Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: 28cc Fairey  (Read 2685 times)

jezzahealy

  • Shipmate
  • *
  • Offline Offline
  • Posts: 6
28cc Fairey
« on: July 28, 2014, 09:27:22 PM »

Hi,


A couple of years ago I purchased a Sovereign 28cc Strimmer motor from eBay for reasonable money. It has been in the garage since awaiting the right project.


I have decided this winter to make a Fairey Huntmans to house the engine. I am planning on leaving it air cooled, opposed to adapting it to have a water cooled head, as I have seen elsewhere on this forum.


I don't have any experience of petrol engines so I am seeking any help anyone can offer.


I was thinking of making the hull around 48" long, does this seem reasonable?


It will be sub-surface drive, will I need a 4mm or 5mm, or even thicker shaft? Can anyone recommend a prop?


I know it won't be the fastest boat, but that isn't my intention.


Any help anyone can provide is greatly appreciated.


Jeremy
Logged

w3bby

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 773
  • Location: Helsingborg, Sweden
Re: 28cc Fairey
« Reply #1 on: July 29, 2014, 12:54:10 PM »

The Huntsman is a closed boat, you are going to need to water cool the engine as I don't believe that you will get enough air flow to do the job....

48" hull should be ok, check that the engine will physically fit in the hull at that size.

A 5mm shaft will do nicely. That is all I use on my petrol FSR-V.

jezzahealy

  • Shipmate
  • *
  • Offline Offline
  • Posts: 6
Re: 28cc Fairey
« Reply #2 on: July 29, 2014, 09:55:00 PM »

Thank you Ian for your response.


I was planning on leaving the cabin windows un-glazed and omitting the rear bulkhead to the cabin to facilitate air flow and heat to escape. In light of this do you feel there will be adequate airflow/ventilation for a air cooled engine?



Logged

w3bby

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 773
  • Location: Helsingborg, Sweden
Re: 28cc Fairey
« Reply #3 on: July 30, 2014, 10:43:22 AM »

You could try but I would bite the bullet and add water.

craig dickson

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 335
  • Location: Brigg North Lincolnshire United Kingdom
Re: 28cc Fairey
« Reply #4 on: July 30, 2014, 07:43:57 PM »

Hi Jeremy

The prospect of fitting out a Huntsman with a petrol engine is an exciting one because they are great hulls and in my opinion ideally suited to IC power plants. In respect of using an air cooled engine that has not being designed for boat or marine use, I think you could be taking a risk of it overheating. If you could easily adapt it to include water cooling I would as suggested already. If not you could take the risk and initially run it for a short period looking out for any signs of overheating when bringing it in. Leaving the window unglazed will give a good flow of air especially when the boat is at speed.

In terms of the prop shaft I agree that a 5mm diameter shaft should be fine. If you fit a hardened spring steel 5mm shaft it should definitely be bullet proof. Alternatively for my smaller engine nitro boats I run with a non hardened 6mm shaft and they have proved fine. Oh, when you mentioned sub surface drive, I am assuming you simply mean submerged drive....? Assuming so, the three key things I would recommend are that a good quality prop tube incorporating a ball race at the end inside the hull is used. Secondly a good quality tough coupling and thirdly take care to ensure accurate alignment of the prop shaft to the engine.

In terms of Huntsman hull size, as mentioned whilst that size Huntsman hull should nicely handle your engine, do check that it will fit inside. The 48 inch Huntsman that I have, the old wooden kit version, has less room at the front due to the slope and curves of the deep V bow section than one might expect. The fibreglass version has more flexibility because you have more scope for fitting any reinforcement bulkheads around the engine as opposed to having to work around a frame and all the internal plywood panels of the wooden kit that I built. Air cooled engines not designed specifically for model boat applications can be rather bulky in size and also the output (crank) shaft will need to be sufficiently low down to enable you keep the prop shaft angle reasonably low.

Out of interest my Huntsman has an old Webra 40 nitro in it so it easily fitted inside.

In terms of prop size, I think you will only get a proper pointer if any members have used a similar engine and can share their experience. The prop that I use on my FSRV multi boat is 58mm in diameter running a tuned 26cc Zenoah. However you might find that your engine may be lower revving with more bottom end torque and needy of a bigger prop. I really don't know on this one. But you really do need an answer on this point as the last thing you want is to install the prop tube with say 30mm gap between its end and the bottom of the hull then find out you can't spin a bigger prop if needed! Conversely, you need to keep that shaft angle as low as possible for best handling of the boat and maximum speed and stability.

Hopefully the above gives some guidance. Do keep us updated on your progress.

Cheers
Craig :-))
Logged
Forget all insults, always remember compliments.

jezzahealy

  • Shipmate
  • *
  • Offline Offline
  • Posts: 6
Re: 28cc Fairey
« Reply #5 on: July 31, 2014, 08:46:40 PM »

Thank you Craig,


That is very helpful.

Logged

madwelshman

  • Shipmate
  • *
  • Offline Offline
  • Posts: 8
  • Model Boat Mayhem is Great!
  • Location: Pembrokeshire, West Wales
Re: 28cc Fairey
« Reply #6 on: February 13, 2015, 09:47:03 PM »

Any updates on this build?

I have a Precedent Perkasa with a 22cc Kawazaki strimmer engine in.
I left the wheelhouse unglazed, put a few air outlets further back in the superstructure and had no problems with overheating.
The problem I did have was couplings separating. I ended up having one made out of brass which lasted fine.
I should now add that this build was back in the 80's/early 90's and that there is a far wider choice of parts these days that will cope with the power.
I sold the model in the late 90's, then found it and bought it back again mid 2000's.
Logged
Fairey Huntsman
Perkasa

martno1fan

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,506
  • Location: Blackpool
Re: 28cc Fairey
« Reply #7 on: February 14, 2015, 06:23:30 AM »

I'm not sure if the engine will fit but i do have lots of experience with that engine,its actually made by zenoah i was told by a guy who used to service strimmers,yes it is air cooled and that could be an issue.
That said id give it a try,so long as you leave the main part of the shroud on which will help direct the incoming air to the engine that will aid cooling,once boats moving the large open windows should allow the air to get where its needed.
As regards the engines power its more than sufficient,i had one in an old woody of 48" and had her to 30 mph which was quite good for what it is,you will need a large prop as they don't rev as high as a zenoah pum or even the air cooled versions. i used a square ended flex cable for mine but not sure how you will do that running a submerged setup but im sure you can come up with something.
Here's a boat i built for an old friend who's no longer with us ,same engine ,this was the first test run.These engines are very reliable i still have a brand new one in its box i plan on using in an air boat  :} ,just use plenty of oil,not the recomended 40-1 ratio but 16 or 18-1 would be my recommendation,also you will need to make a propper exhaust or run a  canister with an external extension tube to get it out of the boat or it will make a right old mess inside the hull.I used a tuned pipe with a home made exh flange adapted to fit,you maybe wont want or need that but you will need to fathom out something ,heres a  few pics also showing the mounts i made to support the motor between 5" rails.
https://www.youtube.com/watch?v=Xz0VD7b9FBk
Logged

martno1fan

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,506
  • Location: Blackpool
Re: 28cc Fairey
« Reply #8 on: February 14, 2015, 06:57:49 AM »

I forgot to mention i removed the part of the shroud that helps direct the air ONLY because i was running in an open cockpit,you will be best leaving it on to help direct the cooling air.
Logged
Pages: [1]   Go Up