on gluing three pieces of foam together, carving the sea hull with a step on it, adding spray rails when sheeting in balsa, and i think glassing for waterproofing and toughness.

The engine pod above the wing (i can go to 10' wing span here!!! i wanna make her huge, if you hadn't guessed by now.) will require some thought......plywood sandwiching the foam???

So, there is my plan, i need ideas from yous guys.

I have a ton o' questions...

Does the fuel tank haveta be in the engine pod or can it be below in the fuse?

I am imagining a 60" fuse and 80" wing or maybe 80" & 120"????

.....hollowing out the foam for the interior.... walling it in thin ply to mount hardware....??? routing control cables under balsa skin.....

MinnFlyer

My Feedback: (4)

About the only thing I can comment on is that if you are using Gas engines, you DON'T have to put the tank in the pod. Gassers will pump the fuel from almost anywhere

Steve-o-RCU

Oay, one small stumbling block outta my way. I thought a gasser would have enough umph to suck fuel 12" up.

So what do you think of my idea Minn?

any ideas how to mount the engine in a somewhat earodynamical pod of sorts?

any advice? foam a good medium? How do i glass the bottom?

the idea is to be lightweight (blue foam), strong & durable (blue foam) ,stable in the air (flat bottom/semi dehi trainer style) and a one off cool project .

Never flown offa H20.... cant be so hard, right?

$599.- for the mariner 120???? no way, this will be in the $100.- range.

Steve-o-RCU

Guess no one is interested?

MinnFlyer

My Feedback: (4)

The idea sounds good. Blue Foam is an excellent medium. Have you ever built a foam wing Steve? Do you know about using a hot bow?

Steve-o-RCU

Today iam starting with the engine, i will post pictures as i go.

I have to take a lot of the unnecessary stuff off of the engine, see how i am gonna adapt the crank to recieve the prop.

Starting at the engine, figuring out the prop pitch & diameter will be first to see what kinda craft she will pull.

From there, the pod construction will begin----More Dow HGigh Density blue foam, wooden dowels inside for structural support and glassing the whole thing seems logical, no?

MinnFlyer

My Feedback: (4)

I would use a 1/2" Plywood post (With lightening holes) embedded into the sheeted Foam wing, and attached to the Firewall. Then, build a pod around it for smooth airflow.

skypupmut

For your engines, go to
http://www.rcuniverse.com/forum/forumid_92/tt.htm

you will find all that is needed there
enjoy
blue foam is great
the skypup ultralight is built mostly out of it and it flew my 200 pounds around for 225 hours

Steve-o-RCU

Wow !!! been consumed reading about converting these engines !!

ok, here is what i got........21.2cc Echo commercial leaf blower engine. 7400 rpm, sounds good?

need help on the mounting of this thing i really want to keep the pull start, devise a mount around it.

I will post pictures here of motor before i start ripping into it. Right now i have a 20-10 prop ----I have to get a longer shaft/nut that holds flywheel on. its a little too short when mounting the prop, only 2 threads showing, and no thrust washers on yet.

the prop i have is only to test the engine, after i have tested it, check the rpms, i will most undoubtedly re-prop to somewhere around a 16-8 or 18-8

jaka

Hi!
A 21cc gas engine will not cope with such a large prop (20x10)!
A 18x6 - 18x8 or 20x6 or even a 20x8 would be those I would try, preferably Menz or an APC prop which are the best props available giving best trust and performance.
As for your plans of making a blue-foam sea-plane ...I would not build it the way you described it by "carving " or sanding the shape of the fuselage and wings..and definitely not using just a yardstik for wingspar.
The way most people build with blue foam or....white foam, which is lighter..is by cutting the wings with a hot wire bow......this is really easy once you know how to do it.

The fuselage could be shaped with a hand saw or a band saw shaping with hand-files...a very laborious work...and dusty too.
Even a fuselage could be cut using a hot bow...R/C Aircombat guys do it frequently to speed up their building of WW 2 fighters.
Foam wings are most of the time covered by balsa , thin plywood or abbachi sheets which is then covered in either glass fiber (25g) and Epoxy (24 hour mold making epoxy ..not the glue variety which is too soft) or polyester resin. Even a plastic film (Oracover or Oratex) covering could be use if utmost lightness is the goal.
I would suggest that you learned more about those specific techniques before you began your big sea-plane project.

