Converting Seamaster .40 to Speed 400
 

Hello!

I have plans for a Seamaster .40 glow plane (from AMA plans archives).

I was looking into the possibility of converting it to a Speed 400 electric plane.

Would I simply scale the plane down a certain percentage based on weight restrictions? Are there any "standard" conversions for doing making this type of conversion?

At this point, I only have plans (so I don't have any actual weight measurements). What would I be up against?

Thanks,

Dan

RE: Converting Seamaster .40 to Speed 400
 

The only advice I can offer is, you should take a survey of typical Speed 400, and typical .40-size, planes. A pattern should start to emerge regarding size and weight, which you can use as targets for your scaled-down version.

RE: Converting Seamaster .40 to Speed 400
 

In attempts to take advantage of the park down the street from me, I have started embarking on a quest to shrink a .40 sized seaplane down into a Speed 400 electric seaplane.

I spent a day doing some calculations and have found that by scaling the plans for this plane down by 50%, I should be OK. It takes the wing area from 667.5" to 166.875" and keeps the aspect ratio the same (4.6354:1). The area is 25% of the original size (with the span and chord 50% of the original size). Thanks to Kinkos, I now have a scaled down set of plans.

Do some research on the web, I came across this site (calculator): http://www.csd.net/~cgadd/eflight/calcs_gloconvert.htm

The chart states that a wing loading of 15 ounces / square foot is good for trainers and 20 ounces / square foot is good for sports planes. I would say that the seaplane I am looking to convert would be somewhere in the middle of a trainer and a sport plane. This has me shooting for a wing loading of about 17 ounces / square foot.

This would mean that I would need to come in at a weight of about 19.2 ounces (@ 1.2 pounds).

Now for my questions:

1) Do these calculations jive?
2) Are there any gross errors that I may have made?
3) Where are the best places to save weight when building?
4) Should I shoot for 1/16" sheeting over 1/8"?
5) Should I use stringers over sheeting?
6) What kind of covering?

Thanks - I'll keep any parties interested in this kind of weird conversion posted via this thread.

Dan

RE: Converting Seamaster .40 to Speed 400
 

Hi Dan,

For your Speed 400 scale-down project, I would use the specs from the old Hobby Lobby Aventura flying boat. This used a direct drive Speed 400 motor with a 5x4 "Zagi" spoon prop on 8-cells.

The Aventura had a 43" wingspan, 34" length, and 333 sq. in. wingarea. The flying weight was around 26-28oz.

Many hop-ups exist for the Speed 400 size planes from longer can motors to brushless to lighter Lithium Polymer cells so don't be afraid if you miss your target. The dynamic range of electric power in this size of plane can easily solve any power or weight issues you run into.

RE: Converting Seamaster .40 to Speed 400
 

Look for plans for the old Ace Puddle Master. It has been published in one of the magazines but I don't remember which one. It is an small electric version of the Sea Master.

RE: Converting Seamaster .40 to Speed 400
 

Buy a Herr Aquastar. Meant for a .061 to .074 which would work fine with a speed 400 and lipoly's. Mine ROW's at the local lake with the norvel .061 with no problems.

Their Website:
http://www.iflyherr.com

RE: Converting Seamaster .40 to Speed 400
 

Doh almost forgot. I take the side pontoons off when I go to my field and it will ROG too! Looks funny skitching along the grass. I even do soft touch and goes with no problems. Always brings smiles to onlookers.