Need input on .12 rigger ideas

[MikeP]

It has been 2 summers since I built my .12 rigger. It is out dated now, I have seen much better here at intlwaters.

I have some ideas I would like some input before I start building. I guess it would be better to call them goals that I want to achive.

1- No rear strut, I think it is a luxury and can be worked around.

2-No rear sponsons added. I should be able to build the tub with the 2.5-3.0 deg attack angle and give the tub sides the hammer cut.

3- No epoxy. built with CA I tried some sealing with it using the paper towel method, it's a little tricky but it seems to work great.

4-No motor mount, bolt the back of the motor to the bulk head. I am still not sure on this, but I know it works on airplanes.

5-With the power of some of the .12's today I would think a little bit bigger hull would be good. 26" to 28" as I understand 24" is more traditional.

Here is whats drawn up.

28" X 2.25" wide tub, the rear 9" is foam core lightly sheeted and has a 2.5deg angle on the bottom, hammer cut on the sides 6" long, nothing mounted to the transom. The rudder is mounted to the side and mounts like a turn fin on a front sponson.

The stuffing tube runs down the center and is cut into the bottom of the hull at the desired depth and extends out 2".

-MikeP

 

[E]

Mike I'll get you some pics of a graphite arrow shaft that will hold a brass cartridge that accomodates 3/16 prop-shaft... Look-Ma no strut!

Since you are on the subject of a struttless boats, why don't you go ahead and make the right side of the tub longer by 1.5" and reinforce it with light ply. Now you can bolt the rudder directly to the side of the elongated tub... Look-Ma no rudder bracket. You know if nothing will be bolted to the transom then you could probably save some weight in that department.

I built the rear end of my boat with foam -so I have a good feel for building-in the rear sponsons. I think that you don't save much time trying to laminate the rears while on the tub. It's hard to do out of the tub I can't even imagine trying to do it with the spoons attached.

The only way this might work is by simplifying the geometry of the spoons. I'll send so pics of what I'm talking about. Sort of difficult to explain with words. You may have something if you hammer cut the spoons then you could go with straight sides -that I can picture.

another time saving idea:

If you do a single large rear spoon (built into the hull) then you could of "stumbled" on the next gen design. This would also help support the strutless prop, because now you will be supporting it partially with the rear spoon. It's also not too difficult to modify a single spoon to remove and/or add lift.

Not sure about the CA method. I use plenty of CA for the inside parts of the boat. for water-proofing(paper towel) and laminating balsa/birch epoxy is still hard to beat. CA stinks and is more expensive than epoxy. It also does not let you reposition parts very well.

Eric Perez

 

[TomMoorehouse]

mike..... for your number 4 i used the dave brown airplane mount in mine... it is a toss up... either extra weight of the bulkhead or weight from the mount. i think in the end it is pretty equal.

I'm thinking 28 might be a little long.... hummm... id try 26 if ya want to go bigger. my ff12 is about 25. keep in mind the way i see it the effective size of the boat is determined by the distance of the rear tip of the front sponsons to the rear tip of the rear sponsons. you can in your drawings do things to make this bigger. such as have the rears extend past the transom by making a gradual rear slope. make the front sponsons have less angle then you can move the tubes further back..... hence the sponsons further forward. When doing this also keep in mind the CG so it dont get too out of wack

carefull sealing with ca it is very bad for your lungs breathing the vapors. id do it outside with a fan blowing the fumes away.

on my hawk where the turn fin mounts to the extension to the tub side I had a little problem. when i would tighten it up it would crush the wood some. then after running for a while the wood kinda crushes a little more and it would be loose. Tighten it again the wood crushes more.... run it.... gets loose again. tighten again wood crushes even more..... get the idea.... i would think about some way to mount it with out crushing wood if that makes sense.

 

[MikeP]

Erick,

Here is a quick drawing in paint for hull. Just to make sure it's clear on the design. Good idea on the built in rudder bracket.

www.ad.kengarff.com/mikep/cf90/concept1.jpg

Tom,

I would like to add a couple inches to the effective length, hmmm I guess I need to know what that is. Some of the length is is used towards the front. I am going to be careful with the front sponson trailing edge to the prop.

-MikeP

 

[Ron Olson]

I'd like to see someone try what John finch is working on, the V-style tub section. Monorigger?