Regards!

Jan K
Sweden

Steve-o-RCU

Hey Jaka-----thanks for your constructive input.....NOT. Thanks for suggesting that i learn more. Appreciate it. You've been so helpful. NOT.


Yes. My new hotbow setup is going to be used to cut. Yes, it is going to be sheeted in balsa.

Yes, I know what i am doing.

Ok, now onward.

Ran the engine up last night (coped just fine with a 20 x 10).
Surprised even me......would not idle, would not run unless choke was almost all the way closed. High and low needles ran through full travel, wouldn't even idle when both needles backed out almost all the way. I have another carb to swap today. This one has a larger bore- still Echo .. I think it is from a 25cc maybe??

But I did get it to hold steady at full throttle with the choke 3/4 way closed.

Anyway, here's what i got......... WFO (<---wide friggen open) = 7800 rpm on my hobbico tach.
Yes, thats 7800RPM... with a 20" prop. I guess a 21cc gas engine will cope with such a large prop. Please don't berate me for choosing a large 20" prop to bench test my engine.

The Echo webpage specs out the PB2100 engine at 7400 RPM --- so i dunno if my #'s are accurate. but dang if it didn't say 7800!!!!!

I am gonna swap carbs today, see what that does, i am sure it will at least idle. Next is a velocity stack to feed clean air.

I will whip out the digital cam and snap some pictures tonight.

Steve-o-RCU

8800 rpm with the 20x10 prop.

Checked it a thousand times, from the front, from the back.

8800 rpm.

not bad, eh?

carb was from a stihl. chainsaw i believe.

larger bore in the throat.

gonna work on the pod.

Steve-o-RCU

hot bow made out of a battery charger is pretty cool.

much experimenting to do.

Ross Kean

Looks interesting. Just one comment about the location of the fuel tank. Make sure the area is WELL fuel proofed. Gasoline will eat blue foam very quickly.

Ross

Steve-o-RCU

the numbers speak for themselves.

1680 idle

avg 9000-10000 rpm WFO

12390 rpm when leaned up a bit.

premium 97 octane, added "104+ Octane Boost"

full synthetic 2 cycle mixed 25:1


Friggen thing scares me.

Sounds like a Weedwacker with a Cessna chasing it.


Oh, by the way, pls dont knock my messy crowded shed/workshop

Steve-o-RCU

more pictures .....

Steve-o-RCU

yes that is the stock muffler.

yes that is a rubber band holding the air cleaner housing together (choke has been removed & engine will not run correctly without cover - too much distrurbed air - velocity stack is coming)

yes this is a blast

jrf

My Feedback: (551)

Wow! 8800 on a 20x10 MAS. Thats' a bit stronger than a MOKI 2.10 or a DA 50. And your little 21cc Echo is only a 1.20. You are truely a miracle worker!

And then you got 12390 out of it without throwing the rod? 12390 rpm on a 20x10 MAS would require 21.7 horsepower and generate 69.5 pounds of thrust at a theoretical speed of 117 mph.

You wouldn't be having a little fun with us would you?

Jim

Steve-o-RCU

listen, I', no math genius, i am just tellin ya what i saw.

or am i doing something wrong?

jrf

My Feedback: (551)

I'd start with a new tach.

Jim

Steve-o-RCU

No way !!!!

i just bought it for $40.-

Steve-o-RCU

In all seriousity........

I know the specs on this motor is 7400-7800 rpm max.

I am suspicious too.

I don't know what is correct.

But i do know this:

With a brand new tach with brand new batteries i measured above 10,000rpm consistently, like fifty times over the course of an hour, on a bone stock Echo 21cc swinging a 20 x 10 MAS.
Period.

jrf

My Feedback: (551)

Sounds like your tach is reading double. 5000 rpm on that prop would require 1.5 hp and that sounds like it would be in the ballpark. If you just bought that tach, take it back.

Borrow someone elses and try again.

Jim