 

[MikeP]

Ron,

I have seen the talk about that, The vee cuts through the rougher water with out slapping it. The problem they have is it rocks on the Vee when the front is light. They are adding small sponsons to the sides in the rear to stabalize it.

I am thinking that the stuffing tube can be used somehow to cut through the water like a Vee.

-MikeP

 

[Hammerhead]

I think 2.5 degrees is too much. Make the angle 1.8 or 2 degrees. I can't remember what the angle is off the top of my head. Ask Wade! I know that the rear sponsons are 27cm long. and 1.2cm deep.

If you make the cuts 6 inches long you will have some really steep angles.

I'm really interested in seeing how you mount your engine.

Hammer

 

[Don Templeton]

Mike, Your ideas sound great and the back end with the hammer cut will release some of the lift and act as an air dump. What really worries me about the back plate mounting is that on airplanes the starter is pushed into the bulkhead but on a boat with flywheel the leverage applied to the mount by the belt will cause you to use a lot of extra strength in the mounting area which adds up to weight. ???

However , by using the formula that you and Propjockey have on boats, I just think rears look better! ;D ;D ;D

Don

 

[Don Templeton]

Mike, Another thought!

What I've been thinking about is a strutless boat but with an enclosed stuffing box of wood & foam, angled out on the sides, that acts as a center rear sponson. Just like the old Crapshooter pictures I sent you.

Not adjustable and maybe a little lower than the shaft, but not any lower than the bottom of a metal strut and I think you could carry more prop. However, your prop would be much closer to the transom and I think the extra length of the tub would be fine. :

Don

 

[Don Templeton]

The more I think about what you propose to do with the rear end, you

will probably end up with the same basic thing I am talking about but even lighter because of the hammer cut to the rear. Sounds like a plan to me! 8)

 

[Ian Inverarity]

Mike,

Are you talking about containing the stuffing box entirely within the hull/rear sponson? That would a pretty neat setup for low drag I would think.

Do you think that making effectively a large single rear sponson may have too much lift at the rear? I suppose it depends a bit on the width of the tub and how large you make the Hammer cut.

Could be an interesting boat! ;D

Nitrocrazed racing: Always interested in new rigger ideas...

 

[Don Templeton]

Mike,

Attached is a quick drawing of a Hammer Cut rear of boat with no metal strut! Is this close to what your thinking is?

 

[MikeP]

Hi,

I have used hammers rear sponsons on the last 2 boats I built, I like the design (I am a HH fan). I would like to build the .12 with the same design just built different. I made a drawing of the HH.12 then shaved off some weight and built the sponsons into the profile of the hull instead of adding them after. I am trying to keep everything as close to the HH.12 as I can for the first go at this. The only difference is I like to run the prop depth a little lower than Hammer does.

www.ad.kengarff.com/mikep/concept2.jpg

I need to stray from a proven design a step at a time.

Don, your drawing is interesting that looks like it could work with very little drag.

Thanks for taking the time to consider these goals.

-MikeP

 

[MikeP]

After spending some time on the scales weighing motor mounts I think the CMD mount that is used on the SG is the lightest. The rubber groumets help absorb some stress off the hull sides and mounting holes letting me get away with 1/8 light ply without renforcement.

www.ad.kengarff.com/mikep/sgmount.jpg

The motor mount system is only .9 oz.

-MikeP

 

[Don Templeton]

"COOL"-This should be very interesting (as usual) when you start on a new project!

Don 8)

 

[Eric Perez]

Does anyone know who built this rigger?

I liked the SG inspired front sponsons.

 

[Don Templeton]

Eric,

I'm pretty sure that is Mike P's origional .12.

Don

 

[Hammerhead]

Yep! That's the same pic that I have in my MikeP project file, so You're right, Don

I can't wait to see his new one.

Hammer

 

[Don Templeton]

Yep,

It was posted on the RCboat forum a long time back. That post and that picture is what got me interested in 12 riggers to start with!

 

[MikeP]

Yep,

That's the old .12, There was only 1 rigger around here and it was a Eagle SG, the guy let me take it home for a while and take some measurements. I just reduced the size. Those sponsons took some time to make, alot of angles and curves. They are foam core with 1/64 ply and light weight kevlar.

-MikeP